IPAC2015 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOAC1	Awake: the Proof-of-principle R&D Experiment at CERN	proton, laser, plasma, experiment	34
	P. Muggli MPI, Muenchen, Germany M. Bernardini, T. Bohl, C. Bracco, A.C. Butterworth, S. Cipiccia, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, A.V. Petrenko, J.S. Schmidt, M. Turner, H. Vincke CERN, Geneva, Switzerland
	The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a proof-of-principle R&D experiment at CERN. It is the world’s first proton driven plasma wakefield acceleration experiment, using a high-energy proton bunch to drive a plasma wakefield for electron beam acceleration. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV proton beam bunches from the SPS, which will be sent to a plasma source. An electron beam will be injected into the plasma cell to probe the accelerating wakefield. Challenging modifications in the area and new installations are required for AWAKE. First proton beam to the experiment is expected late 2016. The accelerating electron physics will start late 2017. This paper gives an overview of the project from a physics and engineering point of view, it describes the main activities, the milestones, the organizational set-up for the project management and coordination.
	Slides MOAC1 [21.632 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOAC1
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MOBC2	High-Performance Simulations of Coherent Synchrotron Radiation on Multicore GPU and CPU Platforms	GPU, simulation, synchrotron, radiation	42
	B. Terzić, A.L. Godunov ODU, Norfolk, Virginia, USA A. Arumugam, D. Ranjan, M. Zubair ODU CS, Norfolk, Virginia, USA
	Coherent synchrotron radiation (CSR) is an effect of self-interaction of an electron bunch as it traverses a curved path. It can cause a significant emittance degradation and microbunching. We present a new high-performance 2D, particle-in-cell code which uses massively parallel multicore GPU/GPU platforms to alleviate computational bottlenecks. The code formulates the CSR problem from first principles by using the retarded scalar and vector potentials to compute the self-interaction fields. The speedup due to the parallel implementation on GPU/CPU platforms exceeds three orders of magnitude, thereby bringing a previously intractable problem within reach. The accuracy of the code is verified against analytic 1D solutions (rigid bunch).
	Slides MOBC2 [4.866 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBC2
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MOBC3	Electron Lenses for Experiments on Nonlinear Dynamics with Wide Stable Tune Spreads in the Fermilab Integrable Optics Test Accelerator	lattice, solenoid, optics, operation	46
	G. Stancari, K. Carlson, M.W. McGee, L.E. Nobrega, A.L. Romanov, J. Ruan, A. Valishev Fermilab, Batavia, Illinois, USA D. Noll IAP, Frankfurt am Main, Germany
	Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy. Recent developments in the study of integrable Hamiltonian systems have led to nonlinear accelerator lattice designs with two transverse invariants. These lattices may drastically improve the performance of high-power machines, providing wide tune spreads and Landau damping to protect the beam from instabilities, while preserving dynamic aperture. To test the feasibility of these concepts, the Integrable Optics Test Accelerator (IOTA) is being designed and built at Fermilab. One way to obtain a nonlinear integrable lattice is by using the fields generated by a magnetically confined electron beam (electron lens) overlapping with the circulating beam. The parameters of the required device are similar to the ones of existing electron lenses. We present theory, numerical simulations, and first design studies of electron lenses for nonlinear integrable optics.
	Slides MOBC3 [11.870 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBC3
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MOPWA002	Nonequilibrium Phase Transitions in Crossed-Field Devices	cathode, space-charge, simulation, injection	74
	S. Marini, R. Pakter, F.B. Rizzato IF-UFRGS, Porto Alegre, Brazil
	Funding: This work was partially supported by CNPq and FAPERGS, Brazil, and by the US-AFOSR under the grant FA9550-09-1-0283. This work presents a fully kinetic description to model the electron flow in the electronic crossed-field configuration observed in a smooth-bore magnetron. Through this model, it has been observed that, according to the electromagnetic field, the injection temperature and the charge density, the electron flow can be classified in two different stationary modes: magnetic insulation mode where most of the electrons returning to the cathode after a transient time and Child-Langmuir mode where most of the electrons reach the anode after a transient time. Focusing on magnetic insulated mode, it has been found that charge density and injection temperature define whether electrons are accelerated (accelerating regime) or decelerated (space-charge limited regime) on the cathode. Besides, when the injection temperature is relatively low (high), a small charge increase causes (does not cause) an abrupt transition between accelerating and space-charge limited regime. Basing on the results, it was possible to identify a critical temperature that separates abrupt and continuous behavior. The results have been verified by using self-consistent computer simulations. S. Marini, F. B. Rizzato, and R. Pakter, Phys. Plasmas 21, 083111 (2014).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA002
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MOPWA009	Channeling Radiation Experiment at Fermilab ASTA	photon, brilliance, experiment, detector	95
	D. Mihalcea, P. Piot Northern Illinois University, DeKalb, Illinois, USA D.R. Edstrom, P. Piot, T. Sen Fermilab, Batavia, Illinois, USA W.D. Rush KU, Lawrence, Kansas, USA
	Electron beams with moderate energy ranging from 4 to 50 MeV can be used to produce x-rays through the Channeling Radiation (CR) mechanism. Typically, the x-ray spectrum from these sources extends up to 140 keV and this range covers the demand for most practical applications. The parameters of the electron beam determine the spectral brilliance of the x-ray source. The electron beam produced at the Fermilab new facility Advanced Superconducting Test Accelerator (ASTA) meets the requirements to assemble an experimental high brilliance CR x-ray source. In the first stage of the experiment the energy of the beam is 20 MeV and due to the very low emittance (100 nm) at low bunch charge (20 pC) the expected average brilliance of the x-ray source is 0.8x10⁷ photons/[s-(mm-mrad)²-0.1%BW]. In the second stage of the experiment the beam energy will be increased to 50 MeV and consequently the average brilliance will be 4.8x10⁸ photons/[s-(mm-mrad)²-0.1%BW]. Also, the x-ray spectrum will be extended from about 30 keV to 140 keV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA009
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MOPWA011	The Damping of Transverse Coherent Instabilities by Harmonic Cavities	synchrotron, betatron, simulation, damping	102
	F.J. Cullinan, R. Nagaoka SOLEIL, Gif-sur-Yvette, France G. Skripka, P.F. Tavares MAX-lab, Lund, Sweden
	At nonzero chromaticity, the threshold current due to transverse coupled bunch instabilities in an electron storage ring is defined by intrabunch head-tail motion of higher than zeroth order. Multibunch tracking simulations predict that this threshold can be increased to several times its original value through the introduction of bunch lengthening harmonic cavities. One previously suggested explanation is the narrower spectra of the elongated bunches but reliable estimates for the threshold currents are not obtainable for anything other than rigid beam motion since the usual Sacherer formulism is not directly applicable to beams in a non-harmonic potential. A new scheme has been developed in which the decay time of a higher than zeroth order transverse head-tail mode may be estimated by taking into account the synchrotron tune spread generated by the harmonic cavity potential. This scheme is presented along with the results of numerical simulations performed in order to confirm the analytical predictions and justify the assumptions made. The extension of the scheme to more complex scenarios is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA011
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MOPWA013	Modeling and Measurements of Spin Depolarization	kicker, resonance, polarization, synchrotron	109
	N. Carmignani, F. Ewald, L. Farvacque, B. Nash, P. Raimondi ESRF, Grenoble, France
	An electron bunch in a storage ring becomes spin polarized due to the Sokolov-Ternov effect. The beam may then be depolarized by applying a horizontal magnetic field oscillating in resonance with the spin tune. This technique has been used to measure the electron energy at numerous synchrotrons. In this paper, we report on modeling and measurements of the polarization and depolarization process at the ESRF. We report the results of a Matlab based parallelized spin tracking code that we developed for these studies. We show the change in depolarization resulting as different physical effects are added to the model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA013
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MOPWA021	Transverse Resonance Island Buckets at the MLS and BESSY II	resonance, operation, radiation, photon	138
	M. Ries, J. Feikes, T. Goetsch, P. Goslawski, J. Li, M. Ruprecht, A. Schälicke, G. Wüstefeld HZB, Berlin, Germany
	By operating the Metrology Light Source (MLS) near horizontal resonances (fx/frev=1/2, 1/3 or 1/4), two, three or four resonance island buckets may be populated for beam storage. This paper presents experimental results and operational experience such as tuning the machine for high current, controlling inter-bucket diffusion rates, improving overall lifetime and extraction of radiation pulses with sub-revolution repetition rate. First approaches to transfer this mode of operation to the BESSY II storage ring will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA021
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MOPWA023	Preserving Information of the Three Spatial Electron Beam Dimensions in One Streak Camera Measurement	operation, synchrotron, photon, diagnostics	144
	M.T. Switka, W. Hillert ELSA, Bonn, Germany
	Funding: Work funded by the DFG within SFB/TRR16 At the pulse stretcher ring ELSA, a streak camera is used for the analysis of visible synchrotron radiation. It functions as fast time resolving beam diagnostic apparatus capable of visualizing dynamics down to the picosecond time range. The optical beamline splits the photon beam and projects the electron beam's image onto the streak camera with transversely perpendicular orientation and slight displacement, thereby providing simultaneous imaging of both transverse planes. Thus, the information of bunch and beam dynamics in three dimensions is preserved and can be observed in slow sweep or synchroscan operation. Characteristics and exemplary measurements, demonstrating the capabilities and limits of this technique, are presented.
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MOPWA024	Estimation of the Ion Density in Accelerators using the Beam Transfer Function Technique	ion, betatron, synchrotron, impedance	147
	D. Sauerland, W. Hillert ELSA, Bonn, Germany A. Meseck HZB, Berlin, Germany
	Funding: Funded by the federal ministry of education and science of Germany The ELSA stretcher ring of Bonn University serves external hadron physics experiments with a quasi continuous electron beam of up to 3.2 GeV energy. Ions, being generated by collisions of the circulating electrons with the residual gas molecules, accumulate inside the beam potential, causing incoherent tune shifts and coherent beam instabilities. Detailed measurements were carried out in which ion dynamics is studied in dependence of beam energy and current, filling patterns and bias voltages of the ion clearing electrodes. By measuring the beam transfer function using a broadband transversal kicker, we were able to derive an estimate of the average ion density from the shift and broadening of the tune peak. In this contribution first results of these measurements are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA024
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MOPWA029	Investigations of the Space-Charge-Limited Emission in the L-Band E-Xfel Photoinjector at Desy-Pitz	simulation, space-charge, gun, cathode	162
	Y. Chen, H. De Gersem, E. Gjonaj, A.V. Tsakanian, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany C. Hernandez-Garcia JLab, Newport News, Virginia, USA M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany
	Funding: work supported by DESY Hamburg and Zeuthen Sites This paper discusses the numerical modelling of electron bunch emission for an L-band normal conducting RF photogun. The main objective is clarifying the discrepancies between measurements and simulations performed for the European X-ray Free Electron Laser (E-XFEL) injector at DESY-PITZ. An iterative beam dynamics simulation procedure is proposed for the calculation of the total extracted bunch charge under the assumption that the emission source operates at the space-charge limit of the gun. This algorithm has been implemented in the three-dimensional full electromagnetic PIC Solver of the CST Particle Studio (CST-PS). Simulation results are in good agreements with measurements for a series of operation parameters. Further comparisons with a conventional Poisson-solver-based (PSB) tracking algorithm demonstrates the great significance of transient electromagnetic field effects for the beam dynamics in high brightness electron sources. Computer Simulation Technology AG, http://www.cst.com/
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MOPWA030	Simulations of Electron Cloud Long Range Wakefields	wakefield, simulation, dipole, proton	165
	F.B. Petrov, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by the BMBF under Contract No. 05H12RD7 A typical approach to electron cloud simulations is to split the problem in two steps: buildup simulations and instability simulations. In the latter step the cloud distribution is usually refreshed after each full interaction with the bunch. This approach does not consider multibunch effects. We present studies of the long range electron cloud wakefields generated in electron clouds after interaction with relativistic proton bunch trains. Several pipe geometries - relevant to CERN accelerators - with and without external magnetic field are considered. Using simple examples we show that the long range wakefields depend significantly on the secondary emission curve as well as on the pipe geometry. Additivity of electron cloud wakefields is studied as well.
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MOPWA034	Coupled-Bunch Instability Suppression Using RF Phase Modulation at the DELTA Storage Ring	damping, synchrotron, storage-ring, feedback	179
	M. Sommer, M. Höner, B.D. Isbarn, S. Khan, B. Riemann, T. Weis DELTA, Dortmund, Germany
	Funding: Work supported by the BMBF under contract no. 05K13PEB The upcoming upgrade of BESSY II, called BESSY-VSR, involves the utilization of superconducting multicell RF-resonators with high accelerating gradients to provide short and long bunches in an electron storage ring simultaneously. Even under the assumption of strongest available damping of beam induced modes, the residual impedances of the cavities may cause collective multibunch instabilities at the frontier of stability available from current bunch-by-bunch feedback systems. At the DELTA electron storage ring, a phase modulation of the driving RF is used to suppress coupled-bunch instabilities and to increase the lifetime. The time dependent frequency variation in the order of the synchrotron frequency gives rise to additional damping of the bunch oscillators by decoherence and Landau damping. The behaviour and the additional damping of the bunch oscillators is investigated by the existing bunch-by-bunch feedback system e.g. the increase of the overall damping might support the capability of feedback systems under extreme operating conditions of BESSY-VSR. G. Wüstefeld et al., Proc. of IPAC'11, San Sebastián, THPC014
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MOPWA042	Sub-fs Electron Bunch Generation Using Magnetic Compressor at SINBAD	simulation, plasma, acceleration, laser	207
	J. Zhu, R.W. Aßmann, U. Dorda, J. Grebenyuk, B. Marchetti DESY, Hamburg, Germany
	In order to achieve high quality electron beams by laser-driven plasma acceleration with external injection, sub-fs bunches with a few fs arrival-time jitter are required. SINBAD (Short Innovative Bunches and Accelerators at DESY) is a proposed dedicated accelerator research and development facility at DESY. One of the baseline experiment at SINBAD is ARES (Accelerator Research Experiment at SINBAD), which will provide ultra-short electron bunches of 100 MeV to one or two connected beam lines. We present start-to-end simulation studies of sub-fs bunches generation at ARES using a magnetic compressor with a slit. In addition, the design of a dogleg with tunable R56 for the second beamline is also presented.
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MOPWA043	FEL Simulations with Ocelot	optics, space-charge, FEL, simulation	210
	I.V. Agapov, G. Geloni XFEL. EU, Hamburg, Germany M. Dohlus, I. Zagorodnov DESY, Hamburg, Germany S.I. Tomin NRC, Moscow, Russia
	Ocelot has been developed as a multiphysics simulation tool for FEL and synchrotron light source studies. In this work we highlight recent code developments focusing on electron tracking in linacs taking into account collective effects and on x-ray optics calculations
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MOPWA045	First Tests of a Beam Transport System from a Laser Wakefield Accelerator to a Transverse Gradient Undulator	quadrupole, undulator, beam-transport, dipole	216
	C. Widmann, V. Afonso Rodríguez, A. Bernhard, A.-S. Müller, R. Rossmanith, W. Werner KIT, Karlsruhe, Germany M. Kaluza, M. Nicolai, M.B. Schwab, A. Sävert IOQ, Jena, Germany M. Kaluza, S. Kuschel HIJ, Jena, Germany
	An experimental setup for the generation of monochromatic undulator radiation at the laser wakefield accelerator (LWFA) in Jena using a transverse gradient undulator (TGU) is planned. Proper matching of the betatron functions and the dispersion of the electron beam to the undulator is essential. Therefor a beam transport system with strong focusing magnets and chromatic correction of these magnets is required. As a first step, a linear beam transport system without chromatic correction was assembled at the LWFA. With this setup the electron beam’s dispersion and the beta function of one selected energy are matched to the required parameters at the TGU. This contribution presents the experimental results of these measurements.
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MOPWA049	Simulation of Crab Waist Collisions in DAΦNE with KLOE-2 Interaction Region	simulation, luminosity, betatron, detector	229
	M. Zobov, A. Drago, A. Gallo, C. Milardi INFN/LNF, Frascati (Roma), Italy D.N. Shatilov BINP SB RAS, Novosibirsk, Russia A. Valishev Fermilab, Batavia, Illinois, USA
	Funding: Research supported by DOE via the US-LARP program and by EU FP7 HiLumi LHC - Grant Agreement 284404. After the successful completion of the SIDDHARTA experiment run with crab waist collisions, the electron-positron collider DAΦNE has started routine operations for the KLOE-2 detector. The new interaction region also exploits the crab waist collision scheme, but features certain complications including the experimental detector solenoid, compensating anti-solenoids, and tilted quadrupole magnets. We have performed simulations of the beam-beam collisions in the collider taking into account the real DAΦNE nonlinear lattice. In particular, we have evaluated the effect of crab waist sextupoles and beam-beam interactions on the DAΦNE dynamical aperture and energy acceptance, and estimated the luminosity that can be potentially achieved with and without crab waist sextupoles in the present working conditions. A numerical analysis has been performed in order to propose possible steps for further luminosity increase in DAΦNE such as a better working point choice, crab sextupole strength optimization, correction of the phase advance between the sextupoles and the interaction region. The proposed change of the e^- ring working point was implemented and resulted in a significant performance increase.
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MOPWA054	Effect of Number of Macro Particles on Resolution in Phase Space Distribution	simulation, operation, linac	242
	T. Miyajima KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS KAKENHI Grant Number 26600147. In order to analyze charged particle beam in an accelerator, a beam model is used to reduce number of degrees of freedom, e.g. charged disk model, charged cylinder model and macro-particle model. In numerical simulation, the macro-particle model, which has same mass-to-charge ratio, is widely used, since it does not require any symmetry of beam shape. However, the estimation of proper number of macro-particles is one of the important issues. In order to study the effect of the number of macro-particles for the numerical model, we defined a simple transformation to generate reduced distribution. The transformation was applied for one dimensional and two dimensional particle distributions. The static electric fields due to the transformed distributions were calculated. As a result, we confirmed the effectiveness of the transformation.
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MOPWA066	Simulation on Buildup of Electron Cloud in Rapid Cycling Synchrotron of China Spallation Neutron Source	proton, simulation, vacuum, neutron	275
	K.W. Li, L. Huang, Y.D. Liu, S. Wang IHEP, Beijing, People's Republic of China
	Funding: Work supported by National Natural Science Foundation of China (11275221) Electron cloud interaction with high energy positive beam are believed responsible for various undesirable effects such as vacuum degradation, collective beam instability and even beam loss in high power proton circular accelerator. An important uncertainty in predicting electron cloud instability lies in the detail processes on the generation and accumulation of the electron cloud. The simulation on the build-up of electron cloud is necessary to further studies on beam instability caused by electron cloud. China Spallation Neutron Source (CSNS) is the largest scientific project in building, whose accelerator complex includes two main parts: an H⁻ linac and a rapid cycling synchrotron (RCS). The RCS accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV with a repetition rate 25 Hz. During the beam injection with lower energy, the emerging electron cloud may cause a serious instability and beam loss on the vacuum pipe. A simulation code has been developed to simulate the build-up, distribution and density of electron cloud in CSNS/RCS.
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MOPWA072	Emittance Exchange Beam Line Design In THU Accelerator Lab	emittance, quadrupole, cavity, simulation	285
	Q. Gao, H.B. Chen, Y.-C. Du, W.-H. Huang, J. Shi TUB, Beijing, People's Republic of China W. Gai ANL, Argonne, Illinois, USA
	Funding: National Natural Science Foundation of China Emittance exchange (EEX) provides a novel tool to enhance the phase space manipulation techniques. Based on Tsinghua Thomson scattering experimental platform, this study presented a beam line design for exchanging the transverse and longitudinal emittance of an electron bunch. This beam line consists of a 2.856 GHz half-one-half cell deflecting cavity with no axis offset and two doglegs. In this paper, by optimizing the beam envelope parameter for Tsinghua Thomson scattering source, we report the theoretical analysis and a good particle tracking simulation result about emittance exchange and longitudinal shaping.
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MOPJE001	Effect on Beam Dynamics From Wakefields in Travelling Wave Structure Excited by Bunch Train	wakefield, simulation, dipole, radiation	289
	D. Wang, C.-X. Tang TUB, Beijing, People's Republic of China W. Gai, C.-J. Jing, J.G. Power ANL, Argonne, Illinois, USA J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA
	Electron bunch train technology is used to excited coherent high power RF radiation in travelling wave (TW) structures. This article concentrates on the analytical expression of wakefields excited by bunch train in TW structures and the effects of wakefields on beam dynamics. We focus on the first monopole mode and the first dipole mode wakefields. The long range wake function has a linear decrease which agrees well with the ABCi simulations. Taking example of the 11.7 GHz wakefields structure at the Argonne Wakefield Accelerator (AWA) facility, with 1.3 GHz interval drive electron bunch train, we have done the beam dynamics simulation with a point to point (P2P) code. Results shows the effects of wakefields on the energy distribution and the transverse instability for each sub-bunch.
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MOPJE003	Measuring Duke Storage Ring Lattice Using Tune Based Technique	storage-ring, quadrupole, lattice, wiggler	293
	W. Li, J.Y. Li USTC/NSRL, Hefei, Anhui, People's Republic of China H. Hao, W. Li, S.F. Mikhailov, V. Popov, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. The Duke electron storage ring is a dedicated driver for oscillator Free-Electron Lasers (FELs). A 34 m long straight section of the storage ring is used to host up to four FEL wigglers in several different configurations. A total of six wigglers, two planar OK-4 wigglers and four helical OK-5 wigglers, are available for FEL research. The storage ring magnetic lattice has to be designed with great flexibility to enable the storage ring operation with different FEL wigglers, at various wiggler settings, and for different electron beam energies. Since 2012, the storage ring has demonstrated all designed characteristics in terms of lattice flexibility and tuning. This work is aimed at gaining better understanding of the real storage ring lattice by performing a series of measurements of the beta-functions along the storage ring. Unlike the LOCO technique, the beta-functions in the quadrupoles are directly measured with good accuracy using a tune meassurement system. We will describe our experimental design and techniques, and measurement procedures. We will also report our preliminary results for the lattice characterization.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE003
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MOPJE006	Electron Gun Longitudinal Jitter: Simulation and Analysis	gun, timing, linac, simulation	297
	M.S. Liu, Y.L. Chi, S. Pei, Y.F. Sui IHEP, Bejing, People's Republic of China
	The beam longitudinal jitter is fatal not only for the electron beam performance but also for the positron yield in routine operation of the Beijing Electron Positron Collider II (BEPCII) linear accelerator (Linac). Practically, longitudinal jitter has been observed many times which decreased the beam performance. We simulated the electron gun longitudinal jitter effect by PARMELA software in bunch capture process and analyzed its results about beam performance including average energy, energy spread, emittance and longitudinal phase of reference particle. We adjusted the electron gun trigger time during one cycle without changing other parameters. The percentage difference between maximum and minimum of average energy, energy spread, emittance and longitudinal phase of reference particle was 11.3%, 42%, 98% and 6.4%, respectively. It is observed and analyzed that gun trigger time longitudinal jitter is fatal for maintaining good beam performance. This analysis also gives a salutary lesson to any other longitudinal jitter which can affect the beam bunching in pre-injector .
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MOPJE008	Suppression of Microbunching Instability via a Transverse Gradient Undulator	linac, simulation, FEL, laser	300
	D. Huang, H.X. Deng, C. Feng, D. Gu, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Funding: the Major State Basic Research Development Program of China (2011CB808300) and the National Natural Science Foundation of China (11275253, 11475250 and 11322550). The microbunching instability in the linear accelerator (linac) of a free-electron laser facility has always been a problem that degrades the electron beam quality. In this paper, a quite simple and inexpensive technique is proposed to smooth the electron beam current profile to suppress the instability. By directly adding a short undulator with transverse gradient field right after the injector to couple the transverse spread into the longitudinal direction, additional density mixing in the electron beam is introduced to smooth the current profile, which results in the reduction of the gain of the microbunching instability. The magnitude of the density mixing can be easily controlled by turning the strength of the undulator magnet field. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in the accelerator of an X-Ray free-electron laser.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE008
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MOPJE022	Physical Model of Partial RF Discharge in Isochronous Cyclotrons	cyclotron, plasma, ion, ion-source	323
	V.S. Dyubkov MEPhI, Moscow, Russia S. Korenev Siemens Medical Solutions Molecular Imaging, Knoxville, TN, USA
	The physical model for the partial RF discharge - based on the ionization of molecules of residual gas by electron detachment as a result of the electro-dissociation of negative hydrogen ions in isochronous cyclotrons - is proposed in this paper. The result of the simulation of the ionization of gas molecules by these electrons using RF voltage inside the Eclipse cyclotron (kinetic energy of 11 MeV) is presented. The analysis of the conductivity of the RF plasma (partial RF discharge) is given. The influence of the magnetic field on the properties of the partial RF discharge is discussed. The application of this model is for isochronous cyclotrons with low kinetic energy (10^-15 MeV).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE022
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MOPJE048	Electron-Cloud Studies for Transversely Split Beams	resonance, simulation, injection, extraction	399
	N. Pradhan, S.S. Gilardoni, M. Giovannozzi, G. Iadarola, G. Rumolo CERN, Geneva, Switzerland N. Pradhan UMiss, University, Mississippi, USA
	Recently, resonance crossing has been proposed as a means of manipulating the transverse beam distribution. This technique has application, among other topics, to injection and extraction schemes. Moreover, the transversely split beams might also be used as a mitigation measure of electron-cloud effects. The results of detailed numerical simulations are discussed in this paper, possibly opening new options for scrubbing of beam pipes in circular accelerators.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE048
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MOPJE051	Effect of Electron Cloud in Quadrupoles on Beam Instability	quadrupole, dipole, simulation, emittance	409
	G. Iadarola, A.P. Axford, H. Bartosik, K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland
	Both simulations and machine experience at the CERN-SPS and LHC have shown that the electron cloud has a lower build up threshold in quadrupoles than in dipoles and field free regions. As a consequence, while beam induced scrubbing can efficiently suppress the electron cloud in both dipoles and field free regions, a residual electron cloud can still survive in the quadrupoles and potentially degrade the beam quality. To study this effect, a PyECLOUD module for electron tracking in quadrupole fields including effects of secondary emission at the vacuum chamber has been implemented in PyHEADTAIL. With this module, the effect of the electron cloud in quadrupoles on beam stability and beam quality preservation can be assessed, as well as its impact on future LHC and HL-LHC operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE051
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MOPJE062	Testing Aspects of Advanced Coherent Electron Cooling Technique	hadron, bunching, FEL, collider	445
	V. Litvinenko, Y.C. Jing, I. Pinayev, G. Wang BNL, Upton, Long Island, New York, USA D.F. Ratner SLAC, Menlo Park, California, USA V. Samulyak SBU, Stony Brook, USA
	An advanced version of the coherent-electron cooling based on the microbunching instability was proposed in . This approach promised to significantly increase the bandwidth of the system and, therefore, significantly shorter cooling time in high energy hadron colliders. In this paper we present our plans of simulating and testing the key aspects of this proposed technique using the set-up of the coherent-electron-cooling proof-of-principle experiment at BNL. D.F. Ratner, Phys. Rev. Lett. 111, 084802 (2013)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE062
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MOPJE070	Reduction of Electron Cloud in Particle Accelerator Beampipes Studied by RF Multipacting	injection, vacuum, detector, network	472
	R. Leber, F. Caspers, P. Costa Pinto, M. Taborelli CERN, Geneva, Switzerland
	For a given beam structure, chamber geometry and magnetic field configuration, the electron cloud (EC) intensity depends on the Secondary Electron Yield (SEY) of the beam pipe. The reduction of the EC density as a function of machine operation time (scrubbing) is attributed to the growth of a low SEY carbon film induced by electron bombardment. In this paper, we study the time evolution of the conditioning of stainless steel beam pipes in a laboratory setup. The EC or multipacting is induced by Radio-Frequency (RF) fields in a coaxial resonator under vacuum. Strip detectors are used to monitor the current of the EC. Induced pressure rise is simultaneously detected. The multipacting intensity shows a linear dependence on the positive DC bias voltage up to 1000 V, applied to the central electrode. An accelerated conditioning is observed for the applied bias voltage. The SEY of samples exposed to the EC is measured and the surface composition is monitored by X-ray Photoelectron Spectroscopy. The measured SEY, surface composition and multipacting behaviour are well correlated. The injection of acetylene and dodecane during multipacting proved to be ineffective in the conditioning.
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MOPJE071	New Electron Cloud Detectors for the CERN Proton Synchrotron	photon, detector, proton, extraction	476
	C. Yin Vallgren, P. Chiggiato, S.S. Gilardoni, H. Neupert, M. Taborelli CERN, Geneva, Switzerland
	Electron cloud (EC) has already been observed during normal operation of the PS using classical shielded button pick-up detectors in drift sections. In the context of the LHC Injector Upgrade (LIU project), similar measurements are also needed for the combined function magnets of the machine, where the access to the vacuum chamber is strongly limited by the presence of the yoke. Two new electron cloud detectors have been studied, developed, and installed during the Long Shutdown (LS1) in one of such magnets. The first is based on current measurement by using a shielded button-type pick-up with a special geometry to reach the bottom surface of the vacuum pipe embedded in the magnet. The second one relies on a newly developed measurement method based on detection of the photons, which are emitted by cathodoluminescence from the electron cloud impinging on the vacuum chamber walls. Part of the emitted photons is collected through a quartz window by a Micro-Channel Plate Photomultiplier Tube (MCP-PMT). First results obtained during machine development runs show the feasibility of the photon detection scheme. The results are discussed and compared with pick-up measurements.
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MOPJE079	Tracking Studies in the LHeC Lattice	lattice, resonance, proton, dynamic-aperture	502
	E. Cruz Alaniz, D. Newton The University of Liverpool, Liverpool, United Kingdom E. Cruz Alaniz, D. Newton Cockcroft Institute, Warrington, Cheshire, United Kingdom R. Tomás CERN, Geneva, Switzerland
	Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289485 The Large Hadron Electron Collider (LHeC) is a proposed upgrade of the LHC to provide electron-proton collisions and explore a new regime of energy and luminosity for nucleon-lepton scattering. A nominal design has previously been presented, featuring a lattice and optical configuration to focus one of the proton beams of the LHC (reaching a value of β^=10 cm) and to collide it head-on with an electron beam to produce collisions with the desired luminosity of L=10³³ cm^-2 s^-1. The proton beam optics is achieved with the aid of a new inner triplet of quadrupoles at L=10 m from the interaction point and the extension of the Achromatic Telescopic Squeezing (ATS) Scheme used for the High Luminosity-LHC project. The flexibility of this design has been studied in terms of minimising β^* and increasing L*. In this work, particle tracking is performed in a thin lens approximation of the LHeC proton lattice to compute the dynamic aperture and perform frequency map analysis for different types of chromatic correction schemes, in order to find the one who will provide the most beam stability and to study the effects of non linearities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE079
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MOPMA003	Reconstruction of Electron Bunch Motion During CSR Bursts using Synchronised Diagnostics	detector, synchrotron, radiation, storage-ring	529
	I.P.S. Martin, R. Bartolini, C. Bloomer, L.M. Bobb, G. Rehm DLS, Oxfordshire, United Kingdom R. Bartolini, A. Finn JAI, Oxford, United Kingdom
	Above a certain threshold current, electron bunches become unstable and emit bursts of coherent synchrotron radiation (CSR). The character and periodicity of these bursts vary with bunch current, RF voltage and lattice momentum compaction. In this paper we describe recent measurements taken at Diamond of how the electron bunch longitudinal profile and energy vary during a burst, and correlate this with CSR emission at a range of wavelengths.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA003
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MOPMA024	A Parallel Particle-Particle, Particle-Mesh Solver for Studying Coulomb Collisions in the Code IMPACT-T	emittance, simulation, plasma, space-charge	593
	C.E. Mitchell, J. Qiang LBNL, Berkeley, California, USA
	Funding: This work is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. In intense charged-particle beams, the presence of Coulomb collisions can result in growth of the beam slice energy spread and emittance that cannot be captured correctly using traditional particle-in-cell codes. Particle-particle, particle-mesh solvers take a hybrid approach, combining features of N-body and particle-in-cell solvers, to correctly capture the effect of short-range particle interactions with less computing time than direct N-body solvers. We describe the implementation and benchmarking of such a solver in the code IMPACT-T for beam dynamics applications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA024
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MOPMA027	Electron Cloud Measurements in Fermilab Main Injector and Recycler	vacuum, proton, injection, operation	604
	J.S. Eldred Indiana University, Bloomington, Indiana, USA M. Backfish, J.S. Eldred, C.-Y. Tan, R.M. Zwaska Fermilab, Batavia, Illinois, USA
	This conference paper presents a series of electron cloud measurements in the Fermilab Main Injector and Recycler. A new instability was observed in the Recycler in July 2014 that generates a fast transverse excitation in the first high intensity batch to be injected. Microwave measurements of electron cloud in the Recycler show a corresponding dependence on the batch injection pattern. These electron cloud measurements are compared to those made with a retarding field analyzer (RFA) installed in a field-free region of the Recycler in November. RFAs are also used in the Main Injector to evaluate the performance of beampipe coatings for the mitigation of electron cloud. Contamination from an unexpected vacuum leak revealed a potential vulnerability in the amorphous carbon beampipe coating. The diamond-like carbon coating, in contrast, reduced the electron cloud signal to 1\% of that measured in uncoated stainless steel beampipe.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA027
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MOPMA031	Simulations of Diamond Detectors with Schottky Contacts	simulation, detector, photon, scattering	617
	G.I. Bell, J.R. Cary, D.A. Dimitrov, D. Meiser, D.N. Smithe, C.D. Zhou Tech-X, Boulder, Colorado, USA M. Gaowei, E.M. Muller SBU, Stony Brook, New York, USA J. Smedley BNL, Upton, Long Island, New York, USA
	Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences, grant numbers DE-SC0006246 and DE-SC0007577. We present simulations of semiconductor devices using the code VSim (formerly Vorpal). The 3D simulations involve the movement and scattering of electrons and holes in the semiconductor, voltages which may be applied to external contacts, and self-consistent electrostatic fields inside the device. Particles may experience a Schottky barrier when moving between the semiconductor and a metal contact. Example devices include MOSFETs as well as a diamond X-ray detector. Our code VSim includes scattering models for GaAs and diamond, and runs in parallel on thousands of processors. We compare our simulation results with experimental results from a prototype diamond X-ray detector.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA031
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MOPMA033	Modeling Electron Emission and Surface Effects from Diamond Cathodes	simulation, cathode, vacuum, scattering	620
	D.A. Dimitrov, J.R. Cary, D.N. Smithe, C.D. Zhou Tech-X, Boulder, Colorado, USA I. Ben-Zvi, T. Rao, J. Smedley, E. Wang BNL, Upton, Long Island, New York, USA
	Funding: We are grateful to the U.S. DoE Office of Basic Energy Sciences for supporting this work under grants DE-SC0006246 and DE-SC0007577. We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 to 17 MV/m along the [100] direction. The simulation results were compared to experimental data when using different emission models, band bending effects, and surface-dependent electron affinity. Simulations using surface patches with different levels of hydrogenation lead to the closest agreement with the experimental data.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA033
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MOPMA037	Electron Cloud Buildup and Dissipation Models For PIP-II	simulation, plasma, proton, space-charge	626
	S.A. Veitzer, P. Stoltz Tech-X, Boulder, Colorado, USA
	Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920). Buildup of electron plasmas in accelerator cavities can cause beam degradation and limit performance in high-intensity circular particle accelerators. This is especially important in machines such as the LHC, and PIP-II, where mitigation techniques such as beam scrubbing in order to decrease the SEY are expensive and time consuming. Modeling of electron cloud buildup and dissipation can provide understanding as to the potential negative effects of electron clouds on beam properties, as well as estimates of the mitigation required to maintain accelerator performance and beam quality as accelerators move to higher intensity configurations. We report here on simulations of electron cloud buildup and dissipation for geometry, beam and magnetic field configurations describing the Recycler at Fermilab. We perform electrostatic simulations in 3D with VSim PIC, including the effects of space charge and secondary electrons. We quantify the expected survival rate of electrons in these conditions, and argue that improvements in reducing the SEY is unlikely to mitigate the electron cloud effects.
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MOPMA039	Secondary Electron Yield Measurement and Electron Cloud Simulation at Fermilab	simulation, proton, vacuum, dipole	629
	Y. Ji IIT, Chicago, Illinois, USA L.K. Spentzouris Illinois Institute of Technology, Chicago, Illinois, USA R.M. Zwaska Fermilab, Batavia, Illinois, USA
	Funding: This work was funded by the National Science Foundation under the grant no. 1205811. Fermilab Main Injector is upgrading the accelerator to double the beam intensity from 24·10¹² protons to 48·10¹² protons, which brings the accelerator into a regime where electron cloud effects may limit the accelerator performance. In fact, an instability that could be caused by electron cloud effects has already been observed in the Recycler. Secondary Electron Yield (SEY) is an important property of the vacuum chamber material that has great influence on the process of building up free electrons. The Main Injector of the Fermilab accelerator complex offers the opportunity to measure SEY and conditioning effects in the environment of a running accelerator, since samples of these materials are located at the beampipe wall. The SEY of stainless steel (SS316L) and TiN coated SS316L in the proximity of the proton beam were measured and compared. A series of simulation studies of electron cloud build up were done for the Main Injector and Recycler using the code POSINST. Parametric studies were done to determine the maximum electron density vs. peak SEY at different beam intensities in the Fermilab Main Injector. Threshold simulations of electron cloud density verus SEY were extended from Main Injector to include the Recycler Ring. It was found that the electron cloud density around the beam depends on bunch location within the bunch train.
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MOPMA043	Longitudinal Bunch Shaping at Picosecond Scales using Alpha-BBO Crystals at the Advanced Superconducting Test Accelerator	gun, laser, linac, space-charge	643
	B. Beaudoin UMD, College Park, Maryland, USA D.R. Edstrom, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Funding: This works is supported by the University Research Association, Inc. Operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy The Integrable Optics Test Accelerator (IOTA) electron injector at Fermilab will enable a broad range of experiments at a national laboratory in order to study and develop solutions to the limitations that prevent the propagation of high intensity beams at picosecond lengths. One of the most significant complications towards increasing short-beam intensity is space-charge, especially in the vicinity of the gun. A few applications that require a longitudinally shaped electron beam at high intensities are for, the generation of THz waves and dielectric wakefields, each of which will encounter the effects of longitudinal space-charge. This paper investigates the effects of longitudinal space-charge on alpha-BBO UV laser shaped electron bunches in the vicinity of the 1½cell 1.3 GHz cylindrically symmetric RF photocathode gun.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA043
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MOPMA044	Barrier Shock Compression with Longitudinal Space Charge	space-charge, simulation, emittance, plasma	646
	B. Beaudoin, I. Haber, R.A. Kishek UMD, College Park, Maryland, USA
	Funding: This work is supported by the US Dept. of Energy, Office of High Energy Physics. Synchrotrons and storage rings routinely employ RF barrier buckets as a means of accumulating charge to increase the peak intensity and preserve longitudinal emittance while minimizing emittance growth [1-3]. This was shown in the main injector and recycler at Fermilab as well as the SIS-18 at GSI Helmholtz center for heavy ion research. The RF cavities typically used are ferrite loaded magnetic alloys with low Q to maximize bandwidth and generate single pulses, either as delta functions, triangular or half/full period sine waves. The University of Maryland Electron Ring (UMER) group is studying a novel scheme of bunch compression in the presence of longitudinal space charge. It has been analytically shown through 1-D computations that the presence of space-charge considerably improves the efficiency of the barrier compression by taking advantage of the shock-front that launches when the barrier moves into a space-charge dominated beam. In this paper, we summarize the initial results of the study.
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MOPMA046	Simulations and experiments in Support of Octupole Lattice Studies at the University of Maryland Electron Ring	lattice, octupole, space-charge, quadrupole	653
	K.J. Ruisard, B. Beaudoin, I. Haber, T.W. Koeth UMD, College Park, Maryland, USA
	Funding: This material is based on work supported by the NSF Graduate Research Fellowship and the NSF Accelerator Science Program We present plans for a nonlinear lattice at the University of Maryland Electron Ring (UMER). Theory predicts that a strong nonlinear lattice can limit resonant behavior without reducing dynamic aperture if the nonlinear fields preserve integrability or quasi-integrability. We discuss plans for a quasi-integrable octupole lattice, based on the work of Danilov and Nagaitsev.* We use Elegant and the WARP PIC code to estimate the octupole-induced tune spread. We discuss improvements to the ring in support of octupole lattice experiments, including generation and detection of emittance-dominated, negligible space charge beams. * V. Danilov, S. Nagaitsev, Phys. Rev. STAB 13, 084002 (2010).
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MOPMA054	Start-to-end Simulation of Free-electron Lasers	FEL, simulation, wiggler, linac	675
	C.C. Hall, S. Biedron, H. Freund, S.V. Milton CSU, Fort Collins, Colorado, USA
	Start-to-end (S2E) modeling of free-electron lasers (FELs) normally requires the use of multiple codes to correctly capture the physics in each region of the machine. Codes such as PARMELA, IMPACT-T or MICHELLE, for instance, may be used to simulate the injector. From there the linac and transport line may be handled by codes such as DIMAD, ELEGANT or IMPACT-Z. Finally, at the FEL a wiggler interaction code such as GENESIS, GINGER, or MINERVA must be used. These codes may be optimized to work with a wide range in magnitude of macro-particle numbers (from 10⁴-10⁸ in different codes) and have different input formats. It is therefore necessary to have translator codes to provide a bridge between each section. It is essential that these translators be able to preserve the statistical properties of the bunch while raising or lowering the number of macro-particles used between codes. In this work we show a suite of such translators designed to facilitate S2E simulations of an FEL with a new wiggler code, MINERVA, and use these codes to provide benchmarking of MINERVA against other common wiggler simulation codes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA054
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MOPMN002	Advances in Parallel Finite Element Code Suite ACE3P	cavity, simulation, radiation, SRF	702
	C.-K. Ng, L. Ge, C. Ko, O. Kononenko, Z. Li, L. Xiao SLAC, Menlo Park, California, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. New capabilities in SLAC's parallel finite element electromagnetics simulation suite ACE3P are reported. These include integrated electromagnetic (Omega3P), thermal and mechanical (TEM3P) modules for multi-physics modeling, an interface to particle-material interaction codes for calculation of radiation effects due to dark current generation (Track3P), and coupled electromagnetic (ACE3P) and beam dynamics (IMPACT) simulation. Results from these applications are presented.
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MOPMN007	An Alternate Ring-Ring Design for eRHIC	ion, collider, proton, linac	713
	Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC05-06OR23177 and No. DE-AC02-06CH11357 I present here a new ring-ring design of eRHIC. It utilizes high repetition rate colliding beams and is likely able to deliver the performance to meet the requirements of the science program with low technical risk and modest accelerator R&D. The expected performance includes high luminosities over multiple collision points and a broad CM energy range with a maximum value up to 2×1034 cm^-2s⁻¹ per detector, and polarization higher than 70% for the colliding electron and light ion beams. This new design calls for reuse of decommissioned facilities in the US, namely, the PEP-II high energy ring and one section of the SLAC linac as a full energy injector.
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MOPMN012	SPACE Code for Beam-Plasma Interaction	plasma, simulation, ion, electromagnetic-fields	728
	K. Yu, V. Samulyak SBU, Stony Brook, USA V. Samulyak BNL, Upton, Long Island, New York, USA
	A parallel particle-in-cell code SPACE has been developed for the simulation of electromagnetic fields, relativistic particle beams, and plasmas. The algorithms include atomic processes in the plasma, proper boundary conditions, an efficient method for highly-relativistic beams in non-relativistic plasma, support for simulations in relativistic moving frames, and special data transfer algorithm from the moving to the laboratory frame that collects particles and fields in the lab frame without time shift due to the Lorentz transform, enabling data analysis and visualization. Plasma chemistry algorithms implement atomic physics processes such as the generation and evolution of plasma, recombination of plasma, and electron attachment on dopants in dense neutral gas. Benchmarks and experimental validation tests are also discussed. The code has been used for the simulation of processes relevant to the eRHIC program at BNL and the high pressure RF cavity (HPRF) program at Fermilab.
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MOPMN013	Simulation of Beam-Induced Plasma in Gas Filled Cavities	plasma, ion, simulation, cavity	731
	K. Yu, V. Samulyak SBU, Stony Brook, USA M. Chung UNIST, Ulsan, Republic of Korea B.T. Freemire IIT, Chicago, Illinois, USA V. Samulyak BNL, Upton, Long Island, New York, USA A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA
	Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.
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MOPMN015	Simulation of Beam-Induced Plasma for the Mitigation of Beam-Beam Effects	plasma, proton, simulation, beam-beam-effects	734
	J. Ma, V. Samulyak, K. Yu SBU, Stony Brook, New York, USA V. Litvinenko, V. Samulyak, G. Wang BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA V. Samulyak SUNY SB, Stony Brook, New York, USA
	One of the main challenges in the increase of luminosity of circular colliders is the control of the beam-beam effect. In the process of exploring beam-beam mitigation methods using plasma, we evaluated the possibility of plasma generation via ionization of neutral gas by proton beams, and performed highly resolved simulations of the beam-plasma interaction using SPACE, a 3D electromagnetic particle-in-cell code. The process of plasma generation is modelled using experimentally measured cross-section coefficients and a plasma recombination model that takes into account the presence of neutral gas and beam-induced electromagnetic fields. Numerically simulated plasma oscillations are consistent with theoretical analysis. In the beam-plasma interaction process, high-density neutral gas reduces the mean free path of plasma electrons and their acceleration. A numerical model for the drift speed as a limit of plasma electron velocity was developed. Simulations demonstrate a significant reduction of the beam electric field in the presence of plasma. Preliminary simulations using fully-ionized plasma have also been performed and compared with the case of beam-induced plasma.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN015
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MOPMN028	Design of Bunch Compressing System with Suppression of Coherent Synchrotron Radiation for ATF Upgrade	emittance, dipole, simulation, linac	760
	Y.C. Jing, M.G. Fedurin, D. Stratakis BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) is in the process of upgrading to ATF2 with higher electron beam energy thus expanding its capabilities. For the fully upgraded electron beam (500 MeV), it will be of great interest to compress the bunch to femto-seconds scale while maintaining high peak current (~7,800 amps) for users. A bunch compressor composed of magnetic chicanes can be utilized for this purpose. However, during such strong compression, beam quality can easily be deteriorated by Coherent Synchrotron Radiation (CSR). In this paper, we present our study for a bunch compressor where this CSR effect is compensated through careful manipulation of phase space. We also show a beam with good quality is preserved through the system by presenting a start to end simulation.
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MOPHA006	A Slow RF-Laser Feedback for PHIL Photoinjector	laser, feedback, gun, controls	784
	N. ElKamchi, V. Chaumat, V. Soskov LAL, Orsay, France
	PHIL is an electron beam accelerator at LAL. It produces low energy (E<5 MeV) and high current (1 nC/bunch) electrons bunch at a repetition frequency of 5Hz. The stability of the beam charge at PHIL is a key issue for the succeful operation of the physic experiences that use the machine. At PHIL, the beam charge is quite stable, but we often note a slow charge drift on long duration experiences. Two ICTs, and a back-end electronics are used to monitor the stability of the beam charge, with an accuracy of about 1pC. Several types of jitter can impact the stability of the beam charge. The fluctuations of the RF power or the RF-laser relative phase drift could have significant influence, due to temperature variations that produce cables dilataion, and electronic components overheating. To correct the phase drift, we describe a method based on a slow analog-digital feedback loop between the RF wave in the gun (3 GHz) and the synchronisation signal of the laser (75MHz). It allows to maintain the jitter between the laser pulse and the RF wave stable at a very low value. As a result, the electron beam charge is maintained at a stable level, to meet the requirements of the users.
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MOPHA007	Modeling/Measurement Comparison of Signal Collection in Diamond Sensors in Extreme Conditions	space-charge, detector, simulation, scattering	787
	V. Kubytskyi, P. Bambade, S. Liu LAL, Orsay, France
	Here we present a study of charge collection dynamics in a Diamond Sensor (DS) subjected to intensities from 1 to 10⁸ Minimum Ionizing Particles (MIP). We developed a model based on the numerical solution of the 1D drift-diffusion equations, using the Scharfetter-Gummel discretization scheme. Inhomogeneity of the space-charge distribution together with the externally applied electric field are taken into account by analytically solving the Poisson equation at each time step. We identified two regimes of charge collection. The first corresponds to 1-10⁵ MIPs, in this case the externally applied electric field is negligibly perturbed by space-charge effects during the separation of the electron/hole clouds. The second corresponds to intensities larger than 10⁷ MIPs, where the space-charge effects significantly slow down the charge collection due to large concentrations of electron/hole pairs in the DS volume. The results of our modeling are in qualitative agreement with the experimental data acquired at the PHoto-Injector electron beam facility at LAL. Our model allows optimizing DS parameters to achieve desired charge collection times for different beam intensities.
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MOPHA008	Investigation of Beam Halo Using In Vacuum Diamond Sensor at ATF2	pick-up, vacuum, controls, laser	791
	S. Liu, P. Bambade, F. Bogard, P. Cornebise, V. Kubytskyi, C. Sylvia LAL, Orsay, France A. Faus-Golfe, N. Fuster-Martínez IFIC, Valencia, Spain T. Tauchi, N. Terunuma KEK, Ibaraki, Japan T. Tauchi, N. Terunuma Sokendai, Ibaraki, Japan
	Funding: Chinese Scholarship Council, CNRS and P2IO LABEX Beam halo transverse distribution measurements are of great importance for the understanding of background sources of the nano-meter beam size monitor at the interaction point (IPBSM) of ATF2. One of the most critical issues for the beam halo measurement is to reach high dynamic range. Two in vacuum diamond sensor beam halo scanners (DSv) with four strips each have been developed for the investigation of beam halo transverse distributions at ATF2. The first DSv was installed for horizontal beam halo scanning after the interaction point (IP) of ATF2, in Nov. 2014. It aims to measure the beam halo distribution with large dynamic range (~10⁶), and investigate the possibility of probing the Compton recoil electrons produced in the interaction with the IPBSM laser beams. Studies to characterize the DS performance and measurements of horizontal beam halo performed in Nov.-Dec. 2014 are presented.
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MOPHA015	Measurement of Momentum Compaction Factor via Depolarizing Resonances at ELSA	resonance, polarization, extraction, experiment	811
	J.F. Schmidt, W. Hillert, M. Schedler, J.-P. Thiry ELSA, Bonn, Germany
	Funding: DFG Measuring beam depolarization at energies in close proximity to a depolarizing integer resonance is an established method to determine the beam energy of a circular accelerator. This technique offers high accuracy due to the small resonance widths. Thus, also other accelerator parameters related to beam energy can be measured based on this method. This contribution presents a measurement of the momentum compaction factor with a high precision of 10^-4. It was performed at the 164 m stretcher ring of the Electron Stretcher Facility ELSA at Bonn University, which provides a polarized electron beam of up to 3.2 GeV.
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MOPHA019	Implementation of a High Level Phase Controller for the Superconducting Injector of the S-DALINAC	controls, cavity, EPICS, injection	814
	T. Bahlo, C. Burandt, F. Hug, N. Pietralla TU Darmstadt, Darmstadt, Germany
	Funding: This work has been supported by the DFG through CRC 634 The Superconducting DArmstadt LINear Accelerator S‑DALINAC is a recirculating electron accelerator with a design energy of 130 MeV. It operates in cw-mode at a radio frequency of 3 GHz and provides either unpolarized or polarized electron beams. Before entering the main accelerator the electron beam passes both, a normal-conducting injector beamline for beam preparation and a superconducting 10 MeV injector beamline for preacceleration. The phase of the beam which is injected into the 40 MeV main accelerator is crucial for the efficiency of the acceleration process and the minimization of the energy spread. Due to thermal drifts of the normal-conducting injector cavities this injection phase varies by about 0.2 degree over a timescale of an hour. In order to compensate these drifts, a high level phase controller has been implemented. It adjusts the phase measured at an rf-monitor at the exit of the superconducting injector by changing the phase of a prebuncher in the normal-conducting injector beamline. We will present the used hardware, the control algorithm as well as measurements showing the phase stabilization achieved by this controller.
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MOPHA020	Automated Transverse Beam Emittance Measurement using a Slow Wire Scanner at the S-DALINAC	emittance, quadrupole, EPICS, controls	817
	P. Dijkstal, M. Arnold, C. Burandt, F. Hug, N. Pietralla TU Darmstadt, Darmstadt, Germany
	Funding: This work has been supported by the DFG through CRC 63 and by the EPS-AG through the EPS-AG student grant program. The superconducting linear accelerator S-DALINAC of the TU Darmstadt provides electron beams of up to 130 MeV in cw mode. It consists of a 10 MeV injector and a 40 MeV main linac, both equipped with elliptical cavities operating in liquid helium at 2 K at a frequency of 3 GHz. The final energy is reached by using up to two recirculation paths. In order to improve beam simulations, it is planned to monitor the transverse beam emittance at different locations along the beam line. A system of slow wire scanners in combination with quadrupole variation is foreseen to accomplish this task. For a first test a wire scanner was installed in the 250 keV section behind the thermionic electron gun of the S-DALINAC. A procedure to automatize measurements was developed and integrated in the EPICS-based control system. We will show the status of the work on the automatized control and the results of first emittance measurements. A report on the future plans will be given.
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MOPHA023	Observation of Coherent Pulses in the Sub-THz Range at DELTA	radiation, detector, laser, synchrotron	823
	C. Mai, F.H. Bahnsen, M. Bolsinger, S. Hilbrich, M. Huck, M. Höner, S. Khan, A. Meyer auf der Heide, R. Molo, H. Rast, G. Shayeganrad, P. Ungelenk DELTA, Dortmund, Germany M. Brosi, B. Kehrer, A.-S. Müller, M.J. Nasse, P. Schönfeldt, P. Schütze, S. Walther KIT, Karlsruhe, Germany H. Huck DESY Zeuthen, Zeuthen, Germany
	Funding: Work supported by the BMBF (05K13PEC). Coherent ultrashort THz pulses induced by a laser-electron interaction are routinely produced and observed at DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund University. The turn-by-turn evolution of the radiation spectrum is known to shift to the sub-THz regime after the initial laser-electron interaction. Recently, an ultrafast YBCO-based THz detector has been permanently installed and a Schottky diode has been tested at the THz beamline. Measurements with these detectors showing the temporal evolution of the coherent signals after several revolutions are presented. Furthermore, the concept of a recently designed Fourier-transform spectrometer optimized for the sub-THz region is shown.
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MOPHA026	Present and Future Optical-to-Microwave Synchronization Systems at REGAE Facility for Electron Diffraction and Plasma Acceleration Experiments	laser, detector, timing, plasma	833
	M. Titberidze, F.J. Grüner, A.R. Maier, B. Zeitler CFEL, Hamburg, Germany S.W. Epp MPSD, Hamburg, Germany M. Felber, K. Flöttmann, T. Lamb, U. Mavrič, J.M. Müller, H. Schlarb, C. Sydlo DESY, Hamburg, Germany F.J. Grüner, A.R. Maier, M. Titberidze Uni HH, Hamburg, Germany E. Janas Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	Relativistic Electron Gun for Atomic Explorations (REGAE) is a Radio Frequency (RF) driven linear accelerator. It uses frequency tripled short photon pulses (~ 35 fs) from the Titanium Sapphire (Ti:Sa.) Laser system in order to generate electron bunches from the photo-cathode. The electron bunches are accelerated up to ~ 5 MeV kinetic energy and compressed down to sub-10 fs using the so called ballistic bunching technique. REGAE currently is used for electron diffraction experiments (by Prof. R.J.D. Miller's Group). In near future within the collaboration of Laboratory for Laser- and beam-driven plasma Acceleration (LAOLA), REGAE will also be employed to externally inject electron bunches into laser driven linear plasma waves. Both experiments require very precise synchronization (sub-50 fs) of the photo-injector laser and RF reference. In this paper we present experimental results of the current and new optical to microwave synchronization systems in comparison. We also address some of the issues related to the current system and give an upper limit in terms of its long-term performance.
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MOPHA027	Transverse Emittance Measurement at REGAE	emittance, detector, background, solenoid	837
	M. Hachmann, K. Flöttmann DESY, Hamburg, Germany
	The linear accelerator REGAE at DESY produces short and low charged electron bunches, on the one hand to resolve the excitation transitions of atoms temporally by pump probe electron diffraction experiments and on the other hand to investigate principal mechanisms of laser plasma acceleration. For both cases a high quality electron beam is required which can be identified with a small beam emittance. A standard magnet scan is used for the emittance measurement which is in case of a low charged bunch most sensitive to the beam size determination (2nd central moment of a distribution). Therefore the diagnostic and a routine to calculate proper central moments of an arbitrary distribution will be introduced and discussed.
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MOPHA029	Operation Experiences with the MICROTCA.4-based LLRF Control System at FLASH	LLRF, operation, radiation, laser	844
	M. Omet, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, M. Hoffmann, F. Ludwig, U. Mavrič, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang DESY, Hamburg, Germany W. Cichalewski, D.R. Makowski TUL-DMCS, Łódź, Poland K. Czuba, K. Oliwa, I. Rutkowski, R. Rybaniec, D. Sikora, W. Wierba, M. Żukociński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland A. Piotrowski FastLogic Sp. z o.o., Łódź, Poland
	The Free-Electron Laser in Hamburg (FLASH) at Deutsches Elektronen-Synchrotron (DESY), Hamburg Germany is a user facility providing ultra-short, femtosecond laser pulses up to the soft X-ray wavelength range. For the precise regulation of the radio frequency (RF) fields within the 60 superconducting cavities, which are organized in 5 RF stations, digital low level RF (LLRF) control systems based on the MTCA.4 standard were implemented in 2013. Until now experiences with failures potentially due to radiation, overheating, and ageing as well as with the general operation of the control systems have been gained. These have a direct impact on the operation and on the performance of FLASH and will allow future improvements. The lessons learned are not only important for FLASH but also in the scope of European X-ray Free-Electron Laser (X-FEL), which will be operated with the same LLRF control system.
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MOPHA038	Studies for a Wakefield-Optimized Near-Field EO Setup at the ANKA Storage Ring	laser, wakefield, simulation, operation	869
	P. Schönfeldt, A. Borysenko, N. Hiller, B. Kehrer, A.-S. Müller KIT, Karlsruhe, Germany
	Funding: This work is funded by the BMBF contract numbers 05K10VKC, and 05K13VKA. ANKA, the synchrotron light source of the Karlsruhe Institute of Technology (KIT), is the first storage ring with a near-field single-shot electro-optical (EO) bunch profile monitor inside its vacuum chamber. Using the method of electro-optical spectral decoding (EOSD), the current setup made it possible to study longitudinal beam dynamics (e.g. microbunching) occurring during ANKA's low-alpha-operation with sub-ps resolution (granularity). However, the setup induces strong wake-fields spanning the distance between consecutive bunches which cause heat load to the in-vacuum setup for high beam currents. This heat load in turn leads to a laser misalignment thus preventing measurements during multi-bunch operation. Fortunately, the EOSD setup also allows us to directly study these wake-fields so simulation results can be compared to measurement data. This paper reviews possible changes of the setup's geometry with respect to a reduction of the wakefield effects.
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MOPHA040	First Results of Energy Measurements with a Compact Compton Backscattering Setup at ANKA	laser, photon, detector, storage-ring	876
	C. Chang, E. Bründermann, E. Hertle, N. Hiller, E. Huttel, A.-S. Müller, M.J. Nasse, M. Schuh, J.L. Steinmann KIT, Karlsruhe, Germany H.-W. Hübers, H. Richter DLR, Berlin, Germany
	Funding: This work is funded by the European Union under contract PITN-GA-2011-289191 An electron energy measurement setup based on the detection of Compton backscattered photons, generated by laser light scattered off the relativistic electron beam, has been proposed and developed for operation at the ANKA storage ring of the Karlsruhe Institute of Technology (KIT). In contrast to conventional methods based on head-on collisions, the setup at ANKA is, for the first time, realized in a transverse configuration where the laser beam hits the electron beam at an angle of ~90°. This makes it possible to achieve a relatively low-cost and very compact setup since it only requires a small side-port instead of a straight section. This development could benefit storage rings with restricted space or where no straight sections are available, for example due to interferences with existing beamlines. The setup and the first measurement results are presented in the paper.
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MOPHA041	Laser Wire Based Transverse Emittance Measurement of H⁻ Beam at Spallation Neutron Source	emittance, laser, neutron, dipole	879
	Y. Liu, A.V. Aleksandrov, C.D. Long, A.A. Menshov, A.P. Zhukov ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. A laser wire based transverse emittance measurement system has been developed at the Spallation Neutron Source (SNS). The system enables a nonintrusive measurement of the transverse emittance in both directions on a 925 MeV/1 MW hydrogen ion (H⁻) beam at the high energy beam transport (HEBT) beam line.
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MOPHA043	Properties of Transition- and Synchrotron Radiation at FLUTE	radiation, synchrotron, synchrotron-radiation, detector	885
	M. Schwarz, A.-S. Müller KIT, Karlsruhe, Germany M.T. Schmelling MPI-K, Heidelberg, Germany
	FLUTE (Ferninfrarot Linac Und Test Experiment) is a 41 MeV linear accelerator currently under construction at KIT. It is aimed at accelerator physics and THz radiation research. For this reason the machine will cover a wide range of bunch charges (1 pC up to 3 nC) and lengths (1 fs to 300 fs). One aim of FLUTE is the study of different mechanisms for the generation of intense THz pulses, such as transition- (TR) or synchrotron radiation (SR). In this contribution, we calculate and compare various pulse properties, such as spectra, and electric fields, for both TR and SR.
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MOPHA044	Testing a Digital Beam Position Stabilization for the P2-experiment at MESA	experiment, FPGA, feedback, controls	888
	M. Dehn, K. Aulenbacher, J. Diefenbach, F. Fichtner, R. Herbertz, W. Klag IKP, Mainz, Germany
	Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) and German Research Foundation (DFG) under the Collaborative Research Center 1044 and the Cluster of Excellence "PRISMA" The Mainz Energy recovering Superconducting Accelerator (MESA) will be built at the institute for nuclear physics at Mainz University. Besides the multi-turn energy recovery mode an external beam mode is foreseen to provide 155 MeV electrons of 85% polarization at 150 μA for parity violating experiments. To achieve the required stability of the main beam parameters a dedicated digital position stabilization is currently developed and tested at the Mainz Microtron (MAMI).
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MOPHA048	Beam Optimization of the DAΦNE Beam Test Facility	diagnostics, linac, software, detector	901
	L.G. Foggetta, B. Buonomo INFN/LNF, Frascati (Roma), Italy P. Valente INFN-Roma, Roma, Italy
	The DAΦNE Beam Test Facility delivers electron and positron beam with a wide spread of parameters in charge, energy, transverse dimensions and time width. Thanks to the recent improvements of the diagnostics, all the beam parameters have been measured and optimized. In particular we report here some results on beam transverse size, divergence, and position stability for different energy and intensity configurations. After the upgrade of the electronic gun of the DAΦNE LINAC, the pulse time width and charge distribution have been also characterized.
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MOPHA050	Online Spill Intensity Monitoring for Improving Extraction Quality at CNAO	proton, ion, electronics, extraction	907
	M. Caldara University of Bergamo, Bergamo, Italy J. Bosser, G.M.A. Calvi, L. Lanzavecchia, A. Parravicini, C. Viviani CNAO Foundation, Milan, Italy E. Rojatti UniPV, Pavia, Italy
	The CNAO Foundation is the first Italian center for deep hadrontherapy with Protons and Carbon Ions, performing treatments since September 2011. The extracted beam energy and intensity can vary over a wide range (60-250 MeV for Protons and 120-400 MeV/u for Carbon Ions, 4e6/10¹⁰ pps); the beam intensity uniformity during the slow extraction process is a fundamental requirement for achieving accurate and fast treatments. CNAO developed an online Fast Intensity Monitor (FIM), not perturbing the extracted beam, capable of measuring beam intensity with a bandwidth of 50kHz and a resolution of 1%. It consists of a thin (0.8 μm) metallic foil that emits secondary electrons when traversed by the beam. The electrons are multiplied by a Channeltron device, polarized at high voltage versus ground. The Channeltron output current is amplified and converted in a Pulse Width Modulated (PWM) signal, which is then decoupled and transmitted to the equipment room, where an FPGA implements a servo-spill. The work presents the detector, the floating electronics, the preliminary measurements with beam and the integration in a closed loop on the synchrotron air-core quadrupole obtaining promising results.
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MOPTY002	Bunch Length Measurement of Femtosecond Electron Beam by Monitoring Coherent Transition Radiation	detector, radiation, gun, linac	940
	I. Nozawa, M. Gohdo, K. Kan, T. Kondoh, A. Ogata, J. Yang, Y. Yoshida ISIR, Osaka, Japan
	Ultrashort electron bunches with durations of femtoseconds and attoseconds are essential for time-resolved measurements, including pulse radiolysis and ultrafast electron microscopy. However, generation of the ultrashort electron bunches is commonly difficult because of bunch length growth due to space charge effect, nonlinear momentum dispersion and so on. Several bunch length measurement methods for the ultrashort electron beams have also been considered so far, which have not been established yet. In this study, the femtosecond electron beams were generated using a laser photocathode radio-frequency gun linac and a magnetic bunch compressor. The bunch length measurement was carried out using a Michelson interferometer based on monitoring coherent transition radiation (CTR), which is characterized by square modulus of the Fourier transform of the longitudinal bunch distribution. Analyzing the experimentally obtained interferograms of CTR, the electron beams with the average duration of 5 fs were generated and measured successfully at the condition of bunch charge of 1 pC. Consideration of the longitudinal bunch shapes was also carried out using the Kramers-Kronig relation.
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MOPTY014	An Experimental Study of Higher-Order Modes Excited by High Repetition Rate Electron Beam in an SRF Cavity	HOM, SRF, cavity, experiment	965
	Y. Gao, J.E. Chen, L.W. Feng, J.K. Hao, S. Huang, L. Lin, K.X. Liu, X. Luo, S.W. Quan, F. Wang, Zh.W. Wang PKU, Beijing, People's Republic of China
	Funding: National Natural Science Foundation of China (No. 11275014) Higher-order modes (HOMs) excited by electron beam traversing a superconducting rf (SRF) cavity contain lots of information and can be used for intra-cavity electron beam diagnostics. Unlike single bunch, multiple bunches would excite HOMs with a much complicated spectrum. In this paper, we present our recent research on HOMs excited by a high repetition rate electron beam in an SRF cavity. Especially, we focus on the integer multiple frequency peaks in the HOM spectrum, which are determined by the nearest eigen HOM peaks. The experiments were carried out on the DC-SRF photoinjector, which was operated at MHz repetition rate. The results agree well with theoretic analysis.
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MOPTY015	Beam Compression Dynamics and Associated Measurement Methods in Superconducting THz Source	controls, simulation, space-charge, gun	969
	Z. Zhou, Y.-C. Du, W.-H. Huang TUB, Beijing, People's Republic of China
	To ensure the quality of high brightness electron beams needed by the terahertz FEL facility at China academy of engineering physics(CAEP), which aims to obtain 100 to 300 terahertz light, a feed-back control system is required to monitor the amplitude and phase jittering by measuring beam arrival time as well as bunch length at the site of the beam position monitor(BPM). In this paper, we make an idealized model of injector section and deduce analytic expressions of bunch arrival time and bunch length. In consideration of the space charge effect on bunch lengthening, bunch arrival time and bunch length as a function of DC gun voltage, buncher field amplitude and buncher phase is carefully calibrated by means of particle in cell (PIC) simulation. With the time and space resolution of the BPM, the control accuracy of phase is estimated to be 0.01 degree, while the amplitude is 0.04%.
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MOPTY034	Distributed Beam Loss Monitor Based on the Cherenkov Effect in Optical Fiber	radiation, positron, beam-losses, storage-ring	1004
	Yu. Maltseva, F.A. Emanov, A.V. Petrenko, V.G. Prisekin BINP SB RAS, Novosibirsk, Russia F.A. Emanov NSU, Novosibirsk, Russia A.V. Petrenko CERN, Geneva, Switzerland
	A distributed beam loss monitor based on the Cherenkov effect in optical fiber has been implemented for the VEPP5 electron and positron linacs and the 510 MeV damping ring at the Budker INP. The monitor operation is based on detection of the Cherenkov radiation generated in optical fiber by means of relativistic particles created in electromagnetic shower after highly relativistic beam particles (electrons or positrons) hit the vacuum pipe. The main advantage of the distributed monitor compared to local ones is that a long optical fiber section can be used instead of a large number of local beam loss monitors. In our experiments the Cherenkov light was detected by photomultiplier tube (PMT). Timing of PMT signal gives the location of the beam loss. In the experiment with 20 m long optical fiber we achieved 3 m spatial resolution. To improve spatial resolution optimization and selection process of optical fiber and PMT are needed and according to our theoretical estimations 0.5 m spatial resolution can be achieved. We also suggest similar techniques for detection of electron (or positron) losses due to Touschek effect in storage rings.
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MOPTY041	Prototype Results with a Complete Beam Loss Monitor System Optimized for Synchrotron Light Sources	detector, injection, electronics, impedance	1019
	P. Leban I-Tech, Solkan, Slovenia K.B. Scheidt ESRF, Grenoble, France
	Beam loss monitors in synchrotron light sources are finding an increasing utility in particular with the trend of numerous light sources pushing to lower emittances and thus higher intra-beam scattering, while operating in top-up injection modes and employing in-vacuum undulators in their rings. The development of an optimized electron BeamLoss Monitor aims at fulfilling, in one single system, all possible functionalities and applications like both the measurement of fast-time-resolved losses at injection and the possibility of ultra-sensitive detection of low & slow electron loss level variations. This optimized beam loss monitor system comprises both the acquisition electronics and up to four sensor head per unit. The sensor heads themselves, that can be configured for different sizes or volumes, are based on the detection of the electromagnetic shower resulting from an electron loss through the use of either Cherenkov radiator or gamma scintillator and a photomultiplier tube, all assembled in a single compact housing ready for installation.
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MOPTY058	Response of Polycrystalline Diamond Particle Detectors Measured with a High Intensity Electron Beam	detector, experiment, radiation, beam-losses	1069
	O. Stein, F. Burkart, B. Dehning, R. Schmidt, C.B. Sørensen, D. Wollmann CERN, Geneva, Switzerland E. Griesmayer CIVIDEC Instrumentation, Wien, Austria
	Comprehensive understanding of beam losses in the LHC is required to ensure full machine protection and efficient operation. The existing BLM system using ionization chambers is not adequate to resolve losses with a time resolution below some 10 us. Ionization chambers are also not adequate to measure very large transient losses, e.g. beam impacting on collimators. Diamond particle detectors with bunch-by-bunch resolution have therefore been used in LHC to measure fast particle losses with a time resolution down to a level of single bunches. Diamond detectors have also successfully been used for material damage studies in other facilities, e.g. HiRadMat at the CERN-SPS. To fully understand their potential, such detectors were characterized with an electron beam at the BTF in LNF INFN Italy, with bunch intensities from 10³ to 10⁹ electrons. The detector response and efficiency has been measured with a 50 Ω and a 1 Ω read-out system. This paper describes the experimental setup and the results of the experiment. In particular, the responses of three samples of 100 um single-crystalline diamond detectors and two samples of 500 um polycrystalline diamond detectors are presented.
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MOPTY065	Beam Stability of the Taiwan Light Source Storage Ring	betatron, storage-ring, injection, network	1091
	H.C. Chen, H.H. Chen, Y.-S. Cheng, S.J. Huang, C.H. Kuo, J.A. Li, Y.K. Lin NSRRC, Hsinchu, Taiwan
	The Taiwan Light Source Storage Ring (SR) has been in operation since many years ago. Maintaining best stability of the electron beam is becoming the main challenge. This study endeavored to improve the electron beam stability of The Taiwan Light Source Storage Ring (SR). Employing the artificial neural network (ANN)-constructed experiment design to analyze and optimize the storage ring betatron tunes .This report outlines the details of the beam stability process experiment.
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MOPTY079	The Installation and Operation of TPS Laser PSD System in TPS Storage Ring	laser, storage-ring, alignment, operation	1123
	M.L. Chen, J.-R. Chen, P.S.D. Chuang, H.C. Ho, K.H. Hsu, D.-G. Huang, C.K. Kuan, W.Y. Lai, C.J. Lin, S.Y. Perng, T.C. Tseng, H.S. Wang NSRRC, Hsinchu, Taiwan
	24 sets of Laser PSD positioning system are parts of the TPS girder auto¬alignment system. Laser PSD positioning systems are installed in the straight¬ section girders of TPS storage ring. The Laser PSD systems are assembled and calibrated in the Lab beforehand. The Laser and PSDs are assembled on girder and transported to TPS storage ring and Installed. During construction the system deviates from the normal position caused by variant temperature and external influence. For absolute position precision, another laser calibration system should be built to recalibrate the laser PSD system. This paper describes the installation of Laser PSD system in TPS storage ring and the status of the PSD system. A new absolute position calibration method for precision upgrade is also discussed.
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MOPTY083	Progress towards Electron-beam Feedback at the Nanometre Level at the Accelerator Test Facility (ATF2) at KEK	feedback, cavity, kicker, extraction	1133
	P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry JAI, Oxford, United Kingdom D.R. Bett CERN, Geneva, Switzerland
	Ultra-low latency beam-based digital feedbacks have been developed by the Feedback On Nanosecond Timescales (FONT) Group and tested at the Accelerator Test Facility (ATF2) at KEK in a programme aimed at beam stabilisation at the nanometre level at the ATF2 final focus. Three prototypes were tested: 1) A feedback system based on high-resolution stripline BPMs was used to stabilise the beam orbit in the beamline region c. 50m upstream of the final focus. 2) Information from this system was used in a feed-forward mode to stabilise the beam locally at the final focus. 3) A final-focus local feedback system utilising cavity BPMs was deployed. In all three cases the degree of beam stabilisation was observed in high-precision cavity BPMs at the ATF2 interaction point. Latest results are reported on stabilising the beam position to below 100 nanometres.
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MOPTY084	Design, Testing and Performance Results of a High-resolution, Broad-band, Low-latency Stripline Beam Position Monitor System	operation, collider, laser, FPGA	1136
	P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry JAI, Oxford, United Kingdom D.R. Bett CERN, Geneva, Switzerland
	A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. The fast analogue front-end signal processor is based on a single-stage RF down-mixer. The processor latency is 15.6 ± 0.1 ns. A position resolution below 300 nm has been demonstrated for beam intensities of around 1 nC, with single-pass beam.
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MOPWI004	Novel Single Shot Bunch Length Diagnostic using Coherent Diffraction Radiation	radiation, experiment, laser, optics	1150
	R.B. Fiorito, C.P. Welsch, H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom A.G. Shkvarunets UMD, College Park, Maryland, USA
	Funding: European Union’s grant agreement no. 624890 and STFC Cockcroft core grant No. ST/G008248/1; US Office of Naval Research and DOD Joint Technology Office. Current beam bunch length monitors which measure the spectral content of beam-associated coherent radiation to determine the longitudinal bunch form factor usually require wide bandwidth detection or Fourier transformation of interferometric data and multiple beam pulses. The data must then be Fourier transformed to obtain the bunch length. In this contribution we discuss progress in the development of a novel single shot method that utilizes the frequency integrated angular distribution (AD) of coherent diffraction radiation (CDR) to measure the RMS bunch length directly. We also present simulation results which show how the AD changes with bunch length for several electron beam linacs, where we are planning to test this new method, our single shot measurement technique and plans for comparison to other bunch length monitors.
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MOPWI006	Development of a Supersonic Gas-jet Monitor to Measure Beam Profile Non-destructively	ion, vacuum, storage-ring, experiment	1157
	H.D. Zhang, A. Jeff, V. Tzoganis, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom A. Jeff CERN, Geneva, Switzerland A. Jeff, V. Tzoganis, C.P. Welsch, H.D. Zhang The University of Liverpool, Liverpool, United Kingdom V. Tzoganis RIKEN, Saitama, Japan
	Funding: This project is supported by Helmholtz Association(VH-NG-328), EU’s 7th Framework Program for research, technological development and demonstration( 215080) and STFC Cockcroft core grant(ST/G008248/1). The measurement of the transverse beam profile is a great challenge for high intensity, high brightness and high power particle beams due to their destructive power. Current non-destructive methods such as residual gas monitors and beam induced fluorescence monitors either require a rather long integration time or residual gas pressures in the order of 10^-7 mbar to make meaningful measurements. A supersonic gas-jet beam profile monitor has been developed by QUASAR group at the Cockcroft Institute, UK and promises significant improvements over these established techniques. In this monitor, a supersonic gas curtain is generated that crosses the beam to be analyzed under an angle of 45°. When both beams interact, ionization of the gas jet particles occurs and these ions are then accelerated by an electrostatic extraction field towards a Micro Channel Plate (MCP). Beam images are then obtained via a phosphor screen-CCD camera combination. In this contribution, we discuss the monitor design and present beam profile measurements of a 5 keV electron beam. These are complemented by results from measurements using a pulsed valve to study the gas jet dynamics.
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MOPWI009	A Multi-pinhole Faraday Cup Device for Measurement of Discrete Charge Distribution of Heavy and Light Ions	ion, diagnostics, experiment, vacuum	1160
	P.K. Roy, S. Dwaraknath, F.U. Naab, S. Taller, O.F. Toader, G. Was NERS-UM, Ann Arbor, Michigan, USA
	It is a difficult task to identify the beam density distribution profile over discrete areas using a standard Faraday cup, as the measurements are provided for the full aperture geometry of the instrument. Ideally, the intensity of the scintillating material would provide a correlation to the beam density, but the low photon efficiency, damage to the scintillator, and camera resolution all limit the practicality of using this system for assessing the spatial resolution of an ion beam. A beam profile monitor (BPM) device has the ability to provide a partial or discrete distribution of an integrated beam profile. The BPM, however, does not discriminate between ions and electrons, the latter of which can be problematic for assessing the full beam profile. To provide a better description of the beam density in spatial dimensions, a multi-pinhole Faraday cup (MPFC) has been designed, developed, and applied to the measurement of energetic ions. This device uses an array of millimeter sized Faraday cups arranged in a grid to measure the current of the beam at discrete locations. This report presents the design of the device, and its performance with ion beams.
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MOPWI014	Design and Development for the Next Generation X-ray Beam Position Monitor System at the APS	undulator, background, photon, coupling	1175
	B.X. Yang, G. Decker, Y. Jaski, S.-H. Lee, M. Ramanathan, N. Sereno, F. Westferro ANL, Argonne, Ilinois, USA
	Funding: Work performed at Argonne National Laboratory, operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357. The proposed Advanced Photon Source (APS) Upgrade will bring storage-ring beam sizes down to several micrometers and require x-ray beam directional stability in 100 nrad range for undulator power exceeding 16 kW. The next generation x-ray beam position monitors (XBPMs) are designed to meet these requirements. We present first commissioning data on the recently installed grazing-incidence insertion device x-ray beam position monitor (GRID-XBPM) based on Cu K-edge x-ray fluorescence from limiting absorbers of the front end for two inline undulators. It demonstrated a 50-fold improvement for signal-to-background ratio over existing photoemission-based XBPMs. Techniques for calibrating the XBPMs will be discussed. We will also present a new XBPM design based Compton scattering from diamond blades. This XBPM is designed for less powerful undulators such as the APS canted-undulator beamlines where each undulator generates < 10 kW of beam power. We will discuss the thermal design of the blade, the optics design of the detector assembly, and computer simulations of expected response to the x-ray beam. Test data of the prototype may be presented if available.
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MOPWI015	A Low Time-Dispersion Refractive Optical Transmission Line for Streak Camera Measurements	experiment, database, resonance, plasma	1178
	J.G. Power, G. Ha ANL, Argonne, Illinois, USA G. Ha POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: Work supported by the U.S. Department of Energy office of High Energy Physics. Streak camera measurements of the charge particle bunch length are limited in resolution due to several factors: (1) the light from the source (optical transition radiation, Cherenkov, synchrotron radiation, etc.); (2) time dispersion introduced in the optical transmission line between the source and the streak camera; and finally (3) the streak camera resolution. The limiting resolution usually arises from the optical transmission line. While an all-reflective transmission line can eliminate dispersion, the system is complicated and expensive. In this paper, we consider how to design a refractive optical transport line to minimize the time dispersion while maximizing the signal. We present a theoretical model of the dispersion, modeling, and measurements of the time dispersion for several different lens materials.
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MOPWI016	Development of a Versatile Bunch-length Monitor for Electron Beams at ASTA	laser, radiation, linac, optics	1181
	A.H. Lumpkin, D.J. Crawford, D.R. Edstrom, J. Ruan, J.K. Santucci, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA
	Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the United States Department of Energy. The generation of bright electron beams at the ASTA/IOTA facility at Fermilab includes implementation of a versatile bunch-length monitor located after the 4-dipole chicane bunch compressor for electron beam energies of 20-50 MeV and integrated charges in excess of 10 nC. The station will include both a Hamamatsu C5680 synchroscan streak camera and a Martin-Puplett interferometer (MPI). An Al-coated Si screen will be used to generate both optical transition radiation (OTR) and coherent transition radiation (CTR) during the beam’s interaction with the screen. A chicane bypass beamline will allow the measurement of the initial bunch length at the same downstream beamline location using OTR and the streak camera. The UV component of the drive laser has previously been characterized with a Gaussian fit σ of 3.5 ps, and the uncompressed electron beam is expected to be similar to this value at low charge per micropulse. In addition, OTR will be transported to the streak camera from the focal plane of the downstream spectrometer to provide an E-t distribution within the micropulse time scale. Commissioning of the system and initial results with beam will be presented as available. A.H. Lumpkin et al., Proceedings of FEL14, MOP021, Basel, Switzerland, www. JACoW.org.
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MOPWI018	New Hadron Monitor By Using A Gas-Filled RF Resonator	plasma, hadron, proton, radiation	1189
	K. Yonehara, A.V. Tollestrup, R.M. Zwaska Fermilab, Batavia, Illinois, USA G. Fasce CNI, Roma, Italy G. Flanagan, R.P. Johnson Muons, Inc, Illinois, USA
	It is trend to build an intense neutrino beam facility for the fundamental physics research, e.g. LBNF at Fermilab, T2K at KEK, and CNGS at CERN. They have investigated a hadron monitor to diagnose the primary/secondary beam quality. The existing hadron monitor based on an ionization chamber is not robust in the high-radiation environment vicinity of MW-class secondary particle production targets. We propose a gas-filled RF resonator to use as the hadron monitor since it is simple and hence radiation robust in this environment. When charged particles pass through the resonator they produce ionized plasma via the Coulomb interaction with the inert gas. The beam-induced plasma changes the permittivity of inert gas. As a result, a resonant frequency in the resonator shifts with the amount of ionized electrons. The radiation sensitivity is adjustable by the inert gas pressure and the RF amplitude. The hadron profile will be reconstructed with a tomography technique in the hodoscope which consists of X, Y, and theta layers by using a strip-shaped gas resonator. The sensitivity and possible system design will be shown in this presentation.
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MOPWI022	Experimental Study of a Two-Color Storage Ring FEL	FEL, wiggler, operation, storage-ring	1198
	J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA S. Huang PKU, Beijing, People's Republic of China J.Y. Li USTC/NSRL, Hefei, Anhui, People's Republic of China N. Vinokurov BINP SB RAS, Novosibirsk, Russia J. Wu SLAC, Menlo Park, California, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. Multi-color Free-electron Lasers (FELs) have been developed on linac based FELs over the past two decades. On the storage ring, the optical klystron (OK) FEL in its early days was demonstrated to produce lasing at two adjacent wavelengths with their spectral separation limited by the bandwidth of single wiggler radiation. Here, we report a systematic experimental study on the two-color operation at the Duke FEL facility, the first experimental demonstration of a tunable two-color harmonic FEL operation of a storage ring based FEL. We demonstrate a simultaneous generation of two FEL wavelengths, one in infrared (IR) and the other in ultraviolet (UV) with a harmonic relationship. The experimental results show a good performance of the two-color FEL operation in terms of two-color wavelength tunability, power tunability and power stability.
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Paper

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MOAC1

Awake: the Proof-of-principle R&D Experiment at CERN

proton, laser, plasma, experiment

34

P. Muggli
MPI, Muenchen, Germany
M. Bernardini, T. Bohl, C. Bracco, A.C. Butterworth, S. Cipiccia, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, A.V. Petrenko, J.S. Schmidt, M. Turner, H. Vincke
CERN, Geneva, Switzerland

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a proof-of-principle R&D experiment at CERN. It is the world’s first proton driven plasma wakefield acceleration experiment, using a high-energy proton bunch to drive a plasma wakefield for electron beam acceleration. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV proton beam bunches from the SPS, which will be sent to a plasma source. An electron beam will be injected into the plasma cell to probe the accelerating wakefield. Challenging modifications in the area and new installations are required for AWAKE. First proton beam to the experiment is expected late 2016. The accelerating electron physics will start late 2017. This paper gives an overview of the project from a physics and engineering point of view, it describes the main activities, the milestones, the organizational set-up for the project management and coordination.

Slides MOAC1 [21.632 MB]

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MOBC2

High-Performance Simulations of Coherent Synchrotron Radiation on Multicore GPU and CPU Platforms

GPU, simulation, synchrotron, radiation

42

B. Terzić, A.L. Godunov
ODU, Norfolk, Virginia, USA
A. Arumugam, D. Ranjan, M. Zubair
ODU CS, Norfolk, Virginia, USA

Coherent synchrotron radiation (CSR) is an effect of self-interaction of an electron bunch as it traverses a curved path. It can cause a significant emittance degradation and microbunching. We present a new high-performance 2D, particle-in-cell code which uses massively parallel multicore GPU/GPU platforms to alleviate computational bottlenecks. The code formulates the CSR problem from first principles by using the retarded scalar and vector potentials to compute the self-interaction fields. The speedup due to the parallel implementation on GPU/CPU platforms exceeds three orders of magnitude, thereby bringing a previously intractable problem within reach. The accuracy of the code is verified against analytic 1D solutions (rigid bunch).

Slides MOBC2 [4.866 MB]

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MOBC3

Electron Lenses for Experiments on Nonlinear Dynamics with Wide Stable Tune Spreads in the Fermilab Integrable Optics Test Accelerator

lattice, solenoid, optics, operation

46

G. Stancari, K. Carlson, M.W. McGee, L.E. Nobrega, A.L. Romanov, J. Ruan, A. Valishev
Fermilab, Batavia, Illinois, USA
D. Noll
IAP, Frankfurt am Main, Germany

Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy.
Recent developments in the study of integrable Hamiltonian systems have led to nonlinear accelerator lattice designs with two transverse invariants. These lattices may drastically improve the performance of high-power machines, providing wide tune spreads and Landau damping to protect the beam from instabilities, while preserving dynamic aperture. To test the feasibility of these concepts, the Integrable Optics Test Accelerator (IOTA) is being designed and built at Fermilab. One way to obtain a nonlinear integrable lattice is by using the fields generated by a magnetically confined electron beam (electron lens) overlapping with the circulating beam. The parameters of the required device are similar to the ones of existing electron lenses. We present theory, numerical simulations, and first design studies of electron lenses for nonlinear integrable optics.

Slides MOBC3 [11.870 MB]

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MOPWA002

Nonequilibrium Phase Transitions in Crossed-Field Devices

cathode, space-charge, simulation, injection

74

S. Marini, R. Pakter, F.B. Rizzato
IF-UFRGS, Porto Alegre, Brazil

Funding: This work was partially supported by CNPq and FAPERGS, Brazil, and by the US-AFOSR under the grant FA9550-09-1-0283.
This work presents a fully kinetic description to model the electron flow in the electronic crossed-field configuration observed in a smooth-bore magnetron. Through this model, it has been observed that, according to the electromagnetic field, the injection temperature and the charge density, the electron flow can be classified in two different stationary modes: magnetic insulation mode where most of the electrons returning to the cathode after a transient time and Child-Langmuir mode where most of the electrons reach the anode after a transient time. Focusing on magnetic insulated mode, it has been found that charge density and injection temperature define whether electrons are accelerated (accelerating regime) or decelerated (space-charge limited regime) on the cathode. Besides, when the injection temperature is relatively low (high), a small charge increase causes (does not cause) an abrupt transition between accelerating and space-charge limited regime. Basing on the results, it was possible to identify a critical temperature that separates abrupt and continuous behavior. The results have been verified by using self-consistent computer simulations*.
*S. Marini, F. B. Rizzato, and R. Pakter, Phys. Plasmas 21, 083111 (2014).

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MOPWA009

Channeling Radiation Experiment at Fermilab ASTA

photon, brilliance, experiment, detector

95

D. Mihalcea, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.R. Edstrom, P. Piot, T. Sen
Fermilab, Batavia, Illinois, USA
W.D. Rush
KU, Lawrence, Kansas, USA

Electron beams with moderate energy ranging from 4 to 50 MeV can be used to produce x-rays through the Channeling Radiation (CR) mechanism. Typically, the x-ray spectrum from these sources extends up to 140 keV and this range covers the demand for most practical applications. The parameters of the electron beam determine the spectral brilliance of the x-ray source. The electron beam produced at the Fermilab new facility Advanced Superconducting Test Accelerator (ASTA) meets the requirements to assemble an experimental high brilliance CR x-ray source. In the first stage of the experiment the energy of the beam is 20 MeV and due to the very low emittance (100 nm) at low bunch charge (20 pC) the expected average brilliance of the x-ray source is 0.8x10⁷ photons/[s-(mm-mrad)²-0.1%BW]. In the second stage of the experiment the beam energy will be increased to 50 MeV and consequently the average brilliance will be 4.8x10⁸ photons/[s-(mm-mrad)²-0.1%BW]. Also, the x-ray spectrum will be extended from about 30 keV to 140 keV.

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MOPWA011

The Damping of Transverse Coherent Instabilities by Harmonic Cavities

synchrotron, betatron, simulation, damping

102

F.J. Cullinan, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France
G. Skripka, P.F. Tavares
MAX-lab, Lund, Sweden

At nonzero chromaticity, the threshold current due to transverse coupled bunch instabilities in an electron storage ring is defined by intrabunch head-tail motion of higher than zeroth order. Multibunch tracking simulations predict that this threshold can be increased to several times its original value through the introduction of bunch lengthening harmonic cavities. One previously suggested explanation is the narrower spectra of the elongated bunches but reliable estimates for the threshold currents are not obtainable for anything other than rigid beam motion since the usual Sacherer formulism is not directly applicable to beams in a non-harmonic potential. A new scheme has been developed in which the decay time of a higher than zeroth order transverse head-tail mode may be estimated by taking into account the synchrotron tune spread generated by the harmonic cavity potential. This scheme is presented along with the results of numerical simulations performed in order to confirm the analytical predictions and justify the assumptions made. The extension of the scheme to more complex scenarios is also discussed.

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MOPWA013

Modeling and Measurements of Spin Depolarization

kicker, resonance, polarization, synchrotron

109

N. Carmignani, F. Ewald, L. Farvacque, B. Nash, P. Raimondi
ESRF, Grenoble, France

An electron bunch in a storage ring becomes spin polarized due to the Sokolov-Ternov effect. The beam may then be depolarized by applying a horizontal magnetic field oscillating in resonance with the spin tune. This technique has been used to measure the electron energy at numerous synchrotrons. In this paper, we report on modeling and measurements of the polarization and depolarization process at the ESRF. We report the results of a Matlab based parallelized spin tracking code that we developed for these studies. We show the change in depolarization resulting as different physical effects are added to the model.

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MOPWA021

Transverse Resonance Island Buckets at the MLS and BESSY II

resonance, operation, radiation, photon

138

M. Ries, J. Feikes, T. Goetsch, P. Goslawski, J. Li, M. Ruprecht, A. Schälicke, G. Wüstefeld
HZB, Berlin, Germany

By operating the Metrology Light Source (MLS) near horizontal resonances (fx/frev=1/2, 1/3 or 1/4), two, three or four resonance island buckets may be populated for beam storage. This paper presents experimental results and operational experience such as tuning the machine for high current, controlling inter-bucket diffusion rates, improving overall lifetime and extraction of radiation pulses with sub-revolution repetition rate. First approaches to transfer this mode of operation to the BESSY II storage ring will also be presented.

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MOPWA023

Preserving Information of the Three Spatial Electron Beam Dimensions in One Streak Camera Measurement

operation, synchrotron, photon, diagnostics

144

M.T. Switka, W. Hillert
ELSA, Bonn, Germany

Funding: Work funded by the DFG within SFB/TRR16
At the pulse stretcher ring ELSA, a streak camera is used for the analysis of visible synchrotron radiation. It functions as fast time resolving beam diagnostic apparatus capable of visualizing dynamics down to the picosecond time range. The optical beamline splits the photon beam and projects the electron beam's image onto the streak camera with transversely perpendicular orientation and slight displacement, thereby providing simultaneous imaging of both transverse planes. Thus, the information of bunch and beam dynamics in three dimensions is preserved and can be observed in slow sweep or synchroscan operation. Characteristics and exemplary measurements, demonstrating the capabilities and limits of this technique, are presented.

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MOPWA024

Estimation of the Ion Density in Accelerators using the Beam Transfer Function Technique

ion, betatron, synchrotron, impedance

147

D. Sauerland, W. Hillert
ELSA, Bonn, Germany
A. Meseck
HZB, Berlin, Germany

Funding: Funded by the federal ministry of education and science of Germany
The ELSA stretcher ring of Bonn University serves external hadron physics experiments with a quasi continuous electron beam of up to 3.2 GeV energy. Ions, being generated by collisions of the circulating electrons with the residual gas molecules, accumulate inside the beam potential, causing incoherent tune shifts and coherent beam instabilities. Detailed measurements were carried out in which ion dynamics is studied in dependence of beam energy and current, filling patterns and bias voltages of the ion clearing electrodes. By measuring the beam transfer function using a broadband transversal kicker, we were able to derive an estimate of the average ion density from the shift and broadening of the tune peak. In this contribution first results of these measurements are presented.

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MOPWA029

Investigations of the Space-Charge-Limited Emission in the L-Band E-Xfel Photoinjector at Desy-Pitz

simulation, space-charge, gun, cathode

162

Y. Chen, H. De Gersem, E. Gjonaj, A.V. Tsakanian, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
C. Hernandez-Garcia
JLab, Newport News, Virginia, USA
M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany

Funding: work supported by DESY Hamburg and Zeuthen Sites
This paper discusses the numerical modelling of electron bunch emission for an L-band normal conducting RF photogun. The main objective is clarifying the discrepancies between measurements and simulations performed for the European X-ray Free Electron Laser (E-XFEL) injector at DESY-PITZ. An iterative beam dynamics simulation procedure is proposed for the calculation of the total extracted bunch charge under the assumption that the emission source operates at the space-charge limit of the gun. This algorithm has been implemented in the three-dimensional full electromagnetic PIC Solver of the CST Particle Studio (CST-PS)*. Simulation results are in good agreements with measurements for a series of operation parameters. Further comparisons with a conventional Poisson-solver-based (PSB) tracking algorithm demonstrates the great significance of transient electromagnetic field effects for the beam dynamics in high brightness electron sources.
* Computer Simulation Technology AG, http://www.cst.com/

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MOPWA030

Simulations of Electron Cloud Long Range Wakefields

wakefield, simulation, dipole, proton

165

F.B. Petrov, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work supported by the BMBF under Contract No. 05H12RD7
A typical approach to electron cloud simulations is to split the problem in two steps: buildup simulations and instability simulations. In the latter step the cloud distribution is usually refreshed after each full interaction with the bunch. This approach does not consider multibunch effects. We present studies of the long range electron cloud wakefields generated in electron clouds after interaction with relativistic proton bunch trains. Several pipe geometries - relevant to CERN accelerators - with and without external magnetic field are considered. Using simple examples we show that the long range wakefields depend significantly on the secondary emission curve as well as on the pipe geometry. Additivity of electron cloud wakefields is studied as well.

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MOPWA034

Coupled-Bunch Instability Suppression Using RF Phase Modulation at the DELTA Storage Ring

damping, synchrotron, storage-ring, feedback

179

M. Sommer, M. Höner, B.D. Isbarn, S. Khan, B. Riemann, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF under contract no. 05K13PEB
The upcoming upgrade of BESSY II, called BESSY-VSR*, involves the utilization of superconducting multicell RF-resonators with high accelerating gradients to provide short and long bunches in an electron storage ring simultaneously. Even under the assumption of strongest available damping of beam induced modes, the residual impedances of the cavities may cause collective multibunch instabilities at the frontier of stability available from current bunch-by-bunch feedback systems. At the DELTA electron storage ring, a phase modulation of the driving RF is used to suppress coupled-bunch instabilities and to increase the lifetime. The time dependent frequency variation in the order of the synchrotron frequency gives rise to additional damping of the bunch oscillators by decoherence and Landau damping. The behaviour and the additional damping of the bunch oscillators is investigated by the existing bunch-by-bunch feedback system e.g. the increase of the overall damping might support the capability of feedback systems under extreme operating conditions of BESSY-VSR.
* G. Wüstefeld et al., Proc. of IPAC'11, San Sebastián, THPC014

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MOPWA042

Sub-fs Electron Bunch Generation Using Magnetic Compressor at SINBAD

simulation, plasma, acceleration, laser

207

J. Zhu, R.W. Aßmann, U. Dorda, J. Grebenyuk, B. Marchetti
DESY, Hamburg, Germany

In order to achieve high quality electron beams by laser-driven plasma acceleration with external injection, sub-fs bunches with a few fs arrival-time jitter are required. SINBAD (Short Innovative Bunches and Accelerators at DESY) is a proposed dedicated accelerator research and development facility at DESY. One of the baseline experiment at SINBAD is ARES (Accelerator Research Experiment at SINBAD), which will provide ultra-short electron bunches of 100 MeV to one or two connected beam lines. We present start-to-end simulation studies of sub-fs bunches generation at ARES using a magnetic compressor with a slit. In addition, the design of a dogleg with tunable R56 for the second beamline is also presented.

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MOPWA043

FEL Simulations with Ocelot

optics, space-charge, FEL, simulation

210

I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany
M. Dohlus, I. Zagorodnov
DESY, Hamburg, Germany
S.I. Tomin
NRC, Moscow, Russia

Ocelot has been developed as a multiphysics simulation tool for FEL and synchrotron light source studies. In this work we highlight recent code developments focusing on electron tracking in linacs taking into account collective effects and on x-ray optics calculations

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MOPWA045

First Tests of a Beam Transport System from a Laser Wakefield Accelerator to a Transverse Gradient Undulator

quadrupole, undulator, beam-transport, dipole

216

C. Widmann, V. Afonso Rodríguez, A. Bernhard, A.-S. Müller, R. Rossmanith, W. Werner
KIT, Karlsruhe, Germany
M. Kaluza, M. Nicolai, M.B. Schwab, A. Sävert
IOQ, Jena, Germany
M. Kaluza, S. Kuschel
HIJ, Jena, Germany

An experimental setup for the generation of monochromatic undulator radiation at the laser wakefield accelerator (LWFA) in Jena using a transverse gradient undulator (TGU) is planned. Proper matching of the betatron functions and the dispersion of the electron beam to the undulator is essential. Therefor a beam transport system with strong focusing magnets and chromatic correction of these magnets is required. As a first step, a linear beam transport system without chromatic correction was assembled at the LWFA. With this setup the electron beam’s dispersion and the beta function of one selected energy are matched to the required parameters at the TGU. This contribution presents the experimental results of these measurements.

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MOPWA049

Simulation of Crab Waist Collisions in DAΦNE with KLOE-2 Interaction Region

simulation, luminosity, betatron, detector

229

M. Zobov, A. Drago, A. Gallo, C. Milardi
INFN/LNF, Frascati (Roma), Italy
D.N. Shatilov
BINP SB RAS, Novosibirsk, Russia
A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: Research supported by DOE via the US-LARP program and by EU FP7 HiLumi LHC - Grant Agreement 284404.
After the successful completion of the SIDDHARTA experiment run with crab waist collisions, the electron-positron collider DAΦNE has started routine operations for the KLOE-2 detector. The new interaction region also exploits the crab waist collision scheme, but features certain complications including the experimental detector solenoid, compensating anti-solenoids, and tilted quadrupole magnets. We have performed simulations of the beam-beam collisions in the collider taking into account the real DAΦNE nonlinear lattice. In particular, we have evaluated the effect of crab waist sextupoles and beam-beam interactions on the DAΦNE dynamical aperture and energy acceptance, and estimated the luminosity that can be potentially achieved with and without crab waist sextupoles in the present working conditions. A numerical analysis has been performed in order to propose possible steps for further luminosity increase in DAΦNE such as a better working point choice, crab sextupole strength optimization, correction of the phase advance between the sextupoles and the interaction region. The proposed change of the e^- ring working point was implemented and resulted in a significant performance increase.

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MOPWA054

Effect of Number of Macro Particles on Resolution in Phase Space Distribution

simulation, operation, linac

242

T. Miyajima
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 26600147.
In order to analyze charged particle beam in an accelerator, a beam model is used to reduce number of degrees of freedom, e.g. charged disk model, charged cylinder model and macro-particle model. In numerical simulation, the macro-particle model, which has same mass-to-charge ratio, is widely used, since it does not require any symmetry of beam shape. However, the estimation of proper number of macro-particles is one of the important issues. In order to study the effect of the number of macro-particles for the numerical model, we defined a simple transformation to generate reduced distribution. The transformation was applied for one dimensional and two dimensional particle distributions. The static electric fields due to the transformed distributions were calculated. As a result, we confirmed the effectiveness of the transformation.

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MOPWA066

Simulation on Buildup of Electron Cloud in Rapid Cycling Synchrotron of China Spallation Neutron Source

proton, simulation, vacuum, neutron

275

K.W. Li, L. Huang, Y.D. Liu, S. Wang
IHEP, Beijing, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (11275221)
Electron cloud interaction with high energy positive beam are believed responsible for various undesirable effects such as vacuum degradation, collective beam instability and even beam loss in high power proton circular accelerator. An important uncertainty in predicting electron cloud instability lies in the detail processes on the generation and accumulation of the electron cloud. The simulation on the build-up of electron cloud is necessary to further studies on beam instability caused by electron cloud. China Spallation Neutron Source (CSNS) is the largest scientific project in building, whose accelerator complex includes two main parts: an H⁻ linac and a rapid cycling synchrotron (RCS). The RCS accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV with a repetition rate 25 Hz. During the beam injection with lower energy, the emerging electron cloud may cause a serious instability and beam loss on the vacuum pipe. A simulation code has been developed to simulate the build-up, distribution and density of electron cloud in CSNS/RCS.

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MOPWA072

Emittance Exchange Beam Line Design In THU Accelerator Lab

emittance, quadrupole, cavity, simulation

285

Q. Gao, H.B. Chen, Y.-C. Du, W.-H. Huang, J. Shi
TUB, Beijing, People's Republic of China
W. Gai
ANL, Argonne, Illinois, USA

Funding: National Natural Science Foundation of China
Emittance exchange (EEX) provides a novel tool to enhance the phase space manipulation techniques. Based on Tsinghua Thomson scattering experimental platform, this study presented a beam line design for exchanging the transverse and longitudinal emittance of an electron bunch. This beam line consists of a 2.856 GHz half-one-half cell deflecting cavity with no axis offset and two doglegs. In this paper, by optimizing the beam envelope parameter for Tsinghua Thomson scattering source, we report the theoretical analysis and a good particle tracking simulation result about emittance exchange and longitudinal shaping.

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MOPJE001

Effect on Beam Dynamics From Wakefields in Travelling Wave Structure Excited by Bunch Train

wakefield, simulation, dipole, radiation

289

D. Wang, C.-X. Tang
TUB, Beijing, People's Republic of China
W. Gai, C.-J. Jing, J.G. Power
ANL, Argonne, Illinois, USA
J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA

Electron bunch train technology is used to excited coherent high power RF radiation in travelling wave (TW) structures. This article concentrates on the analytical expression of wakefields excited by bunch train in TW structures and the effects of wakefields on beam dynamics. We focus on the first monopole mode and the first dipole mode wakefields. The long range wake function has a linear decrease which agrees well with the ABCi simulations. Taking example of the 11.7 GHz wakefields structure at the Argonne Wakefield Accelerator (AWA) facility, with 1.3 GHz interval drive electron bunch train, we have done the beam dynamics simulation with a point to point (P2P) code. Results shows the effects of wakefields on the energy distribution and the transverse instability for each sub-bunch.

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MOPJE003

Measuring Duke Storage Ring Lattice Using Tune Based Technique

storage-ring, quadrupole, lattice, wiggler

293

W. Li, J.Y. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China
H. Hao, W. Li, S.F. Mikhailov, V. Popov, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The Duke electron storage ring is a dedicated driver for oscillator Free-Electron Lasers (FELs). A 34 m long straight section of the storage ring is used to host up to four FEL wigglers in several different configurations. A total of six wigglers, two planar OK-4 wigglers and four helical OK-5 wigglers, are available for FEL research. The storage ring magnetic lattice has to be designed with great flexibility to enable the storage ring operation with different FEL wigglers, at various wiggler settings, and for different electron beam energies. Since 2012, the storage ring has demonstrated all designed characteristics in terms of lattice flexibility and tuning. This work is aimed at gaining better understanding of the real storage ring lattice by performing a series of measurements of the beta-functions along the storage ring. Unlike the LOCO technique, the beta-functions in the quadrupoles are directly measured with good accuracy using a tune meassurement system. We will describe our experimental design and techniques, and measurement procedures. We will also report our preliminary results for the lattice characterization.

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MOPJE006

Electron Gun Longitudinal Jitter: Simulation and Analysis

gun, timing, linac, simulation

297

M.S. Liu, Y.L. Chi, S. Pei, Y.F. Sui
IHEP, Bejing, People's Republic of China

The beam longitudinal jitter is fatal not only for the electron beam performance but also for the positron yield in routine operation of the Beijing Electron Positron Collider II (BEPCII) linear accelerator (Linac). Practically, longitudinal jitter has been observed many times which decreased the beam performance. We simulated the electron gun longitudinal jitter effect by PARMELA software in bunch capture process and analyzed its results about beam performance including average energy, energy spread, emittance and longitudinal phase of reference particle. We adjusted the electron gun trigger time during one cycle without changing other parameters. The percentage difference between maximum and minimum of average energy, energy spread, emittance and longitudinal phase of reference particle was 11.3%, 42%, 98% and 6.4%, respectively. It is observed and analyzed that gun trigger time longitudinal jitter is fatal for maintaining good beam performance. This analysis also gives a salutary lesson to any other longitudinal jitter which can affect the beam bunching in pre-injector .

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MOPJE008

Suppression of Microbunching Instability via a Transverse Gradient Undulator

linac, simulation, FEL, laser

300

D. Huang, H.X. Deng, C. Feng, D. Gu, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Funding: the Major State Basic Research Development Program of China (2011CB808300) and the National Natural Science Foundation of China (11275253, 11475250 and 11322550).
The microbunching instability in the linear accelerator (linac) of a free-electron laser facility has always been a problem that degrades the electron beam quality. In this paper, a quite simple and inexpensive technique is proposed to smooth the electron beam current profile to suppress the instability. By directly adding a short undulator with transverse gradient field right after the injector to couple the transverse spread into the longitudinal direction, additional density mixing in the electron beam is introduced to smooth the current profile, which results in the reduction of the gain of the microbunching instability. The magnitude of the density mixing can be easily controlled by turning the strength of the undulator magnet field. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in the accelerator of an X-Ray free-electron laser.

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MOPJE022

Physical Model of Partial RF Discharge in Isochronous Cyclotrons

cyclotron, plasma, ion, ion-source

323

V.S. Dyubkov
MEPhI, Moscow, Russia
S. Korenev
Siemens Medical Solutions Molecular Imaging, Knoxville, TN, USA

The physical model for the partial RF discharge - based on the ionization of molecules of residual gas by electron detachment as a result of the electro-dissociation of negative hydrogen ions in isochronous cyclotrons - is proposed in this paper. The result of the simulation of the ionization of gas molecules by these electrons using RF voltage inside the Eclipse cyclotron (kinetic energy of 11 MeV) is presented. The analysis of the conductivity of the RF plasma (partial RF discharge) is given. The influence of the magnetic field on the properties of the partial RF discharge is discussed. The application of this model is for isochronous cyclotrons with low kinetic energy (10^-15 MeV).

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MOPJE048

Electron-Cloud Studies for Transversely Split Beams

resonance, simulation, injection, extraction

399

N. Pradhan, S.S. Gilardoni, M. Giovannozzi, G. Iadarola, G. Rumolo
CERN, Geneva, Switzerland
N. Pradhan
UMiss, University, Mississippi, USA

Recently, resonance crossing has been proposed as a means of manipulating the transverse beam distribution. This technique has application, among other topics, to injection and extraction schemes. Moreover, the transversely split beams might also be used as a mitigation measure of electron-cloud effects. The results of detailed numerical simulations are discussed in this paper, possibly opening new options for scrubbing of beam pipes in circular accelerators.

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MOPJE051

Effect of Electron Cloud in Quadrupoles on Beam Instability

quadrupole, dipole, simulation, emittance

409

G. Iadarola, A.P. Axford, H. Bartosik, K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland

Both simulations and machine experience at the CERN-SPS and LHC have shown that the electron cloud has a lower build up threshold in quadrupoles than in dipoles and field free regions. As a consequence, while beam induced scrubbing can efficiently suppress the electron cloud in both dipoles and field free regions, a residual electron cloud can still survive in the quadrupoles and potentially degrade the beam quality. To study this effect, a PyECLOUD module for electron tracking in quadrupole fields including effects of secondary emission at the vacuum chamber has been implemented in PyHEADTAIL. With this module, the effect of the electron cloud in quadrupoles on beam stability and beam quality preservation can be assessed, as well as its impact on future LHC and HL-LHC operation.

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MOPJE062

Testing Aspects of Advanced Coherent Electron Cooling Technique

hadron, bunching, FEL, collider

445

V. Litvinenko, Y.C. Jing, I. Pinayev, G. Wang
BNL, Upton, Long Island, New York, USA
D.F. Ratner
SLAC, Menlo Park, California, USA
V. Samulyak
SBU, Stony Brook, USA

An advanced version of the coherent-electron cooling based on the microbunching instability was proposed in *. This approach promised to significantly increase the bandwidth of the system and, therefore, significantly shorter cooling time in high energy hadron colliders. In this paper we present our plans of simulating and testing the key aspects of this proposed technique using the set-up of the coherent-electron-cooling proof-of-principle experiment at BNL.
* D.F. Ratner, Phys. Rev. Lett. 111, 084802 (2013)

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MOPJE070

Reduction of Electron Cloud in Particle Accelerator Beampipes Studied by RF Multipacting

injection, vacuum, detector, network

472

R. Leber, F. Caspers, P. Costa Pinto, M. Taborelli
CERN, Geneva, Switzerland

For a given beam structure, chamber geometry and magnetic field configuration, the electron cloud (EC) intensity depends on the Secondary Electron Yield (SEY) of the beam pipe. The reduction of the EC density as a function of machine operation time (scrubbing) is attributed to the growth of a low SEY carbon film induced by electron bombardment. In this paper, we study the time evolution of the conditioning of stainless steel beam pipes in a laboratory setup. The EC or multipacting is induced by Radio-Frequency (RF) fields in a coaxial resonator under vacuum. Strip detectors are used to monitor the current of the EC. Induced pressure rise is simultaneously detected. The multipacting intensity shows a linear dependence on the positive DC bias voltage up to 1000 V, applied to the central electrode. An accelerated conditioning is observed for the applied bias voltage. The SEY of samples exposed to the EC is measured and the surface composition is monitored by X-ray Photoelectron Spectroscopy. The measured SEY, surface composition and multipacting behaviour are well correlated. The injection of acetylene and dodecane during multipacting proved to be ineffective in the conditioning.

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MOPJE071

New Electron Cloud Detectors for the CERN Proton Synchrotron

photon, detector, proton, extraction

476

C. Yin Vallgren, P. Chiggiato, S.S. Gilardoni, H. Neupert, M. Taborelli
CERN, Geneva, Switzerland

Electron cloud (EC) has already been observed during normal operation of the PS using classical shielded button pick-up detectors in drift sections. In the context of the LHC Injector Upgrade (LIU project), similar measurements are also needed for the combined function magnets of the machine, where the access to the vacuum chamber is strongly limited by the presence of the yoke. Two new electron cloud detectors have been studied, developed, and installed during the Long Shutdown (LS1) in one of such magnets. The first is based on current measurement by using a shielded button-type pick-up with a special geometry to reach the bottom surface of the vacuum pipe embedded in the magnet. The second one relies on a newly developed measurement method based on detection of the photons, which are emitted by cathodoluminescence from the electron cloud impinging on the vacuum chamber walls. Part of the emitted photons is collected through a quartz window by a Micro-Channel Plate Photomultiplier Tube (MCP-PMT). First results obtained during machine development runs show the feasibility of the photon detection scheme. The results are discussed and compared with pick-up measurements.

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MOPJE079

Tracking Studies in the LHeC Lattice

lattice, resonance, proton, dynamic-aperture

502

E. Cruz Alaniz, D. Newton
The University of Liverpool, Liverpool, United Kingdom
E. Cruz Alaniz, D. Newton
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R. Tomás
CERN, Geneva, Switzerland

Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289485
The Large Hadron Electron Collider (LHeC) is a proposed upgrade of the LHC to provide electron-proton collisions and explore a new regime of energy and luminosity for nucleon-lepton scattering. A nominal design has previously been presented, featuring a lattice and optical configuration to focus one of the proton beams of the LHC (reaching a value of β^*=10 cm) and to collide it head-on with an electron beam to produce collisions with the desired luminosity of L=10³³ cm^-2 s^-1. The proton beam optics is achieved with the aid of a new inner triplet of quadrupoles at L*=10 m from the interaction point and the extension of the Achromatic Telescopic Squeezing (ATS) Scheme used for the High Luminosity-LHC project. The flexibility of this design has been studied in terms of minimising β^* and increasing L*. In this work, particle tracking is performed in a thin lens approximation of the LHeC proton lattice to compute the dynamic aperture and perform frequency map analysis for different types of chromatic correction schemes, in order to find the one who will provide the most beam stability and to study the effects of non linearities.

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MOPMA003

Reconstruction of Electron Bunch Motion During CSR Bursts using Synchronised Diagnostics

detector, synchrotron, radiation, storage-ring

529

I.P.S. Martin, R. Bartolini, C. Bloomer, L.M. Bobb, G. Rehm
DLS, Oxfordshire, United Kingdom
R. Bartolini, A. Finn
JAI, Oxford, United Kingdom

Above a certain threshold current, electron bunches become unstable and emit bursts of coherent synchrotron radiation (CSR). The character and periodicity of these bursts vary with bunch current, RF voltage and lattice momentum compaction. In this paper we describe recent measurements taken at Diamond of how the electron bunch longitudinal profile and energy vary during a burst, and correlate this with CSR emission at a range of wavelengths.

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MOPMA024

A Parallel Particle-Particle, Particle-Mesh Solver for Studying Coulomb Collisions in the Code IMPACT-T

emittance, simulation, plasma, space-charge

593

C.E. Mitchell, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
In intense charged-particle beams, the presence of Coulomb collisions can result in growth of the beam slice energy spread and emittance that cannot be captured correctly using traditional particle-in-cell codes. Particle-particle, particle-mesh solvers take a hybrid approach, combining features of N-body and particle-in-cell solvers, to correctly capture the effect of short-range particle interactions with less computing time than direct N-body solvers. We describe the implementation and benchmarking of such a solver in the code IMPACT-T for beam dynamics applications.

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MOPMA027

Electron Cloud Measurements in Fermilab Main Injector and Recycler

vacuum, proton, injection, operation

604

J.S. Eldred
Indiana University, Bloomington, Indiana, USA
M. Backfish, J.S. Eldred, C.-Y. Tan, R.M. Zwaska
Fermilab, Batavia, Illinois, USA

This conference paper presents a series of electron cloud measurements in the Fermilab Main Injector and Recycler. A new instability was observed in the Recycler in July 2014 that generates a fast transverse excitation in the first high intensity batch to be injected. Microwave measurements of electron cloud in the Recycler show a corresponding dependence on the batch injection pattern. These electron cloud measurements are compared to those made with a retarding field analyzer (RFA) installed in a field-free region of the Recycler in November. RFAs are also used in the Main Injector to evaluate the performance of beampipe coatings for the mitigation of electron cloud. Contamination from an unexpected vacuum leak revealed a potential vulnerability in the amorphous carbon beampipe coating. The diamond-like carbon coating, in contrast, reduced the electron cloud signal to 1\% of that measured in uncoated stainless steel beampipe.

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MOPMA031

Simulations of Diamond Detectors with Schottky Contacts

simulation, detector, photon, scattering

617

G.I. Bell, J.R. Cary, D.A. Dimitrov, D. Meiser, D.N. Smithe, C.D. Zhou
Tech-X, Boulder, Colorado, USA
M. Gaowei, E.M. Muller
SBU, Stony Brook, New York, USA
J. Smedley
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences, grant numbers DE-SC0006246 and DE-SC0007577.
We present simulations of semiconductor devices using the code VSim (formerly Vorpal). The 3D simulations involve the movement and scattering of electrons and holes in the semiconductor, voltages which may be applied to external contacts, and self-consistent electrostatic fields inside the device. Particles may experience a Schottky barrier when moving between the semiconductor and a metal contact. Example devices include MOSFETs as well as a diamond X-ray detector. Our code VSim includes scattering models for GaAs and diamond, and runs in parallel on thousands of processors. We compare our simulation results with experimental results from a prototype diamond X-ray detector.

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MOPMA033

Modeling Electron Emission and Surface Effects from Diamond Cathodes

simulation, cathode, vacuum, scattering

620

D.A. Dimitrov, J.R. Cary, D.N. Smithe, C.D. Zhou
Tech-X, Boulder, Colorado, USA
I. Ben-Zvi, T. Rao, J. Smedley, E. Wang
BNL, Upton, Long Island, New York, USA

Funding: We are grateful to the U.S. DoE Office of Basic Energy Sciences for supporting this work under grants DE-SC0006246 and DE-SC0007577.
We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 to 17 MV/m along the [100] direction. The simulation results were compared to experimental data when using different emission models, band bending effects, and surface-dependent electron affinity. Simulations using surface patches with different levels of hydrogenation lead to the closest agreement with the experimental data.

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MOPMA037

Electron Cloud Buildup and Dissipation Models For PIP-II

simulation, plasma, proton, space-charge

626

S.A. Veitzer, P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920).
Buildup of electron plasmas in accelerator cavities can cause beam degradation and limit performance in high-intensity circular particle accelerators. This is especially important in machines such as the LHC, and PIP-II, where mitigation techniques such as beam scrubbing in order to decrease the SEY are expensive and time consuming. Modeling of electron cloud buildup and dissipation can provide understanding as to the potential negative effects of electron clouds on beam properties, as well as estimates of the mitigation required to maintain accelerator performance and beam quality as accelerators move to higher intensity configurations. We report here on simulations of electron cloud buildup and dissipation for geometry, beam and magnetic field configurations describing the Recycler at Fermilab. We perform electrostatic simulations in 3D with VSim PIC, including the effects of space charge and secondary electrons. We quantify the expected survival rate of electrons in these conditions, and argue that improvements in reducing the SEY is unlikely to mitigate the electron cloud effects.

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MOPMA039

Secondary Electron Yield Measurement and Electron Cloud Simulation at Fermilab

simulation, proton, vacuum, dipole

629

Y. Ji
IIT, Chicago, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA
R.M. Zwaska
Fermilab, Batavia, Illinois, USA

Funding: This work was funded by the National Science Foundation under the grant no. 1205811.
Fermilab Main Injector is upgrading the accelerator to double the beam intensity from 24·10¹² protons to 48·10¹² protons, which brings the accelerator into a regime where electron cloud effects may limit the accelerator performance. In fact, an instability that could be caused by electron cloud effects has already been observed in the Recycler. Secondary Electron Yield (SEY) is an important property of the vacuum chamber material that has great influence on the process of building up free electrons. The Main Injector of the Fermilab accelerator complex offers the opportunity to measure SEY and conditioning effects in the environment of a running accelerator, since samples of these materials are located at the beampipe wall. The SEY of stainless steel (SS316L) and TiN coated SS316L in the proximity of the proton beam were measured and compared. A series of simulation studies of electron cloud build up were done for the Main Injector and Recycler using the code POSINST. Parametric studies were done to determine the maximum electron density vs. peak SEY at different beam intensities in the Fermilab Main Injector. Threshold simulations of electron cloud density verus SEY were extended from Main Injector to include the Recycler Ring. It was found that the electron cloud density around the beam depends on bunch location within the bunch train.

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MOPMA043

Longitudinal Bunch Shaping at Picosecond Scales using Alpha-BBO Crystals at the Advanced Superconducting Test Accelerator

gun, laser, linac, space-charge

643

B. Beaudoin
UMD, College Park, Maryland, USA
D.R. Edstrom, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: This works is supported by the University Research Association, Inc. Operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
The Integrable Optics Test Accelerator (IOTA) electron injector at Fermilab will enable a broad range of experiments at a national laboratory in order to study and develop solutions to the limitations that prevent the propagation of high intensity beams at picosecond lengths. One of the most significant complications towards increasing short-beam intensity is space-charge, especially in the vicinity of the gun. A few applications that require a longitudinally shaped electron beam at high intensities are for, the generation of THz waves and dielectric wakefields, each of which will encounter the effects of longitudinal space-charge. This paper investigates the effects of longitudinal space-charge on alpha-BBO UV laser shaped electron bunches in the vicinity of the 1½cell 1.3 GHz cylindrically symmetric RF photocathode gun.

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MOPMA044

Barrier Shock Compression with Longitudinal Space Charge

space-charge, simulation, emittance, plasma

646

B. Beaudoin, I. Haber, R.A. Kishek
UMD, College Park, Maryland, USA

Funding: This work is supported by the US Dept. of Energy, Office of High Energy Physics.
Synchrotrons and storage rings routinely employ RF barrier buckets as a means of accumulating charge to increase the peak intensity and preserve longitudinal emittance while minimizing emittance growth [1-3]. This was shown in the main injector and recycler at Fermilab as well as the SIS-18 at GSI Helmholtz center for heavy ion research. The RF cavities typically used are ferrite loaded magnetic alloys with low Q to maximize bandwidth and generate single pulses, either as delta functions, triangular or half/full period sine waves. The University of Maryland Electron Ring (UMER) group is studying a novel scheme of bunch compression in the presence of longitudinal space charge. It has been analytically shown through 1-D computations that the presence of space-charge considerably improves the efficiency of the barrier compression by taking advantage of the shock-front that launches when the barrier moves into a space-charge dominated beam. In this paper, we summarize the initial results of the study.

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MOPMA046

Simulations and experiments in Support of Octupole Lattice Studies at the University of Maryland Electron Ring

lattice, octupole, space-charge, quadrupole

653

K.J. Ruisard, B. Beaudoin, I. Haber, T.W. Koeth
UMD, College Park, Maryland, USA

Funding: This material is based on work supported by the NSF Graduate Research Fellowship and the NSF Accelerator Science Program
We present plans for a nonlinear lattice at the University of Maryland Electron Ring (UMER). Theory predicts that a strong nonlinear lattice can limit resonant behavior without reducing dynamic aperture if the nonlinear fields preserve integrability or quasi-integrability. We discuss plans for a quasi-integrable octupole lattice, based on the work of Danilov and Nagaitsev.* We use Elegant and the WARP PIC code to estimate the octupole-induced tune spread. We discuss improvements to the ring in support of octupole lattice experiments, including generation and detection of emittance-dominated, negligible space charge beams.
* V. Danilov, S. Nagaitsev, Phys. Rev. STAB 13, 084002 (2010).

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MOPMA054

Start-to-end Simulation of Free-electron Lasers

FEL, simulation, wiggler, linac

675

C.C. Hall, S. Biedron, H. Freund, S.V. Milton
CSU, Fort Collins, Colorado, USA

Start-to-end (S2E) modeling of free-electron lasers (FELs) normally requires the use of multiple codes to correctly capture the physics in each region of the machine. Codes such as PARMELA, IMPACT-T or MICHELLE, for instance, may be used to simulate the injector. From there the linac and transport line may be handled by codes such as DIMAD, ELEGANT or IMPACT-Z. Finally, at the FEL a wiggler interaction code such as GENESIS, GINGER, or MINERVA must be used. These codes may be optimized to work with a wide range in magnitude of macro-particle numbers (from 10⁴-10⁸ in different codes) and have different input formats. It is therefore necessary to have translator codes to provide a bridge between each section. It is essential that these translators be able to preserve the statistical properties of the bunch while raising or lowering the number of macro-particles used between codes. In this work we show a suite of such translators designed to facilitate S2E simulations of an FEL with a new wiggler code, MINERVA, and use these codes to provide benchmarking of MINERVA against other common wiggler simulation codes.

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MOPMN002

Advances in Parallel Finite Element Code Suite ACE3P

cavity, simulation, radiation, SRF

702

C.-K. Ng, L. Ge, C. Ko, O. Kononenko, Z. Li, L. Xiao
SLAC, Menlo Park, California, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
New capabilities in SLAC's parallel finite element electromagnetics simulation suite ACE3P are reported. These include integrated electromagnetic (Omega3P), thermal and mechanical (TEM3P) modules for multi-physics modeling, an interface to particle-material interaction codes for calculation of radiation effects due to dark current generation (Track3P), and coupled electromagnetic (ACE3P) and beam dynamics (IMPACT) simulation. Results from these applications are presented.

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MOPMN007

An Alternate Ring-Ring Design for eRHIC

ion, collider, proton, linac

713

Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC05-06OR23177 and No. DE-AC02-06CH11357
I present here a new ring-ring design of eRHIC. It utilizes high repetition rate colliding beams and is likely able to deliver the performance to meet the requirements of the science program with low technical risk and modest accelerator R&D. The expected performance includes high luminosities over multiple collision points and a broad CM energy range with a maximum value up to 2×1034 cm^-2s⁻¹ per detector, and polarization higher than 70% for the colliding electron and light ion beams. This new design calls for reuse of decommissioned facilities in the US, namely, the PEP-II high energy ring and one section of the SLAC linac as a full energy injector.

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MOPMN012

SPACE Code for Beam-Plasma Interaction

plasma, simulation, ion, electromagnetic-fields

728

K. Yu, V. Samulyak
SBU, Stony Brook, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA

A parallel particle-in-cell code SPACE has been developed for the simulation of electromagnetic fields, relativistic particle beams, and plasmas. The algorithms include atomic processes in the plasma, proper boundary conditions, an efficient method for highly-relativistic beams in non-relativistic plasma, support for simulations in relativistic moving frames, and special data transfer algorithm from the moving to the laboratory frame that collects particles and fields in the lab frame without time shift due to the Lorentz transform, enabling data analysis and visualization. Plasma chemistry algorithms implement atomic physics processes such as the generation and evolution of plasma, recombination of plasma, and electron attachment on dopants in dense neutral gas. Benchmarks and experimental validation tests are also discussed. The code has been used for the simulation of processes relevant to the eRHIC program at BNL and the high pressure RF cavity (HPRF) program at Fermilab.

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MOPMN013

Simulation of Beam-Induced Plasma in Gas Filled Cavities

plasma, ion, simulation, cavity

731

K. Yu, V. Samulyak
SBU, Stony Brook, USA
M. Chung
UNIST, Ulsan, Republic of Korea
B.T. Freemire
IIT, Chicago, Illinois, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA
A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA

Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.

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MOPMN015

Simulation of Beam-Induced Plasma for the Mitigation of Beam-Beam Effects

plasma, proton, simulation, beam-beam-effects

734

J. Ma, V. Samulyak, K. Yu
SBU, Stony Brook, New York, USA
V. Litvinenko, V. Samulyak, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
V. Samulyak
SUNY SB, Stony Brook, New York, USA

One of the main challenges in the increase of luminosity of circular colliders is the control of the beam-beam effect. In the process of exploring beam-beam mitigation methods using plasma, we evaluated the possibility of plasma generation via ionization of neutral gas by proton beams, and performed highly resolved simulations of the beam-plasma interaction using SPACE, a 3D electromagnetic particle-in-cell code. The process of plasma generation is modelled using experimentally measured cross-section coefficients and a plasma recombination model that takes into account the presence of neutral gas and beam-induced electromagnetic fields. Numerically simulated plasma oscillations are consistent with theoretical analysis. In the beam-plasma interaction process, high-density neutral gas reduces the mean free path of plasma electrons and their acceleration. A numerical model for the drift speed as a limit of plasma electron velocity was developed. Simulations demonstrate a significant reduction of the beam electric field in the presence of plasma. Preliminary simulations using fully-ionized plasma have also been performed and compared with the case of beam-induced plasma.

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MOPMN028

Design of Bunch Compressing System with Suppression of Coherent Synchrotron Radiation for ATF Upgrade

emittance, dipole, simulation, linac

760

Y.C. Jing, M.G. Fedurin, D. Stratakis
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) is in the process of upgrading to ATF2 with higher electron beam energy thus expanding its capabilities. For the fully upgraded electron beam (500 MeV), it will be of great interest to compress the bunch to femto-seconds scale while maintaining high peak current (~7,800 amps) for users. A bunch compressor composed of magnetic chicanes can be utilized for this purpose. However, during such strong compression, beam quality can easily be deteriorated by Coherent Synchrotron Radiation (CSR). In this paper, we present our study for a bunch compressor where this CSR effect is compensated through careful manipulation of phase space. We also show a beam with good quality is preserved through the system by presenting a start to end simulation.

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MOPHA006

A Slow RF-Laser Feedback for PHIL Photoinjector

laser, feedback, gun, controls

784

N. ElKamchi, V. Chaumat, V. Soskov
LAL, Orsay, France

PHIL is an electron beam accelerator at LAL. It produces low energy (E<5 MeV) and high current (1 nC/bunch) electrons bunch at a repetition frequency of 5Hz. The stability of the beam charge at PHIL is a key issue for the succeful operation of the physic experiences that use the machine. At PHIL, the beam charge is quite stable, but we often note a slow charge drift on long duration experiences. Two ICTs, and a back-end electronics are used to monitor the stability of the beam charge, with an accuracy of about 1pC. Several types of jitter can impact the stability of the beam charge. The fluctuations of the RF power or the RF-laser relative phase drift could have significant influence, due to temperature variations that produce cables dilataion, and electronic components overheating. To correct the phase drift, we describe a method based on a slow analog-digital feedback loop between the RF wave in the gun (3 GHz) and the synchronisation signal of the laser (75MHz). It allows to maintain the jitter between the laser pulse and the RF wave stable at a very low value. As a result, the electron beam charge is maintained at a stable level, to meet the requirements of the users.

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MOPHA007

Modeling/Measurement Comparison of Signal Collection in Diamond Sensors in Extreme Conditions

space-charge, detector, simulation, scattering

787

V. Kubytskyi, P. Bambade, S. Liu
LAL, Orsay, France

Here we present a study of charge collection dynamics in a Diamond Sensor (DS) subjected to intensities from 1 to 10⁸ Minimum Ionizing Particles (MIP). We developed a model based on the numerical solution of the 1D drift-diffusion equations, using the Scharfetter-Gummel discretization scheme. Inhomogeneity of the space-charge distribution together with the externally applied electric field are taken into account by analytically solving the Poisson equation at each time step. We identified two regimes of charge collection. The first corresponds to 1-10⁵ MIPs, in this case the externally applied electric field is negligibly perturbed by space-charge effects during the separation of the electron/hole clouds. The second corresponds to intensities larger than 10⁷ MIPs, where the space-charge effects significantly slow down the charge collection due to large concentrations of electron/hole pairs in the DS volume. The results of our modeling are in qualitative agreement with the experimental data acquired at the PHoto-Injector electron beam facility at LAL. Our model allows optimizing DS parameters to achieve desired charge collection times for different beam intensities.

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MOPHA008

Investigation of Beam Halo Using In Vacuum Diamond Sensor at ATF2

pick-up, vacuum, controls, laser

791

S. Liu, P. Bambade, F. Bogard, P. Cornebise, V. Kubytskyi, C. Sylvia
LAL, Orsay, France
A. Faus-Golfe, N. Fuster-Martínez
IFIC, Valencia, Spain
T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
T. Tauchi, N. Terunuma
Sokendai, Ibaraki, Japan

Funding: Chinese Scholarship Council, CNRS and P2IO LABEX
Beam halo transverse distribution measurements are of great importance for the understanding of background sources of the nano-meter beam size monitor at the interaction point (IPBSM) of ATF2. One of the most critical issues for the beam halo measurement is to reach high dynamic range. Two in vacuum diamond sensor beam halo scanners (DSv) with four strips each have been developed for the investigation of beam halo transverse distributions at ATF2. The first DSv was installed for horizontal beam halo scanning after the interaction point (IP) of ATF2, in Nov. 2014. It aims to measure the beam halo distribution with large dynamic range (~10⁶), and investigate the possibility of probing the Compton recoil electrons produced in the interaction with the IPBSM laser beams. Studies to characterize the DS performance and measurements of horizontal beam halo performed in Nov.-Dec. 2014 are presented.

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MOPHA015

Measurement of Momentum Compaction Factor via Depolarizing Resonances at ELSA

resonance, polarization, extraction, experiment

811

J.F. Schmidt, W. Hillert, M. Schedler, J.-P. Thiry
ELSA, Bonn, Germany

Funding: DFG
Measuring beam depolarization at energies in close proximity to a depolarizing integer resonance is an established method to determine the beam energy of a circular accelerator. This technique offers high accuracy due to the small resonance widths. Thus, also other accelerator parameters related to beam energy can be measured based on this method. This contribution presents a measurement of the momentum compaction factor with a high precision of 10^-4. It was performed at the 164 m stretcher ring of the Electron Stretcher Facility ELSA at Bonn University, which provides a polarized electron beam of up to 3.2 GeV.

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MOPHA019

Implementation of a High Level Phase Controller for the Superconducting Injector of the S-DALINAC

controls, cavity, EPICS, injection

814

T. Bahlo, C. Burandt, F. Hug, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: This work has been supported by the DFG through CRC 634
The Superconducting DArmstadt LINear Accelerator S‑DALINAC is a recirculating electron accelerator with a design energy of 130 MeV. It operates in cw-mode at a radio frequency of 3 GHz and provides either unpolarized or polarized electron beams. Before entering the main accelerator the electron beam passes both, a normal-conducting injector beamline for beam preparation and a superconducting 10 MeV injector beamline for preacceleration. The phase of the beam which is injected into the 40 MeV main accelerator is crucial for the efficiency of the acceleration process and the minimization of the energy spread. Due to thermal drifts of the normal-conducting injector cavities this injection phase varies by about 0.2 degree over a timescale of an hour. In order to compensate these drifts, a high level phase controller has been implemented. It adjusts the phase measured at an rf-monitor at the exit of the superconducting injector by changing the phase of a prebuncher in the normal-conducting injector beamline. We will present the used hardware, the control algorithm as well as measurements showing the phase stabilization achieved by this controller.

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MOPHA020

Automated Transverse Beam Emittance Measurement using a Slow Wire Scanner at the S-DALINAC

emittance, quadrupole, EPICS, controls

817

P. Dijkstal, M. Arnold, C. Burandt, F. Hug, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: This work has been supported by the DFG through CRC 63 and by the EPS-AG through the EPS-AG student grant program.
The superconducting linear accelerator S-DALINAC of the TU Darmstadt provides electron beams of up to 130 MeV in cw mode. It consists of a 10 MeV injector and a 40 MeV main linac, both equipped with elliptical cavities operating in liquid helium at 2 K at a frequency of 3 GHz. The final energy is reached by using up to two recirculation paths. In order to improve beam simulations, it is planned to monitor the transverse beam emittance at different locations along the beam line. A system of slow wire scanners in combination with quadrupole variation is foreseen to accomplish this task. For a first test a wire scanner was installed in the 250 keV section behind the thermionic electron gun of the S-DALINAC. A procedure to automatize measurements was developed and integrated in the EPICS-based control system. We will show the status of the work on the automatized control and the results of first emittance measurements. A report on the future plans will be given.

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MOPHA023

Observation of Coherent Pulses in the Sub-THz Range at DELTA

radiation, detector, laser, synchrotron

823

C. Mai, F.H. Bahnsen, M. Bolsinger, S. Hilbrich, M. Huck, M. Höner, S. Khan, A. Meyer auf der Heide, R. Molo, H. Rast, G. Shayeganrad, P. Ungelenk
DELTA, Dortmund, Germany
M. Brosi, B. Kehrer, A.-S. Müller, M.J. Nasse, P. Schönfeldt, P. Schütze, S. Walther
KIT, Karlsruhe, Germany
H. Huck
DESY Zeuthen, Zeuthen, Germany

Funding: Work supported by the BMBF (05K13PEC).
Coherent ultrashort THz pulses induced by a laser-electron interaction are routinely produced and observed at DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund University. The turn-by-turn evolution of the radiation spectrum is known to shift to the sub-THz regime after the initial laser-electron interaction. Recently, an ultrafast YBCO-based THz detector has been permanently installed and a Schottky diode has been tested at the THz beamline. Measurements with these detectors showing the temporal evolution of the coherent signals after several revolutions are presented. Furthermore, the concept of a recently designed Fourier-transform spectrometer optimized for the sub-THz region is shown.

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MOPHA026

Present and Future Optical-to-Microwave Synchronization Systems at REGAE Facility for Electron Diffraction and Plasma Acceleration Experiments

laser, detector, timing, plasma

833

M. Titberidze, F.J. Grüner, A.R. Maier, B. Zeitler
CFEL, Hamburg, Germany
S.W. Epp
MPSD, Hamburg, Germany
M. Felber, K. Flöttmann, T. Lamb, U. Mavrič, J.M. Müller, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany
F.J. Grüner, A.R. Maier, M. Titberidze
Uni HH, Hamburg, Germany
E. Janas
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

Relativistic Electron Gun for Atomic Explorations (REGAE) is a Radio Frequency (RF) driven linear accelerator. It uses frequency tripled short photon pulses (~ 35 fs) from the Titanium Sapphire (Ti:Sa.) Laser system in order to generate electron bunches from the photo-cathode. The electron bunches are accelerated up to ~ 5 MeV kinetic energy and compressed down to sub-10 fs using the so called ballistic bunching technique. REGAE currently is used for electron diffraction experiments (by Prof. R.J.D. Miller's Group). In near future within the collaboration of Laboratory for Laser- and beam-driven plasma Acceleration (LAOLA), REGAE will also be employed to externally inject electron bunches into laser driven linear plasma waves. Both experiments require very precise synchronization (sub-50 fs) of the photo-injector laser and RF reference. In this paper we present experimental results of the current and new optical to microwave synchronization systems in comparison. We also address some of the issues related to the current system and give an upper limit in terms of its long-term performance.

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MOPHA027

Transverse Emittance Measurement at REGAE

emittance, detector, background, solenoid

837

M. Hachmann, K. Flöttmann
DESY, Hamburg, Germany

The linear accelerator REGAE at DESY produces short and low charged electron bunches, on the one hand to resolve the excitation transitions of atoms temporally by pump probe electron diffraction experiments and on the other hand to investigate principal mechanisms of laser plasma acceleration. For both cases a high quality electron beam is required which can be identified with a small beam emittance. A standard magnet scan is used for the emittance measurement which is in case of a low charged bunch most sensitive to the beam size determination (2nd central moment of a distribution). Therefore the diagnostic and a routine to calculate proper central moments of an arbitrary distribution will be introduced and discussed.

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MOPHA029

Operation Experiences with the MICROTCA.4-based LLRF Control System at FLASH

LLRF, operation, radiation, laser

844

M. Omet, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, M. Hoffmann, F. Ludwig, U. Mavrič, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang
DESY, Hamburg, Germany
W. Cichalewski, D.R. Makowski
TUL-DMCS, Łódź, Poland
K. Czuba, K. Oliwa, I. Rutkowski, R. Rybaniec, D. Sikora, W. Wierba, M. Żukociński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
A. Piotrowski
FastLogic Sp. z o.o., Łódź, Poland

The Free-Electron Laser in Hamburg (FLASH) at Deutsches Elektronen-Synchrotron (DESY), Hamburg Germany is a user facility providing ultra-short, femtosecond laser pulses up to the soft X-ray wavelength range. For the precise regulation of the radio frequency (RF) fields within the 60 superconducting cavities, which are organized in 5 RF stations, digital low level RF (LLRF) control systems based on the MTCA.4 standard were implemented in 2013. Until now experiences with failures potentially due to radiation, overheating, and ageing as well as with the general operation of the control systems have been gained. These have a direct impact on the operation and on the performance of FLASH and will allow future improvements. The lessons learned are not only important for FLASH but also in the scope of European X-ray Free-Electron Laser (X-FEL), which will be operated with the same LLRF control system.

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MOPHA038

Studies for a Wakefield-Optimized Near-Field EO Setup at the ANKA Storage Ring

laser, wakefield, simulation, operation

869

P. Schönfeldt, A. Borysenko, N. Hiller, B. Kehrer, A.-S. Müller
KIT, Karlsruhe, Germany

Funding: This work is funded by the BMBF contract numbers 05K10VKC, and 05K13VKA.
ANKA, the synchrotron light source of the Karlsruhe Institute of Technology (KIT), is the first storage ring with a near-field single-shot electro-optical (EO) bunch profile monitor inside its vacuum chamber. Using the method of electro-optical spectral decoding (EOSD), the current setup made it possible to study longitudinal beam dynamics (e.g. microbunching) occurring during ANKA's low-alpha-operation with sub-ps resolution (granularity). However, the setup induces strong wake-fields spanning the distance between consecutive bunches which cause heat load to the in-vacuum setup for high beam currents. This heat load in turn leads to a laser misalignment thus preventing measurements during multi-bunch operation. Fortunately, the EOSD setup also allows us to directly study these wake-fields so simulation results can be compared to measurement data. This paper reviews possible changes of the setup's geometry with respect to a reduction of the wakefield effects.

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MOPHA040

First Results of Energy Measurements with a Compact Compton Backscattering Setup at ANKA

laser, photon, detector, storage-ring

876

C. Chang, E. Bründermann, E. Hertle, N. Hiller, E. Huttel, A.-S. Müller, M.J. Nasse, M. Schuh, J.L. Steinmann
KIT, Karlsruhe, Germany
H.-W. Hübers, H. Richter
DLR, Berlin, Germany

Funding: This work is funded by the European Union under contract PITN-GA-2011-289191
An electron energy measurement setup based on the detection of Compton backscattered photons, generated by laser light scattered off the relativistic electron beam, has been proposed and developed for operation at the ANKA storage ring of the Karlsruhe Institute of Technology (KIT). In contrast to conventional methods based on head-on collisions, the setup at ANKA is, for the first time, realized in a transverse configuration where the laser beam hits the electron beam at an angle of ~90°. This makes it possible to achieve a relatively low-cost and very compact setup since it only requires a small side-port instead of a straight section. This development could benefit storage rings with restricted space or where no straight sections are available, for example due to interferences with existing beamlines. The setup and the first measurement results are presented in the paper.

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MOPHA041

Laser Wire Based Transverse Emittance Measurement of H⁻ Beam at Spallation Neutron Source

emittance, laser, neutron, dipole

879

Y. Liu, A.V. Aleksandrov, C.D. Long, A.A. Menshov, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
A laser wire based transverse emittance measurement system has been developed at the Spallation Neutron Source (SNS). The system enables a nonintrusive measurement of the transverse emittance in both directions on a 925 MeV/1 MW hydrogen ion (H⁻) beam at the high energy beam transport (HEBT) beam line.

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MOPHA043

Properties of Transition- and Synchrotron Radiation at FLUTE

radiation, synchrotron, synchrotron-radiation, detector

885

M. Schwarz, A.-S. Müller
KIT, Karlsruhe, Germany
M.T. Schmelling
MPI-K, Heidelberg, Germany

FLUTE (Ferninfrarot Linac Und Test Experiment) is a 41 MeV linear accelerator currently under construction at KIT. It is aimed at accelerator physics and THz radiation research. For this reason the machine will cover a wide range of bunch charges (1 pC up to 3 nC) and lengths (1 fs to 300 fs). One aim of FLUTE is the study of different mechanisms for the generation of intense THz pulses, such as transition- (TR) or synchrotron radiation (SR). In this contribution, we calculate and compare various pulse properties, such as spectra, and electric fields, for both TR and SR.

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MOPHA044

Testing a Digital Beam Position Stabilization for the P2-experiment at MESA

experiment, FPGA, feedback, controls

888

M. Dehn, K. Aulenbacher, J. Diefenbach, F. Fichtner, R. Herbertz, W. Klag
IKP, Mainz, Germany

Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) and German Research Foundation (DFG) under the Collaborative Research Center 1044 and the Cluster of Excellence "PRISMA"
The Mainz Energy recovering Superconducting Accelerator (MESA) will be built at the institute for nuclear physics at Mainz University. Besides the multi-turn energy recovery mode an external beam mode is foreseen to provide 155 MeV electrons of 85% polarization at 150 μA for parity violating experiments. To achieve the required stability of the main beam parameters a dedicated digital position stabilization is currently developed and tested at the Mainz Microtron (MAMI).

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MOPHA048

Beam Optimization of the DAΦNE Beam Test Facility

diagnostics, linac, software, detector

901

L.G. Foggetta, B. Buonomo
INFN/LNF, Frascati (Roma), Italy
P. Valente
INFN-Roma, Roma, Italy

The DAΦNE Beam Test Facility delivers electron and positron beam with a wide spread of parameters in charge, energy, transverse dimensions and time width. Thanks to the recent improvements of the diagnostics, all the beam parameters have been measured and optimized. In particular we report here some results on beam transverse size, divergence, and position stability for different energy and intensity configurations. After the upgrade of the electronic gun of the DAΦNE LINAC, the pulse time width and charge distribution have been also characterized.

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MOPHA050

Online Spill Intensity Monitoring for Improving Extraction Quality at CNAO

proton, ion, electronics, extraction

907

M. Caldara
University of Bergamo, Bergamo, Italy
J. Bosser, G.M.A. Calvi, L. Lanzavecchia, A. Parravicini, C. Viviani
CNAO Foundation, Milan, Italy
E. Rojatti
UniPV, Pavia, Italy

The CNAO Foundation is the first Italian center for deep hadrontherapy with Protons and Carbon Ions, performing treatments since September 2011. The extracted beam energy and intensity can vary over a wide range (60-250 MeV for Protons and 120-400 MeV/u for Carbon Ions, 4e6/10¹⁰ pps); the beam intensity uniformity during the slow extraction process is a fundamental requirement for achieving accurate and fast treatments. CNAO developed an online Fast Intensity Monitor (FIM), not perturbing the extracted beam, capable of measuring beam intensity with a bandwidth of 50kHz and a resolution of 1%. It consists of a thin (0.8 μm) metallic foil that emits secondary electrons when traversed by the beam. The electrons are multiplied by a Channeltron device, polarized at high voltage versus ground. The Channeltron output current is amplified and converted in a Pulse Width Modulated (PWM) signal, which is then decoupled and transmitted to the equipment room, where an FPGA implements a servo-spill. The work presents the detector, the floating electronics, the preliminary measurements with beam and the integration in a closed loop on the synchrotron air-core quadrupole obtaining promising results.

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MOPTY002

Bunch Length Measurement of Femtosecond Electron Beam by Monitoring Coherent Transition Radiation

detector, radiation, gun, linac

940

I. Nozawa, M. Gohdo, K. Kan, T. Kondoh, A. Ogata, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

Ultrashort electron bunches with durations of femtoseconds and attoseconds are essential for time-resolved measurements, including pulse radiolysis and ultrafast electron microscopy. However, generation of the ultrashort electron bunches is commonly difficult because of bunch length growth due to space charge effect, nonlinear momentum dispersion and so on. Several bunch length measurement methods for the ultrashort electron beams have also been considered so far, which have not been established yet. In this study, the femtosecond electron beams were generated using a laser photocathode radio-frequency gun linac and a magnetic bunch compressor. The bunch length measurement was carried out using a Michelson interferometer based on monitoring coherent transition radiation (CTR), which is characterized by square modulus of the Fourier transform of the longitudinal bunch distribution. Analyzing the experimentally obtained interferograms of CTR, the electron beams with the average duration of 5 fs were generated and measured successfully at the condition of bunch charge of 1 pC. Consideration of the longitudinal bunch shapes was also carried out using the Kramers-Kronig relation.

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MOPTY014

An Experimental Study of Higher-Order Modes Excited by High Repetition Rate Electron Beam in an SRF Cavity

HOM, SRF, cavity, experiment

965

Y. Gao, J.E. Chen, L.W. Feng, J.K. Hao, S. Huang, L. Lin, K.X. Liu, X. Luo, S.W. Quan, F. Wang, Zh.W. Wang
PKU, Beijing, People's Republic of China

Funding: National Natural Science Foundation of China (No. 11275014)
Higher-order modes (HOMs) excited by electron beam traversing a superconducting rf (SRF) cavity contain lots of information and can be used for intra-cavity electron beam diagnostics. Unlike single bunch, multiple bunches would excite HOMs with a much complicated spectrum. In this paper, we present our recent research on HOMs excited by a high repetition rate electron beam in an SRF cavity. Especially, we focus on the integer multiple frequency peaks in the HOM spectrum, which are determined by the nearest eigen HOM peaks. The experiments were carried out on the DC-SRF photoinjector, which was operated at MHz repetition rate. The results agree well with theoretic analysis.

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MOPTY015

Beam Compression Dynamics and Associated Measurement Methods in Superconducting THz Source

controls, simulation, space-charge, gun

969

Z. Zhou, Y.-C. Du, W.-H. Huang
TUB, Beijing, People's Republic of China

To ensure the quality of high brightness electron beams needed by the terahertz FEL facility at China academy of engineering physics(CAEP), which aims to obtain 100 to 300 terahertz light, a feed-back control system is required to monitor the amplitude and phase jittering by measuring beam arrival time as well as bunch length at the site of the beam position monitor(BPM). In this paper, we make an idealized model of injector section and deduce analytic expressions of bunch arrival time and bunch length. In consideration of the space charge effect on bunch lengthening, bunch arrival time and bunch length as a function of DC gun voltage, buncher field amplitude and buncher phase is carefully calibrated by means of particle in cell (PIC) simulation. With the time and space resolution of the BPM, the control accuracy of phase is estimated to be 0.01 degree, while the amplitude is 0.04%.

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MOPTY034

Distributed Beam Loss Monitor Based on the Cherenkov Effect in Optical Fiber

radiation, positron, beam-losses, storage-ring

1004

Yu. Maltseva, F.A. Emanov, A.V. Petrenko, V.G. Prisekin
BINP SB RAS, Novosibirsk, Russia
F.A. Emanov
NSU, Novosibirsk, Russia
A.V. Petrenko
CERN, Geneva, Switzerland

A distributed beam loss monitor based on the Cherenkov effect in optical fiber has been implemented for the VEPP5 electron and positron linacs and the 510 MeV damping ring at the Budker INP. The monitor operation is based on detection of the Cherenkov radiation generated in optical fiber by means of relativistic particles created in electromagnetic shower after highly relativistic beam particles (electrons or positrons) hit the vacuum pipe. The main advantage of the distributed monitor compared to local ones is that a long optical fiber section can be used instead of a large number of local beam loss monitors. In our experiments the Cherenkov light was detected by photomultiplier tube (PMT). Timing of PMT signal gives the location of the beam loss. In the experiment with 20 m long optical fiber we achieved 3 m spatial resolution. To improve spatial resolution optimization and selection process of optical fiber and PMT are needed and according to our theoretical estimations 0.5 m spatial resolution can be achieved. We also suggest similar techniques for detection of electron (or positron) losses due to Touschek effect in storage rings.

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MOPTY041

Prototype Results with a Complete Beam Loss Monitor System Optimized for Synchrotron Light Sources

detector, injection, electronics, impedance

1019

P. Leban
I-Tech, Solkan, Slovenia
K.B. Scheidt
ESRF, Grenoble, France

Beam loss monitors in synchrotron light sources are finding an increasing utility in particular with the trend of numerous light sources pushing to lower emittances and thus higher intra-beam scattering, while operating in top-up injection modes and employing in-vacuum undulators in their rings. The development of an optimized electron BeamLoss Monitor aims at fulfilling, in one single system, all possible functionalities and applications like both the measurement of fast-time-resolved losses at injection and the possibility of ultra-sensitive detection of low & slow electron loss level variations. This optimized beam loss monitor system comprises both the acquisition electronics and up to four sensor head per unit. The sensor heads themselves, that can be configured for different sizes or volumes, are based on the detection of the electromagnetic shower resulting from an electron loss through the use of either Cherenkov radiator or gamma scintillator and a photomultiplier tube, all assembled in a single compact housing ready for installation.

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MOPTY058

Response of Polycrystalline Diamond Particle Detectors Measured with a High Intensity Electron Beam

detector, experiment, radiation, beam-losses

1069

O. Stein, F. Burkart, B. Dehning, R. Schmidt, C.B. Sørensen, D. Wollmann
CERN, Geneva, Switzerland
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria

Comprehensive understanding of beam losses in the LHC is required to ensure full machine protection and efficient operation. The existing BLM system using ionization chambers is not adequate to resolve losses with a time resolution below some 10 us. Ionization chambers are also not adequate to measure very large transient losses, e.g. beam impacting on collimators. Diamond particle detectors with bunch-by-bunch resolution have therefore been used in LHC to measure fast particle losses with a time resolution down to a level of single bunches. Diamond detectors have also successfully been used for material damage studies in other facilities, e.g. HiRadMat at the CERN-SPS. To fully understand their potential, such detectors were characterized with an electron beam at the BTF in LNF INFN Italy, with bunch intensities from 10³ to 10⁹ electrons. The detector response and efficiency has been measured with a 50 Ω and a 1 Ω read-out system. This paper describes the experimental setup and the results of the experiment. In particular, the responses of three samples of 100 um single-crystalline diamond detectors and two samples of 500 um polycrystalline diamond detectors are presented.

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MOPTY065

Beam Stability of the Taiwan Light Source Storage Ring

betatron, storage-ring, injection, network

1091

H.C. Chen, H.H. Chen, Y.-S. Cheng, S.J. Huang, C.H. Kuo, J.A. Li, Y.K. Lin
NSRRC, Hsinchu, Taiwan

The Taiwan Light Source Storage Ring (SR) has been in operation since many years ago. Maintaining best stability of the electron beam is becoming the main challenge. This study endeavored to improve the electron beam stability of The Taiwan Light Source Storage Ring (SR). Employing the artificial neural network (ANN)-constructed experiment design to analyze and optimize the storage ring betatron tunes .This report outlines the details of the beam stability process experiment.

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MOPTY079

The Installation and Operation of TPS Laser PSD System in TPS Storage Ring

laser, storage-ring, alignment, operation

1123

M.L. Chen, J.-R. Chen, P.S.D. Chuang, H.C. Ho, K.H. Hsu, D.-G. Huang, C.K. Kuan, W.Y. Lai, C.J. Lin, S.Y. Perng, T.C. Tseng, H.S. Wang
NSRRC, Hsinchu, Taiwan

24 sets of Laser PSD positioning system are parts of the TPS girder auto¬alignment system. Laser PSD positioning systems are installed in the straight¬ section girders of TPS storage ring. The Laser PSD systems are assembled and calibrated in the Lab beforehand. The Laser and PSDs are assembled on girder and transported to TPS storage ring and Installed. During construction the system deviates from the normal position caused by variant temperature and external influence. For absolute position precision, another laser calibration system should be built to recalibrate the laser PSD system. This paper describes the installation of Laser PSD system in TPS storage ring and the status of the PSD system. A new absolute position calibration method for precision upgrade is also discussed.

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MOPTY083

Progress towards Electron-beam Feedback at the Nanometre Level at the Accelerator Test Facility (ATF2) at KEK

feedback, cavity, kicker, extraction

1133

P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland

Ultra-low latency beam-based digital feedbacks have been developed by the Feedback On Nanosecond Timescales (FONT) Group and tested at the Accelerator Test Facility (ATF2) at KEK in a programme aimed at beam stabilisation at the nanometre level at the ATF2 final focus. Three prototypes were tested: 1) A feedback system based on high-resolution stripline BPMs was used to stabilise the beam orbit in the beamline region c. 50m upstream of the final focus. 2) Information from this system was used in a feed-forward mode to stabilise the beam locally at the final focus. 3) A final-focus local feedback system utilising cavity BPMs was deployed. In all three cases the degree of beam stabilisation was observed in high-precision cavity BPMs at the ATF2 interaction point. Latest results are reported on stabilising the beam position to below 100 nanometres.

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MOPTY084

Design, Testing and Performance Results of a High-resolution, Broad-band, Low-latency Stripline Beam Position Monitor System

operation, collider, laser, FPGA

1136

P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland

A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. The fast analogue front-end signal processor is based on a single-stage RF down-mixer. The processor latency is 15.6 ± 0.1 ns. A position resolution below 300 nm has been demonstrated for beam intensities of around 1 nC, with single-pass beam.

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MOPWI004

Novel Single Shot Bunch Length Diagnostic using Coherent Diffraction Radiation

radiation, experiment, laser, optics

1150

R.B. Fiorito, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
A.G. Shkvarunets
UMD, College Park, Maryland, USA

Funding: European Union’s grant agreement no. 624890 and STFC Cockcroft core grant No. ST/G008248/1; US Office of Naval Research and DOD Joint Technology Office.
Current beam bunch length monitors which measure the spectral content of beam-associated coherent radiation to determine the longitudinal bunch form factor usually require wide bandwidth detection or Fourier transformation of interferometric data and multiple beam pulses. The data must then be Fourier transformed to obtain the bunch length. In this contribution we discuss progress in the development of a novel single shot method that utilizes the frequency integrated angular distribution (AD) of coherent diffraction radiation (CDR) to measure the RMS bunch length directly. We also present simulation results which show how the AD changes with bunch length for several electron beam linacs, where we are planning to test this new method, our single shot measurement technique and plans for comparison to other bunch length monitors.

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MOPWI006

Development of a Supersonic Gas-jet Monitor to Measure Beam Profile Non-destructively

ion, vacuum, storage-ring, experiment

1157

H.D. Zhang, A. Jeff, V. Tzoganis, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
A. Jeff
CERN, Geneva, Switzerland
A. Jeff, V. Tzoganis, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom
V. Tzoganis
RIKEN, Saitama, Japan

Funding: This project is supported by Helmholtz Association(VH-NG-328), EU’s 7th Framework Program for research, technological development and demonstration( 215080) and STFC Cockcroft core grant(ST/G008248/1).
The measurement of the transverse beam profile is a great challenge for high intensity, high brightness and high power particle beams due to their destructive power. Current non-destructive methods such as residual gas monitors and beam induced fluorescence monitors either require a rather long integration time or residual gas pressures in the order of 10^-7 mbar to make meaningful measurements. A supersonic gas-jet beam profile monitor has been developed by QUASAR group at the Cockcroft Institute, UK and promises significant improvements over these established techniques. In this monitor, a supersonic gas curtain is generated that crosses the beam to be analyzed under an angle of 45°. When both beams interact, ionization of the gas jet particles occurs and these ions are then accelerated by an electrostatic extraction field towards a Micro Channel Plate (MCP). Beam images are then obtained via a phosphor screen-CCD camera combination. In this contribution, we discuss the monitor design and present beam profile measurements of a 5 keV electron beam. These are complemented by results from measurements using a pulsed valve to study the gas jet dynamics.

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MOPWI009

A Multi-pinhole Faraday Cup Device for Measurement of Discrete Charge Distribution of Heavy and Light Ions

ion, diagnostics, experiment, vacuum

1160

P.K. Roy, S. Dwaraknath, F.U. Naab, S. Taller, O.F. Toader, G. Was
NERS-UM, Ann Arbor, Michigan, USA

It is a difficult task to identify the beam density distribution profile over discrete areas using a standard Faraday cup, as the measurements are provided for the full aperture geometry of the instrument. Ideally, the intensity of the scintillating material would provide a correlation to the beam density, but the low photon efficiency, damage to the scintillator, and camera resolution all limit the practicality of using this system for assessing the spatial resolution of an ion beam. A beam profile monitor (BPM) device has the ability to provide a partial or discrete distribution of an integrated beam profile. The BPM, however, does not discriminate between ions and electrons, the latter of which can be problematic for assessing the full beam profile. To provide a better description of the beam density in spatial dimensions, a multi-pinhole Faraday cup (MPFC) has been designed, developed, and applied to the measurement of energetic ions. This device uses an array of millimeter sized Faraday cups arranged in a grid to measure the current of the beam at discrete locations. This report presents the design of the device, and its performance with ion beams.

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MOPWI014

Design and Development for the Next Generation X-ray Beam Position Monitor System at the APS

undulator, background, photon, coupling

1175

B.X. Yang, G. Decker, Y. Jaski, S.-H. Lee, M. Ramanathan, N. Sereno, F. Westferro
ANL, Argonne, Ilinois, USA

Funding: Work performed at Argonne National Laboratory, operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
The proposed Advanced Photon Source (APS) Upgrade will bring storage-ring beam sizes down to several micrometers and require x-ray beam directional stability in 100 nrad range for undulator power exceeding 16 kW. The next generation x-ray beam position monitors (XBPMs) are designed to meet these requirements. We present first commissioning data on the recently installed grazing-incidence insertion device x-ray beam position monitor (GRID-XBPM) based on Cu K-edge x-ray fluorescence from limiting absorbers of the front end for two inline undulators. It demonstrated a 50-fold improvement for signal-to-background ratio over existing photoemission-based XBPMs. Techniques for calibrating the XBPMs will be discussed. We will also present a new XBPM design based Compton scattering from diamond blades. This XBPM is designed for less powerful undulators such as the APS canted-undulator beamlines where each undulator generates < 10 kW of beam power. We will discuss the thermal design of the blade, the optics design of the detector assembly, and computer simulations of expected response to the x-ray beam. Test data of the prototype may be presented if available.

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MOPWI015

A Low Time-Dispersion Refractive Optical Transmission Line for Streak Camera Measurements

experiment, database, resonance, plasma

1178

J.G. Power, G. Ha
ANL, Argonne, Illinois, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: Work supported by the U.S. Department of Energy office of High Energy Physics.
Streak camera measurements of the charge particle bunch length are limited in resolution due to several factors: (1) the light from the source (optical transition radiation, Cherenkov, synchrotron radiation, etc.); (2) time dispersion introduced in the optical transmission line between the source and the streak camera; and finally (3) the streak camera resolution. The limiting resolution usually arises from the optical transmission line. While an all-reflective transmission line can eliminate dispersion, the system is complicated and expensive. In this paper, we consider how to design a refractive optical transport line to minimize the time dispersion while maximizing the signal. We present a theoretical model of the dispersion, modeling, and measurements of the time dispersion for several different lens materials.

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MOPWI016

Development of a Versatile Bunch-length Monitor for Electron Beams at ASTA

laser, radiation, linac, optics

1181

A.H. Lumpkin, D.J. Crawford, D.R. Edstrom, J. Ruan, J.K. Santucci, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the United States Department of Energy.
The generation of bright electron beams at the ASTA/IOTA facility at Fermilab includes implementation of a versatile bunch-length monitor located after the 4-dipole chicane bunch compressor for electron beam energies of 20-50 MeV and integrated charges in excess of 10 nC. The station will include both a Hamamatsu C5680 synchroscan streak camera and a Martin-Puplett interferometer (MPI). An Al-coated Si screen will be used to generate both optical transition radiation (OTR) and coherent transition radiation (CTR) during the beam’s interaction with the screen. A chicane bypass beamline will allow the measurement of the initial bunch length at the same downstream beamline location using OTR and the streak camera. The UV component of the drive laser has previously been characterized with a Gaussian fit σ of 3.5 ps*, and the uncompressed electron beam is expected to be similar to this value at low charge per micropulse. In addition, OTR will be transported to the streak camera from the focal plane of the downstream spectrometer to provide an E-t distribution within the micropulse time scale. Commissioning of the system and initial results with beam will be presented as available.
*A.H. Lumpkin et al., Proceedings of FEL14, MOP021, Basel, Switzerland, www. JACoW.org.

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MOPWI018

New Hadron Monitor By Using A Gas-Filled RF Resonator

plasma, hadron, proton, radiation

1189

K. Yonehara, A.V. Tollestrup, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
G. Fasce
CNI, Roma, Italy
G. Flanagan, R.P. Johnson
Muons, Inc, Illinois, USA

It is trend to build an intense neutrino beam facility for the fundamental physics research, e.g. LBNF at Fermilab, T2K at KEK, and CNGS at CERN. They have investigated a hadron monitor to diagnose the primary/secondary beam quality. The existing hadron monitor based on an ionization chamber is not robust in the high-radiation environment vicinity of MW-class secondary particle production targets. We propose a gas-filled RF resonator to use as the hadron monitor since it is simple and hence radiation robust in this environment. When charged particles pass through the resonator they produce ionized plasma via the Coulomb interaction with the inert gas. The beam-induced plasma changes the permittivity of inert gas. As a result, a resonant frequency in the resonator shifts with the amount of ionized electrons. The radiation sensitivity is adjustable by the inert gas pressure and the RF amplitude. The hadron profile will be reconstructed with a tomography technique in the hodoscope which consists of X, Y, and theta layers by using a strip-shaped gas resonator. The sensitivity and possible system design will be shown in this presentation.

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MOPWI022

Experimental Study of a Two-Color Storage Ring FEL

FEL, wiggler, operation, storage-ring

1198

J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA
S. Huang
PKU, Beijing, People's Republic of China
J.Y. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia
J. Wu
SLAC, Menlo Park, California, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Multi-color Free-electron Lasers (FELs) have been developed on linac based FELs over the past two decades. On the storage ring, the optical klystron (OK) FEL in its early days was demonstrated to produce lasing at two adjacent wavelengths with their spectral separation limited by the bandwidth of single wiggler radiation. Here, we report a systematic experimental study on the two-color operation at the Duke FEL facility, the first experimental demonstration of a tunable two-color harmonic FEL operation of a storage ring based FEL. We demonstrate a simultaneous generation of two FEL wavelengths, one in infrared (IR) and the other in ultraviolet (UV) with a harmonic relationship. The experimental results show a good performance of the two-color FEL operation in terms of two-color wavelength tunability, power tunability and power stability.

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MOPWI029

Electron Bombardment of ZnTe EO Bunch Charge Detector for Signal Lifetime Studies in Radiation Environment

lattice, detector, laser, radiation

1220

J.E. Williams, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
S.V. Benson, S. Zhang
JLab, Newport News, Virginia, USA

Electro-optic detection of bunch charge distribution utilizing the nonlinear Pockel's and Kerr effect of materials has been implemented at various facilities as a method of passive detection for beam preservation throughout characterization. Most commonly, the inorganic II-VI material ZnTe is employed due to it's strong Pockel's EO effect and relatively high temporal resolution (~90 fs). Despite early exploration of radiation damage on ZnTe in exploration of semi-conductor materials in the 1970's, full characterization of EO response over radiation lifetime has yet to be performed. The following poster presents a method for ZnTe crystal characterization studies throughout radiation exposure at various energies and dosages by analyzing the changes in index of refraction including bulk uniformity, and THz signal response changes.

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MOPWI031

Microwave Modeling for Electron Cloud Density Measurements at CesrTA

simulation, resonance, synchrotron, storage-ring

1227

J.P. Sikora, Y. Li
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
S. De Santis
LBNL, Berkeley, California, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
The electron cloud (EC) density in accelerator beam-pipe has been measured using resonant microwaves. The resonances are produced by changes in beam-pipe geometry that generate reflections and standing waves, with typical behavior being similar to a section of waveguide with shorted ends. The technique uses fact that the EC density will shift the resonant frequencies. In previous analysis, we have made the simplifying approximation that the standing waves are multiples of a half-wavelength and that the magnitude of the electric field is symmetric about the longitudinal center of the resonance. In this paper we show that some changes in beam-pipe geometry will result in asymmetric electric field magnitudes along the resonant length. When this is combined with an EC density that varies along this length, the magnitude of the frequency shift will be altered. We present our initial attempt to correct for this effect by modeling the existing beam-pipe using CST Microwave Studio(R) to obtain a more realistic electric field distribution. This correction is then applied to data taken with beam at several resonant frequencies. The measurements were made at the Cornell Electron Storage Ring (CESR), which has been reconfigured as a test accelerator (CesrTA) providing electron or positron beams ranging in energy from 2 to 5 GeV.
* http://dx.doi.org/10.1016/j.nima.2014.03.063

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MOPWI032

Analysis of Primary Stripper Foils at SNS by an Electron Beam Foil Test Stand

proton, gun, operation, experiment

1230

E.P. Barrowclough, C.S. Feigerle
University of Tennessee, Knoxville, Tennessee, USA
C.F. Luck, M.A. Plum, R.W. Shaw, L.L. Wilson
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Diamond foils are used at the Spallation Neutron Source (SNS) as the primary strippers of hydride ions. A nanocrystalline diamond film, typically 17x45 mm with an aerial density of 0.35 mg/cm², is deposited on a corrugated silicon substrate by plasma-assisted chemical vapor deposition. After growth, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon handle that can be inserted into SNS for operation. An electron beam test facility was constructed to study stripper foil degradation and impact on foil lifetime. The electron beam capabilities include: current up to 5 mA, focused spot size of 0.30 mm², and rastering in the x- and y-directions. A 30 keV and 1.6 mA/mm² electron beam deposits the same power density on a diamond foil as a 1.4 MW beam on SNS target. Rastering of the electron beam can expose a similar area of the foil as SNS beams. Experiments were conducted using the foil test stand to study: foil flutter and lifetime; effects of corrugation patterns, aerial densities, crystal size (micro vs. nano), and boron doping; temperature distributions and film emissivity; and conversion rate of nanocrystalline diamond into graphite.

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TUXB3

700 kW Main Injector Operations for NOvA at FNAL

booster, proton, operation, experiment

1286

P. Adamson
Fermilab, Batavia, Illinois, USA

Following a successful career as an antiproton storage and cooling ring, the Fermilab Recycler was repurposed as a proton stacker as part of the NOvA project, in order to increase the maximum NuMI beam power from 400 kW to 700 kW. Using the Recycler to prepare beam for acceleration in the Main Injector, we have been able to increase the beam power delivered to NuMI to a sustained weekly average in excess of 400 kW and a best hourly average of 482.8 kW. I discuss the commissioning progress to date, and describe the remaining steps along the way to achieving the 700 kW design goal.

Slides TUXB3 [3.401 MB]

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TUYB1

Progress of SuperKEKB

emittance, positron, gun, linac

1291

T. Miura, T. Abe, T. Adachi, K. Akai, M. Akemoto, A. Akiyama, D.A. Arakawa, Y. Arakida, Y. Arimoto, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J.W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, H. Hisamatsu, H. Honma, T. Honma, R. Ichimiya, N. Iida, H. Iinuma, H. Ikeda, M. Ikeda, T. Ishibashi, H. Ishii, M. Iwasaki, A. Kabe, T. Kageyama, H. Kaji, K. Kakihara, S. Kamada, T. Kamitani, S. Kanaeda, K. Kanazawa, H. Katagiri, S. Kato, S. Kazama, M. Kikuchi, T. Kobayashi, H. Koiso, Y. Kojima, M. Kurashina, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, F. Miyahara, K. Mori, T. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T.T. Nakamura, K. Nakanishi, K. Nakao, H. Nakayama, T. Natsui, M. Nishiwaki, J.-I. Odagiri, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, K. Oide, T. Oki, M. Ono, H. Sakai, Y. Sakamoto, S. Sasaki, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, M. Suetake, Y. Suetsugu, R. Sugahara, H. Sugimoto, T. Suwada, S. Takasaki, T. Takatomi, T. Takenaka, Y. Takeuchi, M. Tanaka, M. Tawada, S. Terui, M. Tobiyama, N. Tokuda, K. Tsuchiya, X. Wang, K. Watanabe, H. Yamaoka, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S.I. Yoshimoto, K. Yoshino, R. Zhang, D. Zhou, X. Zhou, Z.G. Zong
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

This presentation will cover the status of the installation and the injector commissioning status of SuperKEKB. The IR optics and design with very low β^* of less than 1 mm will be discussed.

Slides TUYB1 [6.588 MB]

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TUYB2

Accelerator Physics in ERL Based Polarized Electron Ion Collider

ion, linac, luminosity, radiation

1296

Y. Hao
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This talk will present the current accelerator physics challenges and solutions in designing ERL-based polarized electron-hadron colliders, and illustrate them with examples from eRHIC and LHeC designs. These challenges include multi-pass ERL design, highly HOM-damped SRF linacs, cost effective FFAG arcs, suppression of kink instability due to beam-beam effect, and control of ion accumulation and fast ion instabilities.

Slides TUYB2 [14.101 MB]

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TUYB3

Progress on the Design of the Polarized Medium-energy Electron Ion Collider at JLab

ion, collider, polarization, luminosity

1302

F. Lin, S.A. Bogacz, P.D. Brindza, A. Camsonne, E. Daly, Y.S. Derbenev, D. Douglas, R. Ent, D. Gaskell, R.L. Geng, J.M. Grames, J. Guo, L. Harwood, A. Hutton, K. Jordan, A.J. Kimber, G.A. Krafft, R. Li, T.J. Michalski, V.S. Morozov, P. Nadel-Turonski, F.C. Pilat, M. Poelker, R.A. Rimmer, Y. Roblin, T. Satogata, M. Spata, R. Suleiman, A.V. Sy, C. Tennant, H. Wang, S. Wang, H. Zhang, Y. Zhang, Z.W. Zhao
JLab, Newport News, Virginia, USA
S. Abeyratne, B. Erdelyi
Northern Illinois University, DeKalb, Illinois, USA
D.P. Barber
DESY, Hamburg, Germany
Y. Cai, Y. Nosochkov, M.K. Sullivan, M.-H. Wang, U. Wienands
SLAC, Menlo Park, California, USA
A. Castilla, J.R. Delayen
ODU, Norfolk, Virginia, USA
Y. Filatov
JINR, Dubna, Russia
J. Gerity, T.L. Mann, P.M. McIntyre, N. Pogue, A. Sattarov
Texas A&M University, College Station, Texas, USA
C. Hyde, K. Park
Old Dominion University, Norfolk, Virginia, USA
A.M. Kondratenko, M.A. Kondratenko
Science and Technique Laboratory Zaryad, Novosibirsk, Russia
P.N. Ostroumov
ANL, Argonne, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
The Medium-energy Electron Ion Collider (MEIC) at JLab is designed to provide high luminosity and high polarization needed to reach new frontiers in the exploration of nuclear structure. The luminosity, exceeding 1033 cm^-2s⁻¹ in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm^-2s⁻¹, is achieved by high-rate collisions of short small-emittance low-charge bunches made possible by high-energy electron cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) can be easily preserved and manipulated due to the unique figure-8 shape of the collider rings. A fully consistent set of parameters have been developed considering the balance of machine performance, required technical development and cost. This paper reports recent progress on the MEIC accelerator design including electron and ion complexes, integrated interaction region design, figure-8-ring-based electron and ion polarization schemes, RF/SRF systems and ERL-based high-energy electron cooling. Luminosity performance is also presented for the MEIC baseline design.

Slides TUYB3 [6.245 MB]

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TUYC2

Multi-GeV Plasma Acceleration Results at BELLA

laser, plasma, experiment, injection

1319

A.J. Gonsalves, C. Benedetti, S.S. Bulanov, J. Daniels, E. Esarey, C.G.R. Geddes, H.S. Mao, D.E. Mittelberger, K. Nakamura, C.B. Schroeder, C. Tóth, J. van Tilborg
LBNL, Berkeley, California, USA
W. Leemans
UCB, Berkeley, California, USA

Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231
Laser-plasma accelerators (LPAs)* are being investigated as a compact driver for light sources and high-energy linear colliders. Recently 2 GeV beams were generated by focusing ≈ 100 J laser pulses onto a gas target**. We report here on the generation of beams with energy up to 4.2 GeV using 16 J of laser pulse energy at the BErkeley Lab Laser Accelerator (BELLA)***. This was achieved by using laser pulses of high spatial and temporal quality coupled to a pre-formed capillary discharge waveguide of length 9 cm. The waveguide (in conjunction with self-guiding) allowed for mitigation of diffraction. High spatial quality (Strehl ratio at focus 0.8±0.1) was achieved using a deformable mirror placed before the focusing optic. The dominant contribution to the non-Gaussian content of the focal spot was the near-field intensity profile. For maximum efficiency high-power femtosecond systems employ super-Gaussian near-field profiles of the form I(r)∝e^-2(r/w^N), where I is the intensity, r is the radial coordinate, w is the spot size, and N is the order. Compared with Gaussian laser pulses where N=2, pulses from the BELLA laser system had N=10. Simulations showed that an increased contribution of self-guiding was required to effectively confine the laser energy for optimum acceleration and mitigation of damage to the capillary waveguide. Through appropriate choice of plasma density electron beams with energy up to 4.2 GeV were observed. In this regime the electron beam angular fluctuations were > 2 mrad rms, caused in part by errors in waveguide alignment and by laser-induced damage to the capillary that introduces plasma asymmetry. Improved alignment of the waveguide and mitigation of capillary damage allowed for reduction in angular fluctuations to 0.6 mrad rms. The electron beams had energy of 2.7±0.1 GeV, charge of 150 pC, and divergence less than 1 mrad.
* E. Esarey, et al., Rev. Mod. Phys. 81, 1229 (2009)
** X. Wang, et al., Nat. Communications 4, 1988 (2013)
*** W. P. Leemans, et al., Phys. Rev. Lett. 113, 245002 (2014)

Slides TUYC2 [13.023 MB]

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TUYC3

Scaling Down Synchronous Acceleration: Recent Results, Current Status, and Future Plans of a Subrelativistic Dielectric Laser Acceleration Project

laser, acceleration, experiment, focusing

1325

J.C. McNeur, P. Hommelhoff, M. Kozak, A. Li, N. Schönenberger, A.D. Tafel
University of Erlangen-Nuremberg, Erlangen, Germany

This talk will describe the latest results using laser powered dielectric accelerators. Recent experiments in the US (SLAC) and Europe (MPQ) have fabricated dielectric accelerators powered with optical lasers and used them to accelerate electrons with gradients between 25 and 300 MeV/m. The latest results will be reviewed and prospects and applications for the future will be discussed.

Slides TUYC3 [21.295 MB]

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TUBC2

Multi-GHz Pulse-Train X-Band Capability for Laser Compton X-Ray and Gamma-Ray Sources

laser, brightness, scattering, photon

1363

D.J. Gibson, G.G. Anderson, S.G. Anderson, C.P.J. Barty, R.A. Marsh, M. J. Messerly, M.A. Prantil
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
A wide variety of light-source applications would benefit from increased average brightness, which generally corresponds to increasing average current in the driving accelerator. Presented is an accelerator architecture that is capable of producing hundreds of electron bunches, spaced as close together as every RF cycle, which provides the chance to increase current while maintaining beam quality. This system relies on an X-band photoinjector and a photoinjection drive laser that is driven by the same rf source to ensure synchronization, and an interaction laser system designed to match the duty cycle of the electron pulse train. Results of the photoinjector laser performance and initial experimental measurements of beam quality in accelerated bunch trains are presented, along with a discussion of the impact on the performance of tunable, narrow-bandwidth x-ray and gamma-ray beams based on Compton-scattering.

Slides TUBC2 [20.256 MB]

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TUBC3

Recent Results from FEL seeding at FLASH

FEL, laser, operation, radiation

1366

J. Bödewadt, S. Ackermann, R.W. Aßmann, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, R. Ivanov, T. Laarmann, J.M. Müller, T. Tanikawa
DESY, Hamburg, Germany
S. Ackermann, Ph. Amstutz, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach
Uni HH, Hamburg, Germany
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany

The free-electron laser facility FLASH at DESY operates since several years in SASE mode, delivering high-intensity FEL pulses in the extreme ultra violet and soft x-ray wavelength range for users. In order to get more control of the characteristics of the FEL pulses external FEL seeding has proven to be a reliable method to do so. At FLASH, an experimental setup to test several different external seeding methods has been installed since 2010. After successful demonstration of direct seeding at 38 nm, the setup is now being operated in HGHG and later EEHG mode. Furthermore, other studies on laser induced effects on the electron beam dynamics have been performed. In this contribution, we give an overview of recent experimental results on FEL seeding at FLASH.

Slides TUBC3 [6.651 MB]

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TUPWA001

Measurement of the Incoherent Depth of Field Effect on Horizontal Beam Size Using a Synchrotron Light Interferometer

photon, synchrotron, storage-ring, lattice

1391

M.J. Boland
SLSA, Clayton, Australia
W.J. Corbett
SLAC, Menlo Park, California, USA
T.M. Mitsuhashi
KEK, Ibaraki, Japan

The electron beam size as measured using synchrotron light in a circular accelerator is influenced by the incoherent depth of field effect. This effect comes about due to the instantaneous opening angle of the emitted synchrotron radiation (SR) and the acceptance angle of the SR light monitor beamline. Measurements were made using a visible light interferometer at the visible light beamlines in three circular accelerators at ATF, SPEAR3 and AS. The first order spatial coherence of the beam was measured and from that the horizontal beam size was calculated. The data is compared with a theory of synchrotron radiation with and without the horizontal incoherent field depth effect.

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TUPWA005

Comparison of Bunch Compression Schemes for the AXXS FEL

linac, simulation, FEL, synchrotron

1399

T.K. Charles, D.M. Paganin
Monash University, Faculty of Science, Clayton, Victoria, Australia
A.A. Aksoy
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
M.J. Boland, R.T. Dowd
SLSA, Clayton, Australia
A. Latina, D. Schulte
CERN, Geneva, Switzerland

Different types of electron bunch compression schemes are compared for the AXXS FEL design study. The main linac for the proposed machine is based on CLIC x-band structures. This choice leaves several options for the bunch compression schemes which impact the injection system RF band. Both harmonic linearization and phase modulation linearization are considered and their relative strengths and weaknesses compared. Simulations were performed to compare the performance of an s-band injector with a higher harmonic RF linearization and an x-band injector. One motivation for the study is to optimise the length of the AXXS machine, allowing the linac to fit onto the proposed and also act as the injector to the existing storage ring at the Australian Synchrotron.

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TUPWA008

Mixing and Space-Charge Effects In Free-Electron Lasers

laser, FEL, radiation, space-charge

1410

E.A. Peter, A. Endler, F.B. Rizzato
IF-UFRGS, Porto Alegre, Brazil
A.P.B. Serbeto
UFF, Niterói - RJ, Brazil

Funding: This work was supported by CNPq and FAPERGS, Brazil, and by the Air Force Office of Scientific Research (AFOSR), USA, under the Grant No. FA9550-12-1-0438
Free-electron lasers are devices which efficiently convert the kinetic energy from a relativistic electron beam into electromagnetic radiation, amplifying an initial small sign. The present work revisits the subject of mixing, saturation and space-charge effects in free-electron lasers. Use is made of the compressibility factor, which proves to be a helpful tool in the related systems of charged beams confined by static magnetic fields. The compressibility allows to build a semi-analytical model and to perform analytical estimates of the elapsed time until the onset of mixing, which in turn allows to estimate the saturated amplitude of the radiation field. In addition, the compressibility helps to pinpoint space-charge effects and the corresponding transition from Compton to Raman regimes. The semi-analytical model and the particles simulations are compared, exhibiting a good agreement.*
* E. Peter, A. Endler, F. B. Rizzato, and A. Serbeto, Phys. Plasmas 20,
123104 (2013).
** E. Peter, A. Endler, and F. B. Rizzato, Phys. Plasmas 21, 113104 (2014)

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TUPWA011

Progress on the LUNEX5 project

FEL, laser, undulator, operation

1416

M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, J.D. Bozek, F. Briquez, L. Cassinari, L. Chapuis, J. Da Silva, J. Daillant, Y. Dietrich, M. Diop, J.P. Duval, M.E. El Ajjouri, T.K. El Ajjouri, C. Herbeaux, N. Hubert, M. Khojoyan, M. Labat, P. Lebasque, N. Leclercq, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, F. Marteau, C. Miron, P. Morin, A. Nadji, R. Nagaoka, F. Polack, F. Ribeiro, J.P. Ricaud, P. Rommeluère, P. Roy, G. Sharma, K.T. Tavakoli, M. Thomasset, M. Tilmont, S. Tripathi, M. Valléau, J. Vétéran, W. Yang, D. Zerbib
SOLEIL, Gif-sur-Yvette, France
S. Bielawski, C. Evain
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
B. Carré, D. Garzella
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
X. Davoine
CEA/DAM/DIF, Arpajon, France
N. Delerue
LAL, Orsay, France
G. Devanz, C. Madec, A. Mosnier
CEA/IRFU, Gif-sur-Yvette, France
A. Dubois, J. Lüning
CCPMR, Paris, France
G. Lambert, V. Malka, A. Rousse, C. Thaury
LOA, Palaiseau, France
E. Roussel
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
C. Szwaj
PhLAM/CERLA, Villeneuve d'Ascq, France

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent Free Electron Laser (FEL) pulses in the 40-4 nm spectral range. It comprises a 400 MeV superconducting Linear Accelerator for high repetition rate operation (10 kHz), multi-FEL lines and adapted for studies of advanced FEL schemes, a 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application, a single undulator line enabling advanced seeding and pilot user applications. Different studies such as on two color FEL and R&D programs have been launched. A test experiment for the demonstration of 180 MeV LWFA based FEL amplification at 200 nm is under preparation in collaboration with the Laboratoire d’Optique Appliquée, thanks to a proper electron beam manipulation. Specific hardware is also under development such as a cryo-ready 3 m long undulator of 15 mm period.

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TUPWA016

Modeling of beam losses at ESRF

vacuum, scattering, simulation, detector

1430

R. Versteegen, P. Berkvens, N. Carmignani, J. Chavanne, L. Farvacque, S.M. Liuzzo, B. Nash, T.P. Perron, P. Raimondi, K.B. Scheidt, S.M. White
ESRF, Grenoble, France

As the ESRF enters the second phase of its upgrade towards ultra low emittance, the knowledge of the beam loss pattern around the storage ring is needed for radiation safety calculations and for the new machine design optimization. A model has been developed to simulate the Touschek scattering and the scattering of electrons on residual gas nuclei in view of producing a detailed loss map of the machine. Results of simulation for the ESRF are presented and compared with real beam measurements.

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TUPWA018

Progress Report of the Berlin Energy Recovery Project BERLinPro

gun, SRF, booster, cavity

1438

M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A. Burrill, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, D. Pflückhahn, J. Rahn, J. Rudolph, M. Schmeißer, O. Schüler, J. Völker
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The Helmholtz Zentrum Berlin is constructing the Energy Recovery Linac Project BERLinPro on its site in Berlin Adlershof. The project is intended to expand the required accelerator physics and technology knowledge mandatory for the design, construction and operation of future synchrotron light sources. The project goal is the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beamat 2~ps rms bunch duration or below. The planning phase of the project is completed and the design phase of most of the components is finished. Many of them have already been ordered. After some delay the construction of the building has started in February 2015. The status of the various subprojects as well as a summary of current and future activities will be given. Major project milestones and details of the project time line will be finally introduced.

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TUPWA020

BNL ATF II Beamlines Design

experiment, laser, cavity, linac

1445

M.G. Fedurin, Y.C. Jing, D. Stratakis, C. Swinson
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Brookhaven National Lab. Accelerator Test Facility (BNL ATF) is currently undergoing a major upgrade (ATF-II). Together with a new location and much improved facilities, the ATF will see an upgrade in its major capabilities: electron beam energy and quality and CO2 laser power. The electron beam energy will be increased in stages, first to 100-150 MeV followed by a further increase to 500 MeV. Combined with the planned increase in CO2 laser power (from 1-100 TW), the ATF-II will be a powerful tool for Advanced Accelerator research. A high-brightness electron beam, produced by a photocathode gun, will be accelerated and optionally delivered to multiple beamlines. Besides the energy range (up to a possible 500 MeV in the final stage) the electron beam can be tailored to each experiment with options such as: small transverse beam size (<10 um), flat beam, short bunch length (<100 fs) and, combined short and small bunch options. This report gives a detailed overview of the ATF-II capabilities and beamlines configuration.

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TUPWA021

A New Method to Generate Ultrashort and Coherent Pulses of Short-Wavelength Synchrotron Radiation

laser, radiation, synchrotron, storage-ring

1448

S. Khan
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF (contract 05K13PE3)
A laser-based method to generate ultrashort pulses of synchrotron radiation in electron storage rings is coherent harmonic generation (CHG) using two undulators to produce coherent radiation at harmonics of the initial laser wavelength by microbunching. The bunching factor and thus the pulse intensity, however, decreases exponentially with increasing harmonic order. Echo-enabled harmonic generation (EEHG), proposed in 2009 as FEL seeding scheme*, can be used to produce short synchrotron radiation pulses at higher harmonics, but requires three undulators in a straight section. In this paper, a less space-consuming method based on seeding with intensity-modulated laser pulses is introduced, which also has the potential of significant bunching factors at high harmonics.
* G. Stupakov, PRL 102 (2009), 074801.

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TUPWA022

Characterization and Optimization of Ultrashort and Coherent VUV Pulses at the DELTA Storage Ring

laser, radiation, synchrotron, undulator

1452

S. Khan, F.H. Bahnsen, M. Bolsinger, S. Hilbrich, M. Huck, M. Höner, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, G. Shayeganrad, P. Ungelenk
DELTA, Dortmund, Germany
H. Huck
DESY Zeuthen, Zeuthen, Germany

Funding: Work supported by BMBF (05K13PE3 and 05K13PEC), DFG (INST 212/236-1 FUGG) and the Land NRW
At DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund University, a source for coherent and ultrashort vacuum-ultraviolet (VUV) and terahertz (THz) pulses is now in operation. The VUV source is based on a laser-induced energy modulation and coherent harmonic generation (CHG). A subsequently developing dip in the longitudinal electron distribution gives rise to coherent THz radiation. Recent results regarding the optimization of the laser-electron interaction and characterization of the CHG pulses are presented.

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TUPWA023

A Step Closer to the CW High Brilliant Beam with the ELBE SRF-Gun-II

gun, SRF, cavity, cathode

1456

R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany

In order to achieve the CW electron beam with a high average current up to 1 mA and a very low emittance of 1 μm, an improved superconducting photo-injector (ELBE SRF-Gun-II) has been installed and commissioned at HZDR since 2014. This new gun replaces the first 3.5-cell SRF gun (SRF-Gun-I) at the SC Linac ELBE. The RF performance of the niobium cavity has been evaluated, the beam parameters for low charge bunches have been measured, and the first beam has been guided into the ELBE beam line. The results agree with the simulation very well. The photocathode transfer system has been installed for the first high current beam test planned in 2015. However, the unexpected strong degradation on the cavity and also on the photocathode was found soon after the first photocathode exchange. In this contribution the results of the SRF-Gun-II commissioning and the latest experiment will be presented in detail.

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TUPWA025

Beam Heat Load Analysis with COLDDIAG: A Cold Vacuum Chamber for Diagnostics

storage-ring, diagnostics, vacuum, synchrotron

1459

R. Voutta, S. Casalbuoni, S. Gerstl, A.W. Grau, T. Holubek, D. Saez de Jauregui
KIT, Eggenstein-Leopoldshafen, Germany
R. Bartolini, M.P. Cox, E.C. Longhi, G. Rehm, J.C. Schouten, R.P. Walker
DLS, Oxfordshire, United Kingdom
M. Migliorati, B. Spataro
INFN/LNF, Frascati (Roma), Italy

The knowledge of the heat intake from the electron beam is essential to design the cryogenic layout of superconducting insertion devices. With the aim of measuring the beam heat load to a cold bore and understanding the responsible mechanisms, a cold vacuum chamber for diagnostics (COLDDIAG) has been built. The instrumentation comprises temperature sensors, pressure gauges, mass spectrometers and retarding field analyzers, which allow to study the beam heat load and the influence of the cryosorbed gas layer. COLDDIAG was installed in the storage ring of the Diamond Light Source from September 2012 to August 2013. During this time measurements were performed for a wide range of machine conditions, employing the various measuring capabilities of the device. Here we report on the analysis of the measured beam heat load, pressure and gas content, as well as the low energy charged particle flux and spectrum as a function of the electron beam parameters.

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TUPWA026

Simulation of Optical Transport Beamlines for High-quality Optical Beams for Accelerator Applications

laser, polarization, simulation, FEL

1462

J. Bödewadt, N. Ekanayake
DESY, Hamburg, Germany

High-quality optical beams play already an important role in the field of particle accelerators which will most probably become even more prominent in the view of laser-driven particle accelerators. Nowadays, optical transport systems are needed for particle generation in photo injectors, for particle acceleration in laser-driven plasma wakefield accelerators, for particle beam diagnostics such as synchrotron radiation monitoring systems, or for particle manipulation schemes e.g. for external seeding of free-electron lasers. For the latter case, also the photon beam transport to the user end-stations requires dedicated optical transport system. The utilized wavelengths range from the hard x-ray up to the far-infrared spectral range. Parameters like surface quality, polarization effects, damage thresholds in- and out-of-vacuum, mechanical stability, dispersion effect etc. need to be studied for the variaty of applications. Here, we present the simulation results of the optical transport beamline for the seeding setup at FLASH and give a comparision to our measurement results.

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TUPWA028

Simulation Results of the Beam Transport of Ultra-Short Electron Bunches in Existing Beam Transfer Lines to Sinbad

linac, optics, gun, synchrotron

1466

U. Dorda, R.W. Aßmann, K. Flöttmann, B. Marchetti, Y.C. Nie, J. Zhu
DESY, Hamburg, Germany

SINBAD, the upcoming accelerator R&D facility at DESY, will host multiple independent experiments on the production and acceleration of ultra-short bunches including plasma wakefield experiments. As a possible later upgrade the option to transport higher energy electrons (up to 800 MeV) or positrons (up to 400 MeV) from the existing DESY Linac 2 to the facility is studied. Though existing a possible connection using e.g. a part of the DESY synchrotron as a transfer line and other currently unused transfer-line, these machines were not designed for the desired longitudinal bunch compression and high peak current required by e.g. beam driven plasma wake-field experiments. Simulation results illustrate the modifications to the current layout that would have to be implemented and the corresponding achievable beam parameters are given.

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TUPWA029

ARES: Accelerator Research Experiment at SINBAD

cavity, bunching, experiment, linac

1469

B. Marchetti, R.W. Aßmann, C. Behrens, R. Brinkmann, U. Dorda, K. Flöttmann, J. Grebenyuk, M. Hüning, Y.C. Nie, H. Schlarb, J. Zhu
DESY, Hamburg, Germany

ARES is a planned linear accelerator for R&D for production of ultra-short electron bunches. It will be hosted at the SINBAD facility, at DESY in Hamburg*. The goal of ARES is to produce low charge (0.2-50pC), ultra-short (from few fs to sub-fs) bunches, with high arrival time stability (less than 10fs) for various applications, such as external injection for Laser Plasma Wake-Field acceleration**. The baseline layout of the accelerator foresees an S-band photo-injector which compresses low charge electron bunches via velocity bunching and accelerates them to 100 MeV energy. In the second stage, it is planned to install a third S-band accelerating cavity to reach 200 MeV as well as two X-band cavities: One for the linearization of the longitudinal phase space (subsequently allowing an improved bunch compression) and another one as a transverse deflecting cavity for longitudinal beam diagnostics. Moreover a magnetic bunch compressor is envisaged allowing to cut out the central slice of the beam*** or hybrid bunch compression.
* R. Assmann et al., TUPME047, Proceedings of IPAC 2014.
** R. Assmann, J. Grebenyuk, TUOBB01, Proceedings of IPAC 2014.
*** P. Emma et al., PRL 92 7 (2004).

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TUPWA030

Compression of an Electron-bunch by Means of Velocity Bunching at ARES

bunching, emittance, simulation, plasma

1472

B. Marchetti, R.W. Aßmann, U. Dorda, J. Grebenyuk, J. Zhu
DESY, Hamburg, Germany

ARES is a planned linear accelerator for research and development in the field of production of ultra-short electron bunches. The goal of ARES is to produce low charge (0.2-50pC), ultra-short (from few fs to sub-fs) bunches, with improved arrival time stability (less than 10fs) for various applications, such as external injection for Laser Plasma Wake-Field acceleration. The ARES layout will allow to perform and compare different kind of conventional e-bunch compression techniques, such as pure velocity bunching*, hybrid velocity bunching (i.e. velocity bunching plus magnetic compression) and pure magnetic compression with the slit insertion**. This flexibility will allow to directly compare the different methods in terms of arrival time stability and local peak current. In this paper we present simulation results for the compression of an electron bunch with 0.5 pC charge. We compare the case of pure velocity bunching compression to the one of a hybrid compression using velocity bunching plus a magnetic compressor.
* M. Ferrario et al., Phys. Rev. Lett. 104, 054801 (2010).
** P. Emma et al., PRL 92 7 (2004).

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TUPWA031

Compression of Train of Bunches with Ramped Intensity Profile at SPARC_LAB

linac, laser, cathode, plasma

1476

B. Marchetti
DESY, Hamburg, Germany
A. Bacci
Istituto Nazionale di Fisica Nucleare, Milano, Italy
E. Chiadroni, M. Ferrario, R. Pompili
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy

The production and acceleration of train of bunches with variable spacing in the ps/sub-ps range having ramped intensity profile are interesting to drive a plasma wave in the so-called resonant Plasma Wake-Fields Acceleration (r-PWFA)*. At SPARC_LAB trains having a constant intensity profile have been produced for the first time by using a shaped photo-cathode laser combined with the use of the velocity bunching compression technique**,***,****. If the sub-bunches have ramped intensity, i.e. they have different charge density, the space charge force affects differently the development of the longitudinal phase space of each one of them during the compression. In this paper we present preliminary simulations for the compression of a ramped train of bunches. The differences between the beam dynamics for a train of bunches having constant intensity profile and the ramped train are underlined. We discuss also the possibility of properly tuning the shaping of the photocathode laser to balance the space charge effect.
* SLAC-PUB-3528
** M. Ferrario et al., Phys. Rev. Lett. 104, 054801 (2010).
*** M. Ferrario et al. NIM A 637, S43-S46 (2011).
**** E. Chiadroni et al., Rev. Sci. Instrum. 84, 022703

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TUPWA032

Progress in the Injector Upgrade of the LINAC II at DESY

linac, gun, simulation, solenoid

1479

Y.C. Nie, M. Hüning, C. Liebig, M. Schmitz
DESY, Hamburg, Germany

A new injection system is under development for the LINAC II at DESY to improve the reliability of the machine and mitigate the radiological problem due to electron losses at energy of hundreds of MeV. It consists of a 100 kV triode DC gun, a 2.998 GHz pre-buncher, a novel 2.998 GHz hybrid buncher, and the dedicated beam transport and diagnostic elements. As the key components, the pre-buncher and the hybrid buncher realize a two-stage velocity bunching process including the ballistic bunching and the phase space rotation. Therefore, they produce a certain number of well-bunched 5 MeV micro-bunches from the input 2 ns-50 ns electron pulse for the downstream LINAC II. The overall upgrade plan, developments of the critical components, as well as the latest beam test results will be reported.

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TUPWA038

Optics Compensation for Variable-gap Undulator Systems at FLASH

undulator, optics, quadrupole, FEL

1499

Ph. Amstutz, C. Lechner, T. Plath
Uni HH, Hamburg, Germany
S. Ackermann, J. Bödewadt, M. Vogt
DESY, Hamburg, Germany

Variable-gap undulator systems are widely used in storage rings and linear accelerators to generate soft- and hard x-ray radiation for the photon science community. For cases where the effect of undulator focusing significantly changes the electron beam optics, a compensation is needed in order to keep the optics constant in other parts of the accelerator. Since 2010, the free-electron laser (FEL) facility FLASH is equipped with two undulator sections along the same electron beamline. The first undulator is a variable-gap system used for seeding experiments, the second undulator is a fixed-gap system which serves the user facility with FEL radiation. Varying the gap in the first undulator will change the beam optics such that the FEL process in the second undulator is dramatically disturbed. For the correction of the beam optics an analytical model is used to generate feed forward tables which allows to make part of the beamline indiscernible for the subsequent sections. The method makes use of the implicit function theorem and can be used for any perturbation of the beam optics. Here, we present the method and its implementation as well as measurements performed at FLASH.

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TUPWA039

Transverse Gradient Undulator-Based High-Gain-FELs - a Parameter Study

undulator, laser, FEL, resonance

1502

A. Bernhard, V. Afonso Rodríguez, E. Burkard, A.-S. Müller, C. Widmann
KIT, Karlsruhe, Germany

Transverse gradient undulators (TGU) have recently been discussed as sources for High Gain Free Electron Lasers (FEL) driven by electron beams with an elevated energy spread as for example generated in storage rings or wakefield accelerators. In this contribution we present the results of a parameter study based on the one-dimensional TGU-FEL theory making realistic assumptions on the key parameters achievable for the transverse gradient undulator. We show for which parameter areas LWFA-driven TGU-FELs are virtually technically feasible today and which technical improvements would be required to employ the concept for a laboratory-scale X-Ray FEL.

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TUPWA042

Status of the Accelerator Physics Test Facility FLUTE

gun, linac, diagnostics, laser

1506

M.J. Nasse, A. Bernhard, I. Birkel, A. Borysenko, A. Böhm, S. Hillenbrand, N. Hiller, S. Höninger, S. Marsching, A.-S. Müller, R. Rossmanith, R. Ruprecht, M. Schuh, M. Schwarz, B. Smit, S. Walther, M. Weber, P. Wesolowski
KIT, Karlsruhe, Germany
R.W. Aßmann, M. Felber, K. Flöttmann, C. Gerth, M. Hoffmann, P. Peier, H. Schlarb, B. Steffen
DESY, Hamburg, Germany
R. Ischebeck, B. Keil, V. Schlott, L. Stingelin
PSI, Villigen PSI, Switzerland

A new compact versatile linear accelerator named FLUTE (Ferninfrarot Linac Und Test Experiment) is currently under construction at the Karlsruhe Institute of Technology (KIT). It will serve as an accelerator test facility and allow conducting a variety of accelerator physics studies. In addition, it will be used to generate intense, ultra-short THz pulses for photon science experiments. FLUTE consists of a ~7 MeV photo-injector gun, a ~41 MeV S-band linac and a D-shaped chicane to compress bunches to a few femtoseconds. This contribution presents an overview of the project status and the accompanying simulation studies.

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TUPWA043

Non-interferometric Spectral Analysis of Synchrotron Radiation in the THz regime at ANKA

synchrotron, radiation, synchrotron-radiation, storage-ring

1509

J.L. Steinmann, M. Brosi, E. Bründermann, C.M. Caselle, E. Hertle, N. Hiller, B. Kehrer, A.-S. Müller, M. Schuh, M. Schwarz, P. Schönfeldt, P. Schütze
KIT, Karlsruhe, Germany
J.L. Hesler
Virginia Diodes Inc., Charlottesville, USA

Interferometry is the quasi-standard for spectral measurements in the THz- and IR-range. The frequency resolution, however, is limited by the travel range of the interferometer mirrors. Therefore, a resolution in the low megahertz range would require interferometer arms of about 100 m. As an alternative, heterodyne measurements provide a resolution in the Hertz range, an improvement of 6 orders of magnitude. Here we present measurements done at ANKA with a VDI WR3.4SAX, a mixer that can be tuned to frequencies from 220 GHz to 330 GHz and we show how the bunch filling pattern influences the amplitude of specific frequencies.

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TUPWA044

Test electron source for increased brightness emission by near band gap photoemission

cathode, emittance, vacuum, simulation

1512

S. Friederich, K. Aulenbacher
IKP, Mainz, Germany

Funding: Bundesministerium für Bildung und Forschung/Federal Ministry of Education and Research; Joint project HOPE
A new photoemissive electron source is being built in order to make use of the reduction of ensemble temperature in near band gap photoemission. It will operate at up to 200 kV bias voltage with NEA GaAs photocathodes. High bunch charges will be investigated in pulsed mode with respect to the conservation of emittances at low energy excitations. High field gradients at the cathode surface will also allow further investigation of the field emission process of these photocathodes.

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TUPWA046

Facility Upgrade at PITZ and First Operation Results

gun, laser, plasma, operation

1518

A. Oppelt, P. Boonpornprasert, A. Donat, J.D. Good, M. Groß, H. Huck, I.I. Isaev, L. Jachmann, D.K. Kalantaryan, M. Khojoyan, W. Köhler, G. Koss, G. Kourkafas, M. Krasilnikov, O. Lishilin, D. Malyutin, J. Meissner, D. Melkumyan, M. Otevřel, M. Penno, B. Petrosyan, S. Philipp, M. Pohl, Y. Renier, T. Rublack, B. Schöneich, J. Schultze, F. Stephan, F. Tonisch, G. Trowitzsch, G. Vashchenko, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. A. Bakr
Assiut University, Assiut, Egypt
C. Hernandez-Garcia
JLab, Newport News, Virginia, USA
G. Pathak
Uni HH, Hamburg, Germany
D. Richter
HZB, Berlin, Germany

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops, optimizes and characterizes high brightness electron sources for free electron lasers like FLASH and the European XFEL. In the last year, the facility was significantly upgraded by the installation of a new normal conducting radio- frequency (RF) gun cavity with its new waveguide system for the RF feed, which should allow stable and reliable gun operation, as required for the European XFEL. Other relevant additions include beamline modifications for improving the electron beam transport through the PITZ accelerator, extending the beam-based measurement capabilities, and preparing the installation of a plasma cell. Furthermore, the laser hutch was re-arranged in order to be able to house an additional, new photo cathode drive laser system which should be able to produce 3D ellipsoidal laser pulses to further improve the electron beam quality. This paper describes in detail the aforementioned facility upgrades and reports on the first operation experience with the new gun setup.

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TUPWA047

First Results Attained With the Quasi 3-D Ellipsoidal Photo Cathode Laser Pulse System at the High Brightness Photo Injector PITZ

laser, cathode, emittance, simulation

1522

T. Rublack, J.D. Good, M. Khojoyan, M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany
A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky
IAP/RAS, Nizhny Novgorod, Russia
I. Hartl, S. Schreiber
DESY, Hamburg, Germany
E. Syresin
JINR, Dubna, Moscow Region, Russia

Funding: Funded by the German Federal Ministry of Education and Research (BMBF) project 05K10CHE in the framework of the German-Russian collaboration "Development and Use of Accelerator-Based Photon Sources".
3-D ellipsoidal photo cathode laser pulses are considered as the next step in optimization of photo injectors required for a successful operation of linac based free electron lasers. Beam dynamics simulations using such laser pulses compared to conventional cylindrical pulses have shown a significant improvement in electron beam emittance. In collaboration with the Institute of Applied Physics (Nizhny Novgorod, Russia) and the Joint Institute of Nuclear Research (Dubna, Russia) such a 3-D ellipsoidal laser pulse system has been developed and afterwards installed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). The pulse shaping is realized using the spatial light modulator technique. This allows very fine amplitude modulation within a laser pulse. The characterization of the shape of the laser pulses can be done by cross-correlation measurements. Using this method the ability to generate and measure quasi ellipsoidal laser pulses has been demonstrated. In this contribution the overall set-up, working principle and first results received with the new photo cathode laser system at PITZ will be reported.

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TUPWA053

Influence of a Non-uniform Longitudinal Heating on High Brightness Electron Beams for FEL

laser, FEL, undulator, linac

1535

E. Roussel, E. Allaria, M.B. Danailov, G. De Ninno, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Laser-heater systems are essential tools to control and optimize high-gain free electron lasers (FELs), working in the x-ray wavelength range. Indeed, these systems induce a controllable heating of the energy spread of the electron bunch. The heating allows in turn to suppress longitudinal microbunching instabilities limiting the FEL performance. In this communication, we show that a long-wavelength energy modulation of the electron beam induced by the laser heater can persist until the beam entrance in the undulators, affecting the FEL emission process. This non-uniform longitudinal heating can be exploited to investigate the electron-beam microbunching in the linac, as well as to control the FEL spectral properties. Here, we present experimental, analytical and numerical studies carried out at FERMI.

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TUPWA054

The FERMI Seeded FEL Facility: Operational Experience and Future Perspectives

FEL, laser, experiment, operation

1538

M. Svandrlik, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are now available for users, down to the shortest wavelength of 4 nm. We will report on the completion of the commissioning of the high energy FEL line, FEL-2, and on the operational experience for users, in particular those requiring specific FEL configurations, like two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered by our experience and are aiming to maintain as well as to constantly improve the performance of the facility for our user community.

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TUPWA055

DAΦNE Gamma-Ray Factory

laser, photon, factory, emittance

1542

D. Alesini, S. Guiducci, C. Milardi, A. Variola, M. Zobov
INFN/LNF, Frascati (Roma), Italy
I. Chaikovska, Z.F. Zomer
LAL, Orsay, France

Gamma sources with high flux and spectral densities are the main requirements for new nuclear physics experiments to be performed in several worldwide laboratories with dedicated facilities. The presentation is focalized on a proposal of experiment of gamma photons production using Compton collisions between the DAΦNE electron beam and a high average power laser pulse, amplified in a Fabry-Pérot optical resonator. The calculations show that the resulting gamma beam source has extremely interesting properties in terms of spectral density, energy spread and gamma flux comparable (and even better) with the last generation gamma sources. The energy of the gamma beam depends on the adopted laser wavelength and can be tuned changing the energy of the electron ring. In particular we have analyzed the case of a gamma factory tunable in the 2-9 MeV range. The main parameters of this new facility are presented and the perturbation on the transverse and longitudinal electron beam dynamics is discussed. A preliminary accelerator layout to allow experiments with the gamma beam is presented with a first design of the accelerator optics.

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TUPWA056

New Gun Implementation and Performance of the DAΦNE LINAC

gun, linac, cathode, operation

1546

B. Buonomo, L.G. Foggetta, G. Piermarini
INFN/LNF, Frascati (Roma), Italy

A new electron gun system has been developed for DAΦNE LINAC, and put into operation since January 2014. Several elements of the system were upgraded, including a new grid pulser, an improved bias voltage system and a renewed cathode socket. The new LINAC gun has now a wider range of parameters, i.e. the emission pulse length spans from 1.4ns up to 40ns, while the better control of the grid and bias voltage allows a maximum peak current of 5A with a pulse repetition rate of 50 Hz. This paper describes the details of the pulser, the power supply, the socket, all the service components of the upgraded gun and its integration in the main LINAC control system. A report on the performance of the LINAC with the new gun will follow.

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TUPWA057

DAΦNE LINAC: Beam Diagnostics and Outline of the Last Improvements

linac, klystron, positron, operation

1549

B. Buonomo, L.G. Foggetta
INFN/LNF, Frascati (Roma), Italy

The LINAC of the DAΦNE complex is in operation since 1996, both as injector of the e⁺ e⁻ phi-factory, and, since 2003, for the extraction of electron beam to the Beam Test Facility. In the last years, many improvements has been developed in different sub-systems of the LINAC, aiming at a wider, tunable range of beam parameters, in particular the pulse time width and the pulse charge. A long term measurement campaign has been recently started to characterize the LINAC performance after that many sub-systems has been overhauled and improved, starting from RF power (i.e. klystron substitution, modulator re-newing, RF driver layout, SLED tuning) as well as the timing system, magnets, cooling, vacuum, control system and energy/position diagnostics. This work reports the latest results on the optimization of the fully consolidated system.

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TUPWA059

Modeling of Photoemission and Electron Spin Polarization from NEA GaAs Photocathodes

scattering, polarization, simulation, photon

1556

O. Chubenko, A. Afanasev
GWU, Washington, USA

Funding: Work supported by The George Washington University and Thomas Jefferson National Accelerator Facility.
Many nuclear-physics and particle-physics scientific laboratories, including Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (Jefferson Lab) which studies parity violation and nucleon spin structure, require polarized electron sources. At present, photoemission from strained GaAs activated to negative electron affinity (NEA) is a main source of polarized electrons. Future experiments at advanced electron colliders will require highly efficient polarized electron beams, which sets new requirements for photocathodes in terms of high quantum efficiency (QE) (>>1%) and spin polarization (~85%). Development of such materials includes modeling and design of photocathodes, material growth, fabrication of photocathodes, and photocathode testing. The purpose of the present work is to develop a semi-phenomenological model, which could predict photoemission and electron spin polarization from NEA GaAs photocathodes. Detailed Monte Carlo simulation and modeling of physical processes in photocathodes is important for optimization of their design in order to achieve high QE and reduce depolarization mechanisms. Electron-phonon interactions near the surface and influence of the presence of quantum heterostructures on the diffusion length are studied in depth. Simulation results will be compared to the experimental results obtained at Jefferson Lab and can be used to optimize the photocathode design and material growth, and thus develop high-polarization high-brightness electron source.

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TUPWA062

GaAs Photocathode Activation with CsTe Thin Film

photon, cathode, vacuum, experiment

1567

M. Kuriki, Y. Seimiya, K. Uchida
HU/AdSM, Higashi-Hiroshima, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan

Funding: This work is partly supported by MEXT/JSPS KAKENHI (Grant-in-Aid for scientific research) 24654054.
GaAs is an unique and advanced photocathode which can generate highly polarized and extremely low emittance electron beam. The photo-emission is possible up to 900nm wavelength. These advantages are due to NEA (Negative Electron Affinity) surface where the conduction band minimum is higher than the vacuum energy state. The NEA surface is artificially made with Cs-O/F evaporation on the cleaned GaAs surface, but the NEA surface is fragile, so that the emission is easily lost by poor vacuum environment and high emission density. NEA activation with any vital material is desirable. We found that the GaAs can be activated by CsTe thin film which is known as a vital photo-cathode material. The photo-electron emission spectrum extends up to 900 nm wavelength which corresponds to the band-gap energy of GaAs. The result strongly suggests that the surface becomes effectively NEA state by the CsTe thin film.

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TUPWA065

Generation of Multi-bunch Beam with Beam Loading Compensation by Using RF Amplitude Modulation in Laser Undulator Compact X-ray (LUCX)

cavity, laser, gun, booster

1576

M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
K. Sakaue, M. Washio
RISE, Tokyo, Japan

We have developed a compact X-ray source based on inverse Compton scattering between an electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. The accelerator consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. Our aim is to obtain a clear X-ray image in a shorter period of times and the target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth at present. To achieve this target, it is necessary to increase the intensity of an electron beam to 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches with beam-loading compensation by using the delta T method and the amplitude modulation of RF pulse. The bunch-by-bunch energy difference is within 1.3% peak to peak. We will report the results of the multi-bunch beam generation and acceleration in this accelerator.
This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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TUPWA066

Development of a High Average Power Laser for High Brightness X-ray Source and Imaging at cERL

laser, cavity, detector, photon

1579

A. Kosuge, T. Akagi, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
R. Hajima, M. Mori, T. Shizuma
JAEA, Ibaraki-ken, Japan
R. Nagai
JAEA/ERL, Ibaraki, Japan

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
High brightness X-rays via laser-Compton scattering (LCS) of laser photons stored in an optical cavity by a relativistic electron beam is useful for many scientific and industrial applications such as X-ray imaging. The construction of compact Energy Recovery Linac (cERL) is now in progress at KEK to generate low-emittance and high-current electron beams. In order to demonstrate the generation of high brightness LCS X-rays, it is necessary to develop a high average power injection laser and an optical four-mirror ring cavity with two concave mirrors which is used to produce a small spot laser beam inside the cavity. In this presentation, we will show the result of the development of the high average laser system, the LCS X-rays generation, and the X-ray imaging.

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TUPWA068

Simulation Study of Beam Halo and Loss for KEK Compact ERL

simulation, cavity, laser, gun

1587

O. Tanaka, T. Miyajima, N. Nakamura, S. Sakanaka, M. Shimada
KEK, Ibaraki, Japan

At the KEK Compact ERL (cERL) designed to operate at high-brilliance and high-current electron beams, the maximum averaged current was recorded at 6.5 muA for the beam energy of 20 MeV on March 2014 and should be increased up to 10 mA in a step-by-step manner in a few years. In order to increase the beam current by reducing the beam loss, we need to know the mechanism of the beam loss. For this purpose we investigate beam halo originated from characteristics and imperfections of an electron gun system, using the tracking code GPT (General Particle Tracer). The beam halo can be lost by the beam-pipe apertures and the collimators in the cERL beam line. In this paper, we will present the simulation results including the beam halo formation and the beam loss distribution along the beam line.

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TUPWA070

CST Simulations of THz Cherenkov Smith-purcell Radiation from Corrugated Capillary

radiation, simulation, polarization, laser

1594

K. Lekomtsev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
P. Karataev
JAI, Egham, Surrey, United Kingdom
A. Ponomarenko, A.A. Tishchenko
MEPhI, Moscow, Russia

Recent advances in generation of femtosecond pre-bunched beams have a potential to generate coherent THz radiation occurring via combination of Smith-Purcell radiation (SPR) and Cherenkov radiation (ChR) generated in a corrugated capillary. This mechanism was studied theoretically *. LUCX accelerator at High Energy Accelerator Research Organisation (KEK) has been upgraded by introducing fs Ti:Sa laser system and it is currently generating short tens of fs electron bunches **. In this report we present EM simulations of Ch.SPR generated in a corrugated channel in infinite dielectric and in a dielectric corrugated capillary. CST PIC solver is used as a simulation tool. It was earlier used for simulation of Transition radiation ***. Intensity dependencies of ChR and SPR peaks as functions of the capillary radius and the corrugation depth are compared with the theoretical investigation *. Output of THz radiation from the dielectric capillary with a radiation reflector is simulated.
* A.A. Ponomarenko et. al, NIMB 309 (2013) 223-226.
** M. Fukuda et. al, NIMA 637 (2011) S67.
*** K.V. Lekomtsev et. al, J. Phys.: Conf. Ser. 517, (2014) 012016.

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TUPWA071

Improvements of the Laser System for RF-Gun at SuperKEKB Injector

laser, operation, gun, cryogenics

1598

R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou
KEK, Ibaraki, Japan

For realizing higher charge and low emittance electron and positron beams in SuperKEKB, we have been making improvements in laser system for RF-gun. The difficulty in controlling thermomechanical distortions has been one of the most important factors for preserving high laser conversion efficiency of infrared-to-ultraviolet and operating at higher repetition rate. We demonstrated that efficient removal of waste heat can be realized by adopting Yb:YAG and copper bonding composite via Au-Sn solder. On the other hand, we proposed the novel design of the cascade laser configuration. Base on this, we can improve the quantum efficiency by utilizing other Yb ions doped crystals as active medium which are pumped by 1035 nm Yb:YAG laser. Excellent thermal management and high charge beams have been achieved by improvements of these two aspects. Additionally, in order to employ high duty ratio pump system and realize laser operation at high repetition rate, we investigated the laser operation in cryogenic environment. A perspective towards the next step experiment is also presented in this paper.

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TUPWA072

Coherent Thomson Scattering Radiation Generated by using PEHG

radiation, laser, scattering, undulator

1601

S. Chen, K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
S. Huang
PKU, Beijing, People's Republic of China

In this paper, we present the coherent Thomson scattering of a long wavelength laser with ultrashort electron slices. The ultrashort electron slices are generated by the longitudinal bunch density modulation method of PEHG. Coherent radiation with ultrashort pulse length is generated in EUV regime by this method.

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TUPJE001

Design of Wavelength Tunable Coherent X-Ray Source

radiation, target, optics, emittance

1604

J. Hyun
Sokendai, Ibaraki, Japan
K. Endo
TOYAMA Co., Ltd., Zama-shi, Kanagawa, Japan
K. Hayakawa, Y. Hayakawa, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
I. Sato
Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi, Japan
M. Satoh, M. Yoshida
KEK, Ibaraki, Japan

KEK, Nihon University and TOYAMA CO., Ltd. have been developing the compact shieldless coherent X-ray source that can change the X-ray energy (3-25keV). This X-ray is the Parametric X-ray radiation (PXR) generated by relativistic charged particles passed through a single crystal. It has features that are monochromaticity, coherence and diffraction large angle for the incident beam. These indicate to the possibility for the application to the medical treatment and diagnosis. Furthermore, we try to reduce the radiation which is mainly generated when the high energy beam is damped. This system consists of an accelerating, a decelerating structure and four bending magnets (theta: 90 degree). These structures are operated under low temperature to get the high Q-value for long beam pulse. PXR is generated by colliding with a single crystal after electron beam is accelerated up to 75 MeV. The bunch passed through the crystal is transported into a decelerator structure and then is decelerated to 3 MeV there. Q-magnets are arranged that dispersion function is zero except arc sections. We calculated the beam transport, PXR intensity and emittance blow up. We'll report these details.

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TUPJE002

Demonstration of High-flux Photon Generation from an ERL-based Laser Compton Photon Source

laser, photon, cavity, linac

1607

R. Nagai, R. Hajima, M. Mori, T. Shizuma
JAEA, Ibaraki-ken, Japan
T. Akagi, S. Araki, Y. Honda, A. Kosuge, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

A high-flux photon source from the laser Compton scattering (LCS) by an electron beam in an energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear materials. In order to demonstrate accelerator and laser technologies required for a LCS photon generation, a LCS photon source is under construction at the Compact ERL (cERL). The LCS photon source consists of a mode-locked fiber laser and a laser enhancement cavity. Flux monitors and a data aqcuisition system are also under construction. The commissioning of the LCS photon source will be started in February 2015 and LCS photon generation is scheduled in March 2015. The demonstration result of the LCS photon source will be presented in detail.

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TUPJE004

Narrow Band Coherent Edge Radiation at UVSOR-III

radiation, experiment, laser, storage-ring

1613

M. Hosaka, O. Oodake, Y. Takashima, N. Yamamoto
Nagoya University, Nagoya, Japan
S. Bielawski, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
M. Katoh, T. Konomi, J. Yamazaki
UVSOR, Okazaki, Japan
H. Zen
Kyoto University, Kyoto, Japan

Edge radiation can be an interesting new light source because of its property that the radiation is well collimated and is radially polarized. We are developing coherent light sources in the THz region at UVSOR-III storage ring. We have already succeeded in producing a narrow band coherent THz radiation by manipulating the interaction of a relativistic electron bunch with an amplitude modulated laser with. Recently a simplified tentative beamline for detection of the edge radiation is installed at downstream of a short straight section of UVSOR-III. Coherent radiation from electron bunches after the interaction with the amplitude modulated laser is observed. Detailed measurements of polarizations and special distribution of the radiation are underway. The latest status of the study will be reported.

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TUPJE005

Development of Pulsed Multipole Magnet for Aichi SR Storage Ring

storage-ring, injection, multipole, synchrotron

1616

K. Ito, M. Hosaka, A. Mano, T. Takano, Y. Takashima
Nagoya University, Nagoya, Japan
K. Hayashi, M. Katoh
UVSOR, Okazaki, Japan
N. Yamamoto
KEK, Ibaraki, Japan

The Aichi synchrotron radiation (Aichi SR) center is an industrial oriented synchrotron light source facility. The electron energy and circumference of the storage ring are 1.2 GeV and 72 m. The natural emittance is 53 nm-rad. Since the pulsed multipole injection scheme provides great advantages for relatively smaller SR rings*, we are developing a pulsed multipole injection system for Aichi SR storage ring. In this system, it is essential to minimize the perturbation to the stored beam. To realize the required performances, we have to minimize the residual field at stored beam position, taken into account the field generated by the copper current lead of the input terminal. In addition, we carried out the analytical calculation to estimate the magnet field due to the current lead and optimized the geometrical structure of them. Construction of the multipole magnet will be completed in March 2015 and the field measurement will be carried out in April. In this presentation, we report the detail of the magnet design and the measurement results of pulsed magnetic field for the manufactured magnet.
* N. Yamamoto, et. al., NIM A 767, 26-33 (2014)

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TUPJE007

Measurement of Temporal Electric Field of Electron Bunch using Photoconductive Antenna

laser, linac, polarization, radiation

1623

K. Kan, M. Gohdo, T. Kondoh, I. Nozawa, A. Ogata, T. Toigawa, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

A temporal electric field profile, which is a radially polarized terahertz (THz) pulse from an electron bunch, was measured by a large-aperture photoconductive antenna (PCA) with micro-structured concentric electrodes* for the detection of THz pulses. Photo-induced charge carriers were generated by irradiation of femtosecond laser pulses on semiconductor plane of the electrodes on the PCA. Time-domain measurement of coherent transition radiation (CTR) was conducted by the measurement of electric-field-induced current output from the PCA with sweeping the timing of the laser irradiation. The measurements on femtosecond electron bunches of 32 MeV and >80 pC will be reported.
* K. Kan et al., Appl. Phys. Lett. 102, 221118 (2013).

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TUPJE008

Relocation and Improvement Status of the SCSS Test Accelerator to Provide Dual FEL Drivers at SACLA

acceleration, undulator, linac, laser

1626

Y. Otake
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

To increase user experiment chances at SACLA, Equipping a new beamline and an additional linac as a further FEL driver is effective. For this reason, the SCSS test accelerator as the prototype of SACLA is reused and improved, because of terminating its role. SCSS with an electron beam energy of 250 MeV generated an extreme ultraviolet laser with 50-60 nm. We relocated SCSS into the SACLA undulator hall and improved its performance. Three newly designed C-band accelerator-units for the relocated SCSS accelerator with an acceleration gradient of 47 MeV/m at maximum boost an electron beam energy of up to 420 MeV. By FEL simulation, the EUV-FEL with 30-40 nm and 100 uJ are expected in conditions of the electron energy and 2 modified undulators with 5 m long each. As a further capability, the relocated SCSS accelerator has space to add 9 C-band accelerator units and 2 undulators and the units increase a beam energy of up to 1.4 GeV, as which can generate a soft X-ray FEL. The relocation of the accelerator was finished in the summer of 2014 and its RF conditioning was now started. This paper describes the relocation and improvement status of the modified SCSS accelerator.

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TUPJE009

Study on Frequency Multiplier of a Pulsed Laser Repetition using an Optical Cavity

laser, cavity, gun, cathode

1629

T. Kobayashi
Waseda University, Tokyo, Japan

We have been studying a compact electron accelerator based on an S-band Cs-Te photo-cathode rf gun at Waseda University. The system is using S-band rf of 2856MHz. When a repetition of the electron bunch is integral multiple of rf, it enables a lot of electron bunch acceleration for the rf gun. The repetition of the electron bunch generated by a photo-cathode rf gun depends on the oscillating frequency of the pulsed mode-locked laser. We have been developing a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation (NLPR). However, its repetition is limited by the fiber length to produce NLPR. Therefore, we have started to develop the external optical cavity which is multiplier of a pulsed laser repetition. It would enable the rf gun to generate high-dose electron beam in a very short time. In this conference, we will report design of the external optical cavity to multiply the pulsed laser repetition, the experimental results of the frequency multiplying of a mode-locked Yb-doped fiber laser, and the future prospects.
Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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TUPJE010

Study of Cs-Te Photocathode for RF Electron Gun

gun, vacuum, radiation, scattering

1632

S. Matsuzaki, M. Nishida, K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
H. Iijima
Tokyo University of Science, Tokyo, Japan

At Waseda University, we have been studying high quality electron beam with an rf electron gun. In recent accelerator study and application researches, high quality electron beam are strongly required. Photocathode is a key component to generate higher quality electron beam. Cs-Te photocathode shows high quantum efficiency (Q.E.) (~10%) and has long life time (~several months). From 2013, we built a photocathode evaporation chamber and started photocathode study. In this study, our purpose is to clarify their property and to establish an ideal evaporation recipe. We succeeded in producing high quality Cs-Te photocathode, and electron beam generated by our Cs-Te photocathode shows high charge (4.6nC/bunch) and high Q.E. (1.74%) in our rf electron gun. Furthermore, we found a Q.E. recovery after Cs deposition process and it causes higher Q.E. than usual due to, we believe, Cs deposition quantity or Cs deposition speed. Thus we are now surveying the optimum Cs evaporation parameters. In this conference, we will report a detail of our photocathode development system, the latest progress of optimization study of Cs-Te photocathode and future plans.
Work supported by Cooperative and Supporting Program for Researches and Educations in Universities and NEDO(New Energy and Industrial Technology Development Organization.

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TUPJE011

Laser-Compton Scattering X-ray Source Based on Normal Conducting Linac and Optical Enhancement Cavity

laser, cavity, linac, photon

1635

K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
S. Araki, M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source via laser-Compton scattering (LCS) at KEK-LUCX (Laser Undulator Compact X-ray source) facility. The LUCX system is based on S-band normal conducting linac with an energy of 30 MeV and optical enhancement cavity for photon target. As a photon target, we invented a burst mode laser pulse storage technique for a normal conducting linac, which enables to store the high power laser pulses at the timing of electron bunchs. The peak storage power exceeds to more than 250 kW with 357 MHz repetition. Electron linac is under operation with multi-bunch mode, 1000 bunches/train with 600 pC charge in each bunches. We have succeeded to produce 1000 pulse/train LCS X-ray train. Combining high repetition rate electron linac and burst mode optical enhancement cavity, more than 10⁹ ph./sec/10%b.w. flux would be possible. In this conference, the introduction of our test facility LUCX, recent expermental results, and future prospective including normal conducting LCS X-ray source will be presented.

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TUPJE013

Lattice Design of Low Beta Function at Interaction Point for TTX-II

lattice, quadrupole, dynamic-aperture, scattering

1641

T. Rui, W.-H. Huang
TUB, Beijing, People's Republic of China

TTX-II is a storage ring being designed at Accelerator Laboratory in Tsinghua University as the second phase of Tsinghua Thomson scattering x-ray source (TTX), to increase the average photon flux generated. To achieve a small beta function at the interaction point, four pairs of quadrupole magnets, whose focusing strengths are optimized, are added to the baseline. The lattice design is presented in this work.

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TUPJE014

An X-Band Linac with Tunable Beam Energy

linac, simulation, gun, software

1644

L. Zhang, H.B. Chen, Y.-C. Du, Q.X. Jin, J. Shi, C.-X. Tang, P. Wang, Z. Zhang
TUB, Beijing, People's Republic of China

The low-energy X-band linac has a wide application in medical imaging. In this paper, an X-band linac is designed to produce beam energy between 0.5MeV and 1.5MeV, and the output beam energy is continuously adjustable within this range. Two sections of linacs are combined and powered by a single microwave source. During the experiment, we can tune the RF phase and amplitude of the second section of the linac, the electron beam can see either acceleration or deceleration, which tunes the output energy. This paper presented the production of the whole linac system, as well as the measurement of the continuously-adjustable beam energy.

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TUPJE015

Beta Function Matching and Tune Compensation for HLS-II Insertion Devices

storage-ring, insertion, insertion-device, undulator

1647

B. Li, J.Y. Li, W. Xu, K. Xuan
USTC/NSRL, Hefei, Anhui, People's Republic of China

In order to increase its brightness and improve the performance, the Hefei Light Source (HLS) was completely renovated from 2010 to the end of 2014. The magnet lattice of the new storage ring consists of four double bend achromatic (DBA) cells. There are eight straight sections which can be used to install up to 6 insertion devices (IDs). Currently, five insertion devices have been installed in the storage ring. It is known that the dynamics of the electron beam motion in the storage ring would be influenced by the insertion device, depending on its physical properties. In order to keep high performance operation of the storage ring and make the insertion device transparent to the rest of the storage ring, a complex compensation scheme is developed to match the beta functions at both ends of a ID and perform transverse tune compensation. This scheme has been integrated into the EPICS based control system of the HLS-II. The result indicates that the scheme is very effective to compensate the impact of the insertion devices.

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TUPJE016

COHERENT SYNCHROTRON RADIATION FIELD AND THE ENERGY LOSS IN A WAVY BEAM

radiation, wakefield, synchrotron, synchrotron-radiation

1650

D.R. Xu, H. Xu
USTC/NSRL, Hefei, Anhui, People's Republic of China

The synchrotron radiation will be coherent when the wavelength of the radiation can be compared with the bunch length. There are two approaches to produce Coherent Synchrotron Radiation (CSR) on a storage ring. One is to compress the bunch length, the other one is to produce a wavy beam which has high spatial repetition along the longitudinal direction. The latter one can expand the radiation frequency range of a light source. However, CSR can bring nonlinear effect which brings in extra instability. The Lienard-Wiechert potentials in three-dimensional space may have very complicated forms. The most common way to investigate CSR is numerical method. This paper try to use a simple model to obtain energy loss of the electrons in theory.

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TUPJE017

The Generation of Highly Intense THz Radiation based on Smith-Purcell Radiation

radiation, factory, gun, cathode

1654

Y.F. Xu, Z.G. He, Q.K. Jia, W.W. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China

A photocathode RF gun can generate trains of THz subpicosecond electron bunches by illuminating the cathode with trains of laser pulses. Let this electron bunches passes close to the surface of a lamellar grating, THz radiation will be emitted, which is the so-called Smith-Purcell Radiation (SPR). If the lamellar grating has a narrow groove, this radiation will be narrow-band. By choosing suitable parameter, the SPR frequency can be resonant with the electron bunches frequency, and then generate high intense, narrow band THz radiation.

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TUPJE019

Operating Cascaded High-gain Harmonic Generation with Double-pulse Electron Beams

radiation, laser, FEL, simulation

1661

Z. Wang, C. Feng, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
L. Yu
BNL, Upton, Long Island, New York, USA

Cascaded high gain harmonic generation (HGHG) is the primary candidate for the generation of high power, full temporal coherent radiation at the wavelength of nanometer. However, the experimental results at the existing facility show large fluctuation of the output energy pulse at the second stage of cascading. In this paper, we study the scheme of double-pulse electron beams, which is helpful to increase the stability of pulse energy against the timing jitter. The method to generate double-pulse electron beams is shown in the paper and comparison between double-pulse scheme and standard cascaded HGHG is present base on three-dimensional start-to-end simulation to give a straightforward image on the obviously improvement of the FEL stability.

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TUPJE021

Interaction Chamber Design for a Sub-MeV Laser-compton Gamma-ray Source

laser, photon, scattering, simulation

1665

H.H. Xu, J.H. Chen, G.T. Fan, D. Wang, H.L. Wu, B.J. Xu
SINAP, Shanghai, People's Republic of China

Previously, fixed angle Laser-Compton Scattering (LCS) experiments have been conducted at the terminal of the 100MeV LINAC of the Shanghai Institute of Applied Physics, using SINAP-I* and SINAP-II** facility. Sub-MeV energy continuously tunable laser-Compton light source device (SINAP-Ⅲ) is an updated facility that will allow the collision angle between the laser and electron beam continuously adjustable from 20 to 160 degrees. This new feature will enable convenient control on the peak energy of the generated X/γ ray, especially when the energy of electrons cannot be momentarily adjusted, e.g. on the storage ring. The well control of the status of LCS is necessary. An interaction chamber containing a rotatable structure that holds a series of plane mirrors and convex lens is presented to achieve it. This work is a summary of its design. The simulation of photon production's variation caused by the system errors is performed using a MC code***. The accuracies of installation and adjustment of mirrors and lens are given according to the simulation results. The sizes of these optical devices are also optimized to make the chamber as compact as possible due to space limitation.
* W. Luo et al., Rev. of Sci. Instrum, 81 (2010) 013304
** W. Luo et al., Applied Physics B, 101 (2010)761-771
*** W. Luo et al., NIM A, 660 (2011), p. 108

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TUPJE032

Updates of the PAL-XFEL Undulator Program

undulator, background, FEL, controls

1675

D.E. Kim, M.-H. Cho, Y.-G. Jung, H.-S. Kang, I.S. Ko, H.-G. Lee, S.B. Lee, W.W. Lee, B.G. Oh, K.-H. Park, H.S. Suh
PAL, Pohang, Kyungbuk, Republic of Korea
S. Karabekyan, J. Pflüger
XFEL. EU, Hamburg, Germany

Pohang Accelerator Laboratory (PAL) is developing a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. At the first stage, PAL-XFEL needs two undulator lines for photon source. The hard X-ray undulator line requires 18 units of 5 m long hybrid-type conventional planar undulator and soft X-ray line requires 6 units of 5 m long hybrid type planar undulator with additional few EPUs for final polarization control. PAL is developing undulator magnetic structure based on EU-XFEL concepts. The key parameters are min pole gap of 8.3 mm, with period length 26 mm (HXU), 35 mm (SXU), and 5.0 m magnetic length. . In this report, the prototyping, and the development of pole tuning procedure, the impact of the background field error, and the effects of the girder bending on the optical phase error will be presented.

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TUPJE033

A Research on the Reverse Tapering Method to Gain High Power Polarized Photon Beam with Fixed Wavelength

undulator, radiation, resonance, simulation

1678

C.H. Shim, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Han, Y.W. Parc
PAL, Pohang, Kyungbuk, Republic of Korea

Polarization of soft X-ray photon can be controlled with combination between planar undulators and helical ones. We need to give a reverse tapering to the planar undulators to make microbunching in the electron beam while the linearly polarized radiation power is depressed. In this case, however, resonance wavelengths in each planar undulator are different each other. Therefore, proper initial undulator parameter and tapering strength parameter have to be chosen to obtain high power polarized photon beam with fixed wavelength. In this research, method for deciding suitable reverse tapering is presented using simulation results of PAL-XFEL soft X-ray case with 10 GeV electron beam energy.

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TUPJE034

A Preliminary Report from Louisiana State University CAMD Storage Ring Operating with an 11-pole 7.5 T Wiggler

wiggler, operation, storage-ring, injection

1682

R.S. Amin, P. Jines, D.J. Launey, K.J. Morris, V.P. Suller, Y. Wang
LSU/CAMD, Baton Rouge, Louisiana, USA
V.K. Lev, N.A. Mezentsev, V.A. Shkaruba, V.M. Syrovatin, O.A. Tarasenko, V.M. Tsukanov, A.A. Volkov, A.V. Zorin
BINP SB RAS, Novosibirsk, Russia

Funding: Funded by the National Science Foundation.
Louisiana State University installed a 7.5 T superconducting wiggler in May 2013 on the electron storage ring located at the Bennett Johnson, Sr. Center for Advanced Microstructures and Devices (CAMD). The wiggler’s influence on betatron tunes and functions, orbit, lifetime, performance, and other relevant beam parameters are described. We further comment on device operations and modifications to ring operations that were necessary to provide light for both wiggler and dipole stations.

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TUPJE037

Magnetic Measurements of the NSLS-II Insertion Devices

insertion, insertion-device, undulator, radiation

1693

M. Musardo, D.A. Harder, C.A. Kitegi, T. Tanabe
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
This paper presents the results and the recent progress in the magnetic measurements of the insertion devices (IDs) for the National Synchrotron Light Source-II (NSLS-II) at Brookhaven National Laboratory (BNL). A detailed analysis of the magnetic measurements is carried out for various IDs with particular attention at the influence of the magnetic field errors on the devices spectral performance. Several specific details of the measurements and the recent results from IDs commissioning are presented.

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TUPJE040

Surface Characterization at CERN of Photocathodes for Photoinjector Applications

cathode, laser, gun, operation

1703

I. Martini, E. Chevallay, V. Fedosseev, C. Heßler, H. Neupert, V. Nistor, M. Taborelli
CERN, Geneva, Switzerland

R&D on photocathodes takes place at CERN within the CLIC (Compact Linear Collider) project. Photocathodes are produced as thin films on Oxygen Free copper substrate using a co-deposition technique, and characterized in a dedicated laboratory with a DC photo-electron gun. A new UHV carrier vessel compatible with CERN’s XPS (X-ray Photoelectron Spectroscopy) analysis equipment has been commissioned and is used to transport photocathodes from the production laboratory to perform a systematic study of different compounds used as photoemissive materials. In this paper photocathodes used in a RF photoinjector will be characterized and the correlation of their surface properties with their performance will be investigated.

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TUPJE049

TPS Linac Relocation and Beam Test of the LTB Transfer Line

linac, optics, quadrupole, injection

1731

H.-P. Chang, A.Y. Chen, C.L. Chen, Y.-S. Cheng, C.-S. Fann, K.T. Hsu, S.Y. Hsu, K.-K. Lin, Y.C. Lin, J. Liu, K.L. Tsai
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source (TPS) 150 MeV linac has been relocated from its 2011 test site to the TPS linac tunnel in 2014. After functional test of the linac hardware modules, the beam parameters were carefully examined at a 31-degree bend diagnostic beam line LTD (linac to beam dump) and compared with previous results. Then, the 150 MeV electron beam was delivered to the linac to booster transfer line (LTB) for beam commissioning. The beam optics matching at both the LTB entrance (i.e. linac exit) and the LTB exit (i.e. injection point of booster) was performed for injection optimization purpose. The LTB lattice setting was verified in the beam steering through LTD and LTB with the help of diagnostics tools such as beam profile monitors (SM) and beam position monitors (BPM). The overall performance of the linac and LTB will be described in this report.
#peace@nsrrc.org.tw

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TUPJE050

Design of a Resonant Transition Radiation Source in the soft X-ray Range

photon, radiation, resonance, vacuum

1735

P. Wang, K.C. Leou
NTHU, Hsinchu, Taiwan
N.Y. Huang, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan

Resonant transition radiation (RTR) can be generated from multi-layer structures when they are driven by relativistic electron beams. In consideration of using the NSRRC 90 MeV photoinjector as driver, we examined the feasibility of generating narrow-band soft x-rays from various multi-layer structures. Based on analytical theory, the expected angular-spectral distribution and photon yield of these radiators are calculated and compared.

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TUPJE052

Bunch Compression in the Driver Linac for the Proposed NSRRC VUV FEL

linac, optics, gun, FEL

1738

N.Y. Huang, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan
A. Chao, K. Fang, M.-H. Wang, J. Wu
SLAC, Menlo Park, California, USA

A bunch compressor is designed for the S-band driver linac system of the proposed NSRRC VUV free electron laser (FEL). Instead of using a more conventional rf harmonic linearizer, one main feature of this compressor is to use electron linearization optics to correct the nonlinearity in the energy-time correlation of the electron bunch longitudinal phase space. The strategy of compressor design will be discussed by an analytical calculation and particle tracking simulation. The beam dynamics which include the collective instabilities such as the space charge effects, the wake fields and the coherent synchrotron radiation (CSR) effects are discussed.

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TUPJE055

The Evolution of the Transverse Energy Distribution of Electrons from a GaAs Photocathode as a Function of its Degradation State

detector, cathode, brightness, vacuum

1748

L.B. Jones, B.L. Militsyn, T.C.Q. Noakes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
H.E. Scheibler, A.S. Terekhov
ISP, Novosibirsk, Russia

The brightness of a photoelectron injector is fundamentally limited by the mean longitudinal and transverse energy distributions of the photoelectrons emitted from its photocathode, and is increased significantly if the mean values of these quantities are reduced. To address this, ASTeC constructed a Transverse Energy Spread Spectrometer (TESS)* – an experimental facility designed to measure these transverse and longitudinal energy distributions which can be used for III-V semiconductor, alkali antimonide/telluride and metal photocathode research. We present measurements showing evolution of the transverse energy distribution of electrons from GaAs photocathodes as a function of their degradation state. Photocathodes were activated to negative electron affinity in our photocathode preparation facility (PPF)** with quantum efficiency around 10.5%. They were then transferred to TESS under XHV conditions, and progressively degraded through controlled exposure to oxygen. Data has been collected under photocathode illumination at 635 nm, and demonstrates a constant relationship between energy distribution and the level of electron affinity.
* Proc. FEL ’13, TUPPS033, 290-293
** Proc. IPAC '10, TUPE095, 2347-2349, Proc. IPAC ’11, THPC129, 3185-3187

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TUPJE056

VELA Machine Development and Beam Characterisation

cavity, cathode, gun, klystron

1752

D.J. Scott, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, L.K. Rudge, E. Sneddon, M. Surman, R. Valizadeh, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.D. Barrett, C.P. Topping, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
A. Lyapin
JAI, Egham, Surrey, United Kingdom
M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
C.P. Topping, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom
E. Yamakawa
Royal Holloway, University of London, Surrey, United Kingdom

Recent developments on the VELA (Versatile Electron Linear Accelerator) RF photo-injector at Daresbury Laboratory are presented. These are three-fold; commissioning/installation, characterising and providing beam to users. Measurements for characterising the dark current (DC), 4-D transverse emittance, lattice functions and photoinjector stability are presented. User beam set ups to provide beam for electron diffraction and Cavity Beam Position Monitor development are summarised.

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TUPJE057

Realistic Undulators for Intense Gamma-ray Beams at Future Colliders

undulator, positron, simulation, synchrotron

1756

A.O. Alrashdi, I.R. Bailey
Lancaster University, Lancaster, United Kingdom
D. Newton
The University of Liverpool, Liverpool, United Kingdom

The baseline designs for the ILC and CLIC require the production of an intense flux of gamma rays in their positron sources. In the case of CLIC the gamma rays are produced by a Compton backscattering source, but in this paper we concentrate on undulator-based sources as proposed for the ILC. We present the development of a simulation to generate a magnetic field map based on a Fourier analysis of any measured field map. We have used a field map measured from the ILC helical undulator prototype to calculate the typical distribution of field errors, and used them in our calculations to produce simulated field maps. We show that a loss of gamma ray intensity of ~ 8% could be expected, compared to the ideal case. This leads to a similar drop in positron production which can be compensated for by increasing the undulator length.

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TUPJE058

Preparation of Polycrystalline and Thin Film Metal Photocathodes for Normal Conducting RF Guns

cathode, gun, experiment, cavity

1759

S. Mistry, M.D. Cropper
Loughborough University, Leicestershre, United Kingdom
A.N. Hannah, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

A comparison of quantum efficiency (QE) and work function (wf) measurements of polycrystalline and thin film metal photocathodes for use in NCRF guns, similar to the S-band gun under development for CLARA project at Daresbury, are reported. Cu and Nb thin films were grown onto a Si substrate by magnetron sputtering and subsequently were prepared by annealing and Ar ion sputtering. To determine the surface chemistry, x-ray photoelectron spectroscopy was employed. QE measurements were enabled using a UV laser source giving 266 nm light. Wf measurements were carried out using a kelvin probe and ultraviolet photoelectron spectroscopy. Annealing the Cu thin film to 250°C yielded a QE of 1.2E-4; one order of magnitude higher than the QE for sputter cleaned and post annealed polycrystalline Cu. The optimum QE measurement for Nb thin film was 2.6·10^-4, which was found to be comparable to the results obtained for cleaned bulk Nb. Analysis of XPS data of these metals suggest surface composition and surface chemistry are main contributing factors to the QE and WF.

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TUPJE060

Development of Advanced Fourth Generation Light Sources for the Accelerator Science Laboratory

radiation, simulation, cavity, laser

1765

T. Chanwattana, R. Bartolini, A. Seryi
JAI, Oxford, United Kingdom
R. Bartolini
DLS, Oxfordshire, United Kingdom
E. Tsesmelis
CERN, Geneva, Switzerland

The John Adams Institute for Accelerator Science (JAI) has proposed the realisation of the Accelerator Science Laboratory (ASL) at the University of Oxford as a facility for the development of advanced compact light sources enabling accelerator science research and applications. The installation of a compact light source in the ASL is planned with two options for the accelerating technologies. Firstly, a conventional RF based accelerator is considered to be a driver for a short pulse THz coherent synchrotron radiation (CSR). The other option focusses on the radiation produced by a Laser Plasma Accelerator (LPA) advanced accelerator technique that will provide the possibility to shorten the length of the beamline. This paper presents results of the studies on beam dynamics for both options of compact light sources in the ASL.

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TUPJE064

Calibration of Fast Fiber-Optic Beam Loss Monitors for the Advanced Photon Source Storage Ring Superconducting Undulators

undulator, photon, simulation, vacuum

1780

J.C. Dooling, K.C. Harkay, Y. Ivanyushenkov, V. Sajaev, A. Xiao
ANL, Argonne, Ilinois, USA
A. Vella
University of Illinois at Urbana-Champaign, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under contract number DE-AC02-06CH11357.
We report on the calibration and use of fast fiber-optic (FO) beam loss monitors (BLMs) in the Advanced Photon Source storage ring (SR). A superconducting undulator prototype (SCU0) has been operating in SR Sector 6 since the beginning of CY2013, and another undulator SCU1 (a 1.1-m length undulator that is three times the length of SCU0) is scheduled for installation in Sector 1 in 2015. The SCU0 main coil often quenches during beam dumps. MARS simulations have shown that relatively small beam loss (<1 nC) can lead to temperature excursions sufficient to cause quenching when the SCU0 windings are near critical current. To characterize local beam losses, high-purity fused-silica FO cables were installed in Sector 6 next to the SCU0 cryostat and in Sector 1 where SCU1 will be installed. These BLMs aid in the search for operating modes that protect the SCU structures from beam-loss-induced quenching. In this paper, we describe the BLM calibration process that included deliberate beam dumps at locations of BLMs. We also compare beam dump events where SCU0 did and did not quench.

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TUPJE073

Results of the Magnetic Tuning of 2.8 m Long Vertically Polarizing Undulator with the Dynamic Compensation of Magnetic Forces

undulator, FEL, radiation, free-electron-laser

1809

I. Vasserman
ANL, Argonne, Ilinois, USA

A novel undulator prototype with a horizontal magnetic field and dynamic compensation of magnetic forces has been recently developed at the APS as a part of the LCLS-II R&D program. This undulator should meet stringent requirements for any LCLS-II insertion device. These requirements include limits on the field integrals and phase errors for all operational gaps, and the reproducibility and accuracy of the gap settings. Extensive mechanical testing has resulted in a performance that meets the requirements on the undulator gap setting. The magnetic tuning has been accomplished by applying a set of magnetic shims. As a result, the satisfactory performance of the undulator prototype has been demonstrated.
The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory. Argonne, Contract No. DE-AC02-06CH11357.

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TUPJE074

LCLS Injector Laser Modulation to Improve FEL Operation Efficiency and Performance

laser, optics, FEL, emittance

1813

S. Li, D.K. Bohler, W.J. Corbett, A.S. Fisher, S. Gilevich, Z. Huang, A. Li, D.F. Ratner, J. Robinson, F. Zhou
SLAC, Menlo Park, California, USA
R.B. Fiorito, E.J. Montgomery
UMD, College Park, Maryland, USA
H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom

In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The injector laser strikes a copper photocathode which emits photo-electrons due to photo-electric effect. The emittance of the electron beam is highly related to the transverse shape of the injector laser. Currently the LCLS injector laser has hot spots that degrade the FEL performance. The goal of this project is to use adaptive optics to modulate the transverse shape of the injector laser, in order to produce a desired shape of electron beam. With a more controllable electron transverse profile, we can achieve lower emittance for the FEL, improve the FEL performance and operation reliability. We first present various options for adaptive optics and damage test results. Then we will discuss the shaping process with an iterative algorithm to achieve the desired shape, characterized by Zernike polynomial deconstruction.

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TUPJE081

Model of Dark Current in SRF Linac

cavity, linac, radiation, quadrupole

1834

A.I. Sukhanov, A. Saini, N. Solyak, I.S. Tropin
Fermilab, Batavia, Illinois, USA

Currently, few linacs based on 9-cell TESLA-type SRF cavities are being designed or bult, including XEFL, LCLS-II and ILC. Dark current electron generated by field emission in SRF cavities can be captured and accelerated in the linac up to hundreds MeV before they removed by focusing magnets. Lost dark current electrons interact with the materials surrounding SRF cavities and magnets, produce electromagnetic showers and contribute to the radiation in the linac tunnel. In this paper we present a model of dark current in a linac based on TESLA cavities. We show preliminary results of the simulation applied to ILC main linac.

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TUPMA004

Synthesis of Ultra-Thin Single Crystal MgO/Ag/MgO Multilayer for Controlled Photocathode Emissive Properties

emittance, cathode, laser, simulation

1846

D.G. Velázquez, R.L. Seibert, L.K. Spentzouris, J. Terry, Z.M. Yusof
Illinois Institute of Technology, Chicago, Illinois, USA

Photocathode emission properties are critical for electron beam applications such as photoinjectors for free electron lasers (FEL) and energy recovery Linacs (ERL). We investigate whether emission properties of photocathodes can be manipulated through the engineering of the surface electronic structure. The multilayers described here have been predicted to have emission properties in correlation with the film thickness. This paper describes how ultra-thin multilayered MgO/Ag/MgO films in the crystallographic orientations (001) and (111) multilayers were synthesized and characterized. Preliminary results of work function measurements are provided. Films were grown by pulsed laser deposition at 130 °C for the (001) orientation and 210 °C for the (111) orientation at a background pressure of ~ 5×10^-9 Torr. Epitaxial growth was monitored in-situ using reflection high-energy electron diffraction, which showed single crystal island growth for each stage of the multilayer formation. Photoelectron spectroscopy was used to track the chemical state transition from Ag to MgO during the deposition of successive layers. The Kelvin probe technique was used to measure the change in contact potential difference, and thus work function, for various MgO layer thicknesses in comparison with bare single crystal Ag(001)and Ag(111) thin films. The work function was observed to reduce with increasing thickness of MgO from 0 to 4 monolayers as much as 0.89 eV and 0.72 eV for the (001) and (111) orientations, respectively. Photoelectron spectra near the Fermi level revealed electron density shifts toward zero binding energy for the multilayered surfaces with respect to the clean Ag surfaces.

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TUPMA010

Development of a Field-Emission Type S-band RF-Gun System for High Brightness Electron Source Applications

cathode, gun, emittance, vacuum

1856

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
N. Barov
Far-Tech, Inc., San Diego, California, USA
A.T. Green
Northern Illinois Univerity, Dekalb, Illinois, USA

Electron beams emitted from a cold cathode are thermally stable and mono-energetic with a small phase-space volume*. We have been developing a field-emission type RF-gun system for high brightness electron source applications, including electron scattering/diffraction and tunable coherent X-ray/THz generation. The system consists of a single-gap gun-cavity and an S-band klystron/modulator capable of powering the gun with up to 5.5 MW peak (PRR = 1 Hz, duration = 2.5 μs). The designed gun built with the symmetrised side-couplers has surface field on the cathode ranging 50 – 100 MV/m with 1.3 – 1.7 MW klystron-power and 1.2 field ratio (HFSS). ASTRA simulations also indicate that the gun produces the beam with transverse emittances of less than 1 mm-mrad with 10 – 20 pC bunch charge at 500 keV beam energy. Under the gun operating condition, particle tracking/PIC simulations (CST) show that a single-tip CNT field-emitter** produces short pulsed bunches (~ 1/10 RF-cycle) with small emittance ( 0.01 mm-mrad) and high peak current density ( 10,000 kA/cm²). After the gun is fully installed and commissioned, a CNT-tip cathode will be tested with RF-field emission.
* N. De Jonge, J.-M. Bonard, Phil. Trans. R. Soc. Lond. A 362, 2239 (2004)
** G. S. Bocharov, and A. V. Eletskii, Nanomaterials 3, 393 (2013)

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TUPMA014

Extending OK5 Wiggler Operational Limit at Duke FEL/HIGS Facility

wiggler, FEL, operation, controls

1863

P.W. Wallace, M. Emamian, H. Hao, J.Y. Li, S.F. Mikhailov, V. Popov, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA
J.Y. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033
Since 2007 the HIGS facility has been operated to produce both linearly and circularly polarized gamma-ray beams using two FELs, the planar OK-4 FEL and helical OK-5 FEL. Presently, with the OK-5 FEL operating at 192 nm, we can produce circularly-polarized gamma-ray beams between 1 and 100 MeV for user applications. Gamma-ray production between 80 and 100 MeV required an extension of the OK-5 wiggler operation beyond the designed current limit of 3.0 kA. In 2009, we upgraded cooling and machine protection systems to successfully extend OK-5 operation to 3.5 kA. To realize HIGS gamma-ray operation beyond 100 MeV and ultimately toward 150 MeV (the pion-threshold energy), with various limitations of the VUV mirror technology, the OK-5 wigglers will need to be operated at an even higher current, between 3.6 and 4.0 kA. In this paper we present our technical solution to further extend the operation range of the OK-5 wigglers, and report our preliminary results with high-current wiggler operation.

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TUPMA016

Light Source and Accelerator Physics Research Program at Duke University

FEL, wiggler, storage-ring, operation

1866

Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The light source and accelerator physics research program at Duke Free-Electron Laser Laboratory (DFELL), TUNL, is focused on the development of the storage ring based free-electron lasers (FELs), and a state-of-the-art Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS) which is driven by the storage ring FEL. With a maximum total flux about 3·10¹⁰ gamma/s and a spectral flux of more than 1,000 gamma/s/eV around 10 MeV, the HIGS is the world's most intense Compton gamma-ray source. Operated in the energy range from 1 to 100 MeV, the HIGS is a premier Compton gamma-ray facility in the world for a variety of nuclear physics research programs, both fundamental and applied. In this paper, we will describe our ongoing light source development to produce gamma-ray beams in the higher energy range of 100 and 158 MeV. We will also provide a summary of our recent accelerator physics and FEL physics research activities.

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TUPMA017

Pulsed-wire Measurements for Insertion Devices

undulator, detector, FEL, laser

1869

A. D'Audney, S. Biedron, S.V. Milton, S.A. Stellingwerff
CSU, Fort Collins, Colorado, USA

The performance of a Free Electron Laser (FELs) depends in part on the integrity of the magnetic field in the undulator. The magnetic field on the axis of the undulator is transverse and sinusoidally varying due to the periodic sequence of dipoles. The ideal trajectory of a relativistic electron bunch, inserted along the axis, is sinusoidal in the plane of oscillation. Phase errors are produced when the path of the electron is not the ideal sinusoidal trajectory, due to imperfections in the magnetic field. The result of such phase errors is a reduction of laser gain impacting overall FEL performance. A pulsed-wire method can be used to determine the profile of the magnetic field. This is achieved by sending a square current pulse through the wire, which will induce an interaction with the magnetic field. Measurement of the displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic field. Dispersion in the wire can be corrected using algorithms resulting in higher accuracy. Once the fields are known, magnetic shims are placed where any corrections are needed.

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TUPMA018

An Improved Analytic Model of Electron Back-Bombardment in Thermionic Cathode RF Guns

simulation, gun, cathode, cavity

1872

J.P. Edelen, S. Biedron, J.R. Harris, S.V. Milton
CSU, Fort Collins, Colorado, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

This paper describes work done at Colorado State University to improve upon the recent theory developed to predict the back-bombardment power in single-cell thermionic-cathode electron guns. The previous theory used a square-wave approximation of the time varying field to solve for the total kinetic energy deposited on the cathode due to the back-bombarded electrons. In addition the transit time factor was added as a correction to compensate for the non-sinusoidal field. By solving for the back-bombardment power using a sinusoidal field, the transit time factor can be removed and therefore a better overall model is produced. These alterations continue to accurately predict how back-bombardment varies as a function of the gun parameters and provides improvement when compared to the existing theory.

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TUPMA019

Simulation and Analysis of Laser/Electron Beam interaction for use as a Free Electron Laser

undulator, laser, simulation, free-electron-laser

1875

J. Einstein, S. Biedron, H. Freund, S.V. Milton
CSU, Fort Collins, Colorado, USA
G. Dattoli
ENEA C.R. Frascati, Frascati (Roma), Italy

Through the use of simulation tools and theoretical analysis techniques, the Free Electron Laser process is investigated for a wiggler that is generated by an ultrafast laser system. The development and availability of such systems allows for novel FEL designs due to the high peak power of such lasers. Even though such high powers are possible, difficulties arise due to inhomogeneity in the laser pulse. This project looks at simulation results for a system with a realistic laser pulse profile and looks in to the pulse-shape effects on various system parameters. Models are presented for the expected behavior with important parameters noted, as well as highlighting possible difficulties that might occur experimentally. While head-on interaction has been proven experimentally for the short wavelength regime *, we believe that using a co-propagating laser can provide benefits that have currently been untested. This experimental setup is outlined in Lawler, J et al **, and we are currently simulating how the use of an ultrashort laser pulse as an electromagnetic wiggler will affect characteristics of the output radiation.
* Laundy, D.; et al. NIM-A vol 689. pp 108-114. OCT 11 2012
** Lawler, J.; et al. J. Phys. D: Appl. Phys. 46 (2013) 325501

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TUPMA020

PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons

positron, target, polarization, solenoid

1878

A.H. Adeyemi, P.L. Gueye
Hampton University, Hampton, Virginia, USA
P.A. Adderley, M.M. Ali, H. Areti, J. F. Benesch, L.S. Cardman, J. Clark, S. Covert, C. Cuevas, A. Freyberger, S. Golge, J.M. Grames, P.L. Gueye, J. Hansknecht, P.L. Harrell, C. Hyde, R. Kazimi, Y. Kim, D. Machie, K.L. Mahoney, R.R. Mammei, J.L. McCarter, M.D. McCaughan, M. Poelker, M.L. Stutzman, R. Suleiman, C.-Y. Tsai, D.L. Turner, Y.W. Wang
JLab, Newport News, Virginia, USA
M.A. Baylac, E. Froidefond, M. Marton, J-F. Muraz, J-S. Real, E. J-M. Voutier
LPSC, Grenoble Cedex, France
P. Cole, D. Dale, T.A. Forest
ISU, Pocatello, Idaho, USA
O. Dadoun, A. Variola
LAL, Orsay, France
D. Dale, Y. Kim
IAC, Pocatello, Idaho, USA
EF. Fanchini
INFN Genova, Genova, Italy
S. Golge
NCCU, , North Carolina, USA
S. Golge, C. Hyde
ODU, Norfolk, Virginia, USA
J.L. McCarter
UVa, Charlottesville, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
A. Variola
IN2P3-CNRS, Orsay, France

Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.

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TUPMA022

CESR Upgrade as a High-Energy, High-Brightness X-Ray Light Source

emittance, positron, lattice, storage-ring

1884

J.P. Shanks, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Research supported by NSF grant DMR-1332208.
The Cornell Electron Storage Ring (CESR) operates most of the year as the Cornell High Energy Synchrotron Source (CHESS). CESR was originally designed and operated as an electron/positron collider, circulating high-emittance beams in order to maximize luminosity. Beam lines were developed to extract x-rays from both electron and positron beams. The two beams share a common vacuum chamber, and are electrostatically separated to avoid collisions. The requirement to store counter-rotating beams significantly constrains the storage ring optics, limiting emittance and, beam current, and bunch distributions. The proposed upgrade eliminates two-beam operation in favor of a single optimized on-axis beam. Several new undulator-based beam lines are planned. The horizontal emittance is reduced in steps, first from 90nm to 20nm at 5.3 GeV, and then in a ring-wide upgrade to as low as 300 pm-rad at 6GeV. The low-emittance optics are based on multi-bend achromats with combined function bends. The details of the optics, apertures, and magnet parameters are presented.

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TUPMA023

Two-Dimensional Calculation of Channeling Radiation Spectrum for High-Brightness Hard X-Ray Production

radiation, lattice, ion, brightness

1888

W.D. Rush, J. Shi
KU, Lawrence, Kansas, USA

The channeling radiation spectrum is calculated without using the one-dimensional approximation in the planar channeling radiation model or the single-string approximation in the axial channeling radiation model. The obtained spectrum of the two-dimensional channeling radiaiton is significantly different from those previously calculated with the approximations. The calculation presented here is of the channeling radiation experiments conducted at Fermilab Advanced Superconducting Test Accelerator (ASTA) photoinjector with electron beam energies of 20-50 MeV and a diamond target. The computational method developed in this work can be applied to general cases of different crystals and beams with different energy and emittances.

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TUPMA025

X-Band RF Photoinjector for Laser Compton X-Ray and Gamma-Ray Sources

laser, emittance, dipole, gun

1891

R.A. Marsh, G.G. Anderson, S.G. Anderson, C.P.J. Barty, D.J. Gibson
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Extremely bright narrow bandwidth gamma-ray sources are expanding the application of accelerator technology and light sources in new directions. An X-band test station has been commissioned at LLNL to develop multi-bunch electron beams. This multi-bunch mode will have stringent requirements for the electron bunch properties including low emittance and energy spread, but across multiple bunches. The test station is a unique facility featuring a 200 MV/m 5.59 cell X-band photogun powered by a SLAC XL4 klystron driven by a Scandinova solid-state modulator. This paper focuses on its current status including the generation and initial characterization of first electron beam. Design and installation of the inverse-Compton scattering interaction region and upgrade paths will be discussed along with future applications.

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TUPMA026

Status of the MaRIE X-FEL Accelerator Design

linac, emittance, FEL, undulator

1894

J.W. Lewellen, K. Bishofberger, B.E. Carlsten, L.D. Duffy, F.L. Krawczyk, Q.R. Marksteiner, D.C. Nguyen, S.J. Russell, R.L. Sheffield, N.A. Yampolsky
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the MaRIE program at Los Alamos National Laboratory, under contract DE-AC52-06NA25396
The Matter-Radiation Interactions in Extremes (MaRIE) facility is intended to probe and control the time-dependent properties of materials under extreme conditions. At its core, the “MaRIE 1.0” X-FEL is being designed to deliver pulse trains of ~10¹⁰ 42 keV photons, with a minimum bunch spacing of 2.4 ns, enabling time-dependent studies particularly of mesoscale phenomena. The X-FEL accelerator is also intended to deliver a series of 2 nC electron bunches to enable electron radiography concurrently with the X-ray pulse train, so as to provide multi-probe capability to MaRIE. In 2014, the reference design for the MaRIE X-FEL 12 GeV driver linac was changed from an S-band normal-conducting to an L-band superconducting linac to accommodate pulse trains up to 100 μs in duration. This paper does not present a complete solution for the MaRIE linac design; rather it describes our current reference design, achieved parameters, areas of concern and paths towards mitigation of identified issues.

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TUPMA028

Feasibility Study for an X-ray FEL Oscillator at the LCLS-II

cavity, FEL, undulator, laser

1897

T.J. Maxwell, J. Arthur, Y. Ding, W.M. Fawley, J.C. Frisch, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus
SLAC, Menlo Park, California, USA
W.M. Fawley
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
K.-J. Kim, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin
ANL, Argonne, Ilinois, USA

Funding: This work supported in part under US Department of Energy contract DE-AC02-76SF00515.
We show that a free-electron laser oscillator generating X-ray pulses with hard X-ray wavelengths of order 0.1 nm is feasible using the presently proposed FEL-quality electron beam within the space of existing LCLS-II infrastructure when combined with a low-loss X-ray crystal cavity. In an oscillator configuration driven by the 4 GeV energy electron beam lasing at the fifth harmonic, output x-ray bandwidths as small as a few meV are possible. The delivered average spectral flux is at least two orders of magnitude greater than present synchrotron-based sources with highly stable, coherent pulses of duration 1 ps or less for applications in Mössbauer spectroscopy and inelastic x-ray scattering.

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TUPMA030

Narrowband Continuously Tunable Radiation in the 5 to 10 Terahertz Range by Inverse Compton Scattering

laser, radiation, photon, scattering

1901

Z. Wu, K. Fang, M.-H. Wang, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199.
5 to 10 THz has recently become the frontier of THz radiation sources development, pushed by the growing interests of spectroscopy and pump-probe material study in this frequency range. This spectrum “Gap” lies in between the several THz range covered by Electro-Optical crystal based THz generation, and the tens of THz range covered by the difference frequency generation method. The state-of-the-art EO crystal THz source using tilted pulse front technique has been able to reach ~ 100 MV/m peak field strength, large enough to be used in an inverse Compton scattering process to push these low energy photons to shorter wavelengths of the desired 5-10 THz range. The required electron beam energy is within 1~2 MeV, therefore a compact footprint of the whole system. The process would occur coherently granted the electron beam is bunched to a fraction of the radiation wavelengths (several microns). A system operating at KHz or even MHz repetition rate is possible given the low electron energy and thus low RF acceleration gradient required. This work will explore the scheme with design parameters and simulation results.

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TUPMA031

Dispersive Property of the Pulse Front Tilt of a Short Pulse Optical Undulator

laser, optics, FEL, undulator

1904

M.-H. Wang, J. Wu, Z. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE No. DE-AC02-76SF00515.
A short pulse laser can be used as an optical undulator to achieve a high-gain and high-brightness X-ray free electron laser (FEL) [1]. To extend the interaction duration of electron and laser field, the electron and the laser will propagate toward each other with an small angle. In addition, to maintain the FEL lasing resonant condition, the laser pulse shape need be flattened and the pulse front will be titled. Due to the short pulse duration, the laser pulse has a broad bandwidth. In this paper, we will first describe the method of generalized Gaussian beam propagation using ray matrix. By applying the Gaussian beam ray matrix, we can study the dispersive property after the pulse front of the short laser is tilted. The results of the optics design for the proposal of SLAC Compton scattering FEL are shown as an example in this paper.
[1] C. Chang, et al.,“High-brightness X-ray free-electron laser with an optical undulator by pulse shaping”. Optics Express, Vol. 21, Issue 26, pp. 32013-32018 (2013).

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TUPMA033

A Bunch Compression Method for Free Electron Lasers that Avoids Parasitic Compressions

dipole, laser, FEL, acceleration

1907

S.V. Benson, D. Douglas, C. Tennant, F.G. Wilson
JLab, Newport News, Virginia, USA
D.C. Nguyen
LANL, Los Alamos, New Mexico, USA

Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences.
Virtually all existing high energy (>few MeV) linac-driven FELs compress the electron bunch length though the use of off-crest acceleration on the rising side of the RF waveform followed by transport through a magnetic chicane. This approach has at least three flaws: 1) it is difficult to correct aberrations- particularly RF curvature, 2) rising side acceleration exacerbates space charge-induced distortion of the longitudinal phase space, and 3) all achromatic "negative compaction" compressors create parasitic compression during the final compression process, increasing the CSR-induced emittance growth. One can avoid these deficiencies by using acceleration on the falling side of the RF waveform and a compressor with M56>0. This approach offers multiple advantages: 1) It is readily achieved in beam lines supporting simple schemes for aberration compensation, 2) Longitudinal space charge (LSC)-induced phase space distortion tends, on the falling side of the RF waveform, to enhance the chirp, and 3) Compressors with M56>0 can be configured to avoid spurious over-compression. We will discuss this bunch compression scheme in detail and give results of a successful beam test in April 2012 using the JLab UV Demo FEL

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TUPMA038

Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Brag Reflector

laser, polarization, cathode, vacuum

1923

S. Zhang, M. Poelker, M.L. Stutzman
JLab, Newport News, Virginia, USA
Y. Chen, A. Moy
SVT Associates, Eden Prairie, Minnesota, USA

Funding: This project was supported by the U.S. DOE Basic Energy Sciences under contract No. DE-AC05-060R23177.
Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.

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TUPMA042

THz Radiation Generation in a Multimode Wakefield Structure

radiation, wakefield, experiment, linac

1929

S.P. Antipov, S.V. Baryshev, C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
M.G. Fedurin
BNL, Upton, Long Island, New York, USA
W. Gai, D. Wang, A. Zholents
ANL, Argonne, Illinois, USA

Funding: Work supported by the Department of Energy SBIR program under Contract #DE-SC0009571
A number of methods for producing sub-picosecond beam microbunching have been developed in recent years. A train of these bunches is capable of generating THz radiation via multiple mechanisms like transition, Cherenkov and undulator radiation. We utilize a bunch train with tunable spacing to selectively excite high order TM0n - like modes in a multimode structure. In this paper we present experimental results obtained at the Accelerator Test Facility of Brookhaven National Laboratory.

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TUPMA043

Experimental Test of Semiconductor Dechirper

wakefield, FEL, experiment, emittance

1932

S.P. Antipov, S.V. Baryshev, C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Baturin
LETI, Saint-Petersburg, Russia
M.G. Fedurin, K. Kusche, C. Swinson
BNL, Upton, Long Island, New York, USA
W. Gai, S. Stoupin, A. Zholents
ANL, Argonne, Illinois, USA

Funding: Work supported by the Department of Energy SBIR program under Contract #DE-SC0006299
We report the observation of de-chirping of a linearly chirped (in energy) electron bunch by its passage through a 4 inch long rectangular waveguide loaded with two silicon bars 0.25 inch thick and 0.5 inch wide. Silicon being a semiconductor has a conductivity that allows it to drain the charge fast in case if some electrons get intercepted by the dechirper. At the same time the conductivity is low enough for the skin depth to be large (on the order of 1 cm) making the silicon loaded waveguide a slow wave structure supporting wakefields that dechirp the beam.

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TUPMA047

Multipacting-free Quarter-wavelength Choke Joint Design for BNL SRF

cathode, gun, SRF, cavity

1935

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C.J. Liaw, G.T. McIntyre, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

The BNL SRF gun cavity was operated well at CW mode up to 2 MV. However, the performance suffered due to multipacting in the quarter-wavelength choke-joint. A new multipacting-free cathode stalk was designed and will be conditioned. This paper will describes RF and thermal design of new cathode stalk and conditioning results.
This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.

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TUPMA048

Experimental and Simulational Result of Multipactors in 112 MHz QWR Injector

gun, cavity, cathode, simulation

1938

T. Xin
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, I. Pinayev, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This work was carried out at Brookhaven Science Associates, LLC under Contracts No. DE-AC02-98CH10886 and at Stony Brook University under grant DE-SC0005713 with the U.S. DOE.
The first RF commissioning of 112 MHz QWR superconducting electron gun was done in late 2014. The coaxial Fundamental Power Coupler (FPC) and Cathode Stalk (stalk) were install and tested for the first time. During this experiment, we observed several multipacting barriers at varied gun voltage levels. The simulation work was done within the same range. The comparison between the experimental observation and the simulation results are presented in this paper. The observations during the test are consisted with the simulation predictions. We were able to overcome most of the multipacting barriers and reach 1.7 MV gun voltage under pulsed mode after several round of conditioning processes.

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TUPMA049

First Beam Commissioning at BNL ERL SRF Gun

cathode, SRF, gun, cavity

1941

W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, H. Hahn, L.R. Hammons, T. Hayes, J.P. Jamilkowski, P. K. Kankiya, D. Kayran, N. Laloudakis, R.F. Lambiase, V. Litvinenko, L. Masi, G.T. McIntyre, K. Mernick, T.A. Miller, G. Narayan, D. Phillips, V. Ptitsyn, T. Rao, T. Seda, F. Severino, B. Sheehy, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, M. Wilinski, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn
Stony Brook University, Stony Brook, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz superconducting RF gun successfully generated the first photoemission beam on Nov. 17 2014. This paper will report the latest results of SRF beam commissioning, including the SRF cavity performance, cathode QE measurements, and beam parameter measurements. The beam commissioning setup is described in the paper as well.

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TUPMA055

Analysis of Possible Beam Losses in the NSLS II Storage Ring

radiation, dipole, storage-ring, shielding

1956

S. Seletskiy, R.P. Fliller, W. Guo, S.L. Kramer, Y. Li, B. Podobedov, T.V. Shaftan, W.H. Wahl, F.J. Willeke
BNL, Upton, Long Island, New York, USA

The NSLS-II accelerators are installed within radiation shielding walls that are designed to attenuate the radiation generated from an assumed beam loss power to a level of <0.5mrem/h at the outer surface of the bulk shield walls. Any operational losses greater than specified level are expected to be addressed by installing supplemental shielding near the loss point in order to attenuate the radiation outside the shield wall to the design level. In this paper we report the analysis of the electron beam mis-steering in the NSLS-II storage ring for the determination of supplementary shielding.

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TUPTY006

Study of Electron Cloud Instabilities in FCC-hh

proton, photon, emittance, simulation

2007

K. Ohmi
KEK, Ibaraki, Japan
L. Mether, D. Schulte, F. Zimmermann
CERN, Geneva, Switzerland

Electron cloud effects are serious issue for LHC and future hadron colliders, FCC-hh. Electron cloud causes coherent instabilities due to collective motion between beam and electrons. Electron cloud also causes incoherent emittance growth due to nonlinear force of beam-cloud electron force. We discuss the fast head-tail instability and the emittance growth in FCC-hh.

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TUPTY007

Study of Beam-beam Effects in FCC-he

luminosity, proton, simulation, emittance

2010

K. Ohmi
KEK, Ibaraki, Japan
F. Zimmermann
CERN, Geneva, Switzerland

Beam-beam effects of the ring-ring scheme of FCC-he and LHeC are being studied using weak-strong simulations. The beam-beam tune shift of the electron beam is one order larger than that of proton beam. The study of the electron motion under the beam-beam interaction is the main subject. Luminosity and equilibrium beam size and beam lifetime are analysed.

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TUPTY008

Commissioning Status and Plan of SuperKEKB Injector Linac

emittance, linac, positron, operation

2013

M. Satoh, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, Y. Enomoto, S. Fukuda, Y. Funakoshi, K. Furukawa, T. Higo, H. Honma, N. Iida, M. Ikeda, H. Iwase, H. Kaji, K. Kakihara, T. Kamitani, H. Katagiri, S. Kazama, M. Kikuchi, H. Koiso, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, T. Miura, F. Miyahara, T. Mori, A. Morita, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, Y. Ohnishi, S. Ohsawa, Y. Seimiya, T. Shidara, A. Shirakawa, M. Suetake, H. Sugimoto, T. Suwada, T. Takenaka, M. Tanaka, M. Tawada, Y. Yano, K. Yokoyama, M. Yoshida, R. Zhang, X. Zhou
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

Toward SuperKEKB project, the injector linac upgrade is ongoing at KEK in order to deliver the low emittance electron/positron beams with the high intensity and small emittance. In the September of 2013, the injector linac commissioning has started. In this presentation, we will describe the commissioning status and plan of SuperKEKB injector linac.

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TUPTY010

The Luminosity Reduction with Hourglass Effect and Crossing Angle in an e-p Collider

luminosity, collider, proton, acceleration

2016

Y.M. Peng
IHEP, Beijing, People's Republic of China
Y. Zhang
JLab, Newport News, Virginia, USA

This paper derived the luminosity reduction caused by crossing angle and hourglass effect in an asymmetric collision. Here, we gave the general expressions of the geometrical reduction factor of luminosity for the asymmetric case caused by crossing angle and hourglass effect, for tri-Gaussian bunches colliding. We also gave it simple expression in some special cases to recover the earlier results, such as the formulas for only hour-glass effect exist and only crossing angle exist. The expressions used in e-p collider are also analysed in detail.

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TUPTY019

Realistic Beam Halo Model study in the Extraction Line of ATF2

background, simulation, optics, diagnostics

2038

N. Fuster-Martínez, A. Faus-Golfe
IFIC, Valencia, Spain
P. Bambade, S. Liu, S. Wallon
LAL, Orsay, France
K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
E. Marín, G.R. White
SLAC, Menlo Park, California, USA

Funding: Work supported by IDC-20101074, FPA2013-47883-C2-1-P and ANR-11-IDEX-0003-02
The understanding and control of the transverse beam halo distributions is an important issue to reduce sources of background noise in Future Linear Colliders (FLC) and specifically at ATF2. A realistic model of the beam halo in the old extraction line of the ATF damping ring was obtained in 2005, based on wire scanner measurements. Recently, new measurements were done in the new extraction line of ATF2, using both wire scanners, in 2013, and Optical Transition Radiation monitors (OTR), in 2014. The beam halo propagation through the ATF2 beamline by means of tracking simulations has been investigated using as input a purely Gaussian and uniform beam halo model.

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TUPTY045

Interactions between Macroparticles and High-Energy Proton Beams

proton, simulation, beam-losses, vacuum

2112

S. Rowan, A. Apollonio, B. Auchmann, A. Lechner, O. Picha, W. Riegler, H. Schindler, R. Schmidt, F. Zimmermann
CERN, Geneva, Switzerland

A known threat to the availability of the LHC is the interaction of macroparticles (dust particles) with the LHC proton beam. At the foreseen beam energy of 6.5 TeV during Run 2, quench margins in the superconducting magnets will be 2-3 times lower, and beam losses due such interactions may result in magnet quenches. The study introduce an improved numerical model of such interactions, as well as Monte-Carlo simulations that give the probability that such events will result in a beam-dump during Run 2.

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TUPTY047

ERL with Non-Scaling Fixed Field Alternating Gradient Lattice for eRHIC

linac, hadron, collider, ion

2120

D. Trbojevic, J.S. Berg, S.J. Brooks, Y. Hao, V. Litvinenko, C. Liu, F. Méot, M.G. Minty, V. Ptitsyn, T. Roser, P. Thieberger, N. Tsoupas
BNL, Upton, Long Island, New York, USA

Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy.
The proposed eRHIC electron-hadron collider uses a "non-scaling FFAG" lattice to recirculate 16 turns of different energy through just two beamlines located in the RHIC tunnel. This paper presents lattices for these two FFAGs that are optimised for low magnet field and to minimise total synchrotron radiation across the energy range. The higher number of recirculations in the FFAG allows a shorter linac (1.322GeV) to be used, drastically reducing cost, while still achieving a 21.2GeV maximum energy to collide with one of the existing RHIC hadron rings at up to 250GeV. eRHIC uses many cost-saving measures in addition to the FFAG: the linac operates in energy recovery mode, so the beams also decelerate via the same FFAG loops and energy is recovered from the interacted beam. All magnets will constructed from NdFeB permanent magnet material, meaning chillers and large magnet power supplies are not needed. This paper also describes a smaller prototype ERL-FFAG accelerator that will test all of these technologies in combination to reduce technical risk for eRHIC.

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TUPTY056

Beam-Based Measurements of Long Range Transverse Wakefields in CLIC Main Linac Accelerating Structure

wakefield, positron, linac, experiment

2153

H. Zha, A. Grudiev, A. Latina, D. Schulte, A. Solodko, W. Wuensch
CERN, Geneva, Switzerland
E. Adli
University of Oslo, Oslo, Norway
G. De Michele
EPFL, Lausanne, Switzerland
G. De Michele
PSI, Villigen PSI, Switzerland
N. Lipkowitz, G. Yocky
SLAC, Menlo Park, California, USA

The baseline design of CLIC (Compact Linear Collider) uses X-band accelerating structures in the main linac. Every accelerating structure cell has four waveguides, terminated with individual RF loads, to damp the unwanted long-range transverse wakefields, in order to maintain beam stability in multi-bunch operation. In order to experimentally verify the calculated suppression of the wakefields, a prototype structure has been built and installed in FACET test facility at SLAC. The results of the measurements of the wakefields in the prototype structure by means of positron and electron bunches are presented.

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TUPTY057

Scenarios for Circular Gamma-Gamma Higgs Factories

collider, laser, luminosity, factory

2156

F. Zimmermann, Y. Papaphilippou
CERN, Geneva, Switzerland
R. Aleksan
CEA/DSM/IRFU, France
A. Apyan
NU, Evanston, Illinois, USA

Funding: The research leading to these results has received partial funding from the European Commission under the FP7 Research Infrastructures project EuCARD-2, grant agreement no.312453.
The Higgs boson can be produced directly in gamma-gamma collisions generated by laser Compton back scattering off 80-90 GeV electron or positron beams. We discuss options for realizing a gamma-gamma Higgs factory using a high-energy circular e⁺e⁻ collider, such as FCC-ee or CEPC, and/or its top-up injector ring, and compare the parameters and advantages of such a facility, including the expected performance, with those for a Higgs factory based on a recirculating linac, such as SAPPHiRE.

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TUPTY058

Mitigating Performance Limitations of Single Beam-pipe Circular e⁺e⁻ Colliders

luminosity, collider, synchrotron, operation

2160

M. Koratzinos
DPNC, Genève, Switzerland
F. Zimmermann
CERN, Geneva, Switzerland

Renewed interest in circular e⁺e⁻ colliders has spurred designs of single beam-pipe machines, like the CEPC in China, and double beam pipe ones, such as the FCC-ee effort at CERN. Single beam-pipe designs profit from lower costs but are limited by the number of bunches that can be accommodated in the machine. We analyse these performance limitations and propose a solution that can accommodate O(1000) bunches while keeping more than 90% of the ring with a single beam pipe.

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TUPTY063

FCC-ee: Energy Calibration

polarization, wiggler, storage-ring, simulation

2177

M. Koratzinos, A.P. Blondel
DPNC, Genève, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA
F. Zimmermann
CERN, Geneva, Switzerland

FCC-ee aims to improve on electroweak precision measurements, with goals of 100 keV on the Z mass and width, and a fraction of an MeV on the W mass. Compared to LEP, this implies a much improved knowledge of the centre-of-mass energy when operating at the Z peak and WW threshold. This contribution will describe how it is planned to achieve this, by making systematic use of resonant depolarization. A number of difficulties have been identified, due in particular to the long polarization time and amplified ground motion. However the smaller emittance and energy spread of FCC-ee with respect to LEP should help achieve a much improved performance.

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TUPTY069

Simulation of Hollow Electron Lenses as LHC Beam Halo Reducers using Merlin

collimation, proton, betatron, simulation

2188

H. Rafique, R.J. Barlow
University of Huddersfield, Huddersfield, United Kingdom
R.B. Appleby, S.C. Tygier
UMAN, Manchester, United Kingdom
R. Bruce, S. Redaelli
CERN, Geneva, Switzerland

Funding: Research supported by FP7 HiLumi LHC (Grant agreement 284404)
The Large Hadron Collider (LHC) and its High Luminosity (HL) upgrade foresee unprecedented stored beam energies of up to 700 MJ. The collimation system is responsible for cleaning the beam halo and is vital for successful machine operation. Hollow electron lenses (HEL) are being considered for the LHC, based on Tevatron designs and operational experience, for active halo control. HELs can be used as soft scraper devices, and can operate close to the beam core without undergoing damage. We use the Merlin C++ accelerator libraries to implement a HEL and examine the effect on the beam halo for various test scenarios.

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TUPTY073

An Alternative High Luminosity LHC with Flat Optics and Long-Range Beam-Beam Compensation

luminosity, optics, beam-beam-effects, simulation

2199

S.D. Fartoukh
CERN, Geneva, Switzerland
D.N. Shatilov
BINP SB RAS, Novosibirsk, Russia
A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: Research supported by DOE via the US-LARP program and by EU FP7 HiLumi LHC - Grant Agreement 284404
In the baseline scenario of the High-Luminosity LHC (HL-LHC), the geometric loss of luminosity in the two high luminosity experiments due to collisions with a large crossing angle is recovered by tilting the bunches in the interaction region with the use of crab cavities. A possible backup scenario would rely on a reduced crossing angle together with flat optics (with different horizontal and vertical β^* values) for the preservation of luminosity performance. However, the reduction of crossing angle coupled with the flat optics significantly enhances the strength of long-range beam-beam interactions. This paper discusses the possibility to mitigate the long-range beam-beam effects by current bearing wire compensators (or e-lens). We develop a new HL-LHC parameter list and analyse it in terms of integrated luminosity performance as compared to the baseline. Further, we evaluate the operational scenarios using numerical simulations of single-particle dynamics with beam-beam effects.

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TUPTY078

Fixed-energy Cooling and Stacking for an Electron Ion Collider

ion, ECR, space-charge, collider

2214

P.M. McIntyre, S. Assadi, J. Gerity, A. Sattarov
Texas A&M University, College Station, Texas, USA

The proposed designs for polarized-beam electron-ion colliders require cooling of the ion beam to achieve and sustain high luminosity. One attractive approach is to make a fixed-energy storage ring in which ions are con-tinuously cooled and stacked during a collider store, then transferred to the collider and accelerated for a new store when the luminosity decreases. An example design is reported for a 6 GeV/u superferric storage ring, and for a d.c. electron cooling system in which electron space charge is fully neutralized so that high-current magnetized e-cooling can be used to best advantage.

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TUPTY079

Initial Modeling of Electron Cloud Buildup in the Final-focus Quadrupole Magnets of the SuperKEKB Positron Ring

photon, quadrupole, positron, vacuum

2218

J.A. Crittenden
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: US National Science Foundation contracts PHY-0734867, PHY-1002467, and PHY-1068662, US Department of Energy contract DE-FC02-08ER41538 and the Japan/US Cooperation Program
We present modeling results for electron cloud buildup in the final-focus quadrupole magnet nearest the interaction point in the SuperKEKB positron storage ring. The calculations employ as input recently obtained estimates of synchrotron radiation absorption rates on the vacuum chamber wall including the effect of photon scattering. While the effect both adds to and subtracts from photoelectron production at the points in the ring where unscattered photons strike the wall, it also produces cloud in the other regions. Results for beam-pipe-averaged and beam-averaged cloud densities are presented, as are estimates for the contribution to the fractional vertical coherent tune shift. The effect of the strong magnetic fields is studied and the dependence on the vacuum chamber surface secondary yield characteristics is considered. Cloud buildup is modeled with a 2D particle-in-cell macroparticle tracking code validated using recent measurements of electron trapping in a quadrupole magnet at the Cornell Electron Storage Ring Test Accelerator.

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TUPTY080

Synchrotron Radiation Analysis of the SuperKEKB Positron Storage Ring

photon, positron, scattering, vacuum

2222

J.A. Crittenden, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Ishibashi, Y. Suetsugu
KEK, Ibaraki, Japan

Funding: US National Science Foundation contracts PHY-0734867, PHY-1002467, and PHY-1068662, US Department of Energy contract DE-FC02-08ER41538 and the Japan/US Cooperation Program.
We report on modeling results for synchrotron radiation absorption in the SuperKEKB positron storage ring vacuum chamber including the effects of photon scattering on the interior walls. A detailed model of the geometry of the inner vacuum chamber profile has been developed and used as input to a photon tracking code. Particular emphasis is placed on the photon absorption rates in the electron-positron interaction region.

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TUPTY082

Scanning Synchronization of Colliding Bunches for MEIC Project

cavity, ion, controls, collider

2229

Y.S. Derbenev, V.P. Popov
JLab, Newport News, Virginia, USA
Y.D. Chernousov
ICKC, Novosibirsk, Russia
G.M. Kazakevich
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
Synchronization of colliding beams is one of the major issues of an electron-ion collider (EIC) design because of sensitivity of ion revolution frequency to beam energy. A conventional solution for this trouble is insertion of bent chicanes in the arcs space. In our report we consider a method to provide space coincidence of encountering bunches in the crab-crossing orbits Interaction Region (IR) while repetition rates of two beams do not coincide. The method utilizes pair of fast kickers realizing a bypass for the electron bunches as the way to equalize positions of the colliding bunches at the Interaction Point (IP). A dipole-mode warm or SRF cavities fed by the magnetron transmitters are used as fast kickers, allowing a broad-band phase and amplitude control. The proposed scanning synchronization method implies stabilization of luminosity at a maximum via a feedback loop. This synchronization method is evaluated as perspective for the Medium Energy Electron-Ion collider (MEIC) project of JLab with its very high bunch repetition rate.

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TUPTY083

Conceptual MEIC Electron Ring Injection Scheme using CEBAF as a Full Energy Injector

injection, linac, operation, gun

2232

J. Guo, F. Lin, R.A. Rimmer, H. Wang, S. Wang, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The Medium-energy Electron-Ion Collider (MEIC) proposed by Jefferson Lab is planning to use the newly upgraded 12 GeV CEBAF 1497 MHz SRF CW recirculating linac as a full-energy injector for the electron collider ring. The electron collider ring is proposed to reuse the 476MHz PEP-II RF system to achieve high installed voltage and high beam power. The MEIC electron injection requires 3-10 (or 12) GeV beam in 3-4μs long bunch trains with low duty factor and high peak current, resulting in strong transient beam loading for the CEBAF. In this paper, we propose an injection scheme that can match the two systems’ frequencies with acceptable injection time, and also address the transient beam loading issue in CEBAF. The scheme is compatible with future upgrade to 952.6 MHz SRF system in the electron ring.

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TUPTY084

Update on the MEIC Electron Collider Ring Design

collider, dipole, quadrupole, optics

2236

F. Lin, Y.S. Derbenev, L. Harwood, A. Hutton, V.S. Morozov, F.C. Pilat, Y. Zhang
JLab, Newport News, Virginia, USA
Y. Cai, Y. Nosochkov, M.K. Sullivan, M.-H. Wang, U. Wienands
SLAC, Menlo Park, California, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work also supported by the U.S. DOE Contract No. DE-AC02-76SF00515.
The electron collider ring of the Medium-energy Electron-Ion Collider (MEIC) at Jefferson Lab is designed to accumulate and store a high-current polarized electron beam for collisions with an ion beam. We consider a design of the electron collider ring based on reusing PEP-II components, such as magnets, power supplies, vacuum system, etc. This has the potential to significantly reduce the cost and engineering effort needed to bring the project to fruition. This paper reports on an electron ring optics design considering the balance of PEP-II hardware parameters (such as dipole sagitta, magnet field strengths and acceptable synchrotron radiation power) and electron beam quality in terms of equilibrium emittances.

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TUPWI008

RF Gun Based Ultrafast Electron Microscopy

gun, emittance, cavity, cathode

2259

J. Yang, K. Tanimura, Y. Yoshida
ISIR, Osaka, Japan
J. Urakawa
KEK, Ibaraki, Japan

Ultrafast electron microscopy (UEM) would be a powerful tool for the direct visualization of structural dynamic processes in matter. The resolutions of the observation on femtosecond time scales over sub-nanometer (even atomic) spatial dimensions have long been a goal in science. To achieve such resolutions, we have designed and constructed a femtosecond time-resolved relativistic-energy electron microscopy using a photocathode radio-frequency (RF) electron gun (RF based UEM). The RF gun has successfully generated a high-brightness electron beam with bunch length of 100 fs and emittance of 0.2 mm-mrad, which are essential beam parameters for the achievement of nm-fs space-time resolution in the microscopy. Both the static measurements of both relativistic-energy electron diffraction and image have been succeeded. In this presentation, the activities on RF based UEM are introduced. The requirements and limitations of the beam parameters are reviewed. The concept and design of RF based UEM are reported. Finally, some demonstrations of the relativistic-energy UEM images are reported.

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TUPWI010

Development of a Pulse Radiolysis System by Ultra-fast Super Continuum Probe at Waseda University

laser, polarization, gun, cathode

2265

Y. Ito
Waseda University, Tokyo, Japan
Y. Hosaka, K. Sakaue, M. Washio
RISE, Tokyo, Japan

We have been studying the pulse radiolysis using photo-cathode rf gun at Waseda Univ. Pulse radiolysis is one of the powerful methods to trace early chemical reactions by ionizing radiation. In pulse radiolysis, the probe light absorption, which produced by active species formed by electron beam of rf gun, is measured at each wavelength and made possible to trace reactions. Therefore, we have used the super continuum (SC) light for the probe light. The SC light has a broad spectrum and is generated by nonlinear optical effect caused by injecting picosecond laser to photonic crystal fiber. However, the resulting SC light was unstable because its peak intensity was not enough. We need to use a femtosecond pulsed laser which is expected to be stronger peak intensity than a picosecond laser. We have developed a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation as a femtosecond pulsed laser and the chirped pulse amplification system which will be able to amplify the femtosecond pulse. In this conference, we will report the performance of the SC light using this fiber laser system, recent results of pulse radiolysis experiments and the future plans.
Work supported by NEDO(New Energy and Industrial Technology Development Organization).

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TUPWI017

Single-shot Multi-MeV Ultrafast Electron Diffraction on VELA at Daresbury Laboratory

gun, FEL, scattering, experiment

2278

L.K. Rudge, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, Y.M. Saveliev, D.J. Scott, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P. Aden, R.J. Cash, D.M.P. Holland, M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
P.D. Lane, D.A. Wann
University of York, York, United Kingdom
M. Surman
STFC/DL/SRD, Warrington, Cheshire, United Kingdom
J.G. Underwood
UCL, London, United Kingdom

Funding: This work was funded by STFC
Accelerator based Ultrafast Electron Diffraction (UED) is a technique for obtaining static structures and for studying sub-100 fs dynamic structural changes on the atomic scale. In this paper we present the first electron diffraction results obtained from the VELA accelerator in 2014. The accelerator was operated to provide typically 4MeV/c electron bunches. Diffraction patterns were observed with <<1 pC transported to the detection screen. Single shot and multi-shot accumulated diffraction data are presented from single crystal and polycrystalline samples, including Au, Al, Pt and C. Contamination of the diffraction pattern with dark current contributions is an issue. A variable size aperture directly in front of the sample offers some mitigation, but at the expense of reduced charge contributing to the diffraction pattern. We discuss future developments for electron diffraction on VELA including further beam optimization, measurement of bunch length with a newly installed Transverse Deflecting Cavity, and the planned developments for pump-probe studies.

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TUPWI027

Radiography Capabilities for Matter-Radiation Interactions in Extremes

proton, scattering, quadrupole, linac

2295

P.L. Walstrom, R.L. Barber, C.A. Chapman, R.W. Garnett, T.S. Gomez, J.A. O'Toole, H.R. Salazar
LANL, Los Alamos, New Mexico, USA

Funding: This work is supported by the U. S. Department of Energy Contract DE-AC52-06NA25396.
The Matter-Radiation Interactions in Extremes (MaRIE) experimental facility will be used to discover and design the advanced materials needed to meet 21st century national security and energy security challenges. This new facility will provide the new tools scientists need to develop next-generation materials that will perform predictably and on-demand for currently unattainable lifetimes in extreme environments. The MaRIE facility is based on upgrades to the existing LANSCE 800-MeV proton linac and a new 12-GeV electron linac and associated X-ray FEL to provide simultaneous multiple probe beams, and new experimental areas. In addition to the high-energy photon probe beam, both electron and proton radiography capabilities will be available at the MaRIE facility. Recently, detailed radiography system studies have been performed to develop conceptual layouts of high-magnification electron and proton radiography systems that can meet the experimental requirements for the expected first experiments to be performed at the facility. A description of the radiography systems, their performance requirements, and a proposed facility layout will be presented.

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TUPWI031

Status of the MEIC Ion Collider Ring Design

ion, collider, dipole, optics

2307

V.S. Morozov, Y.S. Derbenev, L. Harwood, A. Hutton, F. Lin, F.C. Pilat, Y. Zhang
JLab, Newport News, Virginia, USA
Y. Cai, Y. Nosochkov, M.K. Sullivan, M.-H. Wang, U. Wienands
SLAC, Menlo Park, California, USA
J. Gerity, T.L. Mann, P.M. McIntyre, N. Pogue, A. Sattarov
Texas A&M University, College Station, Texas, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported in part by the US DOE Contract No. DE-AC02-76SF00515.
We present an update on the design of the ion collider ring of the Medium-energy Electron-Ion Collider (MEIC) proposed by Jefferson Lab. The design is based on the use of super-ferric magnets. It provides the necessary momentum range of 8 to 100 GeV/c for protons and ions, matches the electron collider ring design using PEP-II components, fits readily on the JLab site, offers a straightforward path for a future full-energy upgrade by replacing the magnets with higher-field ones in the same tunnel, and is more cost effective than using presently available current-dominated super-conducting magnets. We describe complete ion collider optics including an independently-designed modular detector region.

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TUPWI034

Capture, Acceleration and Bunching RF Systems for the MEIC Booster and Storage Rings

ion, cavity, collider, bunching

2318

S. Wang, J. Guo, F. Lin, V.S. Morozov, R.A. Rimmer, H. Wang, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The MEIC, proposed by Jefferson Lab, consists of a series of accelerators. The electron collider ring accepts electrons from CEBAF at energies from 3 to 12 GeV. Protons and ions are delivered to a booster and captured in a long bunch before ramping and transfer to the ion collider ring. The ion collider ring accelerates a small number of long ion bunches to colliding energy before they are re-bunched into a high frequency train of very short bunches for colliding. Two sets of low frequency RF systems are needed for the long ion bunch energy ramping in the booster and ion collider ring. Another two sets of high frequency RF cavities are needed for re-bunching in the ion collider ring and compensating synchrotron radiation energy loss in the electron collider ring. The requirements from energy ramping, ion beam bunching, electron beam energy compensation, collective effects, beam loading and feedback capability, RF power capability, etc. are presented. The preliminary designs of these RF systems are presented. Concepts for the baseline cavity and RF station configurations are described, as well as some options that may allow more flexible injection and acceleration schemes.

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TUPWI037

Electron Cooling Study for MEIC

proton, emittance, solenoid, ion

2326

H. Zhang, Y.S. Derbenev, D. Douglas, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC05-06OR23177 and No. DE-AC02-06CH11357.
Electron cooling of the ion beams is one critical R&D to achieve high luminosities in JLab’s MEIC proposal. In the present MEIC design, a multi-staged cooling scheme is adapted, which includes DC electron cooling in the booster ring and bunched beam electron cooling in the collider ring at both the injection energy and the collision energy. We explored the feasibility of using both magnetized and non-magnetized electron beam for cooling, and concluded that a magnetized electron beam is necessary. Electron cooling simulation results for the newly updated MEIC design is also presented.

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TUPWI038

A High Energy e-p/A Collider Based on CepC-SppC

proton, collider, luminosity, ion

2329

Y. Zhang
JLab, Newport News, Virginia, USA
Y.M. Peng
IHEP, Beijing, People's Republic of China

Construction of CepC and SppC, the proposed future energy frontier circular e⁺e⁻ and pp colliders in China, provides an opportunity to realize e-p or e-A collisions in a CM energy range up to 4.1 TeV. This paper presents a preliminary conceptual design of this e-p/A collider. The design parameters and anticipated luminosities will be given. We also discuss staging approaches to realize this collider with a low cost and at an earlier time.

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TUPWI039

Modeling Crabbing Dynamics in an Electron-Ion Collider

proton, betatron, collider, ion

2333

A. Castilla, J.R. Delayen, T. Satogata
ODU, Norfolk, Virginia, USA
A. Castilla, J.R. Delayen, V.S. Morozov, T. Satogata
JLab, Newport News, Virginia, USA
A. Castilla
DCI-UG, León, Mexico

Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A local crabbing scheme requires π/2 (mod π) horizontal betatron phase advances from an interaction point (IP) to the crab cavities on each side of it. However, realistic phase advances generated by sets of quadrupoles, or Final Focusing Blocks (FFB), between the crab cavities located in the expanded beam regions and the IP differ slightly from π/2. To understand the effect of crabbing on the beam dynamics in this case, a simple model of the optics of the Medium Energy Electron-Ion Collider (MEIC) including local crabbing was developed using linear matrices and then studied numerically over multiple turns (1000 passes) of both electron and proton bunches. The same model was applied to both local and global crabbing schemes to determine the linear-order dynamical effects of the synchro-betatron coupling induced by crabbing.

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TUPWI042

Initial Results from Streaked Low-energy Ultra-fast Electron Diffraction System

gun, simulation, diagnostics, experiment

2339

J.J. Hartzell, R.B. Agustsson, S. Boucher, L. Faillace, A.V. Smirnov
RadiaBeam, Santa Monica, California, USA
P. Musumeci, E.W. Threlkeld
UCLA, Los Angeles, USA

RadiaBeam, in collaboration with UCLA, is developing an inexpensive, low-energy, ultra-fast, streaked electron diffraction (S-UED) system which allows one to reconstruct a single ultrafast event with a single pulse of electrons using and RF deflector. The high-frequency (GHz), high voltage, phase-locked RF field in the deflector enables temporal resolution of atomic events as fine as sub-100 fs. In this paper, we present an overview of the system being developed and the initial experimental results. We also discuss the challenges based on our design of a UED system that incorporates a novel, high-resolution dielectric-loaded RF deflector and a solid-state X-band amplifier.

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TUPWI050

Optics Correction for the Multi-pass FFAG ERL Machine eRHIC

simulation, quadrupole, lattice, optics

2363

C. Liu, S.J. Brooks, V. Litvinenko, M.G. Minty, V. Ptitsyn, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Gradient errors in the multi-pass Fixed Field Alternating Gradient (FFAG) Energy Recovery Linac (ERL) machine, eRHIC, distort the beam orbit and therefore cause emittance increase. The localization and correction of gradient errors are essential for an effective orbit correction and emittance preservation. In this report, the methodology and simulation of optics correction for the multi-pass FFAG ERL machine eRHIC will be presented.
The work was performed under Contract No. DE-AC02-98CH10886
with the U.S. Department of Energy.

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TUPWI051

Study of Orbit Correction for eRHIC FFAG Design

lattice, simulation, alignment, ion

2366

C. Liu, Y. Hao, V. Litvinenko, F. Méot, M.G. Minty, V. Ptitsyn, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The chromaticities in the eRHIC linear non-scaling Fixed Field Alternating Gradient (FFAG) lattice are very large. Therefore, particles will decohere in phase space given the presence of lattice errors. The decoherence causes a deviation of the orbit response which is the basis for orbit corrections. In this report we will present a study of the linearity of the orbit response in a lattice with large chromaticity, a comparison of the results of orbit corrections for several cases together with a conclusion that correcting the average orbit with a measured orbit response works as good as an orbit correction for on-momentum particles.
The work was performed under Contract No. DE-AC02-98CH10886
with the U.S. Department of Energy.

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TUPWI052

End-to-end 9-D⁺SR Polarized Bunch Transport in eRHIC Energy-recovery Recirculator, Some Aspects

emittance, polarization, quadrupole, linac

2369

F. Méot, S.J. Brooks, V. Ptitsyn, D. Trbojevic, N. Tsoupas
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The energy-recovery electron beam recirculator, part of the eRHIC electron-ion collider project complex at BNL, is subject to feasibility studies in an FFAG arc based version. We develop here on tracking simulations and their analysis, regarding end-to-end polarized e-bunch transport in presence of synchrotron radiation, magnet alignment and field errors. Simulations include the evolution of energy, orbits, emittances, polarization profiles.

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TUPWI059

Influence of Plasma Loading in a Hybrid Muon Cooling Channel

plasma, ion, cavity, emittance

2381

D. Stratakis
BNL, Upton, Long Island, New York, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
K. Yonehara
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In a hybrid 6D cooling channel, cooling is accomplished by reducing the beam momentum through ionization energy loss in wedge absorbers and replenishing the momentum loss in the longitudinal direction with gas-filled rf cavities. While the gas acts as a buffer to prevent rf breakdown, gas ionization may also occur as the beam passes through a HPRF cavity. The resulting plasma, may gain substantial energy from the rf electric field which it can transfer via collisions to the gas, an effect known as plasma loading. In this paper, we investigate the influence of plasma loading on the cooling performance of a rectilinear hybrid channel. With the aid of numerical simulations we examine the sensitivity in cooling performance and plasma loading to key parameters such as the rf gradient and gas pressure.

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TUPWI060

RHIC Polarized Proton-Proton Operation at 100 GeV in Run 15

proton, polarization, emittance, operation

2384

V. Schoefer, E.C. Aschenauer, G. Atoian, M. Blaskiewicz, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, K.A. Drees, Y. Dutheil, W. Fischer, C.J. Gardner, X. Gu, T. Hayes, H. Huang, J.S. Laster, C. Liu, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, S. Nemesure, P.H. Pile, A. Poblaguev, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, W.B. Schmidke, F. Severino, T.C. Shrey, K.S. Smith, D. Steski, S. Tepikian, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, G. Wang, S.M. White, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang
BNL, Upton, Long Island, New York, USA

The first part of RHIC Run 15 consisted of nine weeks of polarized proton on proton collisions at a beam energy of 100 GeV at two interaction points. In this paper we discuss several of the upgrades to the collider complex that allowed for improved performance this run. The largest effort consisted of commissioning of the electron lenses, one in each ring, which are designed to compensate one of the two beam-beam interactions experienced by the proton bunches. The e-lenses therefore raise the per bunch intensity at which luminosity becomes beam-beam limited. A new lattice was designed to create the phase advances necessary for a functioning e-lens which also has an improved off-momentum dynamic aperture relative to previous runs. In order to take advantage of the new, higher intensity limit without suffering intensity driven emittance deterioration, other features were commissioned including a continuous transverse bunch-by-bunch damper in RHIC and a double harmonic capture scheme in the Booster. Other high intensity protections include improvements to the abort system and the installation of masks to intercept beam lost due to abort kicker pre-fires.

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WEXB1

Coherent Synchrotron Radiation in Energy Recovery Linacs

FEL, experiment, linac, dipole

2387

C.C. Hall, S. Biedron, A.L. Edelen, S.V. Milton
CSU, Fort Collins, Colorado, USA
S.V. Benson, D. Douglas, R. Li, C. Tennant
JLab, Newport News, Virginia, USA
B.E. Carlsten
LANL, Los Alamos, New Mexico, USA

Collective beam effects, including coherent synchrotron radiation (CSR), have been studied on free-electron lasers (FELs). Here we will discuss a particular case of the CSR effects, that in energy-recovery linacs (ERLs). Special consideration is given to these machines because of their high average beam power and the architecture of the machine for energy recovery forces extreme bends. A recent study conducted on the JLab IR FEL looked at how CSR impacts both average energy and the energy spectrum of the beam. Such studies are important, both broadly, to the understanding of CSR and more specifically for a number of proposed ERL projects. A few proposed examples include the MEIC bunched beam cooler ERL design and ERL FELs for potential lithography purposes that would operate in the EUV range.

Slides WEXB1 [16.383 MB]

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WEXB2

Measurement and Analysis of Electron Cloud Induced Emittance Growth at CesrTA

simulation, emittance, feedback, positron

2390

K.G. Sonnad, L.Y. Bartnik, M.G. Billing, G. Dugan, M.J. Forster
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.W. Flanagan, K. Ohmi
KEK, Ibaraki, Japan
R. Holtzapple, K.E. McArdle, M.I. Miller
CalPoly, San Luis Obispo, California, USA
L. Pentecost
Colgate University, Hamilton, New York, USA
M.T.F. Pivi
EBG MedAustron, Wr. Neustadt, Austria
S. Tucker
Cal Poly, San Luis Obispo, California, USA

CesrTA is a test accelerator facility at Cornell University that has been configured to study physics associated with electron and positron damping rings. Electron cloud effects is a concern for positron beams for such damping rings. The presentation will give an overview of recent measurements and simulation results for CesrTA. The measurement conditions were set up in order to study single bunch phenomena by observing a "Witness bunch" behind a train of positron bunches. The beam size and the turn by turn spectra were obeserved for the witness bunch under different conditions. Simulations were performed under similar conditions using the program CMAD.

Slides WEXB2 [2.263 MB]

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WEYC1

Technical Challenges of the LCLS-II

undulator, linac, gun, cavity

2434

T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The LCLS-II will be a CW X-ray FEL upgrade to the existing LCLS X-ray FEL at the SLAC National Accelerator Laboratory (SLAC). This paper describes the overall layout and the technical challenges that the upgrade project faces.

Slides WEYC1 [4.446 MB]

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WEYC3

Commissioning and Operation of the ARIEL Electron Linac at TRIUMF

linac, cavity, cryomodule, TRIUMF

2444

M. Marchetto, F. Ames, Z.T. Ang, R.A. Baartman, I.V. Bylinskii, Y.-C. Chao, D. Dale, K. Fong, R. Iranmanesh, F.W. Jones, D. Kaltchev, J. Kavarskas, P. Kolb, S.R. Koscielniak, A. Koveshnikov, M.P. Laverty, R.E. Laxdal, L. Merminga, N. Muller, R.R. Nagimov, R.B. Nussbaumer, T. Planche, M. Rowe, S. Saminathan, V.A. Verzilov, Z.Y. Yao, Q. Zheng, V. Zvyagintsev
TRIUMF, Vancouver, Canada

Funding: Funded under a contribution agreement with NRC (National Research Council Canada). Capital funding from CFI (Canada Foundation for Innovation).
ARIEL is the new TRIUMF facility for production of radioactive ion beams that will enable the delivery of three simultaneous RIB beams to the ISAC experimental stations. Two additional target stations will produce beams by using either a 50 kW proton or from 500 kW electrons via photo-fission. The electron beam driver is going to be a 50 MeV 10 mA CW superconducting electron linac. The first stage of the e-linac installation is completed and commissioning is underway. The paper will present the e-linac design characteristics, installation, commissioning strategy and current results.

Slides WEYC3 [13.765 MB]

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WEAB1

Compensating Tune Spread Induced by Space Charge in Bunched Beams

hadron, space-charge, proton, collider

2450

V. Litvinenko
Stony Brook University, Stony Brook, USA
G. Wang
BNL, Upton, Long Island, New York, USA

The effects of space charge play a significant role in modern-day accelerators, frequently constraining the beam parameters attainable in an accelerator or in an accelerator chain. They also can limit the luminosity of hadron colliders operating either at low energies or with sub-TeV high-brightness hadron beams. The latter is applied for strongly cooled proton and ion beams in eRHIC – the proposed future electron-ion collider at Brookhaven National Laboratory. Several schemes were proposed to compensate for space charge effects in a coasting (e.g., continuous) hadron beam, and some have been tested. Using an appropriate transverse profile of the electron beam (or plasma column) for a coasting beam would compensate both the tune shift and the tune spread in the hadron beam. But none of these methods address the issue of compensating space-charge induced tune spread in a bunched hadron beam. In this paper we propose and evaluate a novel idea of using a co-propagating electron bunch with miss-matched longitudinal velocity to compensate the space charge induced tune-shift and tune spread. We present several practical examples of such a system.

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WEAB3

Intra-beam Scattering Effects in ELENA

antiproton, emittance, scattering, simulation

2458

J. Resta-López, J.R. Hunt, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.R. Hunt, J. Resta-López, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: Work supported by the EU under Grant Agreement 624854 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
Intra-Beam Scattering (IBS) is one of the main limiting processes for the performance of low energy ion storage rings, such as the Extra Low ENergy Antiproton ring (ELENA) that is being constructed at CERN. IBS effects limit the achievable equilibrium 6D beam phase space volume during the cooling process, as well as the stored beam intensity. In this contribution we analyze the IBS effects on the beam dynamics of the ELENA ring in detail. Numerical simulations using the codes BETACOOL and MAD-X have been performed to compute the beam life time and the equilibrium phase space parameters with electron cooling in the presence of IBS.

Slides WEAB3 [6.222 MB]

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WEBB1

Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation

collimation, solenoid, operation, gun

2462

S. Redaelli, A. Bertarelli, R. Bruce, D. Perini, A. Rossi, B. Salvachua
CERN, Geneva, Switzerland
G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA

Hollow electron lenses are considered as a possible mean to improve the LHC beam collimation system, providing an active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes outside CERN are also discussed.

Slides WEBB1 [3.216 MB]

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WEBB3

Lattice and its Related Beam Dynamics Issues in the CEPC Storage Ring

lattice, quadrupole, positron, factory

2469

H. Geng, S. Bai, Z. Duan, Y.M. Peng, Q. Qin, D. Wang, Y. Wang, G. Xu, Y. Yue, Y. Zhang
IHEP, Beijing, People's Republic of China
W. Chou
Fermilab, Batavia, Illinois, USA

The institute of High Energy Physics has proposed an electron positron collider ring with a circumference of 50-100km to study the Higgs boson. Since the proposal was made, the lattice design for CEPC has been carried out and a preliminary conceptual design report has been written at the end of 2014. In this paper, we will describe the philosophy and results of our lattice design. The procedure of dynamic aperture optimization will be shown. A specific issue for CEPC, the pretzel orbit, which has been found distorting the linear lattice for a considerable amount, will be examined. The ways that we are trying to correct the pretzel orbit effect and the result will be shown. We will also discuss the saw tooth effect on the linear lattice and dynamic aperture of the ring.

Slides WEBB3 [2.599 MB]

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WEAD1

Commissioning and Recent Experimental Results at the Argonne Wakefield Accelerator Facility (AWA)

wakefield, experiment, acceleration, laser

2472

M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, J.H. Shao, D. Wang, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Shao, D. Wang
TUB, Beijing, People's Republic of China

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
The commissioning of the upgraded AWA facility has been recently completed. The L-band electron gun has been fully commissioned and has been successfully operated with its Cesium Telluride photocathode at a gradient of 80 MV/m. Single bunches of up to 100 nC, and bunch trains of up to 32 bunches have been generated. The six new pi-mode accelerating cavities bring the beam energy to 75 MeV. Initial measurements of the beam parameters have been performed. This intense beam has been used to drive high gradient wakefields in several structures. A second beamline provides electron bunches to probe the wakefields generated by the intense drive beam. One of the main goals of the facility is to generate short RF pulses with GW power levels, corresponding to accelerating gradients of hundreds of MV/m and energy gains on the order of 100 MeV per structure.

Slides WEAD1 [2.091 MB]

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WEAD2

Experimental Results of Carbon NanoTube Cathodes inside RF Environment

cathode, gun, emittance, laser

2475

L. Faillace, S. Boucher, J.J. Hartzell, A.Y. Murokh
RadiaBeam, Santa Monica, California, USA
D. Mihalcea, P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
H. Panuganti
Northern Illinois University, DeKalb, Illinois, USA

Funding: Work supported by US DOE SBIR grant # DE-SC0004459
Carbon Nano Tubes (CNT’s) as field-emitters have been investigated for more than two decades and can produce relatively low emittance electron beams for a given cathode size. Unlike thermionic cathodes, CNT cathodes are able to produce electrons at room temperature and relatively low electric field (a few MV/m). In collaboration with FermiLab, we have recently tested CNT cathodes both with DC and RF fields. We observed a beam current close to 1A with a ~1cm² CNT cathode inside an L-band RF gun. Steady operation was obtained up to 650 mA and the measured current vs. surface field plot showed perfect agreement with the Fowler-Nordheim distribution.

Slides WEAD2 [10.445 MB]

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WEAD3

Quantum Efficiency Improvement of Polarized Electron Source using Strain Compensated Super Lattice Photocathode

laser, gun, polarization, collider

2479

N. Yamamoto, M. Hosaka, A. Mano, T. Miyauchi, Y. Takashima, Y. Takeda
Nagoya University, Nagoya, Japan
X.J. Jin, M. Yamamoto
KEK, Ibaraki, Japan

Polarized electron beam is essential for future electron-positron colliders and electron-ion colliders. Improving the quantum efficiency is an important subject to realize those proposed applications. Recently we have developed the strain compensated superlattice (SL) photocathode. In the strain compensated SLs, the equivalent compressive and tensile strains introduced in the well and barrier SL layers so that strain relaxation is effectively suppressed with increasing the SL layer thickness and high crystal quality can be expected. In this study, we fabricated the GaAs/GaAsP strain compensated SLs with the thickness up to 90-pair SL layers. Up to now, the electron spin polarization of 92 % and the quantum efficiency of 1.6 % were simultaneously achieved from 24-pair sample. In the presentation, we show the effect of the superlattice thickness on the photocathode performances and discuss the photocathode physics.

Slides WEAD3 [3.064 MB]

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WEPWA001

Electron Beam Transfer Line for Demonstration of Laser Plasma Based Free Electron Laser Amplification

FEL, undulator, emittance, quadrupole

2489

A. Loulergue, M.-E. Couprie, M. Khojoyan, M. Labat, W. Wang
SOLEIL, Gif-sur-Yvette, France
C. Evain
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France

One direction towards compact Free Electron Lasers is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence is done. Applying seeding techniques enables also to reduce the required undulator length. The rapidly developing LWFA are already able to generate synchrotron radiation. With an electron divergence of typically 1 mrad and an energy spread of the order of 1 %, an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract. A specific design of electron beam transfer line following different steps with strong focusing variable strength permanent magnet quadrupoles, an energy de-mixing chicane with conventional dipoles and second set of quadrupoles for further dedicated focusing in the undulator has been investigated. Beam transfer simulations and expected FEL power in the XUV will be presented.

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WEPWA003

Simulations of Electron-Proton Beam Interaction before Plasma in the AWAKE Experiment

proton, plasma, wakefield, quadrupole

2492

U. Dorda, R.W. Aßmann, J. Grebenyuk
DESY, Hamburg, Germany
C. Bracco, A.V. Petrenko, J.S. Schmidt
CERN, Geneva, Switzerland

The on-axis injection of electron bunches in the proton-driven plasma wake at the AWAKE experiment at CERN implies co-propagation of a low-energy electron beam with the long high-energy proton beam in a common beam pipe over several meters upstream of the plasma chamber. The possible effects of the proton-induced wakefields on the electron bunch phase space in the common beam pipe region may have crucial implications for subsequent electron trapping and acceleration in plasma. We present the CST Studio simulations of the tentative common beam pipe setup and the two beam co-propagating in it. Simulated effects of the proton wakefields on electrons are analysed and compared to analytical predictions.

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WEPWA005

Simulations Study for Self-Modulation Experiment at PITZ

plasma, wakefield, simulation, experiment

2496

G. Pathak, F.J. Grüner
Uni HH, Hamburg, Germany
C. Benedetti, C.B. Schroeder
LBNL, Berkeley, California, USA
M. Groß, F. Stephan
DESY Zeuthen, Zeuthen, Germany
A. Martinez de la Ossa, T.J. Mehrling, J. Osterhoff
DESY, Hamburg, Germany

Self-modulation (SM) of proton beams in plasma has recently gained interest in context with the ongoing PWFA experiment of the AWAKE collaboration at CERN. Instrumental for that experiment is the SM of a proton beam to generate bunchlets for resonant wave excitation and efficient acceleration. A fundamental understanding of the underlying physics is vital, and hence an independent experiment has been set up at the beamline of the Photo Injector Test Facility at DESY, Zeuthen Site (PITZ), to study the SM of electron beams in a plasma. This contribution presents simulation results on SM experiments at PITZ using the particle-in-cell code HiPACE. The simulation study is crucial to optimize the beam and plasma parameters for the experiment. Of particular interest is the energy modulation imprinted onto the beam by means of the generated wakefields in the plasma. With the support of simulations the observation of this information in the experiment can be used to deduce key properties of the accelerating electric fields such as their magnitude and their phase velocity, both of significant importance for the design of self-modulated plasma-based acceleration experiments.

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WEPWA007

The AWAKE Proton-driven Plasma Wakefield Experiment at CERN

plasma, wakefield, injection, experiment

2502

P. Muggli
MPI-P, München, Germany

Funding: For the AWAKE collaboration
The AWAKE experiment at CERN * aims at studying plasma wakefield generation and acceleration driven by proton bunches. The first experiments will focus on the self-modulation instability of the long (~12cm, rms) proton bunch in the plasma. This instability is used to transform the incoming bunch into a train of short bunches with a period approximately equal to the plasma wavelength, ~1.2mm at a nominal plasma electron density of 7·10¹⁴/cc. These experiments are planned for the end of 2016. Later, low energy (~15MeV) electrons will be externally injected to sample the wakefields and be accelerated beyond 1GeV. The main goals of the experiment will be summarized and the progress with the plasma source, beam diagnostics and injection method will be presented.
* AWAKE Collaboration, Plasma Phys. Control. Fusion 56 084013 (2014)

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WEPWA008

Measuring the Self-modulation Instability of Electron and Positron Bunches in Plasmas

plasma, cavity, radiation, positron

2506

P. Muggli, O. Reimann
MPI-P, München, Germany
E. Adli, V.K.B. Olsen
University of Oslo, Oslo, Norway
J. Allen, S.J. Gessner, S.Z. Green, M.J. Hogan, M.D. Litos, B.D. O'Shea, V. Yakimenko
SLAC, Menlo Park, California, USA
L.D. Amorim
IST, Lisboa, Portugal
G. Andonian, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi, O. Williams
UCLA, Los Angeles, California, USA
N.C. Lopes, L.O. Silva, J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal

The self-modulation instability (SMI) * can be used to transform a long, charged particle bunch into a train of periodically spaced shorter bunches. The SMI occurs in a plasma when the plasma wake period is much shorter than the bunch length. The train of short bunches can then resonantly drive wakefields to much larger amplitude that the long bunch can. The SMI will be used in the AWAKE experiment at CERN, where the wakefields will be driven by a high-energy (400GeV) proton bunch. ** However, most of the SMI physics can be tested with the electron and positron bunches available at SLAC-FACET. *** In this case, the bunch is ~10 plasma wavelengths long, but can drive wakefields in the GV/m range. FACET has a meter-long plasma **** and is well equipped in terms of diagnostic for SMI detection: optical transition radiation for transverse bunch profile measurements, coherent transition radiation interferometry for radial modulation period measurements and energy spectrometer for energy loss and gain measurement of the drive bunch particles. The latest experimental results will be presented.
* N. Kumar et al., PRL 104, 255003 (2010)
** AWAKE Collaboration, PPCF 56 084013 (2014)
*** J. Vieira et al., PoP 19, 063105 (2012)
**** S.Z. Green et al., PPCF 56, 084011 (2014)

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WEPWA016

CsKSb Photocathode R&D with High Quantum Efficiency and Long Lifetime

laser, cathode, vacuum, linac

2526

Y. Seimiya, R. Kaku, M. Kuriki, A. Yokota
HU/AdSM, Higashi-Hiroshima, Japan
T. Konomi
UVSOR, Okazaki, Japan
T. Miyajima, M. Yamamoto
KEK, Ibaraki, Japan

Advanced electron linear accelerator such as Energy Recovery Linac and Free Electron Laser needs high brightness electron source. Photocathode is suitable for the high brightness requirement because some of them has low emittance and high quantum efficiency. In the photocathode, CsKSb multi-alkali photocathode has excellent features: high quantum efficiency, long lifetime, and driven by visible light, for example green laser. Therefore, the multi-alkali photocathode is considered to be one of the best candidates for the high brightness electron source of the advanced electron accelerator. We report developments of our evaporation system and results of quantum efficiency and lifetime measurement in Hiroshima University. Multi-alkali surface analyzation has being measured by ultra-violet photoemission spectroscopy to study conditions between the multi-alkali performances and the surface condition in Institute Molecular Science. We also report the status of the progress abort the study.

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WEPWA017

An Optimization of ILC Positron Source for Electron-Driven Scheme

positron, target, beam-loading, linac

2529

Y. Seimiya, M. Kuriki, M. Urano
HU/AdSM, Higashi-Hiroshima, Japan
S. Kashiwagi
Tohoku University, School of Science, Sendai, Japan
T. Okugi, T. Omori, M. Satoh, J. Urakawa
KEK, Ibaraki, Japan
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

International Linear Collider is a future accelerator to find new physics behind the electroweak symmetry breaking by precise measurements of Higgs sector, Top quark, and so on. ILC has capacities to reveal new phenomena beyond Standard model, such as Supersymmetry particles and dark matters. In current design of positron source, undulator scheme is adapted as a baseline. In the scheme, positrons are generated from gamma rays through pair-creation process in Ti-alloy target. Generations of the gamma rays by the undulator radiation requires more than 130 GeV electrons. Therefore, a system demonstration of the scheme is practically difficult prior to the real construction. Consequently, it is desirable to prepare a technical backup of this undulator scheme. We study an optimization of positron source based on the conventional electron-driven scheme for ILC. In this scheme, positron beam is generated by several GeV electron beam impinging on W-Re target. Although heavy heat load and destruction of the target is a potential problem, it can be relaxed by stretching the effective pulse length to 60 ms instead of 1 ms, by a dedicated electron linac for the positron production. In this report, a start-to-end simulation of the electron-driven ILC positron source is performed. Beam-loading effect caused by multi-bunch acceleration in the standing wave RF cavity is also considered.

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WEPWA024

Development of a C-band RF Gun with a Coniferous-tree-type Carbon Nanostructure Field Emission Cathode

cavity, cathode, gun, radiation

2545

Y. Taira, H. Kato, R. Kuroda, H. Toyokawa
AIST, Tsukuba, Ibaraki, Japan

A C-band RF gun for compact radiation sources such as a high energy x-ray and a terahertz radiation is developed at AIST, which is designed to work at the frequency of 5.3 GHz*. A coniferous-tree-type carbon nanostructure (CCNS) is used for a field emission cathode in the C-band RF gun. A graphene sheet composed of carbon has a coniferous form, and the tip has a nanometer-size tubular structure that becomes thicker on the substrate side**. Owing to this configuration, the CCNS has a large field enhancement factor, and is considered to be more stable in high electric fields than Carbon nanotubes. We have fabricated the C-band RF gun of the single cell cavity. Emission current depending on the electric field strength on the CCNS cathode surface was measured. When the electric field strength was 30 MV/m, the total charge per a macro pulse was 30 nC. After applying a stronger electric field, a decline of the field enhancement factor was observed. We will present the experimental result of the field emission measurement of the CCNS and the simulation result of a beam trajectory using a C-band RF gun of a multi cell cavity.
* Y. Taira et al., Nucl. Instr. and Meth. Phys. Res. B 331 (2014) 27.
** R. Suzuki, Synthesiology 2 (3) (2009) 221.

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WEPWA026

Loading of a Plasma-Wakefield Accelerator Section Driven by a Self-Modulated Proton Bunch

plasma, proton, simulation, beam-loading

2551

V.K.B. Olsen, E. Adli
University of Oslo, Oslo, Norway
L.D. Amorim
IST, Lisboa, Portugal
P. Muggli
MPI, Muenchen, Germany
J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal

We investigate beam loading of a plasma wake driven by a self-modulated proton beam using particle-in-cell simulations for phase III of the AWAKE project. We address the case of injection after the proton beam has already experienced self-modulation in a previous plasma. Optimal parameters for the injected electron bunch in terms of initial beam energy and beam charge density are investigated and evaluated in terms of witness bunch energy and energy spread. An approximate modulated proton beam is emulated in order to reduce computation time in these simulations.

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WEPWA027

Gas Flow Influence on Negative Hydrogen Ion Generation within the Microwave-Driven Negative Ion Source

ion, ion-source, operation, experiment

2555

S.X. Peng, J.E. Chen, Z.Y. Guo, H.T. Ren, Y. Xu, A.L. Zhang, J.F. Zhang, T. Zhang, J. Zhao
PKU, Beijing, People's Republic of China
J. Zhao
State Key Laboratory of Nuclear Physics and Technology, Beijing, Haidian District, People's Republic of China

H⁻ ion was generated through two processes within a volume Cs- free source. The density of molecule hydrogen gas will impact the electron temperature within the primary discharge chamber that will influence the population of vibrationally excited H2*. Within the extraction region, the interaction between molecule hydrogen and H⁻ ion will is cause the dissociation of negative ion. To better understand the gas flow influence on H⁻ ion generation within a volume negative ion source, a new Cs-free volume microwave-driven H⁻ source body with two gas inlets was developed at Peking University (PKU). Experiment on gas flow and gas pressure distribution within the plasma chamber was carried out with this source body. In the meantime a two dimensional (2D) model for gas flow was developed. Details will be presented in this paper.
[1] S.X. Peng, H.T. Ren, Y. Xu, T. Zhang, etc., CW/Pulsed H⁻ Ion Beam Generation with PKU Cs-free 2.45 GHz Microwave Driven Ion Source. O5-06, NIBS 2014, Accepted for publication in AIP, 2014/11/04.

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WEPWA028

Numerical Simulation on Emittance Growth Caused by Roughness of a Metallic Photocathode

simulation, emittance, cathode, laser

2559

Z. Zhang, C.-X. Tang
TUB, Beijing, People's Republic of China

The roughness of a photocathode could lead to an additional uncorrelated divergence of the emitted electrons and therefore to an increased thermal emittance. The randomness of the real-life photocathode surface makes it unrealistic to perform typical beam dynamics simulation to study the roughness emittance growth. We developed a numerical simulation code based on the point spread function (PSF) and an estimated form of electric field distribution on an arbitrary gently undulating surface to deal with the problem. The simulation result surprisingly shows that the emittance growth factor is much smaller than expected (1.5 ~ 2).

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WEPWA033

Characterization of Laser-plasma Accelerated Electron Beam for a Compact Storage Ring

laser, plasma, target, storage-ring

2569

S. H. Park, Y. Cha, Y.U. Jeong, J.S. Jo, H.N. Kim, K.N. Kim, K. Lee, W.J. Ryu, J.S. Shinn, N. Vinokurov
KAERI, Daejon, Republic of Korea
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

A compact radiation source can be utilized by an electron beam from a Laser-plasma acceleration combined with localized shielding in a small laboratory. The stability of synchrotron radiation in wavelength and power depends on the shot-to-shot jitters of the energy and charge of an electron beam, which is strongly influenced by the plasma density of target and the jitters of a laser beam. With the 30 TW fs laser in KAERI, the optimization for generating the electron beam have done using the different shape of gas nozzle. We also present the pointing stability and the energy spread of the laser-accelerated electron beams.

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WEPWA038

Mode Transformation in Waveguide with Transversal Boundary Between Vacuum and Partially Dielectric Area

vacuum, wakefield, radiation, acceleration

2581

A.A. Grigoreva, T.Yu. Alekhina, S.N. Galyamin, A.V. Tyukhtin
Saint-Petersburg State University, Saint-Petersburg, Russia

We consider the mode transformation in a circular waveguide with a transversal boundary between a vacuum part and a part with a cylindrical dielectric layer and a vacuum channel. It is assumed that an incident mode can be both propagating and evanescent. Analysis is carried out with the using the mode decomposition technique. Numerical algorithm for calculating the mode transformation at an arbitrary channel radius is also developed. Typical dependences for the reflection and transmission coefficients on the channel radius are presented and discussed.

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WEPWA039

The AWAKE Electron Primary Beam Line

proton, plasma, dipole, wakefield

2584

J.S. Schmidt, J. Bauche, B. Biskup, C. Bracco, E. Bravin, S. Döbert, M.A. Fraser, B. Goddard, E. Gschwendtner, L.K. Jensen, O.R. Jones, S. Mazzoni, M. Meddahi, A.V. Petrenko, F.M. Velotti, A.S. Vorozhtsov
CERN, Geneva, Switzerland
U. Dorda
DESY, Hamburg, Germany
L. Merminga, V.A. Verzilov
TRIUMF, Vancouver, Canada
P. Muggli
MPI, Muenchen, Germany

The AWAKE project at CERN is planned to study proton driven plasma wakefield acceleration. The proton beam from the SPS will be used in order to drive wakefields in a 10 m long Rb plasma cell. In the first phase of this experiment, scheduled in 2016, the self-modulation of the proton beam in the plasma will be studied in detail, while in the second phase an external electron beam will be injected into the plasma wakefield to probe the acceleration process. The installation of AWAKE in the former CNGS experimental area and the required optics flexibility define the tight boundary conditions to be fulfilled by the electron beam line design. The transport of low energy (10-20 MeV) bunches of 1.25·10⁹ electrons and the synchronous copropagation with much higher intensity proton bunches (3E11) determines several technological and operational challenges for the magnets and the beam diagnostics. The current status of the electron line layout and the associated equipments are presented in this paper.

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WEPWA040

Generation and Radiation of PHz Ring-Like Electron-Pulse Train

radiation, cathode, acceleration, bunching

2587

F.H. Chao, C.H. Chen, Y.-C. Huang
NTHU, Hsinchu, Taiwan
P.J. Chou
NSRRC, Hsinchu, Taiwan

In a superradiant FEL, the constructive interference of the radiation fields from a periodic electron-pulse train rapidly increases the radiation power at the harmonics of the pulse frequency with a narrow spectrum bandwidth. To generate radiation in the X-ray spectrum, the corresponding pulse frequency of the pre-bunched electron beam should be few tens or even few hundreds PHz. The repetition rate of electron pulses generated from an ordinary RF photoinjector is usually at 10-100 Hz. Even though a superconducting RF accelerator could further increase the repetition rate of electron pulses to few MHz, it is far below the pulse frequency required for a superradiant XFEL. In this paper, we study a technique to generate a PHz ring-like electron-pulse train from an RF photoinjector with a spatially modulated driver laser and a structured photocathode. Our simulation in PARMELA confirms the feasibility of generating such a structured electron-pulse train from the photoinjector. We present our study on the beam dynamics of the structured electron-pulse train during acceleration and the radiation behavior of it in the far field in comparison with that of an ordinary electron beam.

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WEPWA045

Development of a Spectrometer for Proton Driven Plasma Wakefield Accelerated Electrons at AWAKE

plasma, dipole, proton, simulation

2601

L.C. Deacon, S. Jolly, F. Keeble, M. Wing
UCL, London, United Kingdom
B. Biskup
Czech Technical University, Prague 6, Czech Republic
B. Biskup, E. Bravin, A.V. Petrenko
CERN, Geneva, Switzerland
M. Wing
DESY, Hamburg, Germany
M. Wing
University of Hamburg, Hamburg, Germany

The AWAKE experiment is to be constructed at the CERN Neutrinos to Gran Sasso facility (CNGS). This will be the first experiment to demonstrate proton-driven plasma wakefield acceleration. The 400 GeV proton beam from the CERN SPS will excite a wakefield in a plasma cell several metres in length. To observe the plasma wakefield, electrons of 10–20 MeV will be injected into the wakefield following the head of the proton beam. Simulations indicate that electrons will be accelerated to GeV energies by the plasma wakefield. The AWAKE spectrometer is intended to measure both the peak energy and energy spread of these accelerated electrons. Improvements to the baseline design are presented, with an alternative dipole magnet and quadrupole focussing, with the resulting energy resolution calculated for various scenarios. The signal to background ratio due to the interaction of the SPS protons with upstream beam line components is calculated, and CCD camera location, shielding and light transport are considered.

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WEPWA047

Emittance Growth in a Plasma Wakefield Accelerator

plasma, emittance, scattering, wakefield

2609

Ö. Mete, K. Hanahoe, G.X. Xia
UMAN, Manchester, United Kingdom
M. Labiche
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The interaction of the witness beam with the surrounding plasma particles and wakefields was studied. The implications of the elastic scattering process on beam emittance and, emittance evolution under the focusing and acceleration provided by plasma wakefields were discussed. Simulations results from GEANT4 are presented in this paper.

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WEPWA048

Design Studies and Commissioning Plans for PARS Experimental Program

plasma, acceleration, wakefield, beam-loading

2612

Ö. Mete, K. Hanahoe, J. Wright, G.X. Xia
UMAN, Manchester, United Kingdom
M. Dover, M. Wigram, J. Zhang
University of Manchester, Manchester, United Kingdom
J.D.A. Smith
Tech-X, Boulder, Colorado, USA

Funding: Science and Technology Facilities Council and Cockcroft Institute Core Grant
PARS (Plasma Acceleration Research Station) is an electron beam driven plasma wakefield acceleration test stand proposed for VELA/CLARA facility in Daresbury Laboratory. In order to optimise various operational configurations, 2D numerical studies were performed by using VSIM for a range of parameters such as bunch length, radius, plasma density and positioning of the bunches with respect to each other for the two-beam acceleration scheme. In this paper, some of these numerical studies and considered measurement methods are presented.

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WEPWA049

Low Energy Beam Tracking Under Scattering for a Cold Electron Source in Manchester

scattering, emittance, extraction, experiment

2615

R.B. Appleby, W. Bertsche, O. Mete, G.X. Xia
UMAN, Manchester, United Kingdom
M.A. Harvey, M. Jones, A.J. Murray
The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
B. Kyle
University of Manchester, Manchester, United Kingdom

High quality electron beams, with high spatial and temporal resolution, have an important use in electron diffraction experiments to probe and study the constituents of matter. A cold electron source is being developed based on electron ionisation from an atom cloud trapped by using AC magneto-optical methods in the University of Manchester. The technique will produce bunches of electrons well suited for high precision and single shot electron diffraction. In this paper issues of modelling at low energies for this state of art electron source with very low energy spread are presented, with a focus on newly developed tools to model the scattering in the meshes used to support the extraction electric fields. The dependence on emittance growth on mesh wire thickness is studied.

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WEPWA051

Investigations into Dielectric Laser-Driven Accelerators using the CST and VSIM Simulation Codes

acceleration, laser, simulation, vacuum

2618

Y. Wei, C.P. Welsch, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom
K. Hanahoe, K. Hanahoe, O. Mete, G.X. Xia
UMAN, Manchester, United Kingdom
J. Smith
Tech-X, Boulder, Colorado, USA
Y. Wei, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: European Union’s 7th Framework Programme for research, development and demonstration under grant agreement no 289191 and the STFC Cockcroft core grant No.ST/G008248/1.
Dielectric laser-driven accelerators (DLAs) based on gratings structures confine the laser-induced accelerating field in a narrow vacuum channel where the electrons travel and are being accelerated. Recent proof-of-principle experiments have successfully demonstrated acceleration of electrons with accelerating gradients of up to 250 MV/m in such novel structures. This contribution presents detailed numerical studies into the acceleration of relativistic and non-relativistic electrons in double gratings silica structures. The optimization of these structures with regards to maximum acceleration efficiency for different spatial harmonics is discussed. Simulations were carried out using the commercial CST and VSIM simulation codes and results from both codes are shown in comparison.

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WEPWA053

First Acceleration in a Resonant Optical-Scale Laser-Powered Structure

laser, acceleration, alignment, timing

2624

R.B. Yoder
Goucher College, Baltimore, Maryland, USA
R.J. England, Z. Wu
SLAC, Menlo Park, California, USA
K.S. Hazra, B. Matthews, J.C. McNeur, E.B. Sozer, G. Travish
UCLA, Los Angeles, USA
E.A. Peralta, K. Soong
Stanford University, Stanford, California, USA

Funding: U.S. DTRA grant HDTRA1-09-1-0043
The Micro-Accelerator Platform (MAP), an optical-scale dielectric laser accelerator (DLA) based on a planar resonant structure that was developed at UCLA, has been tested experimentally. Successful acceleration was observed after a series of experimental runs at SLAC’s NLCTA facility, in which the input laser power was well below the predicted breakdown limit. Though acceleration gradients were modest (<50 MeV/m), these are the first proof-of-principle results for a resonant DLA structure. We present more detailed results and some implications for future work.

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WEPWA055

Proton Injection into the Fermilab Integrable Optics Test Accelerator (IOTA)

rfq, proton, optics, injection

2627

E. Prebys, S. A. Antipov, H. Piekarz
Fermilab, Batavia, Illinois, USA
S. A. Antipov
University of Chicago, Chicago, Illinois, USA

Funding: This work is supported by the DOE, under Contract No. De-AC02-07CH11359.
The Integrable Optics Test Accelerator (IOTA) is an experimental synchrotron being built at Fermilab to test the concept of non-linear "integrable optics". These optics are based on a lattice including non-linear elements that satisfies particular conditions on the Hamiltonian. The resulting particle motion is predicted to be stable but without a unique tune. The system is therefore insensitive to resonant instabilities and can in principle store very intense beams, with space charge tune shifts larger than those which are possible in conventional linear synchrotrons. The ring will initially be tested with pencil electron beams, but this poster describes the ultimate plan to install a 2.5 MeV RFQ to inject protons, which will produce tune shifts on the order of unity. Technical details will be presented, as well as simulations of protons in the ring.

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WEPWA056

The Sinuous Target

target, radiation, proton, lattice

2630

R.M. Zwaska
Fermilab, Batavia, Illinois, USA

We report on the concept for a target material comprised of a multitude of interlaced wires of small dimension. This target material concept is primarily directed at high-power neutrino targets where the thermal shock is large due to small beam sizes and short durations; it also has applications to other high-power targets, particularly where the energy deposition is great or a high surface area is preferred. This approach ameliorates the problem of thermal shock by engineering a material with high strength on the microscale, but a very low modulus of elasticity on the mesoscale. The low modulus of elasticity is achieved by constructing the material of spring-like wire segments much smaller than the beam dimension. The intrinsic bends of the wires will allow them to absorb the strain of thermal shock with minimal stress. Furthermore, the interlaced nature of the wires provides containment of any segment that might become loose. We will discuss the progress on studies of analogue materials and fabrication techniques for sinuous target materials.

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WEPWA059

RF Plasma-Based Ion Source Modeling on Unstructured Meshes

ion, simulation, ion-source, plasma

2637

S.A. Veitzer, K.R.C. Beckwith, M. Kundrapu
Tech-X, Boulder, Colorado, USA

Funding: This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585.
Ion source performance for accelerators and industrial applications can be improved through detailed numerical modeling and simulation. There are a number of technical complexities with developing robust models, including a natural separation of important time scales (rf, electron and ion motion), inclusion of plasma chemistry, and surface effects such as secondary electron emission and sputtering. Due to these computational requirements, it is typically difficult to simulate ion sources with Particle-In-Cell codes. An alternative is to use fluid-based codes coupled with electromagnetics in order to model ion sources. These types of models can simulate plasma evolution and rf-driven flows while maintaining good performance. We show here recent results on modeling the H⁻ ion source for the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) using the fluid plasma modeling code USim. We present new meshing capabilities for generating and parallelizing unstructured computational meshes that have increased our parallel code performance and enabled us to model inductively coupled plasmas for long periods of operation.

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WEPWA060

Interaction of a Volumetric Metamaterial Structure with an Electron Beam

wakefield, radiation, acceleration, coupling

2640

X.Y. Lu, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: The U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0010075 and the Air Force Office of Scientific Research under MURI Grant Number FA550-12-1-0489.
A volumetric metallic metamaterial structure with a cubic unit cell is introduced. The unit cells can naturally fill all of space without additional substrates or waveguides. The structure can support a negative longitudinal electric mode that can couple to an electron beam. The dispersion characteristics of the unit cell are modeled by the effective medium theory with spatial dispersion. The theory also predicts the correct resonant frequencies of the emitted radiation excited by an electron beam traversing the structure. In the wakefield simulations, a backward radiation pattern is observed. The proposed metamaterial can be applied to beam diagnostics and wakefield acceleration.

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WEPWA063

Beam-Plasma Effects in Muon Ionization Cooling Lattices

plasma, simulation, space-charge, ion

2649

J.S. Ellison, P. Snopok
IIT, Chicago, Illinois, USA

Funding: Work is supported by the U.S. Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon based accelerator experiments. One of the crucial physics processes specific to muon accelerators that has not yet been implemented in any current simulation code is beam induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the progress of developing the required simulation tools and applying them to study the properties of plasma and its effects on the beam in muon ionization cooling channels.

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WEPWA066

The Advancement of Cooling Absorbers in COSY Infinity

scattering, simulation, controls, proton

2655

J.D. Kunz
IIT, Chicago, Illinois, USA
M. Berz, K. Makino
MSU, East Lansing, Michigan, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Work is supported by the U.S. Department of Energy.
COSY Infinity is an arbitrary-order beam dynamics simulation and analysis code. It can determine high-order transfer maps of combinations of particle optical elements of arbitrary field configurations. For precision modeling, design, and optimization of next-generation muon beam facilities, its features make it a very attractive code. New features are being developed for inclusion in COSY to follow the distribution of charged particles through matter. To study in detail some of the properties of muons passing through material, the transfer map approach alone is not sufficient. The interplay of beam optics and atomic processes must be studied by a hybrid transfer map–Monte-Carlo approach in which transfer map methods describe the average behavior of the particles in the accelerator channel including energy loss, and Monte-Carlo methods are used to provide small corrections to the predictions of the transfer map accounting for the stochastic nature of scattering and straggling of particles. The advantage of the new approach is that it is very efficient in that the vast majority of the dynamics is represented by fast application of the high-order transfer map of an entire element and accumulated stochastic effects as well as possible particle decay. The gains in speed are expected to simplify the optimization of muon cooling channels which are usually very computationally demanding due to the need to repeatedly run large numbers of particles through large numbers of configurations. Progress on the development of the required algorithms is reported.

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WEPWA070

Considerations for an Efficient Terahertz-driven Electron Gun

acceleration, gun, laser, controls

2664

F. Lemery, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

We investigate a dispersion-controlled-acceleration scheme of low-energy electrons to mitigate phase slipping using a tapered dielectric lined waveguide (DLW). Our approach matches the velocity of an electron being accelerated in a slab-symmetric structure in a constant electric field. We also present first experimental results of a THz pulse propagating in a slab-symmetric DLW.

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WEPWA071

A Compact X-Ray Source Based on a Low-Energy Beam-Driven Wakefield Accelerator

acceleration, wakefield, laser, bunching

2667

F. Lemery, D. Mihalcea, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
K. Chouffani
IAC, Pocatello, Idaho, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Accelerator-based X-ray sources have led to many scientific breakthroughs. Yet, their limited availability in large national laboratory settings due to the required infrastructure is a major limitation to their disseminations to a larger user community. In this contribution we explore the use of a low-energy electron beam produced out of a photoinjector coupled to a dielectric structure to produce a higher energy (~10-20 MeV) beam via a beam-driven acceleration scheme. The accelerated beam can then be used to produce X-ray via inverse Compton scattering. This paper discusses the concept and presents start-to-end simulations of the proposed setup.

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WEPWA072

Feasibility of Continuously Focused TeV/m Channeling Acceleration with CNT-Channel

acceleration, plasma, wakefield, simulation

2670

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
A.H. Lumpkin, V.D. Shiltsev, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Atomic channels in crystals are known to consist of 10 – 100 V/Å potential barriers capable of guiding and collimating a high energy beam and continuously focused acceleration with exceptionally high gradients (TeV/m)*,**,***. However, channels in natural crystals are only angstrom-size and physically vulnerable to high energy interactions. Carbon-based nano-crystals such as carbon-nanotubes (CNTs) and graphenes have a large degree of dimensional flexibility and thermo-mechanical strength, which could be suitable for channeling acceleration of MW beams. Nano-channels of the synthetic crystals can accept a few orders of magnitude larger phase-space volume of channeled particles with much higher thermal tolerance than natural crystals****. Our particle-in-cell simulations with 100 um long effective CNT model indicated that a beam-driven self-acceleration produces 1 – 2 % net energy gain in the quasi-linear regime (off-resonance beam-plasma coupling, np = 1000 nb) with ASTA 50 MeV injector beam parameters. This paper presents current status of CNT-channeling acceleration experiment planned at the Advanced Superconducting Test Accelerator (ASTA) in Fermilab.
* T. Tajima, PRL 59, 1440 (1987)
** P. Chen and R. Noble, slac-pub-4187
*** Y. M. Shin, APL 105, 114106 (2014)
**** Y.M. Shin, D. A. Still, and V. Shiltsev, Phys. Plasmas 20, 123106 (2013)

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WEPJE001

Optimal Positron-Beam Excited Plasma Wakefields in Hollow and Ion-Wake Channels

plasma, positron, wakefield, ion

2674

A. A. Sahai, T.C. Katsouleas
Duke ECE, Durham, North Carolina, USA

Funding: DE-SC-0010012, NSF-PHY-0936278
A positron-beam interacting with the plasma electrons drives radial suck-in, in contrast to an electron-beam driven blow-out in the over-dense regime, n_b>n₀. In a homogeneous plasma, the electrons are radially sucked-in from all the different radii. The electrons collapsing from different radii do not simultaneously compress on-axis driving weak fields. A hollow-channel allows electrons from its channel-radius to collapse simultaneously exciting coherent fields *. We analyze the optimal channel radius. Additionally, the low ion density in the hollow allows a larger region with focusing phase. We have shown the formation of an ion-wake channel behind a blow-out electron bubble-wake. Here we explore positron acceleration in the over-dense regime comparing an optimal hollow-plasma channel to the ion-wake channel **. The condition for optimal hollow-channel radius is also compared. We also address the effects of a non-ideal ion-wake channel on positron-beam excited fields.
* S Lee, T Katsouleas, Phys. Rev. E, vol 64, 045501(R) (2001)
** A A Sahai, T Katsouleas, Non-linear ion-wake excitation by ultra relativistic electron wakefields, in review (http://arxiv.org/pdf/1504.03735v1.pdf)

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WEPJE002

Photoinjector Improvement and Control by Surface Acoustic Waves

photon, experiment, controls, linac

2678

R.P. Johnson
Muons, Inc, Illinois, USA
A. Afanasev, C.E. Korman
GWU, Washington, USA

A new technique is being developed to enhance the efficiency of photocathodes used for electron sources to improve emission capabilities of electron sources, such as bunch charge and average current. The proposed technique is based on the use of surface acoustical waves (SAW) generated on the piezoelectric surface of a GaAs photocathode. The generation of SAW on piezoelectric substrates is known to produce strong piezoelectric fields that propagate on the surface of the material. These fields can significantly suppress recombination effects and result in enhanced quantum efficiency of photoemission. Experimental measurements of photoemission quantum efficiency will be done on semiconductors used as photocathode materials (e.g., GaAs) in presence of SAW with varied parameters. The experimental results will be used as input for physics modeling that will provide a basis for design of operational SAW-enhanced photocathodes. While the improved quantum efficiency and parameter control expected from the use of SAW will be useful for many research devices and accelerators, the commercialization of such a widespread field as electron microscopy is compelling.

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WEPJE006

Dielectric Wakefield Accelerator Experiments at ATF

wakefield, experiment, dipole, controls

2681

D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
S.P. Antipov
Euclid TechLabs, LLC, Solon, Ohio, USA
M.G. Fedurin
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
Dielectric wakefield acceleration (DWA) presents us with means to achieve the accelerating gradient high above the limits of conventional accelerators. In a typical DWA scheme a higher energy lower charge main bunch is accelerated in the wakefield produced by a preceding lower energy higher charge drive bunch inside of a hollow metal-encapsulated dielectric tube. To make use of as much energy of the drive bunch as possible, it is highly important that all parts of it decelerate uniformly. Close to uniform drive bunch deceleration can be achieved if its current is properly shaped.* At Accelerator Test Facility (ATF) at BNL we shaped the current of a chirped electron beam with an adjustable mask placed inside of the highly dispersive region in the magnetic dogleg. We passed the shaped beam current through a quartz tube and observed the beam particles’ energy modulation at the tube’s output with a spectrometer. By tuning the mask we were able to control the beam energy modulation and thus the wakefield profile in the tube.
* B. Jiang, C. Jing, P. Schoessow, J. Power, and W. Gai, PRSTAB 15, 011301 (2012).

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WEPJE008

Experimental Study of Wakefields in an X-band Photonic Band Gap Accelerating Structure

wakefield, HOM, higher-order-mode, coupling

2689

E.I. Simakov, S. Arsenyev, C.E. Buechler, R.L. Edwards, W.P. Romero
LANL, Los Alamos, New Mexico, USA
M.E. Conde, G. Ha, C.-J. Jing, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: This work is supported by U.S. Department of Energy (DOE) Office of Science Early Career Research Program.
We designed an experiment to conduct a detailed investigation of higher order mode spectrum in a room-temperature traveling-wave photonic band gap (PBG) accelerating structure at 11.7 GHz. It has been long recognized that PBG structures have great potential in reducing long-range wakefields in accelerators. The first ever demonstration of acceleration in room-temperature PBG structures was conducted at MIT in 2005. Since then, the importance of that device has been recognized by many research institutions. However, the full experimental characterization of the wakefield spectrum in a beam test has not been performed to date. The Argonne Wakefield Accelerator (AWA) test facility at the Argonne National Laboratory represents a perfect site where this evaluation could be conducted with a single high charge electron bunch and with a train of bunches. Here we describe fabrication and tuning of PBG cells, the final cold-test of the traveling-wave accelerating structure, and the results of the beam testing at AWA.

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WEPJE011

High Reliability, Long Lifetime, Continuous Wave H⁻ Ion Source

ion, ion-source, plasma, extraction

2695

P. Barrows, G.E. Becerra
PNL, Madison, Wisconsin, USA

Funding: Small Business Innovation Research (SBIR) Phase II
Phoenix Nuclear Labs (PNL) is developing a high-current, long-lifetime negative hydrogen (H⁻) ion source in partnership with Fermilab as part of an ion beam injector for future Intensity Frontier particle accelerators. In this application, continuous output with long lifetime and high reliability and efficiency are critical. Existing ion sources at Fermilab rely on plasma-facing electrodes and are limited to lifetimes of a few hundred hours, while requiring relatively high gas loads on downstream components. PNL's H⁻ ion source uses an electrodeless microwave plasma generator which has been extensively developed in PNL's positive ion source systems, demonstrating 1000+ hours of operation and >99% continuous uptime. A magnetic filter preferentially blocks energetic electrons produced in the plasma, while allowing cold electrons and fast neutrals through toward a cesiated surface converter to produce the desired H⁻ ions, which are extracted into a low energy beam using electrostatic lenses. The design specifications are 5-10 mA of continuous H⁻ current at 30 keV with <0.2 pi-mm-mrad beam emittance. Construction and testing of the H⁻ ion source is underway at PNL.

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WEPJE012

Design and Optimisation of Dielectric Laser Deflecting Structures

laser, acceleration, undulator, simulation

2698

K.P. Wootton, R.J. England, I.V. Makasyuk, Z. Wu
SLAC, Menlo Park, California, USA
R.L. Byer, E.A. Peralta
Stanford University, Stanford, California, USA
A.D. Tafel
Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany

Funding: This work was supported by the U.S. Department of Energy under Grants DE-AC02-76SF00515, and DE-FG02-13ER41970.
Recent experimental demonstrations of dielectric laser-driven accelerator structures offer a path to the miniaturisation of accelerators. In order to accelerate particles to higher energies using a staged sequence of accelerating structures, integrating compatible micrometre-scale transverse deflecting structures into these accelerators is necessary. Using simulations, the present work outlines the design and optimisation of a fused-silica laser-driven grating deflecting structure for relativistic electron beams. Implications for device fabrication and experiments are outlined.

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WEPJE013

A New Accelerating Mode in a Silicon Woodpile Structure and Its High-efficiency Power Coupler Design

laser, acceleration, coupling, simulation

2702

Z. Wu, R.J. England, C. Lee, C.-K. Ng, K.P. Wootton
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199.
Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser-driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode with ideal Gaussian transverse profile is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in better beam loading and higher achievable acceleration gradient. Several travelling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile accelerator coupler design based on this new accelerating mode. A forward-wave-coupled, highly efficient silicon woodpile accelerator is achieved. Simulation shows high efficiency of over 70% of the drive laser power coupled to this fundamental woodpile accelerating mode, with less than 15% backward wave excitation. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 um wavelength, can reach roughly 185 MV/m.

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WEPJE019

Simulations of Field-Emission Electron Beams from CNT Cathodes in RF Photoinjectors

cathode, simulation, gun, emittance

2711

D. Mihalcea, H. Panuganti, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
L. Faillace
RadiaBeam, Santa Monica, California, USA
P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Average field emission currents of up to 700 mA were produced by Carbon Nano Tube (CNT) cathodes in a 1.3 GHz RF gun at Fermilab High Brightness Electron Source Lab. (HBESL). The CNT cathodes were manufactured at Xintek and tested under DC conditions at RadiaBeam. The electron beam intensity as well as the other beam properties are directly related to the time-dependent electric field at the cathode and the geometry of the RF gun. This report focuses on simulations of the electron beam generated through field-emission and the results are compared with experimental measurements. These simulations were performed with the time-dependent Particle In Cell (PIC) code WARP.

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WEPJE021

Fabrication and Demonstration of a Silicon Buried Grating Accelerator

laser, acceleration, vacuum, simulation

2717

A.C. Ceballos, R.L. Byer, K.J. Leedle, E.A. Peralta, O. Solgaard, K. Soong
Stanford University, Stanford, California, USA
R.J. England, I.V. Makasyuk, K.P. Wootton, Z. Wu
SLAC, Menlo Park, California, USA
A. Hanuka
Technion, Haifa, Israel
A.D. Tafel
Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany

Funding: Work supported by the U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG06-97ER41276.
Using optical electromagnetic fields in dielectric microstructures, we can realize higher-energy accelerator systems in a more compact, low-cost form than the current state-of-the-art. Dielectric, laser-driven accelerators (DLA) have recently been demonstrated using fused silica structures to achieve about an order-of-magnitude increase in accelerating gradient over conventional RF structures.* We leverage higher damage thresholds of silicon over metals and extensive micromachining capability to fabricate structures capable of electron acceleration. Our monolithic structure, the buried grating, consists of a grating formed on either side of a long channel via a deep reactive ion etch (DRIE).** The grating imposes a phase profile on an incoming laser pulse such that an electron experiences a net change in energy over the course of each optical cycle. This results in acceleration (or deceleration) as electrons travel down the channel. We have designed and fabricated such structures and begun testing at the SLAC National Accelerator Laboratory. We report on the progress toward demonstration of acceleration in these structures driven at 2um wavelength.
* E.A. Peralta et al., Nature 503 (2013)
** C.M. Chang and O. Solgaard, Appl. Phys. Lett. 104 (2014)

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WEPJE023

Cathode Performance during Two Beam Operation of the High Current High Polarization Electron Gun for eRHIC

cathode, gun, vacuum, operation

2720

O.H. Rahman
Stony Brook University, Stony Brook, USA
M.A. Ackeret, J.R. Pietz
Transfer Engineering and Manufacturing, Inc, Fremont, California, USA
I. Ben-Zvi, C. Degen, D.M. Gassner, R.F. Lambiase, A.I. Pikin, T. Rao, B. Sheehy, J. Skaritka, E. Wang
BNL, Upton, Long Island, New York, USA
E. Dobrin, R.C. Miller, K.A. Thompson, C. Yeckel
Stangenes Industries, Palo Alto, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place at Stangenes Industries in Palo Alto, CA, where the cathodes were placed in radially opposite locations inside the high voltage shroud. No significant cross talking between the cathodes were found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test, including the QE and lifetimes of the photocathodes at various steps of the experiment.

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WEPJE024

Progress on the Study of Direct Laser Electron Acceleration in Density-Modulated Plasma Waveguides

plasma, laser, simulation, acceleration

2723

M.W. Lin, B.W. Morgan
The Pennsylvania State University, University Park, Pennsylvania, USA
S.-H. Chen, C.-Y. Hsieh, Y.-L. Liu
NCU, Chung Li, Taiwan
I. Jovanovic
Penn State University, University Park, Pennsylvania, USA

Funding: This work is supported by the United States Defense Threat Reduction Agency through contract HDTRA1-11-1-0009 and the Ministry of Science and Technology in Taiwan by Grant No. MOST103-2112-M-008-004.
Direct laser acceleration of electrons can be achieved by utilizing the axial field of a guided, radially polarized laser pulse in a density-modulated plasma waveguide*. When a short fs electron bunch is injected, our particle-in-cell simulations show that the electrostatic field, arising from plasma electrons perturbed by the laser ponderomotive force, increases the transverse divergence of the bunch electrons**. Simulations are performed to study the method in which a precursor electron bunch is introduced prior to the main accelerated bunch. The precursor induces a focusing electrostatic field in the background plasma, which can considerably reduce the transverse expansion of the accelerated electrons. Based on the ignitor-heater scheme, density-modulated plasma waveguides are produced in experiments with high-Z gas targets and used to test the guiding of laser pulses. Supersonic gas jet nozzles for producing gas targets are simulated, designed, and then fabricated via direct digital deposition manufacturing. Surface quality of the nozzles and the produced gas target density profiles are evaluated with computerized tomography and optical interferometry, respectively.
* A. G. York, et al., Phys. Rev. Lett. 100, 195001 (2008).
** M.-W. Lin et al., Phys. Plasmas 21, 093109 (2014)

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WEPJE026

Conceptual Design of a Quadrupole Magnet for eRHIC

quadrupole, permanent-magnet, target, simulation

2729

H. Witte, J.S. Berg
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
eRHIC is a proposed upgrade to the existing Relativistic Heavy Ion Collider (RHIC) hadron facility at Brookhaven National Laboratory, which would allow collisions of up to 21 GeV polarized electrons with a variety of species from the existing RHIC accelerator. eRHIC employs an Energy Recovery Linac (ERL) and an FFAG lattice for the arcs. The arcs require open-midplane quadrupole magnets of up to 30 T/m gradient of good field quality. In this paper we explore initial quadrupole magnet design concepts based on permanent magnetic material which allow to modify the gradient during operation.

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WEPJE033

The Progress of Funnelling Gun High Voltage Condition and Beam Test

cathode, gun, high-voltage, radiation

2735

E. Wang, I. Ben-Zvi, D.M. Gassner, R.F. Lambiase, W. Meng, A.I. Pikin, T. Rao, B. Sheehy, J. Skaritka
BNL, Upton, Long Island, New York, USA
M.A. Ackeret, J.R. Pietz
Transfer Engineering and Manufacturing, Inc, Fremont, California, USA
E. Dobrin, R.C. Miller, K.A. Thompson, C. Yeckel
Stangenes Industries, Palo Alto, California, USA
O.H. Rahman
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A prototype of a high average current polarized electron funneling gun as an eRHIC injector has been built at BNL. The gun was assembled and tested at Stangenes Incorporated. Two beams were generated from GaAs photocathodes and combined by a switched combiner field. We observed the combined beams on a YAG crystal and measured the photocurrent by a Faraday cup. The gun has been shipped to Stony Brook University and is being tested there. In this paper we will describe the major components of the gun and recent beam test results. High voltage conditioning is discussed as well.

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WEPMA007

Experimental Study of Multipactor Suppression in Dielectric Materials

multipactoring, vacuum, Windows, target

2753

M. El Khaldi, W. Kaabi
LAL, Orsay, France

A novel coaxial resonator to investigate two-surface multipactor discharges on metal and dielectric surfaces in the gap region under vacuum conditions (~10^-8 mbar) has been designed and tested. The resonator is ~ 100 mm in length with an outer diameter of ~ 60 mm (internal dimensions). A pulsed RF source delivers up to 30 W average power over a wide frequency range 650-900 MHz to the RF resonator. The incident and reflected RF signals are monitored by calibrated RF diodes. An electron probe provides temporal measurements of the multipacting electron current with respect to the RF pulses. In this paper we compare and contrast the results from the RF power tests of the alumina (97.6% Al2O3) and quartz samples without a coating, “the non-coated samples” and the Alumina and quartz samples with a thick TiN coating in order to evaluate a home made sputtered titanium nitride (TiN) thin layers as a Multipactor suppressor. The effectiveness of this method is presented and discussed in the paper.

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WEPMA009

3 GHz Single Cell Cavity Optimization Design

accelerating-gradient, linac, simulation, cavity

2761

L. Garolfi, M. El Khaldi
LAL, Orsay, France
N. Faure
PMB-ALCEN, PEYNIER, France

In order to develop a high gradient S-band electron accelerating structure, an optimized travelling wave (TW) single-cell cavity operating at the frequency of 3 GHz with 2π/3 phase advance, is proposed. Starting from the well-known accelerating cells design developed by the Laboratoire de l'Accélérateur Linéaire (LAL) and the Stanford Linear Accelerator Centre (SLAC), for linear accelerators; it is possible to improve the main RF parameters, such as quality factor, shunt impedance, enhancement factor and group velocity, by choosing a suitable shape of the inner surface. Even though surface electric field is being considered as the only main quantity limiting the accelerating gradient; the importance of power flow and the modified Poynting vector*, has been highlighted from high-gradient experimental data. In this context, the new field quantity (Sc) is derived from a model describing the RF breakdown trigger phenomenon wherein field emission currents from potential breakdown sites produce local pulsed heating. In particular, the modified Poynting vector takes into account both active and reactive power flow travelling along the structure. The main results presented in this paper have been carried out with the 3D electromagnetic simulation codes: High Frequency Structural Simulator solver (HFSS) and CST MICROWAVE STUDIO (CST MWS).
* A. Grudiev et al., "New local field quantity describing the high gradient limit of accelerating structures", PRST:AB 12, 102001 (2009).

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WEPMA015

Water-cooled Thin Walled Beam Pipes of the Fast Ramping Storage Ring ELSA

radiation, synchrotron, dipole, synchrotron-radiation

2780

P. Hänisch, W. Hillert, B. Neff
ELSA, Bonn, Germany

At the Electron Stretcher Facility ELSA of Bonn University thin walled beam pipes are in use to reduce eddy current loss to a minimum. The operation of the accelerator places high demands on the beam pipes like static stress because of the inner vacuum and additional one-sided thermal stress caused by synchrotron radiation. A first generation of thin walled beam pipes had been developed and manufactured during the construction of the stretcher ring in 1985. These pipes were successfully in operating stage the following ten years. The beam pipes had a wall thickness of 0.3mm, a length of 3m, and a bending radius of ca. 10.5m. Special pipes with a sideway branch for synchrotron radiation experiments have been manufactured in the same assembly dimension. In the course of an intensity upgrade, a second generation of beam pipes has been developed in 1995. To reduce the thermal stress caused by the synchrotron radiation an internal water cooling was mounted. In this contribution the design and manufacturing principles of the thin walled beam pipes with water cooling are presented.

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WEPMA016

A New RF station for the ELSA Stretcher Ring

klystron, cavity, LLRF, synchrotron

2783

M. Schedler, A. Dieckmann, P. Hänisch, W. Hillert
ELSA, Bonn, Germany

At the Electron Stretcher Facility ELSA of Bonn University, an increase of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 6 GeV/s from 1.2 GeV to 3.2 GeV and afterwards a slow extraction over a few seconds to the hadron physics experiments. The beam current is mainly limited due to missing RF power at highest energies in order to compensate for synchrotron radiation losses. The current stretcher ring's RF station is based on a single 200 kW klystron driving two 5-cell PETRA type cavities. To achieve the desired beam current at maximum energy two additional 7-cell PETRA type cavities, drivin by a second klystron, will be installed. With this upgrade, sufficient beam lifetime for slow beam extraction will be provided and thus ensure an adequate duty cycle of the external beam current. The general setup of the new RF station as well as the changes in operation when switching from one to two stations will be presented.

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WEPMA017

Alvarez DTL Cavity Design for the UNLAC Upgrade

cavity, DTL, impedance, simulation

2786

X. Du, L. Groening, S. Mickat
GSI, Darmstadt, Germany
A. Seibel
IAP, Frankfurt am Main, Germany

The 10⁸.4 MHz drift tube linac (DTL) accelerator for GSI’s UNLAC upgrade project is in its initial design stage using CST-MWS code. Optimization criteria for cavity design are effective shunt impedance (ZTT), transit-time factor, and electrical breakdown limit. In geometrical op-timization we have aimed at increase of the energy gain in each RF gap of the DTL cells by maximizing ZTT per peak surface field with special designed tube profile. Mul-ti-pacting probability is evaluated for one gap of typical single cell. For the beta profile design, a code based on VBA macros of CST is developed to perform cell by cell design with pre-optimized 3D tube structures. With this code several beta profile designs are presented and com-pared for the balance of power consumption, ZTT, tank length, and breakdown possibility of the complete cavity. The stability of the field has been taken into account and for this the crossed stem arrangement is assessed. This paper gives a short introduction of the method, presents some important results. Possible countermeas-ures are discussed.

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WEPMA030

Design and Characterization of Permanent Magnetic Solenoids for REGAE

solenoid, emittance, experiment, simulation

2822

M. Hachmann, K. Flöttmann, T. Gehrke, F. Mayet
DESY, Hamburg, Germany

REGAE is a small electron linear accelerator at DESY. In order to focus short and low charged electron bunches down to a few micrometre permanent magnetic solenoids were designed, assembled and field measurements were done. Due to a shortage of space close to the operation area an in-vacuum solution has been chosen. Furthermore a tworing design made of wedges has been preferred in terms of beam dynamic issues. To keep the field quality of a piecewise built magnet still high a sorting algorithm for the wedge arrangement has been developed and used for the construction of the magnets. The magnetic field of these solenoids has been measured with high precision and has been compared to the simulated magnetic field.

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WEPMA031

Timing Jitter Studies for sub-fs Electron Bunch Generation at SINBAD

laser, gun, simulation, acceleration

2826

J. Zhu, R.W. Aßmann, U. Dorda, J. Grebenyuk, B. Marchetti
DESY, Hamburg, Germany

Generation of ultra-short electron bunches with a few femtoseconds arrival-time jitter is the major challenge in plasma acceleration with external injection. Meanwhile, peak current stability is also one of the crucial factors for user experiments when the electron bunch is used for free-electron laser (FEL) generation. ARES (Accelerator Research Experiment at SINBAD) will consist of a compact S-band normal-conducting photo-injector providing ultra-short electron bunches of 100 MeV. We present bunch arrival-time jitter studies for two different compression schemes, velocity bunching and magnetic compression with a slit, at ARES with start-to-end simulations. Contributions from various jitter sources are quantified.

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WEPMA044

25 Hz, Sub-mJ Ytterbium Laser Source of RF Gun for SuperKEKB Linac

laser, gun, cavity, polarization

2862

X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang
KEK, Ibaraki, Japan

For injector linac of SuperKEKB project, the 5 nC electron beams with double-bunch is expected to be generated in the photocathode RF gun. For the repetition rate of electrum beam, the optional of 2 Hz, 5 Hz, 25 Hz and 50 Hz are requested. Although, more than 5 nC electron with single-bunch has been generated in the 2 Hz and 5 Hz, when the repetition rate increases to 25 Hz, the condition of the laser amplifier system such as the thermal lens effect is changed seriously. To correspond to 25 Hz repetition rate, the ytterbium-doped laser system was reformed. An AuSu (80:20) heat-dissipating solder is employed to reduce the thermal lens effect. Because of the damage threshold limitation of the thin-disk crystal and optical mirrors, Some improvement were performed to increase the quality of the pulses rather than the amplify power, which cause the SHG conversion efficiency is up to 60% and 30% with 2ω and 4ω respectively. More than 3 nC electron beam is obtained with 25 Hz.

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WEPMA053

Multipactor Simulations in 325 MHz Superconducting Spoke Cavity for an Electron Accelerator

cavity, simulation, multipactoring, laser

2892

T. Kubo, T. Saeki
KEK, Ibaraki, Japan
E. Cenni, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, Japan

Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
In order to realize a compact industrial-use X-ray source with the laser-Compton scattering, a 325MHz superconducting spoke cavity for an electron accelerator operated at 4K is under development. After design-optimizations of the first cavity, we started fabrication process. In this paper, multipactor analyses carried out as parts of the design-optimization efforts are briefly summarized. Relations between cavity geometries and averaged secondary electron emission yield are discussed.

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WEPMA056

Development of Superconducting Spoke Cavities for Laser Compton Scattered X-ray Sources

cavity, operation, linac, brightness

2902

R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, Japan
E. Cenni, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Kubo, T. Saeki
KEK, Ibaraki, Japan

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
A 5-year research program on the development of superconducting spoke cavities for electron accelerators has been funded by MEXT, Japan since 2013. The purpose of our program is establishing design and fabrication processes of superconducting spoke cavity optimized for compact X-ray sources based on laser Compton scattering. The spoke cavity is expected to realize a compact industrial-use X-ray source with a reasonable cost and easy operation. We have chosen a cavity frequency at 325 MHz due to possible operation at 4 K and carried out cavity shape optimization in terms of electromagnetic and mechanical properties. Production of press-forming dies is also in progress. In this paper, we present overview and up-to-date status of the research program.

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WEPMA060

The Development of Cavity Frequency Tracking Type RF Control System for SRF-TEM

cavity, SRF, LLRF, acceleration

2914

N. Higashi
The University of Tokyo, Graduate School of Science, Tokyo, Japan
A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, M. Nishiwaki, H. Sakai, M. Sawabe, K. Ueno, M. Yamamoto
KEK, Ibaraki, Japan
M. Kuriki
HU/AdSM, Higashi-Hiroshima, Japan
S. Yamashita
ICEPP, Tokyo, Japan

Superconducting accelerating cavities used in high-energy accelerators can generate high electric fields of several 10 MV/m by supplying radio frequency waves (RF) with frequencies matched with resonant frequencies of the cavities. Generally, frequencies of input RFs are fixed, and resonant frequencies of cavities that are fluctuated by Lorentz force detuning and Microphonics are corrected by feedbacks of cavity frequency tuners and input RF power. Now, we aim to develop the cavity frequency tracking type RF control system where the frequency of input RF is not fixed and consistently modulated to match the varying resonant frequency of the cavity. In KEK (Tsukuba, Japan), we are developing SRF-TEM that is a new type of transmission electron microscope using special-shaped superconducting cavity. By applying our new RF control system to the SRF-TEM, it is expected to obtain stable accelerating fields so that we can acquire good spatial resolution. In this presentation, we will explain the required stabilities of accelerating fields for SRF-TEM and the feasibility of SRF-TEM in the case of applying the cavity frequency tracking type RF control system.

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WEPMN003

The Magnetic Measurement for Low Magnetic Field Stability of Dipole Magnet for CEPC

collimation, positron, dipole, collider

2917

Z. Zhang, F.S. Chen, H. Geng, B. Yin
IHEP, Beijing, People's Republic of China

The CEPC (China Electron-Positron Collider) project is in the pre-research stage. When the beam energy of booster is 120 GeV, the magnetic field of deflection magnet is 640 G. In order to save funds for scientific research, we are ready to select the injection energy for 6 GeV, this corresponds to a magnetic field about 32 G. In such a low magnetic field, the effects of earth's magnetic field and ambient temperature variations cannot be ignored. In this paper, first written the collection procedures for magnetic field value and ambient temperature values by Labview software, then used a one-dimensional probe to measure the background magnetic field for three directions (Bx, By, Bz) and the value of the ambient temperature values, the time of data collection for each direction are more than 24 hours (every minute collecting a set of values). Finally, plus the different currents (3A, 6A.. 15A) to the dipole magnet, the time of measured and the data collected by over 24 hours. Based on the results of the analysis of large amounts of data, summarized and analyzed the effect of Earth's magnetic field and ambient temperature for dipole magnet in a low magnetic field.

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WEPMN012

Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun

cathode, cavity, gun, impedance

2940

P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2011CB808302)
The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.

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WEPMN013

Development of DC-SRF Injector at Peking University

SRF, cavity, laser, cathode

2944

J.K. Hao, J.E. Chen, P.L. Fan, L.W. Feng, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Zh.W. Wang, X.D. Wen, H.M. Xie, K. Zhao, F. Zhu
PKU, Beijing, People's Republic of China

DC-SRF electron injector, which combines a DC Pierce gun and a 3.5 cell 1.3 GHz superconductor cavity in a cryomodule, has been developed at Peking University. Based on the improvements of beam line, LLRF system and 2K cryogenic system, stable operation of the DC-SRF injector has been carried out recently. Electron beams with 3.4 MeV energy and the currents of ~1mA in a macro-pulse mode was obtained. As the first application of this DC-SRF injector, THz radiation produced with a 10 period undulator was also detected. The description of the experiment process and results will be presented in this paper.

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WEPMN014

A C-band Deflecting Cavity Design for High-precision Bunch Length Measurement

cavity, simulation, electromagnetic-fields, coupling

2948

J. Jiang, H.B. Chen, J. Shi, P. Wang
TUB, Beijing, People's Republic of China

Funding: NSFC 11375098 and 11327902
A standing wave RF deflecting structure has been designed as a tool for high-precision bunch length measurement. This 3-cell deflecting cavity is designed to operate at a frequency of 5.712GHz. In this paper, the RF design and thermal analysis of the deflecting cavity are introduced. We study the electromagnetic field distribution inside the cavity. The coupler design is also discussed. And the beam dynamics simulation is shown.

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WEPMN015

Dark Current Imaging Experiment in an L-band RF Gun

cathode, solenoid, gun, experiment

2952

J.H. Shao, H.B. Chen, J. Shi, D. Wang
TUB, Beijing, People's Republic of China
S.P. Antipov, S.V. Baryshev, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
F.Y. Wang, L. Xiao
SLAC, Menlo Park, California, USA

The localized high electric field enhancement or low work function is the trigger for strong field emission, which however has yet been well experimentally studied. Using an L-band photocathode gun test stand at Argonne Wakefield Accelerator Facility (AWA), we’ve constructed an imaging beam line to observe field emission current from predefined emitters on cathode. Preliminary experiment results are present. Future plan is discussed.

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WEPMN017

High Power RF Radiation at W-band Based on Wakefields Excited by Intense Electron Beam

wakefield, simulation, experiment, radiation

2960

D. Wang, C.-X. Tang
TUB, Beijing, People's Republic of China
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA

We report the experiment design and preliminary results on high power RF generation at W-band based on coherent wakefields from the metallic periodic structure of 91 GHz PETS (power extraction and transfer structure), excited by intense electron beam at the Argonne Wakefield Accelerator (AWA) facility. The recently output RF power is 0.7 MW, with 67 MeV, 1.4 nC single electron beam going through the structure. The RF pulse length is 3.4 ns. We measure the energy loss of electron beam as reference to the RF generation, which agrees well with the simulation results. Next run is to increase the output RF power with higher charge and to excite coherent wakefields with electron bunch train. The output RF peak power is expected to be ~100 MW and the electrical field gradient can reach up to 400 MV/m, with RF pulse duration adjustable from few ns to 30 ns when excited with 5~10 nC charge in a single bunch and up to 32 sub bunches in total.

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WEPMN021

Design and Research of Secondary Electron Emission Test Equipment with Low Electron Energy

gun, vacuum, ion, accumulation

2970

Y.H. Xu, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

In particle accelerators, the secondary electrons resulting from the interaction between particles and vacuum chamber have a great impact on beam quality. Especially for positron, proton and heavy ion accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. We have studied the secondary electron emission (SEE) of metal used for accelerators. A secondary electron emission measurement system with low electron energy has been designed and used to measure the SEE yield of metal and non-evaporable getter materials. With the equipment, we have obtained the characteristic of the SEE yield of stainless steel and oxygen free copper (OFC).

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WEPMN022

Optimization Design of Ti Cathode in Ceramic Pipe Film Coating Based on the Simulation Result of CST

vacuum, cathode, simulation, target

2973

J. Wang, L. Fan, Y.Z. Hong, X.T. Pei, Y. Wang, W. Wei, Y.H. Xu, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

The injection chamber at Hefei Light Source II (HLS II) consists of four ceramic vacuum chambers whose inner surface were coated with TiN thin film. The cross section of ceramic pipes is special racetrack structure. In order to improve the uniformity of the film, the structure of the cathode Ti plate needed to be optimized. In this article, CST PARTICLE STUDIOTM software had been used to simulate the influence of different target structure on discharge electric field distribution and electrons trajectories. Furthermore, the reliability of the simulation were analysed compared with the experimental results. Also, we put forward the optimization design of Ti cathode structure which could satisfy the requirement of uniformity of the thin film.

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WEPMN025

Harmonic Resonant Kicker Design for the MEIC Electron Circular Cooler Ring

cavity, impedance, kicker, ion

2981

Y.L. Huang
IMP/CAS, Lanzhou, People's Republic of China
R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177.
Bunched-beam electron cooling of the high-energy ion beam emittance may be a crucial technology for the proposed Medium energy Electron Ion Collider (MEIC) to achieve its design luminosity. A critical component is a fast kicker system in the Circular Ring (CR) that periodically switches electron bunches in and out of the ring from and to the driver Energy Recovery Linac (ERL). Compared to a conventional strip-line type kicker, a quarter wave resonator (QWR) based deflecting structure has a much higher shunt impedance and so requires much less RF power. The cavity has been designed to resonate simultaneously at many harmonic modes that are integer multiples of the fundamental mode. In this way the resulting waveform will kick only a subset of the circulating bunches. In this paper, analytical shunt impedance optimization, the electromagnetic simulations of this type of cavity, as well as tuner and coupler concept designs to produce 5 odd and 5 even harmonics of 47.63MHz will be presented, in order to kick every 10th bunch in a 476.3 MHz bunch train.

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WEPMN034

Electron Emission from Surface Roughness on Cavity in Low Temperature

radiation, cavity, gun, vacuum

3003

H. Kim, H.J. Cha, S. Choi, W.K. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea
Y. Chang
Hanshin University, Kyungki, Republic of Korea

Electron emission phenomenon from surface roughness on cavity is investigated. The distribution of the electric field from the surface roughness can be obtained on cavity surface. The field emission is calculated from the electric field distribution. The generalized electron emission from electric field and temperature effect is also calculated on the surface roughness of the cavity.

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WEPMN041

Technical Overview of Bunch Compressor System for PAL XFEL

dipole, quadrupole, vacuum, diagnostics

3018

H.-G. Lee, Y.-G. Jung, H.-S. Kang, D.E. Kim, K.W. Kim, S.B. Lee, D.H. Na, B.G. Oh, K.-H. Park, H.S. Suh, Y.J. Suh
PAL, Pohang, Kyungbuk, Republic of Korea

Pohang Accelerator Laboratory (PAL) is developing a SASE X-ray Free Electron Laser based on 10 GeV linear accelerator. Bunch compressor (BC) systems are developed to be used for the linear accelerator tunnel. It consists of three hard X-ray line and one soft X-ray line. BC systems are composed of four dipole magnets, three quadrupole magnet, BPM and collimator. The support system is based on an asymmetric four-dipole magnet chicane in which asymmetry can be optimized. This flexibility is achieved by allowing the middle two dipole magnets to move transversely. In this paper, we describe the design of the stages used for precise movement of the bunch compressor magnets and associated diagnostics components.

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WEPMN050

A Pinger Magnet System for the ALBA Synchrotron Light Source

storage-ring, kicker, high-voltage, simulation

3039

M. Pont, N. Ayala, G. Benedetti, M. Carlà, Z. Martí, R. Núñez-Prieto
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

A pinger magnet system consisting of two short kickers, one for each transversal plane, has been recently commissioned at the ALBA Synchrotron Light Source. The kickers can excite large betatron oscillations on the electron beam in order to probe the linear and non-linear beam dynamics regime together with the turn-by turn capabilities of the BPMs. The kickers are mounted in a single Ti coated ceramic vacuum chamber, have a length of 0.3 m each and provide a half sine pulse with a pulse length of 1 μs at an amplitude of 1.4 mrad and the pulser unit is based on solid state technology. This report summarises the steps followed from its design until its installation, electric and magnetic characterisation in the laboratory, and the first results with beam.

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WEPMN056

High Power Testing of the First Re-buncher Cavity for LIPAC

cavity, vacuum, radiation, low-level-rf

3051

F. Toral, D. Gavela, I. Podadera, D. Regidor, M. Weber, C. de la Morena
CIEMAT, Madrid, Spain
B. Bravo, R. Fos, J.R. Ocampo, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Funding: This work is partially supported by the Spanish Ministry of Economy and Competitiveness under projects AIC-A-2011-0654 and the Agreement as published in BOE, 16/01/2013, page 1988
Two re-buncher cavities will be installed at the Medium Energy Beam Transport (MEBT) of the LIPAc accelerator, presently being built at Rokkasho (Japan). They are IH-type cavities with 5 gaps and will provide an effective voltage of 350 kV at 175 MHz for deuterons at 5 MeV. The first prototype has been designed at CIEMAT and built by the Spanish industry. The high power tests and RF conditioning have been successfully performed at the ALBA/CELLS RF laboratory. A solid state power amplifier, which has been developed by CIEMAT and its partner companies at Spain for the LIPAc RF System, has been used for the tests. The cavity has shown a performance according to calculations, regarding the dissipated power, peak temperatures and coupling factor. RF conditioning was started with a duty cycle of 3%, which was increased gradually till continuous wave (CW), which is the nominal working mode in LIPAc.

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WEPHA002

Electromagnetic Characterization of NEG Properties Above 200 GHz for the CLIC Damping Rings

simulation, impedance, damping, network

3097

E. Koukovini-Platia, G. Iadarola, G. Rumolo, C. Zannini
CERN, Geneva, Switzerland

Non-Evaporable Getter (NEG) will be used in the CLIC electron damping rings (EDR) to suppress fast beam ion instabilities due to its effective pumping ability. The electromagnetic (EM) characterization of the NEG properties up to high frequencies is required for the correct impedance modeling of the DR components. The properties are determined using WR-3.4 and WR-1.5 rectangular waveguides, based on a combination of experimental measurements of the complex transmission coefficient S21 with a Vector Network Analyzer (VNA) and CST 3D EM simulations, for the frequency range of 220-330 GHz and 500-750 GHz. The results obtained using NEG-coated Aluminum (Al) waveguides are presented in this paper.

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WEPHA006

Recommissioning of the COLDEX Experiment at CERN

cryogenics, vacuum, controls, experiment

3109

R. Salemme, V. Baglin, F. Bellorini, G. Bregliozzi, K. Brodzinski, P. Chiggiato, P. Costa Pinto, P. Gomes, A. Gutierrez, V. Inglese, B. Jenninger, R. Kersevan, E. Michel, M. Pezzetti, B. Rio, A. Sapountzis
CERN, Geneva, Switzerland

COLDEX (Cold bore Experiment), installed in the Super Proton Synchrotron (SPS) at CERN, is a test vacuum sector used in 2001-2004 to validate the Large Hadron Collider (LHC) cryogenic vacuum system with LHC type proton beams. Its cryostat houses a 2.2 m long copper perforated beam screen surrounded by a stainless steel cold bore, both individually temperature controlled down to 5 and 3 K, respectively. In the framework of the development for the High Luminosity upgrade of the LHC (HL-LHC), COLDEX has been re-commissioned in 2014. The objective of this re-commissioning is the validation of the performance of amorphous carbon coatings at cryogenic temperature with LHC type beams. The existing COLDEX beam screen has been dismounted and carbon coated, while a complete overhaul of the vacuum, cryogenic and control systems has been carried out. This contribution describes the phases of re-commissioning and reviews the current experimental set-up. An overview of the possible measurements with COLDEX, in view of its HL-LHC experimental program, is also presented.

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WEPHA007

Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment

cryogenics, vacuum, simulation, experiment

3112

R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan
CERN, Geneva, Switzerland

Extrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs.

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WEPHA010

The Vacuum System of the Extra-Low Energy Antiproton Decelerator ELENA at CERN

vacuum, antiproton, dipole, ion

3119

R. Kersevan
CERN, Geneva, Switzerland

The Extra-Low ENergy Antiproton decelerator (ELENA) project is under way since 2011. In the past 3 years, it has considerably evolved into a detailed design for the ring and the transfer lines. It is a small machine, ~30 m in circumference, with a rather tight specification for the average pressure seen by the anti-proton beams injected by the anti-proton decelerator (AD). The average pressure in ELENA must be limited to 4x10^-12 mbar (H2-equivalent) in order to limit the charge-exchange losses during the rather long deceleration process (several tens of seconds), during which the energy of the beam is reduced and the electron-cooler is used twice in order to decrease the transverse emittance of the anti-proton beam. This paper will discuss the design of the chambers of the injection line, extraction line and the ring. It will also mention the actual status of the vacuum system for the transfer lines to the experiments, LNE, which are under finalisation. The results of detailed 3D simulations made with the test-particle montecarlo code Molflow+ will be discussed, alongside with the choice for the pumping system, mainly distributed NEG-coatings and integrated NEG/ion-pumps.

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WEPHA011

Photodesorption and Electron Yield Measurements of Thin Film Coatings for Future Accelerators

vacuum, photon, experiment, solenoid

3123

R. Kersevan, M. Ady, P. Chiggiato
CERN, Geneva, Switzerland
T. Honda, Y. Tanimoto
KEK, Tsukuba, Japan

The performance of future accelerators could be limited by electron cloud phenomena and high photodesorption yields. For such a reason, the study of secondary electron and photodesorption yields of vacuum materials is essential. The eradication or mitigation of both secondary electron and molecule desorption could strongly reduce the beam scrubbing time and increase the availability of nominal beams for experiments. Surface modifications with the desired characteristics can be achieved by thin-film coatings, in particular made of amorphous carbon and non-evaporable getters (NEG). In the framework of a new collaboration, several vacuum chambers have been produced, and different coatings on each of them have been applied. The samples were then irradiated at KEK’s Photon Factory with SR light of 4 keV critical energy during several days, allowing the measurement of the photodesorption yield as a function of the photon dose. This paper presents the experiment and briefly summarizes the preliminary photodesorption and photoelectron yield data of different coatings. The results can be used for future machine design with similar conditions, such as the FCC-hh.

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WEPHA019

Development and Production of Non-evaporable Getter Coatings for MAX IV

photon, cathode, vacuum, cavity

3145

P. Costa Pinto, B. Bártová, B. Holliger, S. Marques Dos Santos, V. Nistor, A. Sapountzis, M. Taborelli, I. Wevers
CERN, Geneva, Switzerland
J. Ahlbäck, E. Al-Dmour, M.J. Grabski, C. Pasquino
MAX-lab, Lund, Sweden

MAX IV is presently under construction at Lund, Sweden, and the first beam for the production of synchrotron radiation is expected to circulate in 2016. The whole set of 3-GeV ring beam pipes is coated with Ti-Zr-V Non Evaporable Getter (NEG) thin film in order to fulfil the average pressure requirement of 1x10^-9 mbar, despite the compact magnet layout and the large aspect ratio of the vacuum chambers. In this work, we present the optimisations of the coating process performed at CERN to coat different geometries and mechanical assembling used for the MAX IV vacuum chambers; the morphology of the thin films is analysed by Scanning Electron Microscopy; the composition and thickness is measured by Energy Dispersive X-ray analysis; the activation of the NEG thin film is monitored by X-ray Photoemission Spectroscopy; the vacuum performance of the coated beam pipes is evaluated by the measurement of hydrogen sticking coefficient. The results of the coating production characterisation for the 84 units coated at CERN are presented.

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WEPHA020

Titanium Coating of Ceramics for Accelerator Applications

vacuum, cathode, Windows, target

3148

W. Vollenberg, P. Costa Pinto, B. Holliger, A. Sapountzis, M. Taborelli
CERN, Geneva, Switzerland

Titanium thin films can be deposited on ceramics, in particular alumina, without adherence problems. Even after air exposure their secondary electron yield is low compared to alumina and can be further reduced by conditioning or beam scrubbing. In addition, depending on the film thickness, titanium provides different surface resistances that fulfil requirements of ceramics in particle accelerators. Titanium thin films (MOhm square range) are used to suppress electron multipacting and evacuate charges from ceramic surfaces. Thicker films (5-25 Ω square range) are applied to lower the surface resistance so that the beam impedance is reduced. In this contribution, we present the results of a development aimed at coating 2-meter long alumina vacuum chambers with a uniform surface resistivity by a dedicated DC magnetron sputtering configuration.

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WEPHA022

Characterization of Nb Coating in HIE-ISOLDE QWR Superconducting Accelerating Cavities by means of SEM-FIB and TEM

cavity, interface, ion, niobium

3155

B. Bártová, S. Calatroni, A. Sublet, M. Taborelli
CERN, Geneva, Switzerland
A.B. Aebersold, D.T.L. Alexander, M. Cantoni
EPFL, Lausanne, Switzerland

The Quarter Wave Resonators (QWR) high-β cavities (0.3m diameter and 0.9m height) are made from OFE 3D-forged copper and are coated by DC-bias diode sputtering with a thin superconducting layer of niobium. The Nb film thickness, morphology, purity and quality are critical parameters for RF performances of the cavity. They have been investigated in a detailed material study. The coating structure at different positions along a test cavity was observed by cross-section imaging using SEM-FIB instrument. The samples from the top of the cavity showed presence of unexpected porosities, whose volume was investigated using FIB tomography. TEM lamella was prepared for two samples (top part and inner conductor of the cavity) to study in detail the grain orientation in the coating, its chemical composition and structure. The 14-layer structure in thick coating was indeed evidenced by the TEM analysis. Chemical mapping revealed the presence of a few nm in size copper precipitates close to the Nb/Cu interface and a passivating oxide layer of 10 nm thickness on top of the coating and around porosities. However no impurities or interface layer along the coating profile were present.

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WEPHA046

Outgassing Analysis During Transport for 14m Long Arc-Cell Vacuum Chambers of the Taiwan Photon Source

vacuum, ion, photon, storage-ring

3219

L.H. Wu, C.K. Chan, C.H. Chang, C.-C. Chang, S.W. Chang, Y.P. Chang, B.Y. Chen, J.-R. Chen, Z.W. Chen, C.M. Cheng, G.-Y. Hsiung, S-N. Hsu, H.P. Hsueh, C.S. Huang, Y.T. Huang, T.Y. Lee, I.C. Yang
NSRRC, Hsinchu, Taiwan
J.-R. Chen
National Tsing Hua University, Hsinchu, Taiwan

An outgassing analysis during transportation for the large, 14-m-long, ultra-high-vacuum aluminum arc-cell chambers of the Taiwan Photon Source (TPS) was performed using residual gas analysis (RGA). Each cell was baked to 150 °C in the laboratory to achieve ultra-high vacuum. Under pumping by primarily ion pumps (IP) and non-evaporable getter (NEG) pumps, the cells obtained pressures of 6.4×10^-9 Pa on average, and the main residual gas was H2. Here, vacuum pressure measurements and residual gas analyses were performed in situ while a cell chamber was being transported. It was found that the vibration of the arc-cell vacuum chamber caused the pressure to rise abruptly; in this case, the main outgassing gas was CH4. Once the arc cell had been fully installed, the vacuum pressure gradually decreased to the original vacuum pressure because of the pumping effect of the ion gauges.

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WEPHA054

Commissioning of the Transverse Deflecting Cavity on VELA at Daresbury Laboratory

cavity, klystron, vacuum, coupling

3239

A.E. Wheelhouse, R.K. Buckley, S.R. Buckley, L.S. Cowie, P. Goudket, L. Ma, J.W. McKenzie, A.J. Moss
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, M. Jenkins
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

A 9-cell S-band transverse deflecting copper cavity (TDC) has been designed and built to provide a 5 MV transverse kick in order to perform longitudinal profile measurements of the electron bunch on the Versatile Electron Linear Accelerator (VELA) at Daresbury Laboratory. The cavity has been manufactured by industry and has been field flatness tuned using a beadpull system. The cavity has then been installed on to the VELA facility and commissioned for operation with the electron beam. This paper discusses the tuning and the RF conditioning of the cavity.

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WEPHA057

High Gradient Testing of an X-band Crab Cavity at XBox2

cavity, wakefield, klystron, network

3242

B.J. Woolley, P.K. Ambattu, R. Apsimon, G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A. Grudiev, I. Syratchev, R. Wegner, B.J. Woolley, W. Wuensch
CERN, Geneva, Switzerland

CERN’s Compact linear collider (CLIC) will require crab cavities to align the bunches to provide effective head-on collisions. An X-band quasi-TM11 deflecting cavity has been designed and manufactured for testing at CERN’s Xbox-2 high power standalone test stand. The cavity is currently under test and has reached an input power level in excess of 40MW, with a measured breakdown rate of better than 10^-5 breakdowns per pulse. This paper also describes surface field quantities which are important in assessing the expected BDR when designing high gradient structures.

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WEPTY002

Studies into Electron Beam Generation, Acceleration and Diagnostics within LA³NET

laser, network, acceleration, diagnostics

3256

C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

The Laser Applications at Accelerators Network (LA³NET) is receiving funding of up to 4.6 M€ from the European Union within the 7th Framework Programme to carry out R&D into laser-based particle sources, laser acceleration schemes and laser-based beam diagnostics. This international network joins universities, research centres and private companies and has been training 19 early stage researchers at network nodes across Europe since 2011. This contribution presents research outcomes from LA³NET’s main work packages, covering electron beam generation, acceleration and diagnostics. Results from surface studies of photocathodes for photo injector applications in the framework of the CLIC project are presented along with information about expected accelerating gradients in dielectric laser-driven accelerators as identified for non-relativistic and relativistic electron beams using the CST and VSIM simulation codes. Initial results from energy measurements using Compton backscattering at the ANKA Synchrotron at KIT are also presented. In addition, a summary of recent and upcoming international events organized by the LA³NET consortium is also given.
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191.

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WEPTY030

Breakdown Characterization in 805 MHz Pillbox-like Cavity in Strong Magnetic Fields

cavity, site, pick-up, vacuum

3335

A.V. Kochemirovskiy, D.L. Bowring, A. Moretti, D.W. Peterson, K. Yonehara
Fermilab, Batavia, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
G. Flanagan, G.M. Kazakevich
Muons, Inc, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

RF Breakdown in strong magnetic fields has a negative impact on a cavity performance. The MuCool Test Area at Fermilab has unique capabilities that that allow us to study the effects of static magnetic field on RF cavity operation. We have tested an 805 MHz pillbox-like cavity in external magnetic fields up to 5T. Results confirm our basic model of breakdown in strong magnetic fields. We have measured maximum achievable surface gradient dependence on external static magnetic field. Damage inspection of cavity walls revealed a unique observed breakdown pattern. We present the analysis of breakdown damage distribution and propose the hypothesis to explain certain features of this distribution

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WEPTY051

Stripline Kicker for Integrable Optics Test Accelerator

kicker, impedance, proton, operation

3390

S. A. Antipov
University of Chicago, Chicago, Illinois, USA
A. Didenko, V.A. Lebedev, A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
We present a design of a stripline kicker for Integrable Optics Test Accelerator (IOTA). For its experimental program IOTA needs two full-aperture kickers, capable to create an arbitrary controllable kick in 2D. For that reason their strengths are variable in a wide range of amplitudes up to 16 mrad, and the pulse length 100 ns is less than a revolution period for electrons. In addition, the kicker has a physical aperture of 40 mm for a proposed operation with proton beam, and an outer size of 70 mm to fit inside existing quadrupole magnets to save space in the ring. Computer simulations using CST Microwave Studio show high field uniformity and wave impedance close to 50 Ω.

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WEPTY056

Novel High Power Sources for the Physics of Ionospheric Modification

gun, cathode, simulation, impedance

3398

B. Beaudoin, T.M. Antonsen, I. Haber, T.W. Koeth, A.H. Narayan, G.S. Nusinovich, K.J. Ruisard
UMD, College Park, Maryland, USA
J. Rodgers
Naval Research Laboratory (NRL), Washington, USA

Funding: This work is supported by the Air Force Office of Scientific Research under grant FA95501410019.
The ionosphere plays a controlling role in the performance of critical civilian and DoD systems including the ELF-ULF communications. The objective of Ionospheric Modification is to control triggered processes to improve the performance of trans-ionospheric C3I systems and develop new applications that take advantage of the ionosphere as an active plasma medium. A key instrument is the Ionospheric Heater, a powerful HF transmitter that modifies the properties of the ionospheric plasma by modulating the electron temperature at preselected altitudes. A major reason for the development of a mobile source is that it would allow investigators to conduct the needed research at different latitudes without building permanent installations. As part of a MURI, UMD will develop a powerful RF source utilizing IOT technology in class-D amplifier mode. This technology was chosen because it has the potential to operate at very high efficiency. Some of the technical challenges presented in this paper will include a gun design that minimizes intercepted current, a compact tunable cavity, an efficient modulator system capable of modulating a high power beam and output couplers to feed the antennas.

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WEPTY060

Virtual Welding as a Tool for Superconducting Cavity Coarse Tuning

cavity, target, proton, operation

3412

A. Facco, C. Compton, J. Popielarski, G.J. Velianoff
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Reaching the final frequency in the construction of Superconducting Half-Wave Resonators (HWR), either coaxial or spoke, is often a painful and time consuming process which requires several intermediate frequency tests and parts machining between subsequent welding steps. In spite of that, the final frequency error after final welding is often far from the target due to difficult to predict material contraction and cavity deformation induced by electron beam welding (EBW). Final coarse tuning is required by plastic deformation or differential etching. In coaxial HWR, both can decrease the cavity frequency but are not easily suitable to increase it. A novel method developed at MSU is “virtual” welding, i.e. deformation of the cavity shape by applying systematically EBW on the cavity outer surface to induce controlled Nb material contraction in strategic positions. This technique allows to increase the cavity frequency with excellent precision and predictability, thus simplifying and making less expensive and more reliable HWR coarse tuning. Method and experimental results will be described and discussed.

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WEPTY062

Multipactor Breakdown Modelling Using an Averaged Version of Furman's SEY Model

multipactoring, simulation, cavity, plasma

3419

S.A. Rice, J.P. Verboncoeur
Michigan State University, East Lansing, Michigan, USA

Funding: Work supported by a MSU Strategic Partnership Grant.
Furman's seconday electron yield model is commonly used for the simulation of multipactor in accelerating cavities and other resonant structures. While accurate, the stochastic model requires many Monte Carlo simulations in order to characterize susceptibility to multipactor. This paper generalizes our previous research in characterizing a reduced-order Furman model, in which we replace the stochastic Furman model with a deterministic model based upon the Furman model's underlying statistics. Favorable comparisons between the full Furman model and the reduced-order Furman model are shown for multipactor simulations in a coaxial cavity, and the results are expected to generalize to other geometries.

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WEPTY063

Co-Linear X-Band Energy Booster (XCEB) Cavity and RF System Details

cavity, impedance, extraction, linac

3421

T. Sipahi, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA

Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers. At the Colorado State University Accelerator Laboratory (CSUAL) we would like to adapt this technology to our 1.3-GHz, L-band accelerator system in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the design details of the X-band structures that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structure while driven solely by the beam from the L-band system.

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WEPTY067

Thermal and Mechanical Analysis of a Waveguide to Coax Symmetric Coupler for Superconducting Cavities

niobium, simulation, cavity, dipole

3434

R.G. Eichhorn, J.A. Robbins, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

As kicks from fundamental power couplers become a concern for low emittance future accelerators, a design for a symmetric coupler for superconducting accelerating cavities has been started. In this coupler, a rectangular waveguide transforms into a coaxial line inside the beam pipe to feed the cavity. So far the RF design revealed an extremely low transversal kick but concerns about cooling and the thermal stability of the coaxial transition line remained. Our contribution will address this. We will calculate heating, heat transfer and thermal stability of this coupler and evaluate the risk of quenching due to particle losses on the coupler.

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WEPWI001

An Overview of the MaRIE X-FEL and Electron Radiography Linac RF Systems

linac, klystron, cavity, FEL

3482

J.T. Bradley III, D. Rees, A. Scheinker, R.L. Sheffield
LANL, Los Alamos, New Mexico, USA

The purpose of the Matter-Radiation Interactions in Extremes (MaRIE) facility at Los Alamos National Laboratory is to investigate the performance limits of materials in extreme environments. The MaRIE facility will utilize a 12 GeV linac to drive an X-ray FEL. Most of the same linac will also be used to perform electron radiography. The main linac is driven by two shorter linacs; one short linac optimized for X-FEL pulses and one for electron radiography. The RF systems have historically been the one of the largest single component costs of a linac. We will describe the details of the different types of RF systems required by each part of the linacs. Starting with the High Power RF system, we will present our methodology for the choice of RF system peak power and pulselength with respect to klystrons parameters, modulator parameters, performance requirements and relative costs. We will also present an overview of the low level RF systems that are proposed for MaRIE and briefly describe their use with some proposed control schemes. *
* A. Scheinker, "Adaptive Accelerator Tuning", Proc. of IPAC'15.

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WEPWI003

Design of a Radial Klystron

cavity, klystron, space-charge, bunching

3489

M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DEAC03-76SF00515.
The radial klystron is a multidimensional rf source where the beam is generated by a cylindrical gun and it propagates in the radial dimension. The advantage of this design is that the space charge effects are balanced in the azimuthal dimension and a lower magnetic fields is required to focus the electron beam. The bunching is made with concentric coaxial resonators, connected by drift tube. The electron beam interaction with the cavity fields has been analyzed by means of particle tracking software in order to evaluate the beam bunching and the beam dynamics. This paper shows the klystron design, optimizing the shape and the position of each cavity, in order to maximize the efficiency of the device.

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WEPWI012

First Attempt of At-cavity X-ray Detection in a CEBAF Cryomodule for Field Emission Monitoring

cavity, cryomodule, cryogenics, ion

3515

R.L. Geng, E. Daly, M.A. Drury, A.D. Palczewski
JLab, Newport News, Virginia, USA

We report on the first result of at-cavity X-ray detection in a CEBAF cryomodule for field emission monitoring. In the 8-cavity cryomodule F100, two silicon diodes were installed near the end flange of each cavity. Each cavity was individually tested during the cryomodule test in JLab’s cryomodule test facility. The behaviors of these at-cavity cryogenic X-ray detectors were compared with those of the standard “in air” Geiger-Muller tubes. Our initial experiments establish correlation between X-ray response of near diodes and the field emission source cavity in the 8-cavity string. For two out of these eight cavities, we also carried out at-cavity X-ray detection experiment during their vertical testing. The aim is to track field emission behavior uniquely from vertical cavity testing to horizontal cavity testing in the cryomodule.

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WEPWI022

RF System Requirements for a Medium-Energy Electron-Ion Collider (MEIC) at JLab

ion, collider, booster, SRF

3536

R.A. Rimmer, J. Guo, J. Henry, H. Wang, S. Wang
JLab, Newport News, Virginia, USA
Y.L. Huang
IMP/CAS, Lanzhou, People's Republic of China

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
JLab is studying options for a medium energy electron-ion collider that could fit on the JLab site and use CEBAF as a full-energy electron injector. A new ion source, linac and booster would be required, together with collider storage rings for the ions and electrons. In order to achieve the maximum luminosity these will be high current storage rings with many bunches. We present the high level RF system requirements for the storage rings, ion booster ring and high-energy ion beam cooling system, and describe the technology options under consideration to meet them. We also present options for staging that might reduce the initial capital cost while providing a smooth upgrade path to a higher final energy. The technologies under consideration may also be useful for other proposed storage ring colliders or ultimate light sources.

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WEPWI024

Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source

ion, vacuum, background, gun

3540

M.L. Stutzman, P.A. Adderley, M. Poelker
JLab, Newport News, Virginia, USA
M.A. Mamun
Old Dominion University, Norfolk, Virginia, USA

Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.

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WEPWI032

Mechanical Properties of Niobium Cavities

cavity, niobium, SRF, cryogenics

3554

G. Ciovati, P. Dhakal, J. Matalevich, G.R. Myneni
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

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WEPWI033

Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples

plasma, cavity, gun, vacuum

3558

M. Basovic, S. Popović, M. Tomovic, L. Vušković
ODU, Norfolk, Virginia, USA
F. Čučkov, A. Samolov
University of Massachusetts Boston, Boston, Massachusetts, USA

Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.

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WEPWI044

High-Power Magnetron Transmitter for the Electron Collider Ring of the MEIC Facility

controls, SRF, cavity, injection

3587

G.M. Kazakevich
Euclid TechLabs, LLC, Solon, Ohio, USA
B.E. Chase, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
Y.S. Derbenev
JLab, Newport News, Virginia, USA

Operation of the 3-12 GeV electron collider 8-shape ring of the MEIC facility causes a Synchrotron Radiation (SR) of electrons in arcs with energy loss of ~20 kW/m at beam current of ~3 A. The total SR loss up to 2 MW per a revolution is presumed to compensate by Superconducting RF (SRF) accelerating cavities. To minimize the beam emittance, each individual SRF cavity is proposed to feed by an individual and independent RF source allowing a wide-band control in phase and power. Most efficient and less expensive in capital and maintenance costs the high-power transmitters based on magnetrons, injection-locked by phase-modulated signals, controlled in wide-band are proposed as the RF sources. The magnetron RF sources utilizing 2-cascade magnetrons allowing a wide-band phase and power control by the injection-locking phase-modulated signals were experimentally modelled by 2.45 GHz, CW, 1 kW magnetrons. Results of the modelling and adequacy of the transmitters for the SRF cavities are discussed in the presented article.

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WEPWI049

Commissioning of the 112 MHz SRF Gun and 500 MHz Bunching Cavities for the CeC PoP Linac

gun, SRF, bunching, experiment

3597

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, G. Narayan, P. Orfin, I. Pinayev, T. Rao, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, T. Xin
Stony Brook University, Stony Brook, USA
P.A. McIntosh, A.J. Moss, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase I a 112 MHz superconducting RF photoemission gun and two 500 MHz normal conducting bunching cavities were installed and commissioned. The paper describes the Phase I linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems.

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WEPWI050

SRF and RF Systems for LEReC Linac

cavity, SRF, gun, booster

3600

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, S. Polizzo, K.S. Smith, R. Than, J.E. Tuozzolo, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow beams. For the first stage of the project, LEReC-1, we will to install a 704 MHz superconducting RF cavity and two normal conducting cavities operating at 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.

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WEPWI051

Update on the CeC POP 704 MHz 5-Cell Cavity Cryomodule Design and Fabrication

cavity, SRF, cryomodule, linac

3603

J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, I. Pinayev, J. Skaritka, L. Snydstrup, R. Than, J.E. Tuozzolo, W. Xu
BNL, Upton, Long Island, New York, USA
S.M. Gerbick, M.P. Kelly, T. Reid
ANL, Argonne, USA
T.L. Grimm, R. Jecks, J.A. Yancey
Niowave, Inc., Lansing, Michigan, USA
Y. Huang
Fermilab, Batavia, Illinois, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A 5-cell SRF cavity operating at 704 MHz will be used for the Coherent Electron Cooling Proof of Principle (CeC PoP) system currently under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. The cavity will accelerate 2 MeV electrons from a 112 MHz SRF gun up to 22 MeV. Novel mechanical designs, including the helium vessel, vacuum vessel, tuner mechanism, and FPC are presented. This paper provides an overview of the design, the project status and schedule of the 704 MHz 5-cell SRF for the CeC PoP experiment.
.

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WEPWI061

Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

cavity, impedance, resonance, simulation

3634

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, K.S. Smith, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for bunch stretching and energy spread correction. In this paper we report the design of these two cavities.

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THPF018

Simulation Studies of Plasma-based Charge Strippers

target, plasma, ion, heavy-ion

3721

O.S. Haas
TEMF, TU Darmstadt, Darmstadt, Germany

Calculations on the charge state distributions in different charge stripping media are presented. The main focus of this work is the width and peak efficiency of the final charge state distribution. For equal number densities fully-stripped plasma stripping media achieve much higher charge states than gas stripping media of the same nuclear charge. This is due to the reduced electron capture rates of free target electrons compared to bound target electrons. Furthermore, targets with low nuclear charge like hydrogen achieve higher charge states than targets with high nuclear charge like nitrogen in the case of both a plasma and a gas target. Equal final mean charge states can thus be achieved with lower density for plasmas and targets with low nuclear charge. The widths of the charge state distributions are very similar, slightly smaller for plasmas due to the different scaling of the dielectronic recombination rate. In comparison with calculations and measurements published in literature this work underestimates the width of targets with higher nuclear charge like, e.g., nitrogen gas. This is mainly due to the omission of multiple loss processes in the presented calculations. In the future we intend to expand the methods and models used in this work to improve the agreement with different measurements on charge state distributions in plasmas and gases.

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THPF029

Preparation of an Ion Source for an Extra Low Energy Synchrotron

ion, extraction, ion-source, antiproton

3755

R. Gebel, O. Felden, R. Maier, S. Mey, D. Prasuhn
FZJ, Jülich, Germany

Funding: The work is supported within the framework of the Helmholtz Association’s Accelerator Research and Development (ARD) program.
ELENA* is a compact ring for cooling and further deceleration of 5.3 MeV antiprotons delivered by the CERN Antiproton Decelerator (AD) down to 100 keV. Because of the long AD cycle of 100 s, it is foreseen to use a source for protons and H⁻ with a kinetic energy of 100 keV for commissioning and start-ups. The source, designed to provide 0.2 to 2.0μsec pulses with 3x10⁷ ions, is based on a proven multicusp volume source used at the COSY/Jülich** injector cyclotron. The source and its auxiliaries were refurbished, upgraded to ±100 keV operation at the Forschungszentrum Jülich and have been set in operation at CERN in April 2015 for first tests of new equipments.
* V. Chohan [ed.], ELENA ring and its Transfer Lines – Design Report
Geneva 2014, DOI 10.5170/CERN-2014-002
** R. Maier Nucl. Instr. Meth. A 390 (1997) P.1.

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THPF059

RHIC Electron Lenses Upgrades

proton, cathode, ion, controls

3830

X. Gu, Z. Altinbas, S. Binello, D. Bruno, M.R. Costanzo, K.A. Drees, W. Fischer, D.M. Gassner, M. Harvey, J. Hock, K. Hock, Y. Luo, A. Marusic, K. Mernick, C. Mi, R.J. Michnoff, T.A. Miller, M.G. Minty, A.I. Pikin, G. Robert-Demolaize, T. Samms, V. Schoefer, T.C. Shrey, Y. Tan, R. Than, P. Thieberger
BNL, Upton, Long Island, New York, USA
S.M. White
ESRF, Grenoble, France

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the Relativistic Heavy Ion Collider (RHIC) 100 GeV polarized proton run in 2015[1], two electron lenses [2] were used for the first time to partially compensate for the head-on beam-beam effect. Here, we describe the design of the current electron lens, detailing the hardware modifications made after the 2014 commissioning run with heavy ions. A new electron gun with 15-mm diameter cathode is characterized. The electron beam transverse profile was measured using a YAG screen and fitted with a Gaussian distribution. During operation, the overlap of the electron and proton beams was achieved using the electron backscattering detector in conjunction with an automated orbit control program.

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THPF074

Progress on Superconducting Linac for the RAON Heavy Ion Accelerator

cavity, linac, cryomodule, ion

3851

H.J. Kim, H.C. Jung, W.K. Kim
IBS, Daejeon, Republic of Korea

The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to Uranium. Proton and Uranium beams are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the prototyping of superconducting cavity and cryomodule.

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THPF091

Detailed Studies of Beam Induced Scrubbing in the CERN-SPS

injection, proton, emittance, operation

3908

G. Iadarola, H. Bartosik, T. Bohl, B. Goddard, G. Kotzian, K.S.B. Li, L. Mether, G. Rumolo, M. Schenk, E.N. Shaposhnikova, M. Taborelli
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade (LIU) program, it is foreseen to take all the necessary measures to avoid electron cloud effects in the CERN-SPS. This can be achieved by either relying on beam induced scrubbing or by coating the vacuum chambers with intrinsically low Secondary Electron Yield (SEY) material over a large fraction of the ring. To clearly establish the potential of beam induced scrubbing, and to eventually decide between the two above options, an extensive scrubbing campaign is taking place at the SPS. Ten days in 2014 and two full weeks in 2015 are devoted to machine scrubbing and scrubbing qualification studies. This paper summarizes the main findings in terms of scrubbing efficiency and reach so far, addressing also the option of using a special doublet beam and its implication for LHC.

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THPF104

Design of a Scaled High Duty Factor High Current Negative Penning Surface Plasma Source

plasma, cathode, ion, simulation

3956

D.C. Faircloth, S.R. Lawrie, T. Rutter, M. Whitehead, T. Wood
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
V.G. Dudnikov
Muons, Inc, Illinois, USA

The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) requires a 60 mA, 2 ms, 50 Hz H− beam. The present source can only deliver the current and pulse length requirements at 25 Hz. At 50 Hz there is too much droop in the beam current. To rectify this, a scaled source is being developed. This paper details the new source design and the experiments conducted that are guiding the design.

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THPF108

EBIS Charge Breeder at ANL and its Integration into ATLAS

ion, beam-transport, dipole, simulation

3969

A. Perry, A. Barcikowski, G.L. Cherry, C. Dickerson, B. Mustapha, P.N. Ostroumov
ANL, Argonne, Illinois, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357.
An Electron Beam Ion Source charge breeder (EBIS-CB) has been developed to breed CARIBU radioactive beams at ATLAS and is in the final stages of off-line commissioning. Within the next year, the EBIS-CB will replace the existing ECR charge breeder to increase the intensity and improve the purity of reaccelerated radioactive ion beams. Integration of the new EBIS-CB requires: a. Building a compact fully electrostatic low energy beam transport line (LEBT) from CARIBU to the EBIS-CB that satisfies the spatial constraints and ensures the successful ion seeding into the EBIS trap. b. Modifications to the existing ATLAS LEBT to purify the EBIS beams by q/A selection and accommodate the injection of the charge bred ions into ATLAS. In this paper, we will describe the beam line design and present beam dynamics simulation results.

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THPF110

Offline Testing of the CARIBU EBIS Charge Breeder

ion, operation, ion-source, rfq

3973

C. Dickerson, S.A. Kondrashev, P.N. Ostroumov, R.C. Vondrasek
ANL, Argonne, Illinois, USA
A. Perry
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357.
In 2015 an electron beam ion source (EBIS) will be installed at the ATLAS facility to charge breed radioactive beams from the Californium Rare Isotope Breeder Upgrade (CARIBU). Currently an ECR ion source is used to charge breed CARIBU beams. The EBIS will provide beams with much less contamination and higher breeding efficiencies. In preparation for its installation at ATLAS the EBIS has been successfully commissioned offline. The EBIS was configured in the offline facility to closely mimic the conditions expected in the ATLAS installation, so commissioning results should be representative of its performance with CARIBU. The EBIS breeding efficiency was tested with pulses of 133Cs¹⁺ from a surface ionization source, and for multiple operational modes maximum breeding efficiencies greater than 25% could be achieved. After transmission losses the total efficiency of the system was 15-20%. The contaminants were expectedly very low for a UHV system with nominal pressures of ~1 – 3 x 10^-10 Torr.

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THPF128

Accelerator Physics and Technology Research Toward Future Multi-MW Proton Accelerators

proton, target, SRF, experiment

4019

V.D. Shiltsev, P. Hurh, A. Romanenko, A. Valishev, R.M. Zwaska
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance, LLC operates Fermilab under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy
Recent P5 report indicated the accelerator-based neutrino and rare decay physics research as a centrepiece of the US domestic HEP program. Operation, upgrade and development of the accelerators for the near-term and longer-term particle physics program at the Intensity Frontier face formidable challenges. Here we discuss accelerator physics and technology research toward future multi-MW proton accelerators.

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THPF133

Textured-Powder BI-2212 Ag Wire Technology Development

interface, dipole, hadron, collider

4030

P.M. McIntyre, J.N. Kellams, J.M. Vandergrifft
Texas A&M University, College Station, Texas, USA
K.C. Damborsky
Oxford Instruments, Semiconductor Systems, Carteret, New Jersey, USA
L. Motowidlo
SupraMagnetics, Inc., Plantsville, Connecticut, USA
N. Pogue
PSI, Villigen, Villigen, Switzerland

Progress is reported in developing textured-powder Bi-2212 cores as a new approach to Bi-2212/Ag wire tech-nology. The process builds upon earlier work in which Bi-2212 fine powder can be highly textured in its a-b plane orientation and fabricated into square-cross-section bars. The current work concerns an Enhanced Textured Powder (ETP) process, in which silver nanopowder is homogeneously mixed with the Bi-2212 powder. We report studies of the effect of the addition on the phase dynamics near melt temperature. ETP cores are being prepared for compounding into a billet to fabricate multi-filament wire.

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THPF142

High Intensity Source of He Negative Ions

ion, ion-source, target, polarization

4057

V.G. Dudnikov
Muons, Inc, Illinois, USA
A.V. Dudnikov
BINP SB RAS, Novosibirsk, Russia
V.S. Morozov
JLab, Newport News, Virginia, USA

He- ion can be formed by an attachment of additional electron to the excited metastable 23S1 He atom. Electron affinity in this metastable He- ion is A=0.08 eV with excitation energy 19.8 eV. Production of He- ions is difficult because the formation probability is very small but destruction probability is very high. Efficiency of He- ions generation was improved by using of an alkali vapor targets for charge exchange He- sources. Low current He- beams were used in tandem accelerators for research and technological diagnostics (Rutherford scattering). The development of high-intensity high-brightness arc-discharge ion sources at the Budker Institute of Nuclear Physics (BINP) has opened up an opportunity for efficient production of more intense and more brighter He- beam which can be used for alpha particles diagnostics in a fusion plasma and for realization of a new type of a polarized 3He− ion source. This report discusses the high intense He- beams production and a polarized 3He− ion source based on the large difference of extra-electron auto-detachment lifetimes of the different 3He− ion hyperfine states.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THPF142

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THPF143

Saddle Antenna RF Ion Sources for Efficient Positive and Negative Ions Production

plasma, ion, extraction, operation

4060

V.G. Dudnikov, R.P. Johnson
Muons, Inc, Illinois, USA
G. Dudnikova
UMD, College Park, Maryland, USA
B. Han, S.N. Murray, T.R. Pennisi, C. Piller, M. Santana, M.P. Stockli, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA

Funding: Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0011323.
Existing RF Surface Plasma Sources (SPS) for accelerators have specific efficiencies for H⁺ and H⁻ ion generation ~3-5 mA/cm² kW, where about 50 kW of RF power is typically needed for 50 mA beam current production. The Saddle Antenna (SA) SPS described here was developed to improve H⁻ ion production efficiency, reliability and availability. In SA RF ion source the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm² kW. After cesiation, the current of negative ions to the collector was increased from 1 mA to 10 mA with RF power ~1.5 kW in the plasma (6 mm diameter emission aperture) and up to 30 mA with ~4 kW RF. Continuous wave (CW) operation of the SA SPS has been tested on the test stand. The general design of the CW SA SPS is based on the pulsed version. Some modifications were made to improve the cooling and cesiation stability. CW operation with negative ion extraction was tested with RF power up to 1.8 kW from the generator (~1.2 kW in the plasma) with production up to Ic=7 mA. Long term operation was tested with 1.2 kW from the RF generator (~0.8 kW in the plasma) with production of Ic=5 mA, Iex ~15 mA (Uex=8 kV, Uc=14 kV).

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THPF144

Analysis of FEL-based CeC Amplification at High Gain Limit

space-charge, FEL, free-electron-laser, laser

4063

G. Wang, Y.C. Jing, V. Litvinenko
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
An analysis of CeC amplifier based on 1D FEL theory was previously performed with exact solution of the dispersion relation, assuming electrons having Lorentzian energy distribution *. At high gain limit, the asymptotic behavior of the FEL amplifier can be better understood by Taylor expanding the exact solution of the dispersion relation with respect to the detuning parameter **. In this work, we make quadratic expansion of the dispersion relation for Lorentzian energy distribution * *** and investigate how longitudinal space charge and electrons’ energy spread affect the FEL amplification process.
* G. Wang, PhD Thesis, SUNY Stony Brook, 2008.
** G. Stupakov, M.S. Zolotorev, Comment on “Coherent Electron Cooling”, PRL 110 (2013) 269503.
*** E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, The Physics of Free Electron Lasers, 1999.

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THPF146

Spin Coherence Time Lengthening of a Polarized Deuteron Beam Using Sextupole FieldsFields

polarization, sextupole, storage-ring, emittance

4066

G. Guidoboni
UNIFE, Ferrara, Italy

Funding: Forschungszentrum Jülich is a member of the Helmholtz Association
The measurement of a non-zero electric dipole moment (EDM) aligned along the spin of sub-atomic particles would probe new physics beyond the standard model. It has been proposed to search for the EDM of charged particles using a storage ring and a longitudinally polarized beam. The EDM signal would be a rotation of the polarization from the horizontal plane toward the vertical direction as a consequence of the radial electric field always present in the particle frame. This experiment requires ring conditions that can ensure a lifetime of the in-plane polarization (spin coherence time, SCT) up to 1000 s. At the COoler SYnchrotron (COSY) located at the Forschungszentrum Jülich, the JEDI collaboration has begun to examine the effects of emittance and momentum spread on the SCT of a polarized deuteron beam at 0.97 GeV/c. The set of data presented here shows how second-order effects from emittance and momentum spread of the beam affect the lifetime of the horizontal polarization of a bunched beam. It has been observed that sextupole fields can correct for depolarizing sources and increase the spin coherence time up to hundreds of seconds while setting the chromaticities equal to zero.

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