IPAC2015 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOAB1	High Beam Intensity Harp Studies and Developments at SNS	data-acquisition, electronics, proton, target	17
	W. Blokland 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 The Spallation Neutron Source (SNS) Harp consists of 30 wires for each of the horizontal, vertical, and diagonal planes. The purpose of the harp is to measure the position, profile, and peak density of the high intensity beam coming out of the accumulator ring and going onto the spallation target. The data-acquisition hardware is now over ten years old and many of the electronics parts are obsolete. Occasionally, the electronics must be rebooted to reset the sample-and-hold circuitry. To evaluate options for a new system, the signals from the harp were studied. This paper will describe these studies’ results, the design, and initial results of the new and simpler data-acquisition system..
	Slides MOAB1 [4.335 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOAB1
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MOBC2	High-Performance Simulations of Coherent Synchrotron Radiation on Multicore GPU and CPU Platforms	GPU, electron, 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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MOBD2	Design and Prototyping of HL-LHC Double Quarter Wave Crab Cavities for SPS Test	cavity, luminosity, proton, HOM	64
	S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA L. Alberty, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, N. Kuder, R. Leuxe, C. Zanoni CERN, Geneva, Switzerland S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA Z. Li SLAC, Menlo Park, California, USA A. Ratti LBNL, Berkeley, California, USA
	Funding: Work supported by US DOE via US LARP program, through BSA LLC contract No.DE-AC02-98CH10886 and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231. The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double-Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. A couple of DQW crab cavities are under preparation and will be tested with beam in the Super Proton Synchrotron (SPS) of CERN by 2017. This paper describes the design and prototyping of DQW crab cavities for the SPS test.
	Slides MOBD2 [6.909 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD2
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MOPWA001	Instability Thresholds and Tune Shift Estimation for Sirius	impedance, feedback, emittance, damping	70
	F.H. de Sá, L. Liu, N. Milas, X.R. Resende LNLS, Campinas, Brazil
	In this work we present the evaluation of longitudinal and transverse instability thresholds as well as tune shifts for Sirius using time and frequency domain codes that are being developed in-house and take into account various effects on the beam instability, such as bunch by bunch feedback system, quadrupolar impedances from undulator chambers and tune spreads.
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MOPWA002	Nonequilibrium Phase Transitions in Crossed-Field Devices	electron, cathode, space-charge, 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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MOPWA003	Optimal Generalized Finite Difference Solution to the Particle-in-Cell Problem	framework, plasma, space-charge, factory	77
	X. Wang, X. Jiao, H. Liu, V. Samulyak, K. Yu SBU, Stony Brook, USA V. Samulyak BNL, Upton, Long Island, New York, USA
	The particle-in-cell (PIC) method is widely used in applications, such as in electromagnetics, but the accuracy of its solutions degrades when the particle distribution is highly non-uniform. In our work, we propose an adaptive PIC method with optimal point distribution and a generalized finite difference (GFD) scheme. Our method replaces the Cartesian grid in the classical PIC with adaptive computational nodes or particles, to which the charges from the sample particles are assigned by a weighted least-square approximations. The partial differential equation is then discretized using a GFD method and solved with fast linear solvers. The density of computational particles is chosen adaptively, so that the error from GFD and that from Monte Carlo integration are balanced and the total error is approximately minimized. We also present the verification results using electrostatic problems and comparison of accuracy and solution time of our method with the classical PIC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA003
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MOPWA004	Reformulation of the Action and Phase Jump Method to Obtain Magnetic Errors in the LHC IRs	quadrupole, lattice, interaction-region, framework	80
	A.C. García-Bonilla, J.F. Cardona UNAL, Bogota D.C, Colombia
	Funding: Fundación Para la Promoción de la Investigación y la Tecnología del Banco de la República and Division de Investigación Bogotá (DIB). One of the major problems when doing the commissioning of an accelerator is to identify and correct the linear components of magnetic errors. The Action and Phase Jump Technique is one of the available methods to perform this task. For this method to work, it is necessary to have one BPM measurement at the IR, the region where the magnetic error is evaluated. In some cases, this BPM measurement become the biggest source of uncertainty when the action and phase jump technique is used. In this paper, a new formulation based on this method is presented. This new formulation doesn't make any use of BPM measurements at the IR, thereby allowing more robust error estimations. Quadrupole errors in the LHC lattice are estimated with this new formulation, using both, simulated data and LHC experimental data. A comparison with the previous formulation is included. The results on simulated data show that the reformulation leads to a reduction in the uncertainty, while for the experimental case, the reduction is not so clear. Explanations for this behavior and possible remedies will also be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA004
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MOPWA005	Comparison between Digital Filters and Singular Value Decomposition to Reduce Noise in LHC Orbits used for Action and Phase Jump Analysis	quadrupole, collider, resonance, hadron	83
	A.C. García-Bonilla, J.F. Cardona UNAL, Bogota D.C, Colombia
	Funding: Fundación Para la Promoción de la Investigación y la Tecnología del Banco de la República and DIB (División de Investigación de Bogotá). One of the initial difficulties to apply the Action and Phase Jump (APJ) analysis to LHC orbits was the high level of noise present in the BPM measurements. On the other hand, the unprecedented number of turns for LHC allows us to use all sort of filters. In this paper, we evaluate the effectiveness of digital filters like the band-pass filter and compare them with a filter based on Singular Value Decomposition, when magnetic error estimations are made using a recent version of the APJ method. First, mainly results on simulated orbits with noise are presented, and then, plots and results are shown for the filters effect on experimental data. The analysis indicates that a combination of filters leads to measurements with the least uncertainty.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA005
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MOPWA006	Core-Halo Limit as an Indicator of High Intensity Beam Internal Dynamics	space-charge, emittance, linac, vacuum	86
	P.A.P. Nghiem, N. Chauvin, N. Pichoff, D. Uriot, M. Valette CEA/DSM/IRFU, France
	The dynamics of high-intensity beams is mainly governed by their internal space charge forces. These forces induce emittance growth and halo generation. They contribute to shape the beam density profile. As a consequence, a careful analysis of this profile can help revealing the internal dynamics of the beam. This paper recalls the precise core-halo limit determination proposed earlier , then studies its behavior through a wide range of beam profiles and finally shows its relevance as an indicator of the limit separating the two specific space charge field regimes of the core and the halo. P. A. P. Nghiem et al., Appl. Phys. Lett. 104, 074109 (2014)
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MOPWA007	The SARAF-LINAC Beam Dynamics	linac, rfq, emittance, proton	89
	N. Pichoff, D. Uriot CEA/DSM/IRFU, France B. Dalena CEA/IRFU, Gif-sur-Yvette, France
	SNRC and CEA collaborate to the upgrade of the SARAF Accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). This paper presents the beam dynamics in the reference design of the SARAF-LINAC (from the 4 m long 176 MHz RFQ to the HWR Superconducting linac’s end). The beam losses, mostly in longitudinal direction, estimated from error studies, are compared with acceptable losses defined for hands-on maintenance.
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MOPWA008	Status of TraceWin Code	linac, space-charge, cavity, diagnostics	92
	D. Uriot, N. Pichoff CEA/DSM/IRFU, France
	Well known in the community of high-intensity linear accelerators, the transport code TraceWin * is able to simulate a beam from the source to the target using either simple linear model or multiparticle simulations including 2D or 3D space-charge. Continuously developed at CEA Saclay since 15 years, it is today the reference code for projects such IFMIF, ESS, MYRRHA, SPIRAL2, IPHI … The accuracy of his predictions associated with an original and powerful GUI and its numerous features have made its success, with a community of 200 users worldwide. It is now used on a larger perimeter that its initial skills. The aim of this paper is to summarize the TraceWin capabilities, including implemented last ones. * http://irfu.cea.fr/Sacm/logiciels/
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MOPWA010	Emittances of the Core and of the Halo	emittance, linac, space-charge, extraction	99
	M. Valette, P.A.P. Nghiem CEA/IRFU, Gif-sur-Yvette, France
	In high intensity accelerators, the beam is often space charge dominated. The density profile then takes a shape very different from a Gaussian one, with a more or less sharp core and a more or less compact halo. Furthermore, the core and the halo can be differently focused and thus differently oriented in the phase spaces. In these conditions, classically characterizing the beam by a global set of rms values, namely Emittance and Twiss parameters, is no more meaningful. This paper extends the core-halo limit defined ealier in 1D real space * to the 2D phase space, allowing to define for the very first time Emittances and Twiss parameters for the core and the halo separately. Applications to the IFMIF accelerators are given as an example of more appropriate beam characterization for high intensity linacs. * P. A. P. Nghiem et al., Appl. Phys. Lett. 104, 074109 (2014)
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MOPWA011	The Damping of Transverse Coherent Instabilities by Harmonic Cavities	synchrotron, betatron, damping, electron	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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MOPWA014	New Functionality for Beam Dynamics in Accelerator Toolbox (AT)	lattice, radiation, dipole, emittance	113
	B. Nash, N. Carmignani, L. Farvacque, S.M. Liuzzo, T.P. Perron, P. Raimondi, R. Versteegen, S.M. White ESRF, Grenoble, France
	Accelerator Toolbox is a widely used code for beam dynamic simulations based on Matlab. To continue the development of the code in a collaborative manner, a SourceForge project and SVN repository called atcollab has been established. Here we describe the contributions to atcollab from the ESRF beam dynamics group. Additional modules have been developed: general matching (atmatch), improved plotting (atplot), Touschek lifetime computation via the Piwinski formula, nonlinear dynamics computations such as resonance driving terms, improved reporting of lost particles and improvements and additions to the integration routines. One example of the latter includes diffusion due to quantum fluctuations. Modeling of collective effects may now be performed using pass methods representing a variety of impedance models. Finally, routines to replace the full ring with a compact representation have been developed, facilitating studies in which many turns and many particles are required.
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MOPWA018	Loss Factor and Impedance Analysis of Warm Components of BERLinPro	factory, impedance, operation, wakefield	128
	H.-W. Glock, M. Abo-Bakr, J. Kolbe, F. Pflocksch, A. Schälicke HZB, Berlin, Germany H.-W. Glock, C. Potratz COMPAEC e.G., Rostock, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association The ongoing component design for the HZB 50 MeV, 100mA ERL project BERLinPro is accompanied by loss factor and impedance computations. A list of accelerator components including bellows, collimators, tapers, shutter valves etc. is given, some of them with alternative shapes. Loss factors, calculated using CSTParticleStudio®, are presented together with important properties of the impedance spectrum. Scaling of the loss factors with respect to bunch length is calculated on base of the numerical simulations and is used to extrapolate down to a bunch length (1 standard deviation) of 0.6 mm, which is hard to reach directly in numerical simulations.
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MOPWA020	Longitudinal Stability Of Short Bunches in Storage Rings with Strong Longitudinal Focusing	impedance, synchrotron, dipole, resonance	135
	P. Kuske HZB, Berlin, Germany
	Funding: work supported by the BMBF In the BESSY VSR project, the variable bunch length storage ring, two high gradient accelerating structures at 1.5 and 1.75 GHz will be phased such that long and short bunches can be stored simultaneously. The longitudinal stability of the short bunches is investigated taking into account the shielded CSR- and a purely inductive impedance. Multi particle tracking studies and numerical solutions of the Vlasov-Fokker-Planck equation show that threshold currents for short bunches do not follow the simple scaling law which was found for long bunches. The inductive impedance can even lower the thresholds for the instability. With an 80 times increased accelerating gradient and reasonable assumptions on the inductive impedance for shorter bunches stable operation can be expected with bunches 1.8 ps long (RMS-value) and 0.8 mA current. According to the calculations and operating in a dedicated low-α mode will produce stable 40 μA bunches with 400 fs length
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MOPWA022	Influence of Transient Beam Loading on the Longitudinal Beam Dynamics at BESSY VSR	beam-loading, synchrotron, damping, cavity	141
	M. Ruprecht, P. Goslawski, A. Jankowiak, A. Neumann, M. Ries, G. Wüstefeld HZB, Berlin, Germany T. Weis DELTA, Dortmund, Germany
	BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed . The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. If the bunch fill pattern exhibits a significant inhomogeneity, e.g. due to gaps, transient beam loading causes a distortion of the longitudinal phase space which is different for each bunch. The result are variations along the fill pattern in synchronous phase, synchrotron frequency and bunch shape. This paper presents investigations of transient beam loading and depicts the consequences on bunch length, phase stability and longitudinal multi-bunch oscillations for the projected setup of BESSY VSR. G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain
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MOPWA025	Simulation of Laser Cooling of Heavy Ion Beams at High Intensities	laser, synchrotron, ion, scattering	150
	L. Eidam, O. Boine-Frankenheim, D.F.A. Winters GSI, Darmstadt, Germany
	In the past the principle of Doppler laser cooling was investigated and verified in storage rings in the low energy regime. Within the FAIR project the laser cooling will be applied to high intensity and high energy beams for the first time. The laser cooling results in a further increase of the longitudinal phase space density and in non-Gaussian longitudinal beam profiles. In order to ensure stable operation and optimize the cooling process the interplay of the laser force and high intensity effects has to be studied numerically. This contribution will identify constrains of the cooling scheme for an efficient reduction of momentum spread. For high beam energies the scattering of photons has to be treated stochastically instead of using averaged forces. The modeling of the laser force in a particle in cell tracking code will be discussed.
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MOPWA029	Investigations of the Space-Charge-Limited Emission in the L-Band E-Xfel Photoinjector at Desy-Pitz	space-charge, gun, cathode, electron	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	electron, wakefield, 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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MOPWA031	A New Approach for Resistive Wakefield Calculations in Time Domain	wakefield, impedance, cavity, controls	168
	A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany M. Dohlus, I. Zagorodnov DESY, Hamburg, Germany
	We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.
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MOPWA036	Status of Injection Studies into the Figure-8 Storage Ring	injection, experiment, kicker, ion	187
	J.F. Wagner, A. Ates, M. Droba, O. Meusel, H. Niebuhr, D. Noll, U. Ratzinger IAP, Frankfurt am Main, Germany
	The ongoing investigations on the design of the Figure-8 Storage Ring* at Frankfurt University focus on the beam injection. The research includes simulations as well as a scaled down experiment. The studies for an optimized adiabatic magnetic injection channel, starting from a moderate magnetic field up to a maximum of 6 Tesla, with a realistic field model of toroidal coils due to beam dynamics with space charge will be shown. For the envisaged ExB kicker system the simulations deal with beam potential constraints and a multi-turn injection concept in combination with an adiabatic magnetic compression. To investigate the concept of the beam injection into a toroidal magnetic field, a scaled down room temperature experiment is implemented at the university. It is composed of two 30 degree toroidal segments, two volume ion sources, two solenoids and two different types of beam detectors. The experiment is used to investigate the beam transport and dynamics of the laterally injected and “circulating” beam through the magnetic configuration. To set up the injection experiment, theoretical calculations and beam simulations with bender** are used. * M. Droba et al., Proc. of IPAC'14, Dresden, Germany, TUPRO045 ** D. Noll, M. Droba, O. Meusel, U. Ratzinger, K. Schulte, C.Wiesner, Proc. of HB2014, East Lansing, USA, WEO4LR02
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MOPWA042	Sub-fs Electron Bunch Generation Using Magnetic Compressor at SINBAD	electron, 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, electron	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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MOPWA044	Quasi-frozen Spin Method for EDM Deuteron Search	dipole, storage-ring, proton, lattice	213
	Y. Senichev, A. Lehrach, B. Lorentz, R. Maier FZJ, Jülich, Germany S.N. Andrianov, A.N. Ivanov St. Petersburg State University, St. Petersburg, Russia M. Berz, E. Valetov MSU, East Lansing, Michigan, USA S. Chekmenev RWTH, Aachen, Germany
	To search for EDM using proton storage ring with purely electrostatic elements the concept of frozen spin method has been proposed by BNL. This method is based on two facts: in the equation of the spin precession the magnetic field dependence is entirely eliminated and at “magic” energy the spin precession frequency coincides with the precession frequency of the momentum. In case of deuteron the anomalous magnetic moment is negative (G=-0.142), therefore we have to use the electrical and magnetic field simultaneously keeping the frozen spin direction along the momentum as in the pure electrostatic ring. In this article we suggest the concept of the quasi-frozen spin when the spin oscillates around the momentum direction within the half value of the advanced spin phase each time returning back by special optics. Due to the low value of the anomalous magnetic moment of deuteron an effective contribution to the expected EDM effect is reduced only by a few percent.
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MOPWA046	Lattice and Beam Dynamics of the Energy Recovery Mode of the Mainz Energy-recovering Superconducting Accelerator MESA	linac, cryomodule, lattice, experiment	220
	D. Simon, K. Aulenbacher, R.G. Heine, F. Schlander IKP, Mainz, Germany
	Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) and German Research Foundation (DFG) under the Cluster of Excellence PRISMA. The mainz energy recovering superconducting accelerator (MESA) is a proposed multi-turn energy recovery linac for particle physics experiments. It will be built at the institute for nuclear physics (KPH) at Mainz University. Because of the multi-turn energy recovery mode there are particular demands at the beam dynamics. We present the current status of the lattice development.
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MOPWA049	Simulation of Crab Waist Collisions in DAΦNE with KLOE-2 Interaction Region	luminosity, electron, 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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MOPWA050	Beam Dynamics Studies to Develop a High-energy Luminosity Model for the LHC	luminosity, beam-beam-effects, collider, emittance	233
	G. Campogiani Rome University La Sapienza, Roma, Italy Y. Papaphilippou CERN, Geneva, Switzerland
	Funding: support provided by the EPS-AG through the EPS-AG student grant program Luminosity, the key figure of merit of a collider as the LHC, depends on the brightness of the colliding beams. This makes the intensity dependent beam-beam effect the dominant performance limiting factor at collision. The parasitic interactions due to the electromagnetic mutual influence of the beams in the interaction region of a collider induce a diffusive behaviour in the tails of the beam. The evolution of charge density distribution is studied to model the beam tails evolution in order to characterize beam lifetime and luminosity. To achieve this, tools are developed for tracking distributions of arbitrary number of single particles interacting with the opposing strong-beam, to analyse the halo formation processes due to the combined effect of beam-beam and machine non-linearities. This paper presents preliminary results of the simulations, both for the LHC Run I and nominal LHC parameters. The former will be used to benchmark simulations while the latter aims at supporting luminosity estimate for the Run II.
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MOPWA053	Emittance Preservation in SuperKEKB Injector	emittance, wakefield, linac, injection	239
	S. Kazama, Y. Ogawa, M. Satoh, H. Sugimoto, M. Yoshida KEK, Ibaraki, Japan
	Injector linac at KEK is now under the way to produce high current and low emittance beams for SuperKEKB. The target luminosity for SuperKEKB is 40 times higher than that of KEKB. Short-range transverse wakefield and dispersive effects at the linac cause an emittance growth, and longitudinal wakefield effect enlarges an energy spread of the beams. In this presentation, we will report simulation studies of the emittance preservation issues and how to suppress the increase of the energy spread of the beams.
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MOPWA054	Effect of Number of Macro Particles on Resolution in Phase Space Distribution	electron, 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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MOPWA056	Transverse Multi-Pass Beam Breakup Simulation for KEK ERL Light Source	HOM, cavity, linac, cryomodule	248
	S. Chen, N. Nakamura, M. Shimada, D. Zhou KEK, Ibaraki, Japan S. Huang, K.X. Liu PKU, Beijing, People's Republic of China
	In this paper, the multi-pass BBU of such a high energy ERL is studied based on the simulation on a 3 GeV ERL light source proposed by KEK.
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MOPWA057	Space Charge Simulation and Matching at Low Energy Section of J-PARC Linac	rfq, space-charge, emittance, solenoid	251
	S. Artikova, T. Morishita JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Kondo JAEA, Ibaraki-ken, Japan
	An intensity upgrade of Japan Proton Accelerator Research Complex (J-PARC) included the installation of a new ion source (IS) and a radio-frequency quadrupole (RFQ) which to be used at first stage of acceleration. The linac is divided into two sections on the basis of operating frequencies and three sections on the basis of family of RF cavities to be used for the acceleration of 50 mA beam of H⁻ ions from 50 keV to 400 MeV. Low energy part of linac consists of an IS, a two-solenoid low energy beam transport (LEBT) and the RFQ. The transition from one section to another can limit the acceptance of the linac if these are not matched properly in both longitudinal and transverse plane. We performed a study to calculate the acceptance of the RFQ at zero current in which space charge effects are not considered. In addition, a particle tracking technique is employed to study the space charge effects in LEBT of the J-PARC linac after the intensity upgrade in order to match the beam to the RFQ. Also, RFQ tank level and intervene voltage calibration factor is determined by comparing the simulation results of the beam transmission with the test measurement of tank level vs. transmission.
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MOPWA062	Optimization of the Momentum Bandwidth for Final Focus System in CEPC	sextupole, factory, luminosity, collider	269
	S. Bai, T.J. Bian, J. Gao, H. Geng, D. Wang, Y. Wang, M. Xiao IHEP, Beijing, People's Republic of China F. Su Institute of High Energy Physics (IHEP), People's Republic of China
	With the discovery of the higgs boson at around 125GeV, a circular higgs factory design with high luminosity (L ~ 10³⁴ cm^-2s^-1) is becoming more popular in the accelerator world. To achieve such high luminosity, a final focus system in non-local chromaticity correction scheme with very low β functions at the interaction point is designed. The narrow momentum bandwidth is a crucial problem of this kind of design. It is shown that by introducing additional sextupoles the momentum acceptance of the CEPC final focus system can be increased by about a factor of four.
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MOPWA065	Uniformization of the Transverse Beam Profile by a New Type Nonlinear Magnet	octupole, target, multipole, dipole	272
	G. Gu, W.B. Liu IHEP, Beijing, People's Republic of China
	The uniform particle beam is desirable in many beam applications. One method to get this type of beam distribution is using octupoles, but loss of particles in the halo will be produced by this method. To reduce the beam loss, a new type of magnet is proposed in this paper. The field in the middle region of the new type magnet is similar to the octupole magnet field, but the rate of rise decline quickly in the edge. So that the particle in the edge experience a lower magnet field, and this would result in less particle loss. We also add a mechanical structure on the new type magnet to make it possible to adjust the size of middle region. So that the magnet can adapt to different transverse dimensions of the beam, and this would further reduce particle loss. Some numerical simulations have been done respectively with octuples and the new type of magnet. The simulation results show that the new type of magnet could get the uniform distribution of particle beam with less particle loss. We are processing a magnet now, and an experiment to test the magnet will be arranged on CPHS.
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MOPWA066	Simulation on Buildup of Electron Cloud in Rapid Cycling Synchrotron of China Spallation Neutron Source	electron, proton, 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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MOPWA069	Upgrades on a Scalable Software Package for Large Scale Beam Dynamic Simulations	software, DTL, space-charge, solenoid	282
	X.T. Dong, K. Du, J. Xu, R. Zhao IS, Beijing, People's Republic of China Y. He, Z.J. Wang IMP/CAS, Lanzhou, People's Republic of China C. Li, Q. Qin, Y.L. Zhao IHEP, Beijing, People's Republic of China
	Large-scale particle tracking is important for precise design and optimization of the linear accelerator. In this paper a parallel software recently developed for beam dynamics simulation has been benchmarked. The software is based on Particle-In-Cell method, and calculates space charge field by an efficient three-dimension parallel fast Fourier transform method. It uses domain decomposition and MPI library for parallelization. The characteristics of this software are optimized software structure and suitable for modern supercomputers. Several standard accelerating devices have been used to compare the simulation results with other beam dynamics software. They have been run on several different platforms, such as INSPUR cluster at RDCPS, and SHENGTENG7000 at IMPCAS. At first, some simulation results for RFQ with large number of particles will be shown.
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MOPWA072	Emittance Exchange Beam Line Design In THU Accelerator Lab	emittance, quadrupole, cavity, electron	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, electron, 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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MOPJE006	Electron Gun Longitudinal Jitter: Simulation and Analysis	gun, electron, timing, linac	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	electron, linac, 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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MOPJE017	Error Analysis and Correction at the Main LEBT of RAON Heavy Ion Accelerator	ion, GUI, rfq, heavy-ion	314
	H. Jin, I.S. Hong, H. Jang, J.-H. Jang IBS, Daejeon, Republic of Korea
	The main Low Energy Beam Transport (LEBT) section of Rare isotope Accelerator Of Newness (RAON) heavy ion accelerator is designed to transport the ion beams which are generated by Electron Cyclotron Resonance Ion Source (ECR-IS) to the Radio Frequency Quadrupole (RFQ). In the main LEBT, one or two beams are selected among a variety of ion beams to meet the beamline experiment requirements such as beam charge and current. In a uranium beam case, two charge-state, 33+ and 34+, beams are chosen and transported to the RFQ. For transportation of two charge-state beams, beams can be seriously affected by dipole kick or unexpected dispersion caused by magnet errors. These effects of magnet or cavity errors lead to beam loss at the main LEBT or RFQ. Therefore, the effect to the beam orbit and size should be identified and the research for reducing such effect should be required in the main LEBT. In this paper, we will examine the orbit distortion and beam size growth caused by magnet errors and discuss the correction of errors by using correctors and BPMs.
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MOPJE023	3D Computer Simulations of the Ultrarelativistic Beam Dynamics in Super Colliders	collider, focusing, experiment, plasma	326
	M.A. Boronina, V.A. Vshivkov ICM&MG SB RAS, Novosibirsk, Russia G. Dudnikova ICT SB RAS, Novosibirsk, Russia
	Funding: The work is supported by RFBR Grants 14-01-31088, 14-01-00392, 14-07-00241. The problem of numerical modeling of beam-beam interaction with high relativistic factor (~10⁴) is considered. We present 3D a self-consistent simulation model based on particle-in-cell method. The mixed Euler-Lagrangian decomposition is used in parallel algorithm for achieving good load balancing and reducing communication cost. Stable regimes of beam dynamics, depending on the beams configuration (beta-function, emittance, energy, currents and relative offset) can be found on the base of the model. In the calculations we used 10⁸ particles on the grid 100x100x100, the number of processors depends highly on the beam shape. The Lomonosov Super Computer and Siberian Supercomputer Centre cluster were used to perform the presented simulations.
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MOPJE026	Revision of the Impedance Model for the Interpretation of the Single Bunch Measurements at ALBA	impedance, vacuum, undulator, storage-ring	330
	T.F.G. Günzel, U. Iriso ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	Recent measurements showed that the ALBA transverse impedance model was able to explain 65% of the measured single bunch vertical detuning. * This report shows the revision of the impedance model developed to match latest single bunch measurements performed to evaluate the total effective machine impedance and impedance of specific elements, like in-vacuum undulators or a recently installed pinger magnet. The model improvement includes a better bunch length parameterisation, re-calculation of several vacuum chamber elements with Gdfidl, and inclusion of elements neglected so far in the impedance budget. We also show and discuss the computation of the resistive wall impedance using ImpedanceWake2D. * T.Günzel, U.Iriso, F.Perez, E.Koukovini-Platia, G.Rumolo, "Analysis of the single bunch measurements at the ALBA Storage Ring", TUPRI052, proc. of IPAC14 (2014).
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MOPJE027	Beam-based Impedance Characterization of the ALBA Pinger Magnet	impedance, vacuum, injection, synchrotron	334
	U. Iriso, T.F.G. Günzel ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain H. Bartosik, E. Koukovini-Platia, G. Rumolo CERN, Geneva, Switzerland
	The ALBA pinger magnet consists on two short kickers (for horizontal and vertical planes) installed in a single Titanium coated ceramic vacuum chamber. Single bunch measurements in the vertical plane were performed in the ALBA Synchrotron Light Source before and after the pinger installation, and by comparing the Transverse Mode Coupling Instability (TMCI) thresholds for zero chromaticity, we infer the pinger impedance and compare it with the model predictions. We also perform measurements for negative chromaticities and results are reported in this paper.
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MOPJE029	A Linear Accelerator Simulation Framework	framework, ground-motion, collider, lattice	341
	J. Snuverink JAI, Egham, Surrey, United Kingdom N. Fuster-Martínez IFIC, Valencia, Spain J. Pfingstner CERN, Geneva, Switzerland J. Pfingstner University of Oslo, Oslo, Norway
	Many good tracking tools are available for simulations for linear accelerators. However, several simple tasks need to be performed repeatedly, like lattice definitions, beam setup, output storage, etc. In addition, complex simulations can become unmanageable quite easily. A high level layer would therefore be beneficial. We propose LinSim, a linear accelerator framework with the codes PLACET and Guinea-Pig. It provides a documented well-debugged high level layer of functionality. Users only need to provide the input settings and essential code and/or use some of the many implemented imperfections and algorithms. It can be especially useful for first-time users. Currently the following accelerators are implemented: ATF2, ILC, CLIC and FACET. This paper discusses the framework design and shows its strength in some condensed examples.
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MOPJE035	An Extended SPS Longitudinal Impedance Model	impedance, vacuum, kicker, resonance	360
	J.V. Campelo, T. Argyropoulos, T. Bohl, F. Caspers, J. F. Esteban Müller, J.B. Ghini, A. Lasheen, D. Quartullo, B. Salvant, E.N. Shaposhnikova, C. Zannini CERN, Geneva, Switzerland
	Longitudinal multi-bunch instability in the CERN SPS with a very low intensity threshold is a serious limitation for the future doubling of bunch intensity required by Hi-Lumi LHC project. A complete and accurate impedance model is essential to understand the nature of this instability and to plan possible cures. This contribution describes in detail the current longitudinal impedance model of the SPS. Recently, the model was updated with new findings and includes now the impedance of accelerating cavities, kicker and septum magnets, beam position monitors, vacuum Flanges, shielded and unshielded pumping ports, electrostatic septa and resistive wall. Electromagnetic simulations and bench measurements were used to build the model. The contribution from each element is described and compared to the total machine impedance. Together with relevant beam measurements and simulations, the analysis of the different sources of impedance is used to identify the source of the longitudinal instability limiting the SPS performance so that the responsible elements can be acted upon.
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MOPJE036	Longitudinal Impedance Characterization of the CERN SPS Vacuum Flanges	impedance, resonance, vacuum, damping	363
	J.V. Campelo CERN, Geneva, Switzerland
	This contribution describes the thorough studies carried out to characterize the longitudinal impedance of the CERN SPS vacuum flanges, which are believed to be the main source of LHC beam instability. Around 500 high-impedance flanges of 8 different types have been identified. Three factors play an important role in the characterization of these flanges: the type of vacuum chambers that the flange interconnects, whether or not both sides are electrically isolated (by means of an enamel coating) and, finally, the presence of damping resistors which damp high-Q resonances. Not only, full-wave electromagnetic field simulations, but also RF measurements have been used to evaluate the impedance of these elements. The R/Q of the relevant resonances was measured using the well-known bead-pull technique. In particular, a subset of around 150 flanges has been found to be the source of a high-impedance resonance at 1.4 GHz, also observed in beam measurements. Guidelines on how to reduce the impedance of these elements are also presented.
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MOPJE038	Impedance Studies of the LHC Injection Kicker Magnets for HL-LHC	impedance, coupling, kicker, injection	370
	H.A. Day, M.J. Barnes, L.M.C. Feliciano CERN, Geneva, Switzerland
	The LHC injection kicker magnets (MKIs) experienced strong heating during the first operational run, identified as being caused by power loss due to wakefields induced by stored beam. Studies of the beam coupling impedance of the beam screen, a series of conductors embedded in a ceramic tube placed in the ferrite yoke to screen the ferrite from the beam, resulted in new design offering improved screening: this is predicted to reduce the heating to acceptable levels for operation with 25ns beam during Run 2 of the LHC. However higher beam intensities proposed for HL-LHC operation are predicted to again cause strong heating to occur. Further studies have been carried out to reduce the beam induced power loss by optimising the beam screen design, some key results and findings of which are presented here.
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MOPJE039	Generalised Truncated Power Series Algebra for Fast Particle Accelerator Transport Maps	operation, optics, lattice	374
	L. Deniau, C.I. Tomoiagă CERN, Geneva, Switzerland
	New Generalised Truncated Power Series Algebra (TPSA) has been developed for extending, simplifying and optimising the transport maps used by particle accelerator simulation codes. TPSA are intensively used in optics code to describe transport maps of the elements constituting the particle accelerator to any order. Generalised TPSA extend the degrees to inhomogeneous ones, where separate degrees can be specified for each variables and constrained by two total orders, one for canonical variables and one for ordinary variables. This allows to track inhomogeneous planes of the 6D phase space with many extra variables. A complete set of new formulas and data structures have been derived to address the problem of memory consumption required for efficient computation of high order TPSA, including generalised indexing, multiplication and composition of inhomogeneous multivariate polynomials. The implementation has been benchmarked against well established libraries for the common subset with TPSA, and outperforms all of them for supported differential algebra operators on low and high orders, and high number of variables.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE039
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MOPJE042	Longitudinal Injection Schemes For the CERN PS Booster at 160 MeV Including Space Charge Effects	space-charge, injection, linac, emittance	378
	V. Forte, E. Benedetto, A.M. Lombardi, D. Quartullo CERN, Geneva, Switzerland
	In the frame of the LHC Injectors Upgrade project, the CERN PS Booster will be equipped with a H⁻ injection system at 160 MeV to tailor the initial transverse and longitudinal profiles. We are here reviewing the different multi-turn longitudinal injection schemes, from the beam dynamics point of view, taking into account the needs of the large variety of the PSB users, spanning in intensity from 5·10⁹ to about 1.6·10¹³ protons per bunch. The baseline of the longitudinal injection has always been the longitudinal stacking with central energy modulation: this scheme has the advantage of filling uniformly the RF bucket and mitigate transverse space charge, but it requires at least 40 turns of injection. A simpler injection protocol without energy modulation is here analyzed in detail to find the optimum initial conditions in terms of bucket filling and reduction of transverse and longitudinal space charge effects, with the advantage of minimizing the number of turns for the LHC beams. Simulations with space charge of the longitudinal injection process from different Linac4 trains are presented to fix possible longitudinal injection scenarios during the future commissioning and operation with Linac4.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE042
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MOPJE043	Design and Optimization of Electrostatic Deflectors for ELENA	focusing, vacuum, antiproton, alignment	382
	D. Barna University of Tokyo, Tokyo, Japan W. Bartmann, M.A. Fraser, R. Ostojić CERN, Geneva, Switzerland
	The ELENA ring will decelerate the antiprotons ejected from the Antiproton Decelerator (AD) at 5.3 MeV down to 100 keV kinetic energy. The slow antiprotons will be delivered to experiments using electrostatic beamlines, consisting of quadrupoles, correctors and deflectors. An extensive simulation study was carried out to find solutions to minimize the aberrations of the deflectors. These solutions will be presented together with the actual design of these devices.
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MOPJE044	Beam Dynamics Studies of the ELENA Electrostatic Transfer Lines	experiment, quadrupole, antiproton, optics	385
	M.A. Fraser, W. Bartmann, R. Ostojić CERN, Geneva, Switzerland D. Barna University of Tokyo, Tokyo, Japan
	The low-energy ELENA ring at the Antiproton Decelerator (AD) facility at CERN will lower the kinetic energy of antiproton beams from 5.3 MeV to 100 keV, significantly increasing the antiproton trapping efficiency at the experiments. The antiprotons from ELENA will be distributed to two experimental areas housing several different experiments through a system of electrostatic transfer lines totalling 90 m in length. A significant optimisation of the electrostatic optical elements (deflectors, quadrupoles, and correctors) has been carried out to improve the beam quality delivered to the experiments and facilitate installation of the beam lines into the AD hall. A general overview of the beam optics is presented, including end-to-end particle tracking and error studies from the extraction point in the ELENA ring to the experiments.
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MOPJE045	Fixed Points in Presence of Space Charge in Circular Particle Accelerators	space-charge, vacuum, extraction, resonance	389
	M. Giovannozzi, S.S. Gilardoni, A. Huschauer CERN, Geneva, Switzerland S. Machida, C.R. Prior, S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	Recent measurements performed in the framework of the multi-turn extraction (MTE) studies showed a dependence of the position of beamlets obtained by crossing a stable transverse resonance on the total beam intensity. This novel observation has triggered a number of studies aiming at understanding the source of the observed effect. In this paper the results of numerical simulations performed in different conditions are discussed in detail.
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MOPJE048	Electron-Cloud Studies for Transversely Split Beams	electron, resonance, 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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MOPJE049	Benchmarking the CERN-SPS Transverse Impedance Model with Measured Headtail Growth Rates	impedance, kicker, optics, vacuum	402
	C. Zannini, H. Bartosik, G. Iadarola, G. Rumolo, B. Salvant CERN, Geneva, Switzerland
	The latest SPS transverse impedance model includes kicker magnets, wall impedance, transition pieces (e.g. flanges and vacuum chamber discontinuities), beam position monitors and RF cavities. The model has already been successfully benchmarked against coherent tune shift and transverse mode coupling instability measurements. In this paper we present measurements of the headtail growth rates for a wide range of negative chromaticities and for two different configurations of machine optics (nominal and low gamma transition). The measurement results are compared with HEADTAIL simulations using the wake fields obtained from the SPS transverse impedance model.
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MOPJE050	Transverse Impedance Model of the CERN-PSB	impedance, space-charge, kicker, vacuum	406
	C. Zannini, G. Iadarola, K.S.B. Li, T.L. Rijoff, G. Rumolo CERN, Geneva, Switzerland B. Jones STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom T.L. Rijoff TU Darmstadt, Darmstadt, Germany
	In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices before installation in the machine. This paper describes the PSB impedance model which includes resistive wall, indirect space charge, flanges, step transitions, ejection kicker including cables, injection kickers and cavities. Each impedance contribution has been computed for different energies in the PSB cycle. Measurements of the coherent tune shifts have been performed and compared to calculations based on the impedance model.
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MOPJE051	Effect of Electron Cloud in Quadrupoles on Beam Instability	quadrupole, electron, dipole, 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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MOPJE052	Observations of an Anomalous Octupolar Resonance in the LHC	resonance, dipole, betatron, hadron	412
	F.S. Carlier, J.M. Coello de Portugal, A. Langner, E.H. Maclean, T. Persson, R. Tomás, R. Westenberger CERN, Geneva, Switzerland
	While linear LHC dynamics is mostly understood and under control, non-linear beam dynamics will play an increasingly important role in the challenging regimes of future LHC operation. In 2012, turn-by-turn measurements of large betatron excitations of LHC Beam 2 at injection energy were carried out. These measurements revealed an unexpectedly large spectral line in the horizontal motion with frequency Qx+2Qy. Detailed analyses and simulations are presented to unveil the nature of this spectral line.
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MOPJE054	Developments of the Segment-by-Segment Technique for Optics Corrections in the LHC	optics, coupling, betatron, quadrupole	419
	A. Langner, J.M. Coello de Portugal, P.K. Skowroński, R. Tomás CERN, Geneva, Switzerland
	Optics correction algorithms will become even more critical for the operation of the LHC at 6.5 TeV. For the computation of local corrections the segment-by-segment technique is used. We present improvements to this technique and an advanced error analysis, which increase the sensitivity for finding local corrections. Furthermore, we will investigate limitations of this method for lower beta-star optics as they will be used in the high-luminosity LHC (HL-LHC) upgrade.
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MOPJE056	OMC Software Improvements in 2014	software, optics, GUI, operation	426
	J.M. Coello de Portugal, F.S. Carlier, A. Langner, T. Persson, P.K. Skowroński, R. Tomás CERN, Geneva, Switzerland
	We present the LHC Optics Measurement and Corrections (OMC) software developments done during 2014 on stability, performance and usability. This software is used to analyze turn-by-turn data and compute optics corrections to get the best performance of the LHC. The main developments have been an automatic local correction script to get faster and more accurate corrections in the interaction regions, a self contained test for the whole software package to avoid mistakes during the software development and the improvements in the software quality and efficiency of the Segment by Segment technique script. We also present a study of the code quality in its current status.
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MOPJE064	Beam Impedance Optimization of the TOTEM Roman Pots	impedance, detector, cavity, vacuum	452
	N. Minafra CERN, Geneva, Switzerland
	The TOTEM experiment has been designed to measure the total proton-proton cross section and to study elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots (RP), special beam pipe insertions, to move silicon detectors close to the beams to detect particles very near the beam axis. In the first period of running of the LHC no problems were detected with retracted Roman Pots and during insertions in special runs; however, during close insertions to highest intensity beam, impedance heating has been observed. After the LS1 the LHC beam current will increase and the equipment that can interact with the beam needed to be optimized. A new RP, optimized to minimize the beam coupling, has been designed with the help of CST Particle Studio; a prototype has been used to test the simulation results in the laboratory with wire and probe measurements. Furthermore, in both the old and the new RPs, new ferrites have been installed. The new ferrite material has a higher Curie temperature than the one used before LS1 and a thermal treatment at 1000°C has been applied to reduce the out-gassing.
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MOPJE065	Contribution of Optical Aberrations to Spot-size Increase with Bunch Intensity at ATF2	emittance, damping, optics, extraction	455
	M. Patecki, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan M. Patecki Warsaw University of Technology, Warsaw, Poland G.R. White SLAC, Menlo Park, California, USA
	A primary goal of ATF2 (Accelerator Test Facility) is to demonstrate a low vertical beam size at the interaction point (IP) of about 37 nm. Measurements over the past years indicate that the ATF2 vertical beam size strongly rises with bunch intensity. Several different origins of this increase are considered, e.g. wakefields occurring between the ATF damping ring and the IP, and/or intrabeam scattering (IBS) causing the increase of transverse emittances and energy spread in the damping ring with the increase of the bunch intensity. In this paper we address the second possibility. Past measurements and simulations of the IBS effects in the ATF are used to model the intensity-dependent initial emittances and energy spread at the entrance of the final focus. Particle tracking simulations predict the IP vertical beam size growth expected from the known optical aberrations for initial beam parameters corresponding to varying bunch intensities. Comparing simulation results with emittance measurements at different locations allows us to draw some conclusions about the impact of IBS in the damping ring on the IP spot size, and about possible single-bunch wakefields in the ATF2.
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MOPJE067	Applications of PLACET2 to the CTF3 Combiner Ring	dipole, quadrupole, optics, wiggler	462
	D. Pellegrini, R. Corsini, D. Gamba, A. Latina CERN, Geneva, Switzerland
	The CTF3 Combiner Ring (CR) is an isochronous ring that employs RF-injection to combine multiple bunch trains (up to five) into a single one with higher bunch frequency. The length of the CR plays a critical role in obtaining the correct structure of the recombined train. PLACET2: the new recirculating version of the code PLACET is particularly suited to simulate the operational scenario. In order to validate this code, three different case studies have been considered: ring-length variations due to energy detuning, fast-beam decoherence due to uncorrected chromatic effects and vertical instabilities due to bunch-to-bunch wakefield effects. The first two effects have been measured during the last run and the predictions have been validated. The instability has been compared with previous studies. The results are presented and discussed.
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MOPJE068	PLACET2: A Novel Code for Beam Dynamics in Recirculating Machines	linac, dipole, lattice, operation	465
	D. Pellegrini, A. Latina, D. Schulte CERN, Geneva, Switzerland
	Efforts have been taken to enable the simulation of recirculating machines in PLACET. The new version, PLACET2, allows handling multiple interconnected beamlines in order to obtain a realistic model of a machine. Two new elements, injectors and dumps, have been introduced and are active components of any working machine. Trains of bunches are routed through beamlines and tracked simultaneously in a parallel manner. Tracking through time-dependent elements is possible, and care is made to preserve the correct time-structure of the beam in case of beam recombination. This allows straightforward computations of multi-bunch effects arising with high-charge and shortly spaced bunch trains, even with variable train structure. The main features of the code are presented together with its working principles and its key ideas. Two case studies are introduced: LHeC and the CTF3 combiner ring.
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MOPJE069	General Functionality for Turn-Dependent Element Properties in SixTrack	cavity, HOM, collimation, optics	468
	K.N. Sjobak, H. Burkhardt, R. De Maria, A. Mereghetti, A. Santamaría García CERN, Geneva, Switzerland
	In order to facilitate studies of how dynamically changing element attributes affect the dynamics of the beam and beam losses, the functionality for dynamic kicks (DYNK) of SixTrack has been significantly extended. This functionality can be used for the simulation of dynamic scenarios, such as when crab cavities are switched on, orbit bumps are applied, optics are changed, or failures occur. The functionality has been extended with a more general and flexible implementation, such that arbitrary time-dependent functions can be defined and applied to different attributes of families or individual elements, directly from the user input files. This removes the need for source code manipulation, and it is compatible with LHC@Home which offers substantial computing resources from volunteers. In this paper, the functionality and implementation of DYNK is discussed, along with examples of application to the HL-LHC crab cavities.
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MOPJE075	Tracking Through Analytic Quadrupole Fringe Fields With GPT	quadrupole, space-charge, interface, multipole	489
	S.B. van der Geer, M.J. de Loos Pulsar Physics, Eindhoven, The Netherlands B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	In the early design stages it is customary to work with a highly simplified analytic model to describe the beam line. Dipoles and quadrupoles are often based on hard-edged approximations. This is not only unrealistic, it also significantly slows down time-domain spacecharge tracking codes such as the General Particle Tracer (GPT) code. The underlying reason for the poor performance is that despite the fact that the simple hard-edged field equations are fast to evaluate, they force the integration process to use excessively small step sizes near the fields discontinuities in order to achieve the desired accuracy. In other worlds, the apparently simple equations turn out to be the most difficult ones to evaluate numerically. An obvious solution is to switch to field-maps, but this is not practical in the early design stages. In this contribution we show a new solution implemented in the GPT code based on analytical expressions for the fringes where the transverse size of the magnet is properly taken into account. In addition to producing more realistic results, the smooth fields increase tracking speed by over an order of magnitude for typical test cases.
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MOPJE077	Progress on Simulation of Fixed Field Alternating Gradient Accelerators	closed-orbit, betatron, experiment, acceleration	495
	S.L. Sheehy JAI, Oxford, United Kingdom A. Adelmann PSI, Villigen PSI, Switzerland M. Haj Tahar, F. Méot BNL, Upton, Long Island, New York, USA Y. Ishi, Y. Kuriyama, Y. Mori, M. Sakamoto, T. Uesugi Kyoto University, Research Reactor Institute, Osaka, Japan D.J. Kelliher, S. Machida, C.R. Prior, C.T. Rogers STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	Fixed Field Alternating Gradient accelerators have been realised in recent decades thanks partly to computational power, enabling detailed design and simulation prior to construction. We review the specific challenges of these machines and the range of different codes used to model them including ZGOUBI, OPAL and a number of in-house codes from different institutes. The current status of benchmarking between codes is presented and compared to the results of recent characterisation experiments with a 150 MeV FFAG at KURRI in Japan. Finally, we outline plans toward ever more realistic simulations including space charge, material interactions and more detailed models of various components.
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MOPJE078	Beam Delivery Simulation - Recent Developments and Optimization	collider, background, toolkit, linear-collider	499
	J. Snuverink, S.T. Boogert, H. Garcia Morales, S.M. Gibson, R. Kwee-Hinzmann, L.J. Nevay JAI, Egham, Surrey, United Kingdom L.C. Deacon UCL, London, United Kingdom
	Funding: Research supported by FP7 HiLumi LHC - grant agreement 284404 and by the STFC via the JAI3 grant Beam Delivery Simulation (BDSIM) is a particle tracking code that simulates the passage of particles through both the magnetic accelerator lattice as well as their interaction with the material of the accelerator itself. The Geant4 toolkit is used to give a full range of physics processes needed to simulate both the interaction of primary particles and the production and subsequent propagation of secondaries. BDSIM has already been used to simulate linear accelerators such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC), but it has recently been adapted to simulate circular accelerators as well, producing loss maps for the Large Hadron Collider (LHC). In this paper the most recent developments, which extend BDSIM's functionality as well as improve its efficiency are presented. Improvement and refactorisation of the tracking algorithms are presented alongside improved automatic geometry construction for increased particle tracking speed.
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MOPJE084	Particle-in-cell Simulations of a Plasma Lens at Daresbury Laboratory	plasma, focusing, emittance, experiment	518
	K. Hanahoe, O. Mete, G.X. Xia UMAN, Manchester, United Kingdom D. Angal-Kalinin, J.K. Jones STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.D.A. Smith TXUK, Warrington, United Kingdom
	Feasibility of a focusing element using the transverse fields provided by a plasma cell was studied numerically. In this paper, an experimental set up is proposed for various beam parameters available from the VELA and CLARA beam lines at Daresbury Laboratory. 2D simulation results from VSim, and expected results from planned measurement stations are presented. Field properties and the advantages and disadvantages of such an instrument compared to conventional focusing elements are discussed.
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MOPMA001	Comparison of Measurements and Simulations for Single Bunch Instabilities at Diamond	impedance, wakefield, radiation, synchrotron	521
	M. Atay, R. Bartolini JAI, Oxford, United Kingdom R. Bartolini, R.T. Fielder, I.P.S. Martin DLS, Oxfordshire, United Kingdom
	The single bunch dynamics in the Diamond storage ring has been analysed with a multiparticle tracking code and compared with the results of a wealth of diagnostics, including streak camera, Schottky diodes and FTIR spectra. The interplay of various wakefield sources has been studied and it has been found that the THz spectrum can be reproduced in many cases with simple impedance models, both below and above the bursting threshold.
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MOPMA004	Numerical Optimization of Accelerators within oPAC	network, lattice, controls, quadrupole	533
	C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	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. Powerful simulation tools are required for every accelerator and light source to study the motion of charged particles through electromagnetic fields during the accelerator design process, to optimize the performance of machine diagnostics and to assess beam stability and non-linear effects. The Optimization of Particle Accelerators (oPAC) Project is funded by the EU within the 7th Framework Programme and currently supports 23 Fellows that are based at institutions across Europe. This large network carries out R&D that closely links beam physics studies with the development of diagnostics and beyond state-of-the-art simulation tools. This contribution presents selected research outcomes from oPAC, including the numerical optimization of beam loss monitor locations along the European Spallation Source’s 5 MW proton linac, results from tracking studies for the LHeC lattice that allow beam stability to be assessed, and multi-objective optimization of the linear and non-linear beam dynamics of the synchrotron SOLEIL. In addition, an overview of recent and future oPAC events is also given.
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MOPMA007	Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade	cavity, feedback, timing, impedance	543
	M. Borland, T.G. Berenc, R.R. Lindberg, A. Xiao ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.
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MOPMA008	Simulation of Gas-Scattering Lifetime using Position- and Species-Dependent Pressure and Aperture Profiles	scattering, vacuum, storage-ring, photon	546
	M. Borland, J.A. Carter, H. Cease, B.K. Stillwell ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. When computing gas-scattering lifetime for storage rings, it is common to use the average pressure, even though it is known that the pressure varies with location in the ring and varies differently for different gas species. In addition, other simplifications are commonly made, such as assuming that the apertures in the horizontal and vertical planes are independent and assuming that the momentum acceptance can be characterized by a single value. In this paper, we describe computation of the elastic- and bremsstrahlung-scattering lifetimes that includes species-specific gas pressure profiles computed with VACCALC and MOLFLOW. In addition, the computations make use of the detailed shape of the dynamic acceptance and the position-dependent momentum acceptance. Comparisons are made to simpler methods for the Advanced Photon Source storage ring and the multi-bend achromat upgrade lattice.
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MOPMA009	Improvements in Modeling of Collective Effects in ELEGANT	cavity, collective-effects, lattice, impedance	549
	M. Borland, R.R. Lindberg, A. Xiao ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.
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MOPMA010	Commissioning Simulations for the APS Upgrade Lattice	lattice, coupling, quadrupole, closed-orbit	553
	V. Sajaev, M. Borland ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A hybrid seven-bend-achromat lattice has been proposed for the APS upgrade that will feature very strong focusing elements and relatively small vacuum chamber. Achieving design lattice parameters during commissioning will need to be accomplished in a short period of time to minimize dark time for APS users. We describe here start-to-end simulation of the machine commissioning beginning from first-turn trajectory correction, performing orbit and lattice correction, and finally evaluating nonlinear performance of the corrected lattice in terms of dynamic aperture and lifetime.
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MOPMA012	Intra-Beam and Touschek Scattering Computations for Beam with Non-Gaussian Longitudinal Distributions	scattering, emittance, distributed, lattice	559
	A. Xiao, M. Borland ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 Both intra-beam scattering (IBS) and the Touschek effect become prominent for multi-bend-achromat- (MBA-) based ultra-low-emittance storage rings. To mitigate the transverse emittance degradation and obtain a reasonably long beam lifetime, a higher harmonic rf cavity (HHC) is often proposed to lengthen the bunch. The use of such a cavity results in a non-gaussian longitudinal distribution. However, common methods for computing IBS and Touschek scattering assume Gaussian distributions. Modifications have been made to several simulation codes that are part of the {\tt elegant} toolkit to allow these computations for arbitrary longitudinal distributions. After describing these modifications, we review the results of detailed simulations for the proposed hybrid seven-bend-achromat (H7BA) upgrade lattice for the Advanced Photon Source.
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MOPMA015	Applications of an MPI Enhanced Simulated Annealing Algorithm on nuSTORM and 6D Muon Cooling	sextupole, lattice, storage-ring, emittance	568
	A. Liu Fermilab, Batavia, Illinois, USA
	The nuSTORM decay ring is a compact racetrack storage ring with a circumference ∼ 480 m using large aperture (∅=60 cm) magnets. The design goal of the ring is to achieve a momentum acceptance of 3.8±10\% GeV/c and a phase space acceptance of 2000 μm·rad. The design has many challenges because the acceptance will be affected by many nonlinearity terms with large particle emittance and/or large momentum offset. In this paper, we present the application of a meta-heuristic optimization algorithm to the sextupole correction in the ring. The algorithm is capable of finding a balanced compromise among corrections of the nonlinearity terms, and finding the largest acceptance. This technique can be applied to the design of similar storage rings that store beams with wide transverse phase space and momentum spectra. We also present the recent study on the application of this algorithm to a part of the 6D muon cooling channel. The technique and the cooling concept will be applied to design a cooling channel for the extracted muon beam at nuSTORM in the future study.
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MOPMA017	Numerical simulations of transverse modes in Gaussian bunches with space charge	space-charge, damping, lattice, synchrotron	575
	A. Macridin, J.F. Amundson, E.G. Stern Fermilab, Batavia, Illinois, USA
	The transverse modes and the intrinsic Landau damping in Gaussian bunched beams with space charge are numerically investigated. The evolution of the phase space density is calculated with the Synergia accelerator modeling package and analyzed with Dynamic Mode Decomposition (DMD) method. DMD is a relatively new technique used to calculate mode dynamics in both linear and nonlinear systems. The properties of the first three space charge modes, including their shape, damping rates and tune shifts are calculated over the entire range of the space charge interaction.
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MOPMA018	Simulation of Multipacting in SC Low Beta Cavities at FNAL	cavity, niobium, operation, linac	579
	G.V. Romanov, P. Berrutti, T.N. Khabiboulline Fermilab, Batavia, Illinois, USA
	Proton Improvement Plan-II at Fermilab is a plan for improvements to the accelerator complex aimed at providing a beam power capability of at least 1 MW on target at the initiation of LBNE (Long Base Neutrino Experiment) operations. The central element of the PIP-II is a new 800 MeV superconducting linac, injecting into the existing Booster. Multipacting affects superconducting RF cavities in the entire range from high energy elliptical cavities to coaxial resonators for low-beta applications. This work is focused on multipacting study in the low-beta 325 MHz spoke cavities; namely SSR1 and SSR2, which are especially susceptible to the phenomena. The extensive simulations of multipacting in the cavities with updated material properties and comparison of the results with experimental data helped us to improve overall reliability and accuracy of these simulations. Our practical approach to the simulations is described in details. For SSR2, which has a high multipacting barrier right at the operating power level, some changes of the cavity shape to mitigate this harmful phenomenon are proposed.
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MOPMA019	Simulations of the Fermilab Recycler for Losses and Collimation	space-charge, collimation, proton, target	582
	E.G. Stern, R. Ainsworth, J.F. Amundson, B.C. Brown Fermilab, Batavia, Illinois, USA
	Fermilab has recently completed an upgrade to the com- plex with the goal of delivering 700 kW of beam power as 120 GeV protons to the NuMI target. A major part of boost- ing beam power is to shorten the beam cycle by accumulating up to 12 bunches of 0.5 × 10 11 protons in the Recycler ring through slip-stacking during the Main Injector ramp. This introduces much higher intensities into the Recycler than it has had before. Meeting radiation safety requirements with high intensity operations requires understanding the ef- fects of space charge induced tune spreads and resulting halo formation, and aperture restrictions in the real machine to de- velop a collimation strategy. We report on initial simulations of slip-stacking in the Recycler performed with Synergia.
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MOPMA024	A Parallel Particle-Particle, Particle-Mesh Solver for Studying Coulomb Collisions in the Code IMPACT-T	emittance, electron, 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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MOPMA025	CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs	impedance, dipole, lattice, damping	596
	C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA D. Douglas, R. Li, C. Tennant JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.
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MOPMA029	Experiences Simulating Nonlinear Integrable Optics	lattice, optics, diagnostics, emittance	611
	S.D. Webb, D.L. Bruhwiler RadiaSoft LLC, Boulder, Colorado, USA V.V. Danilov ORNL, Oak Ridge, Tennessee, USA R.A. Kishek UMD, College Park, Maryland, USA S. Nagaitsev, A. Valishev Fermilab, Batavia, Illinois, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011340. With increasing interest in the nonlinear integrable optics, it is important that early experiences with simulating the lattices be shared to save time and point out potential difficulties in the simulations. We present here some details of simulating the nonlinear integrable lattices. We discuss correctly implementing and testing the elliptic element kicks, and the limits of the thin lens approximation. We also discuss generating a properly matched bunch in the transverse phase space, and how to analyze the resulting computational data from simulations.
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Paper

Title

Other Keywords

Page

MOAB1

High Beam Intensity Harp Studies and Developments at SNS

data-acquisition, electronics, proton, target

17

W. Blokland
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
The Spallation Neutron Source (SNS) Harp consists of 30 wires for each of the horizontal, vertical, and diagonal planes. The purpose of the harp is to measure the position, profile, and peak density of the high intensity beam coming out of the accumulator ring and going onto the spallation target. The data-acquisition hardware is now over ten years old and many of the electronics parts are obsolete. Occasionally, the electronics must be rebooted to reset the sample-and-hold circuitry. To evaluate options for a new system, the signals from the harp were studied. This paper will describe these studies’ results, the design, and initial results of the new and simpler data-acquisition system..

Slides MOAB1 [4.335 MB]

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MOBC2

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

GPU, electron, 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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MOBD2

Design and Prototyping of HL-LHC Double Quarter Wave Crab Cavities for SPS Test

cavity, luminosity, proton, HOM

64

S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
L. Alberty, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, N. Kuder, R. Leuxe, C. Zanoni
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
Z. Li
SLAC, Menlo Park, California, USA
A. Ratti
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE via US LARP program, through BSA LLC contract No.DE-AC02-98CH10886 and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231.
The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double-Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. A couple of DQW crab cavities are under preparation and will be tested with beam in the Super Proton Synchrotron (SPS) of CERN by 2017. This paper describes the design and prototyping of DQW crab cavities for the SPS test.

Slides MOBD2 [6.909 MB]

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MOPWA001

Instability Thresholds and Tune Shift Estimation for Sirius

impedance, feedback, emittance, damping

70

F.H. de Sá, L. Liu, N. Milas, X.R. Resende
LNLS, Campinas, Brazil

In this work we present the evaluation of longitudinal and transverse instability thresholds as well as tune shifts for Sirius using time and frequency domain codes that are being developed in-house and take into account various effects on the beam instability, such as bunch by bunch feedback system, quadrupolar impedances from undulator chambers and tune spreads.

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MOPWA002

Nonequilibrium Phase Transitions in Crossed-Field Devices

electron, cathode, space-charge, 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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MOPWA003

Optimal Generalized Finite Difference Solution to the Particle-in-Cell Problem

framework, plasma, space-charge, factory

77

X. Wang, X. Jiao, H. Liu, V. Samulyak, K. Yu
SBU, Stony Brook, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA

The particle-in-cell (PIC) method is widely used in applications, such as in electromagnetics, but the accuracy of its solutions degrades when the particle distribution is highly non-uniform. In our work, we propose an adaptive PIC method with optimal point distribution and a generalized finite difference (GFD) scheme. Our method replaces the Cartesian grid in the classical PIC with adaptive computational nodes or particles, to which the charges from the sample particles are assigned by a weighted least-square approximations. The partial differential equation is then discretized using a GFD method and solved with fast linear solvers. The density of computational particles is chosen adaptively, so that the error from GFD and that from Monte Carlo integration are balanced and the total error is approximately minimized. We also present the verification results using electrostatic problems and comparison of accuracy and solution time of our method with the classical PIC.

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MOPWA004

Reformulation of the Action and Phase Jump Method to Obtain Magnetic Errors in the LHC IRs

quadrupole, lattice, interaction-region, framework

80

A.C. García-Bonilla, J.F. Cardona
UNAL, Bogota D.C, Colombia

Funding: Fundación Para la Promoción de la Investigación y la Tecnología del Banco de la República and Division de Investigación Bogotá (DIB).
One of the major problems when doing the commissioning of an accelerator is to identify and correct the linear components of magnetic errors. The Action and Phase Jump Technique is one of the available methods to perform this task. For this method to work, it is necessary to have one BPM measurement at the IR, the region where the magnetic error is evaluated. In some cases, this BPM measurement become the biggest source of uncertainty when the action and phase jump technique is used. In this paper, a new formulation based on this method is presented. This new formulation doesn't make any use of BPM measurements at the IR, thereby allowing more robust error estimations. Quadrupole errors in the LHC lattice are estimated with this new formulation, using both, simulated data and LHC experimental data. A comparison with the previous formulation is included. The results on simulated data show that the reformulation leads to a reduction in the uncertainty, while for the experimental case, the reduction is not so clear. Explanations for this behavior and possible remedies will also be discussed.

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MOPWA005

Comparison between Digital Filters and Singular Value Decomposition to Reduce Noise in LHC Orbits used for Action and Phase Jump Analysis

quadrupole, collider, resonance, hadron

83

A.C. García-Bonilla, J.F. Cardona
UNAL, Bogota D.C, Colombia

Funding: Fundación Para la Promoción de la Investigación y la Tecnología del Banco de la República and DIB (División de Investigación de Bogotá).
One of the initial difficulties to apply the Action and Phase Jump (APJ) analysis to LHC orbits was the high level of noise present in the BPM measurements. On the other hand, the unprecedented number of turns for LHC allows us to use all sort of filters. In this paper, we evaluate the effectiveness of digital filters like the band-pass filter and compare them with a filter based on Singular Value Decomposition, when magnetic error estimations are made using a recent version of the APJ method. First, mainly results on simulated orbits with noise are presented, and then, plots and results are shown for the filters effect on experimental data. The analysis indicates that a combination of filters leads to measurements with the least uncertainty.

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MOPWA006

Core-Halo Limit as an Indicator of High Intensity Beam Internal Dynamics

space-charge, emittance, linac, vacuum

86

P.A.P. Nghiem, N. Chauvin, N. Pichoff, D. Uriot, M. Valette
CEA/DSM/IRFU, France

The dynamics of high-intensity beams is mainly governed by their internal space charge forces. These forces induce emittance growth and halo generation. They contribute to shape the beam density profile. As a consequence, a careful analysis of this profile can help revealing the internal dynamics of the beam. This paper recalls the precise core-halo limit determination proposed earlier *, then studies its behavior through a wide range of beam profiles and finally shows its relevance as an indicator of the limit separating the two specific space charge field regimes of the core and the halo.
* P. A. P. Nghiem et al., Appl. Phys. Lett. 104, 074109 (2014)

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MOPWA007

The SARAF-LINAC Beam Dynamics

linac, rfq, emittance, proton

89

N. Pichoff, D. Uriot
CEA/DSM/IRFU, France
B. Dalena
CEA/IRFU, Gif-sur-Yvette, France

SNRC and CEA collaborate to the upgrade of the SARAF Accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). This paper presents the beam dynamics in the reference design of the SARAF-LINAC (from the 4 m long 176 MHz RFQ to the HWR Superconducting linac’s end). The beam losses, mostly in longitudinal direction, estimated from error studies, are compared with acceptable losses defined for hands-on maintenance.

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MOPWA008

Status of TraceWin Code

linac, space-charge, cavity, diagnostics

92

D. Uriot, N. Pichoff
CEA/DSM/IRFU, France

Well known in the community of high-intensity linear accelerators, the transport code TraceWin * is able to simulate a beam from the source to the target using either simple linear model or multiparticle simulations including 2D or 3D space-charge. Continuously developed at CEA Saclay since 15 years, it is today the reference code for projects such IFMIF, ESS, MYRRHA, SPIRAL2, IPHI … The accuracy of his predictions associated with an original and powerful GUI and its numerous features have made its success, with a community of 200 users worldwide. It is now used on a larger perimeter that its initial skills. The aim of this paper is to summarize the TraceWin capabilities, including implemented last ones.
* http://irfu.cea.fr/Sacm/logiciels/

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MOPWA010

Emittances of the Core and of the Halo

emittance, linac, space-charge, extraction

99

M. Valette, P.A.P. Nghiem
CEA/IRFU, Gif-sur-Yvette, France

In high intensity accelerators, the beam is often space charge dominated. The density profile then takes a shape very different from a Gaussian one, with a more or less sharp core and a more or less compact halo. Furthermore, the core and the halo can be differently focused and thus differently oriented in the phase spaces. In these conditions, classically characterizing the beam by a global set of rms values, namely Emittance and Twiss parameters, is no more meaningful. This paper extends the core-halo limit defined ealier in 1D real space * to the 2D phase space, allowing to define for the very first time Emittances and Twiss parameters for the core and the halo separately. Applications to the IFMIF accelerators are given as an example of more appropriate beam characterization for high intensity linacs.
* P. A. P. Nghiem et al., Appl. Phys. Lett. 104, 074109 (2014)

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MOPWA011

The Damping of Transverse Coherent Instabilities by Harmonic Cavities

synchrotron, betatron, damping, electron

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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MOPWA014

New Functionality for Beam Dynamics in Accelerator Toolbox (AT)

lattice, radiation, dipole, emittance

113

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

Accelerator Toolbox is a widely used code for beam dynamic simulations based on Matlab. To continue the development of the code in a collaborative manner, a SourceForge project and SVN repository called atcollab has been established. Here we describe the contributions to atcollab from the ESRF beam dynamics group. Additional modules have been developed: general matching (atmatch), improved plotting (atplot), Touschek lifetime computation via the Piwinski formula, nonlinear dynamics computations such as resonance driving terms, improved reporting of lost particles and improvements and additions to the integration routines. One example of the latter includes diffusion due to quantum fluctuations. Modeling of collective effects may now be performed using pass methods representing a variety of impedance models. Finally, routines to replace the full ring with a compact representation have been developed, facilitating studies in which many turns and many particles are required.

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MOPWA018

Loss Factor and Impedance Analysis of Warm Components of BERLinPro

factory, impedance, operation, wakefield

128

H.-W. Glock, M. Abo-Bakr, J. Kolbe, F. Pflocksch, A. Schälicke
HZB, Berlin, Germany
H.-W. Glock, C. Potratz
COMPAEC e.G., Rostock, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The ongoing component design for the HZB 50 MeV, 100mA ERL project BERLinPro is accompanied by loss factor and impedance computations. A list of accelerator components including bellows, collimators, tapers, shutter valves etc. is given, some of them with alternative shapes. Loss factors, calculated using CSTParticleStudio®, are presented together with important properties of the impedance spectrum. Scaling of the loss factors with respect to bunch length is calculated on base of the numerical simulations and is used to extrapolate down to a bunch length (1 standard deviation) of 0.6 mm, which is hard to reach directly in numerical simulations.

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MOPWA020

Longitudinal Stability Of Short Bunches in Storage Rings with Strong Longitudinal Focusing

impedance, synchrotron, dipole, resonance

135

P. Kuske
HZB, Berlin, Germany

Funding: work supported by the BMBF
In the BESSY VSR project, the variable bunch length storage ring, two high gradient accelerating structures at 1.5 and 1.75 GHz will be phased such that long and short bunches can be stored simultaneously. The longitudinal stability of the short bunches is investigated taking into account the shielded CSR- and a purely inductive impedance. Multi particle tracking studies and numerical solutions of the Vlasov-Fokker-Planck equation show that threshold currents for short bunches do not follow the simple scaling law which was found for long bunches. The inductive impedance can even lower the thresholds for the instability. With an 80 times increased accelerating gradient and reasonable assumptions on the inductive impedance for shorter bunches stable operation can be expected with bunches 1.8 ps long (RMS-value) and 0.8 mA current. According to the calculations and operating in a dedicated low-α mode will produce stable 40 μA bunches with 400 fs length

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MOPWA022

Influence of Transient Beam Loading on the Longitudinal Beam Dynamics at BESSY VSR

beam-loading, synchrotron, damping, cavity

141

M. Ruprecht, P. Goslawski, A. Jankowiak, A. Neumann, M. Ries, G. Wüstefeld
HZB, Berlin, Germany
T. Weis
DELTA, Dortmund, Germany

BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed *. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. If the bunch fill pattern exhibits a significant inhomogeneity, e.g. due to gaps, transient beam loading causes a distortion of the longitudinal phase space which is different for each bunch. The result are variations along the fill pattern in synchronous phase, synchrotron frequency and bunch shape. This paper presents investigations of transient beam loading and depicts the consequences on bunch length, phase stability and longitudinal multi-bunch oscillations for the projected setup of BESSY VSR.
* G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain

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MOPWA025

Simulation of Laser Cooling of Heavy Ion Beams at High Intensities

laser, synchrotron, ion, scattering

150

L. Eidam, O. Boine-Frankenheim, D.F.A. Winters
GSI, Darmstadt, Germany

In the past the principle of Doppler laser cooling was investigated and verified in storage rings in the low energy regime. Within the FAIR project the laser cooling will be applied to high intensity and high energy beams for the first time. The laser cooling results in a further increase of the longitudinal phase space density and in non-Gaussian longitudinal beam profiles. In order to ensure stable operation and optimize the cooling process the interplay of the laser force and high intensity effects has to be studied numerically. This contribution will identify constrains of the cooling scheme for an efficient reduction of momentum spread. For high beam energies the scattering of photons has to be treated stochastically instead of using averaged forces. The modeling of the laser force in a particle in cell tracking code will be discussed.

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MOPWA029

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

space-charge, gun, cathode, electron

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

electron, wakefield, 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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MOPWA031

A New Approach for Resistive Wakefield Calculations in Time Domain

wakefield, impedance, cavity, controls

168

A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
M. Dohlus, I. Zagorodnov
DESY, Hamburg, Germany

We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.

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MOPWA036

Status of Injection Studies into the Figure-8 Storage Ring

injection, experiment, kicker, ion

187

J.F. Wagner, A. Ates, M. Droba, O. Meusel, H. Niebuhr, D. Noll, U. Ratzinger
IAP, Frankfurt am Main, Germany

The ongoing investigations on the design of the Figure-8 Storage Ring* at Frankfurt University focus on the beam injection. The research includes simulations as well as a scaled down experiment. The studies for an optimized adiabatic magnetic injection channel, starting from a moderate magnetic field up to a maximum of 6 Tesla, with a realistic field model of toroidal coils due to beam dynamics with space charge will be shown. For the envisaged ExB kicker system the simulations deal with beam potential constraints and a multi-turn injection concept in combination with an adiabatic magnetic compression. To investigate the concept of the beam injection into a toroidal magnetic field, a scaled down room temperature experiment is implemented at the university. It is composed of two 30 degree toroidal segments, two volume ion sources, two solenoids and two different types of beam detectors. The experiment is used to investigate the beam transport and dynamics of the laterally injected and “circulating” beam through the magnetic configuration. To set up the injection experiment, theoretical calculations and beam simulations with bender** are used.
* M. Droba et al., Proc. of IPAC'14, Dresden, Germany, TUPRO045
** D. Noll, M. Droba, O. Meusel, U. Ratzinger, K. Schulte, C.Wiesner, Proc. of HB2014, East Lansing, USA, WEO4LR02

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MOPWA042

Sub-fs Electron Bunch Generation Using Magnetic Compressor at SINBAD

electron, 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, electron

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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MOPWA044

Quasi-frozen Spin Method for EDM Deuteron Search

dipole, storage-ring, proton, lattice

213

Y. Senichev, A. Lehrach, B. Lorentz, R. Maier
FZJ, Jülich, Germany
S.N. Andrianov, A.N. Ivanov
St. Petersburg State University, St. Petersburg, Russia
M. Berz, E. Valetov
MSU, East Lansing, Michigan, USA
S. Chekmenev
RWTH, Aachen, Germany

To search for EDM using proton storage ring with purely electrostatic elements the concept of frozen spin method has been proposed by BNL. This method is based on two facts: in the equation of the spin precession the magnetic field dependence is entirely eliminated and at “magic” energy the spin precession frequency coincides with the precession frequency of the momentum. In case of deuteron the anomalous magnetic moment is negative (G=-0.142), therefore we have to use the electrical and magnetic field simultaneously keeping the frozen spin direction along the momentum as in the pure electrostatic ring. In this article we suggest the concept of the quasi-frozen spin when the spin oscillates around the momentum direction within the half value of the advanced spin phase each time returning back by special optics. Due to the low value of the anomalous magnetic moment of deuteron an effective contribution to the expected EDM effect is reduced only by a few percent.

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MOPWA046

Lattice and Beam Dynamics of the Energy Recovery Mode of the Mainz Energy-recovering Superconducting Accelerator MESA

linac, cryomodule, lattice, experiment

220

D. Simon, K. Aulenbacher, R.G. Heine, F. Schlander
IKP, Mainz, Germany

Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) and German Research Foundation (DFG) under the Cluster of Excellence PRISMA.
The mainz energy recovering superconducting accelerator (MESA) is a proposed multi-turn energy recovery linac for particle physics experiments. It will be built at the institute for nuclear physics (KPH) at Mainz University. Because of the multi-turn energy recovery mode there are particular demands at the beam dynamics. We present the current status of the lattice development.

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MOPWA049

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

luminosity, electron, 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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MOPWA050

Beam Dynamics Studies to Develop a High-energy Luminosity Model for the LHC

luminosity, beam-beam-effects, collider, emittance

233

G. Campogiani
Rome University La Sapienza, Roma, Italy
Y. Papaphilippou
CERN, Geneva, Switzerland

Funding: support provided by the EPS-AG through the EPS-AG student grant program
Luminosity, the key figure of merit of a collider as the LHC, depends on the brightness of the colliding beams. This makes the intensity dependent beam-beam effect the dominant performance limiting factor at collision. The parasitic interactions due to the electromagnetic mutual influence of the beams in the interaction region of a collider induce a diffusive behaviour in the tails of the beam. The evolution of charge density distribution is studied to model the beam tails evolution in order to characterize beam lifetime and luminosity. To achieve this, tools are developed for tracking distributions of arbitrary number of single particles interacting with the opposing strong-beam, to analyse the halo formation processes due to the combined effect of beam-beam and machine non-linearities. This paper presents preliminary results of the simulations, both for the LHC Run I and nominal LHC parameters. The former will be used to benchmark simulations while the latter aims at supporting luminosity estimate for the Run II.

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MOPWA053

Emittance Preservation in SuperKEKB Injector

emittance, wakefield, linac, injection

239

S. Kazama, Y. Ogawa, M. Satoh, H. Sugimoto, M. Yoshida
KEK, Ibaraki, Japan

Injector linac at KEK is now under the way to produce high current and low emittance beams for SuperKEKB. The target luminosity for SuperKEKB is 40 times higher than that of KEKB. Short-range transverse wakefield and dispersive effects at the linac cause an emittance growth, and longitudinal wakefield effect enlarges an energy spread of the beams. In this presentation, we will report simulation studies of the emittance preservation issues and how to suppress the increase of the energy spread of the beams.

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MOPWA054

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

electron, 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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MOPWA056

Transverse Multi-Pass Beam Breakup Simulation for KEK ERL Light Source

HOM, cavity, linac, cryomodule

248

S. Chen, N. Nakamura, M. Shimada, D. Zhou
KEK, Ibaraki, Japan
S. Huang, K.X. Liu
PKU, Beijing, People's Republic of China

In this paper, the multi-pass BBU of such a high energy ERL is studied based on the simulation on a 3 GeV ERL light source proposed by KEK.

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MOPWA057

Space Charge Simulation and Matching at Low Energy Section of J-PARC Linac

rfq, space-charge, emittance, solenoid

251

S. Artikova, T. Morishita
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Kondo
JAEA, Ibaraki-ken, Japan

An intensity upgrade of Japan Proton Accelerator Research Complex (J-PARC) included the installation of a new ion source (IS) and a radio-frequency quadrupole (RFQ) which to be used at first stage of acceleration. The linac is divided into two sections on the basis of operating frequencies and three sections on the basis of family of RF cavities to be used for the acceleration of 50 mA beam of H⁻ ions from 50 keV to 400 MeV. Low energy part of linac consists of an IS, a two-solenoid low energy beam transport (LEBT) and the RFQ. The transition from one section to another can limit the acceptance of the linac if these are not matched properly in both longitudinal and transverse plane. We performed a study to calculate the acceptance of the RFQ at zero current in which space charge effects are not considered. In addition, a particle tracking technique is employed to study the space charge effects in LEBT of the J-PARC linac after the intensity upgrade in order to match the beam to the RFQ. Also, RFQ tank level and intervene voltage calibration factor is determined by comparing the simulation results of the beam transmission with the test measurement of tank level vs. transmission.

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MOPWA062

Optimization of the Momentum Bandwidth for Final Focus System in CEPC

sextupole, factory, luminosity, collider

269

S. Bai, T.J. Bian, J. Gao, H. Geng, D. Wang, Y. Wang, M. Xiao
IHEP, Beijing, People's Republic of China
F. Su
Institute of High Energy Physics (IHEP), People's Republic of China

With the discovery of the higgs boson at around 125GeV, a circular higgs factory design with high luminosity (L ~ 10³⁴ cm^-2s^-1) is becoming more popular in the accelerator world. To achieve such high luminosity, a final focus system in non-local chromaticity correction scheme with very low β functions at the interaction point is designed. The narrow momentum bandwidth is a crucial problem of this kind of design. It is shown that by introducing additional sextupoles the momentum acceptance of the CEPC final focus system can be increased by about a factor of four.

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MOPWA065

Uniformization of the Transverse Beam Profile by a New Type Nonlinear Magnet

octupole, target, multipole, dipole

272

G. Gu, W.B. Liu
IHEP, Beijing, People's Republic of China

The uniform particle beam is desirable in many beam applications. One method to get this type of beam distribution is using octupoles, but loss of particles in the halo will be produced by this method. To reduce the beam loss, a new type of magnet is proposed in this paper. The field in the middle region of the new type magnet is similar to the octupole magnet field, but the rate of rise decline quickly in the edge. So that the particle in the edge experience a lower magnet field, and this would result in less particle loss. We also add a mechanical structure on the new type magnet to make it possible to adjust the size of middle region. So that the magnet can adapt to different transverse dimensions of the beam, and this would further reduce particle loss. Some numerical simulations have been done respectively with octuples and the new type of magnet. The simulation results show that the new type of magnet could get the uniform distribution of particle beam with less particle loss. We are processing a magnet now, and an experiment to test the magnet will be arranged on CPHS.

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MOPWA066

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

electron, proton, 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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MOPWA069

Upgrades on a Scalable Software Package for Large Scale Beam Dynamic Simulations

software, DTL, space-charge, solenoid

282

X.T. Dong, K. Du, J. Xu, R. Zhao
IS, Beijing, People's Republic of China
Y. He, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China
C. Li, Q. Qin, Y.L. Zhao
IHEP, Beijing, People's Republic of China

Large-scale particle tracking is important for precise design and optimization of the linear accelerator. In this paper a parallel software recently developed for beam dynamics simulation has been benchmarked. The software is based on Particle-In-Cell method, and calculates space charge field by an efficient three-dimension parallel fast Fourier transform method. It uses domain decomposition and MPI library for parallelization. The characteristics of this software are optimized software structure and suitable for modern supercomputers. Several standard accelerating devices have been used to compare the simulation results with other beam dynamics software. They have been run on several different platforms, such as INSPUR cluster at RDCPS, and SHENGTENG7000 at IMPCAS. At first, some simulation results for RFQ with large number of particles will be shown.

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MOPWA072

Emittance Exchange Beam Line Design In THU Accelerator Lab

emittance, quadrupole, cavity, electron

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, electron, 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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MOPJE006

Electron Gun Longitudinal Jitter: Simulation and Analysis

gun, electron, timing, linac

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

electron, linac, 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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MOPJE017

Error Analysis and Correction at the Main LEBT of RAON Heavy Ion Accelerator

ion, GUI, rfq, heavy-ion

314

H. Jin, I.S. Hong, H. Jang, J.-H. Jang
IBS, Daejeon, Republic of Korea

The main Low Energy Beam Transport (LEBT) section of Rare isotope Accelerator Of Newness (RAON) heavy ion accelerator is designed to transport the ion beams which are generated by Electron Cyclotron Resonance Ion Source (ECR-IS) to the Radio Frequency Quadrupole (RFQ). In the main LEBT, one or two beams are selected among a variety of ion beams to meet the beamline experiment requirements such as beam charge and current. In a uranium beam case, two charge-state, 33+ and 34+, beams are chosen and transported to the RFQ. For transportation of two charge-state beams, beams can be seriously affected by dipole kick or unexpected dispersion caused by magnet errors. These effects of magnet or cavity errors lead to beam loss at the main LEBT or RFQ. Therefore, the effect to the beam orbit and size should be identified and the research for reducing such effect should be required in the main LEBT. In this paper, we will examine the orbit distortion and beam size growth caused by magnet errors and discuss the correction of errors by using correctors and BPMs.

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MOPJE023

3D Computer Simulations of the Ultrarelativistic Beam Dynamics in Super Colliders

collider, focusing, experiment, plasma

326

M.A. Boronina, V.A. Vshivkov
ICM&MG SB RAS, Novosibirsk, Russia
G. Dudnikova
ICT SB RAS, Novosibirsk, Russia

Funding: The work is supported by RFBR Grants 14-01-31088, 14-01-00392, 14-07-00241.
The problem of numerical modeling of beam-beam interaction with high relativistic factor (~10⁴) is considered. We present 3D a self-consistent simulation model based on particle-in-cell method. The mixed Euler-Lagrangian decomposition is used in parallel algorithm for achieving good load balancing and reducing communication cost. Stable regimes of beam dynamics, depending on the beams configuration (beta-function, emittance, energy, currents and relative offset) can be found on the base of the model. In the calculations we used 10⁸ particles on the grid 100x100x100, the number of processors depends highly on the beam shape. The Lomonosov Super Computer and Siberian Supercomputer Centre cluster were used to perform the presented simulations.

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MOPJE026

Revision of the Impedance Model for the Interpretation of the Single Bunch Measurements at ALBA

impedance, vacuum, undulator, storage-ring

330

T.F.G. Günzel, U. Iriso
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Recent measurements showed that the ALBA transverse impedance model was able to explain 65% of the measured single bunch vertical detuning. * This report shows the revision of the impedance model developed to match latest single bunch measurements performed to evaluate the total effective machine impedance and impedance of specific elements, like in-vacuum undulators or a recently installed pinger magnet. The model improvement includes a better bunch length parameterisation, re-calculation of several vacuum chamber elements with Gdfidl, and inclusion of elements neglected so far in the impedance budget. We also show and discuss the computation of the resistive wall impedance using ImpedanceWake2D.
* T.Günzel, U.Iriso, F.Perez, E.Koukovini-Platia, G.Rumolo, "Analysis of the single bunch measurements at the ALBA Storage Ring", TUPRI052, proc. of IPAC14 (2014).

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MOPJE027

Beam-based Impedance Characterization of the ALBA Pinger Magnet

impedance, vacuum, injection, synchrotron

334

U. Iriso, T.F.G. Günzel
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
H. Bartosik, E. Koukovini-Platia, G. Rumolo
CERN, Geneva, Switzerland

The ALBA pinger magnet consists on two short kickers (for horizontal and vertical planes) installed in a single Titanium coated ceramic vacuum chamber. Single bunch measurements in the vertical plane were performed in the ALBA Synchrotron Light Source before and after the pinger installation, and by comparing the Transverse Mode Coupling Instability (TMCI) thresholds for zero chromaticity, we infer the pinger impedance and compare it with the model predictions. We also perform measurements for negative chromaticities and results are reported in this paper.

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MOPJE029

A Linear Accelerator Simulation Framework

framework, ground-motion, collider, lattice

341

J. Snuverink
JAI, Egham, Surrey, United Kingdom
N. Fuster-Martínez
IFIC, Valencia, Spain
J. Pfingstner
CERN, Geneva, Switzerland
J. Pfingstner
University of Oslo, Oslo, Norway

Many good tracking tools are available for simulations for linear accelerators. However, several simple tasks need to be performed repeatedly, like lattice definitions, beam setup, output storage, etc. In addition, complex simulations can become unmanageable quite easily. A high level layer would therefore be beneficial. We propose LinSim, a linear accelerator framework with the codes PLACET and Guinea-Pig. It provides a documented well-debugged high level layer of functionality. Users only need to provide the input settings and essential code and/or use some of the many implemented imperfections and algorithms. It can be especially useful for first-time users. Currently the following accelerators are implemented: ATF2, ILC, CLIC and FACET. This paper discusses the framework design and shows its strength in some condensed examples.

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MOPJE035

An Extended SPS Longitudinal Impedance Model

impedance, vacuum, kicker, resonance

360

J.V. Campelo, T. Argyropoulos, T. Bohl, F. Caspers, J. F. Esteban Müller, J.B. Ghini, A. Lasheen, D. Quartullo, B. Salvant, E.N. Shaposhnikova, C. Zannini
CERN, Geneva, Switzerland

Longitudinal multi-bunch instability in the CERN SPS with a very low intensity threshold is a serious limitation for the future doubling of bunch intensity required by Hi-Lumi LHC project. A complete and accurate impedance model is essential to understand the nature of this instability and to plan possible cures. This contribution describes in detail the current longitudinal impedance model of the SPS. Recently, the model was updated with new findings and includes now the impedance of accelerating cavities, kicker and septum magnets, beam position monitors, vacuum Flanges, shielded and unshielded pumping ports, electrostatic septa and resistive wall. Electromagnetic simulations and bench measurements were used to build the model. The contribution from each element is described and compared to the total machine impedance. Together with relevant beam measurements and simulations, the analysis of the different sources of impedance is used to identify the source of the longitudinal instability limiting the SPS performance so that the responsible elements can be acted upon.

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MOPJE036

Longitudinal Impedance Characterization of the CERN SPS Vacuum Flanges

impedance, resonance, vacuum, damping

363

J.V. Campelo
CERN, Geneva, Switzerland

This contribution describes the thorough studies carried out to characterize the longitudinal impedance of the CERN SPS vacuum flanges, which are believed to be the main source of LHC beam instability. Around 500 high-impedance flanges of 8 different types have been identified. Three factors play an important role in the characterization of these flanges: the type of vacuum chambers that the flange interconnects, whether or not both sides are electrically isolated (by means of an enamel coating) and, finally, the presence of damping resistors which damp high-Q resonances. Not only, full-wave electromagnetic field simulations, but also RF measurements have been used to evaluate the impedance of these elements. The R/Q of the relevant resonances was measured using the well-known bead-pull technique. In particular, a subset of around 150 flanges has been found to be the source of a high-impedance resonance at 1.4 GHz, also observed in beam measurements. Guidelines on how to reduce the impedance of these elements are also presented.

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MOPJE038

Impedance Studies of the LHC Injection Kicker Magnets for HL-LHC

impedance, coupling, kicker, injection

370

H.A. Day, M.J. Barnes, L.M.C. Feliciano
CERN, Geneva, Switzerland

The LHC injection kicker magnets (MKIs) experienced strong heating during the first operational run, identified as being caused by power loss due to wakefields induced by stored beam. Studies of the beam coupling impedance of the beam screen, a series of conductors embedded in a ceramic tube placed in the ferrite yoke to screen the ferrite from the beam, resulted in new design offering improved screening: this is predicted to reduce the heating to acceptable levels for operation with 25ns beam during Run 2 of the LHC. However higher beam intensities proposed for HL-LHC operation are predicted to again cause strong heating to occur. Further studies have been carried out to reduce the beam induced power loss by optimising the beam screen design, some key results and findings of which are presented here.

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MOPJE039

Generalised Truncated Power Series Algebra for Fast Particle Accelerator Transport Maps

operation, optics, lattice

374

L. Deniau, C.I. Tomoiagă
CERN, Geneva, Switzerland

New Generalised Truncated Power Series Algebra (TPSA) has been developed for extending, simplifying and optimising the transport maps used by particle accelerator simulation codes. TPSA are intensively used in optics code to describe transport maps of the elements constituting the particle accelerator to any order. Generalised TPSA extend the degrees to inhomogeneous ones, where separate degrees can be specified for each variables and constrained by two total orders, one for canonical variables and one for ordinary variables. This allows to track inhomogeneous planes of the 6D phase space with many extra variables. A complete set of new formulas and data structures have been derived to address the problem of memory consumption required for efficient computation of high order TPSA, including generalised indexing, multiplication and composition of inhomogeneous multivariate polynomials. The implementation has been benchmarked against well established libraries for the common subset with TPSA, and outperforms all of them for supported differential algebra operators on low and high orders, and high number of variables.

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MOPJE042

Longitudinal Injection Schemes For the CERN PS Booster at 160 MeV Including Space Charge Effects

space-charge, injection, linac, emittance

378

V. Forte, E. Benedetto, A.M. Lombardi, D. Quartullo
CERN, Geneva, Switzerland

In the frame of the LHC Injectors Upgrade project, the CERN PS Booster will be equipped with a H⁻ injection system at 160 MeV to tailor the initial transverse and longitudinal profiles. We are here reviewing the different multi-turn longitudinal injection schemes, from the beam dynamics point of view, taking into account the needs of the large variety of the PSB users, spanning in intensity from 5·10⁹ to about 1.6·10¹³ protons per bunch. The baseline of the longitudinal injection has always been the longitudinal stacking with central energy modulation: this scheme has the advantage of filling uniformly the RF bucket and mitigate transverse space charge, but it requires at least 40 turns of injection. A simpler injection protocol without energy modulation is here analyzed in detail to find the optimum initial conditions in terms of bucket filling and reduction of transverse and longitudinal space charge effects, with the advantage of minimizing the number of turns for the LHC beams. Simulations with space charge of the longitudinal injection process from different Linac4 trains are presented to fix possible longitudinal injection scenarios during the future commissioning and operation with Linac4.

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MOPJE043

Design and Optimization of Electrostatic Deflectors for ELENA

focusing, vacuum, antiproton, alignment

382

D. Barna
University of Tokyo, Tokyo, Japan
W. Bartmann, M.A. Fraser, R. Ostojić
CERN, Geneva, Switzerland

The ELENA ring will decelerate the antiprotons ejected from the Antiproton Decelerator (AD) at 5.3 MeV down to 100 keV kinetic energy. The slow antiprotons will be delivered to experiments using electrostatic beamlines, consisting of quadrupoles, correctors and deflectors. An extensive simulation study was carried out to find solutions to minimize the aberrations of the deflectors. These solutions will be presented together with the actual design of these devices.

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MOPJE044

Beam Dynamics Studies of the ELENA Electrostatic Transfer Lines

experiment, quadrupole, antiproton, optics

385

M.A. Fraser, W. Bartmann, R. Ostojić
CERN, Geneva, Switzerland
D. Barna
University of Tokyo, Tokyo, Japan

The low-energy ELENA ring at the Antiproton Decelerator (AD) facility at CERN will lower the kinetic energy of antiproton beams from 5.3 MeV to 100 keV, significantly increasing the antiproton trapping efficiency at the experiments. The antiprotons from ELENA will be distributed to two experimental areas housing several different experiments through a system of electrostatic transfer lines totalling 90 m in length. A significant optimisation of the electrostatic optical elements (deflectors, quadrupoles, and correctors) has been carried out to improve the beam quality delivered to the experiments and facilitate installation of the beam lines into the AD hall. A general overview of the beam optics is presented, including end-to-end particle tracking and error studies from the extraction point in the ELENA ring to the experiments.

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MOPJE045

Fixed Points in Presence of Space Charge in Circular Particle Accelerators

space-charge, vacuum, extraction, resonance

389

M. Giovannozzi, S.S. Gilardoni, A. Huschauer
CERN, Geneva, Switzerland
S. Machida, C.R. Prior, S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

Recent measurements performed in the framework of the multi-turn extraction (MTE) studies showed a dependence of the position of beamlets obtained by crossing a stable transverse resonance on the total beam intensity. This novel observation has triggered a number of studies aiming at understanding the source of the observed effect. In this paper the results of numerical simulations performed in different conditions are discussed in detail.

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MOPJE048

Electron-Cloud Studies for Transversely Split Beams

electron, resonance, 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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MOPJE049

Benchmarking the CERN-SPS Transverse Impedance Model with Measured Headtail Growth Rates

impedance, kicker, optics, vacuum

402

C. Zannini, H. Bartosik, G. Iadarola, G. Rumolo, B. Salvant
CERN, Geneva, Switzerland

The latest SPS transverse impedance model includes kicker magnets, wall impedance, transition pieces (e.g. flanges and vacuum chamber discontinuities), beam position monitors and RF cavities. The model has already been successfully benchmarked against coherent tune shift and transverse mode coupling instability measurements. In this paper we present measurements of the headtail growth rates for a wide range of negative chromaticities and for two different configurations of machine optics (nominal and low gamma transition). The measurement results are compared with HEADTAIL simulations using the wake fields obtained from the SPS transverse impedance model.

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MOPJE050

Transverse Impedance Model of the CERN-PSB

impedance, space-charge, kicker, vacuum

406

C. Zannini, G. Iadarola, K.S.B. Li, T.L. Rijoff, G. Rumolo
CERN, Geneva, Switzerland
B. Jones
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
T.L. Rijoff
TU Darmstadt, Darmstadt, Germany

In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices before installation in the machine. This paper describes the PSB impedance model which includes resistive wall, indirect space charge, flanges, step transitions, ejection kicker including cables, injection kickers and cavities. Each impedance contribution has been computed for different energies in the PSB cycle. Measurements of the coherent tune shifts have been performed and compared to calculations based on the impedance model.

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MOPJE051

Effect of Electron Cloud in Quadrupoles on Beam Instability

quadrupole, electron, dipole, 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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MOPJE052

Observations of an Anomalous Octupolar Resonance in the LHC

resonance, dipole, betatron, hadron

412

F.S. Carlier, J.M. Coello de Portugal, A. Langner, E.H. Maclean, T. Persson, R. Tomás, R. Westenberger
CERN, Geneva, Switzerland

While linear LHC dynamics is mostly understood and under control, non-linear beam dynamics will play an increasingly important role in the challenging regimes of future LHC operation. In 2012, turn-by-turn measurements of large betatron excitations of LHC Beam 2 at injection energy were carried out. These measurements revealed an unexpectedly large spectral line in the horizontal motion with frequency Qx+2Qy. Detailed analyses and simulations are presented to unveil the nature of this spectral line.

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MOPJE054

Developments of the Segment-by-Segment Technique for Optics Corrections in the LHC

optics, coupling, betatron, quadrupole

419

A. Langner, J.M. Coello de Portugal, P.K. Skowroński, R. Tomás
CERN, Geneva, Switzerland

Optics correction algorithms will become even more critical for the operation of the LHC at 6.5 TeV. For the computation of local corrections the segment-by-segment technique is used. We present improvements to this technique and an advanced error analysis, which increase the sensitivity for finding local corrections. Furthermore, we will investigate limitations of this method for lower beta-star optics as they will be used in the high-luminosity LHC (HL-LHC) upgrade.

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MOPJE056

OMC Software Improvements in 2014

software, optics, GUI, operation

426

J.M. Coello de Portugal, F.S. Carlier, A. Langner, T. Persson, P.K. Skowroński, R. Tomás
CERN, Geneva, Switzerland

We present the LHC Optics Measurement and Corrections (OMC) software developments done during 2014 on stability, performance and usability. This software is used to analyze turn-by-turn data and compute optics corrections to get the best performance of the LHC. The main developments have been an automatic local correction script to get faster and more accurate corrections in the interaction regions, a self contained test for the whole software package to avoid mistakes during the software development and the improvements in the software quality and efficiency of the Segment by Segment technique script. We also present a study of the code quality in its current status.

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MOPJE064

Beam Impedance Optimization of the TOTEM Roman Pots

impedance, detector, cavity, vacuum

452

N. Minafra
CERN, Geneva, Switzerland

The TOTEM experiment has been designed to measure the total proton-proton cross section and to study elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots (RP), special beam pipe insertions, to move silicon detectors close to the beams to detect particles very near the beam axis. In the first period of running of the LHC no problems were detected with retracted Roman Pots and during insertions in special runs; however, during close insertions to highest intensity beam, impedance heating has been observed. After the LS1 the LHC beam current will increase and the equipment that can interact with the beam needed to be optimized. A new RP, optimized to minimize the beam coupling, has been designed with the help of CST Particle Studio; a prototype has been used to test the simulation results in the laboratory with wire and probe measurements. Furthermore, in both the old and the new RPs, new ferrites have been installed. The new ferrite material has a higher Curie temperature than the one used before LS1 and a thermal treatment at 1000°C has been applied to reduce the out-gassing.

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MOPJE065

Contribution of Optical Aberrations to Spot-size Increase with Bunch Intensity at ATF2

emittance, damping, optics, extraction

455

M. Patecki, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
M. Patecki
Warsaw University of Technology, Warsaw, Poland
G.R. White
SLAC, Menlo Park, California, USA

A primary goal of ATF2 (Accelerator Test Facility) is to demonstrate a low vertical beam size at the interaction point (IP) of about 37 nm. Measurements over the past years indicate that the ATF2 vertical beam size strongly rises with bunch intensity. Several different origins of this increase are considered, e.g. wakefields occurring between the ATF damping ring and the IP, and/or intrabeam scattering (IBS) causing the increase of transverse emittances and energy spread in the damping ring with the increase of the bunch intensity. In this paper we address the second possibility. Past measurements and simulations of the IBS effects in the ATF are used to model the intensity-dependent initial emittances and energy spread at the entrance of the final focus. Particle tracking simulations predict the IP vertical beam size growth expected from the known optical aberrations for initial beam parameters corresponding to varying bunch intensities. Comparing simulation results with emittance measurements at different locations allows us to draw some conclusions about the impact of IBS in the damping ring on the IP spot size, and about possible single-bunch wakefields in the ATF2.

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MOPJE067

Applications of PLACET2 to the CTF3 Combiner Ring

dipole, quadrupole, optics, wiggler

462

D. Pellegrini, R. Corsini, D. Gamba, A. Latina
CERN, Geneva, Switzerland

The CTF3 Combiner Ring (CR) is an isochronous ring that employs RF-injection to combine multiple bunch trains (up to five) into a single one with higher bunch frequency. The length of the CR plays a critical role in obtaining the correct structure of the recombined train. PLACET2: the new recirculating version of the code PLACET is particularly suited to simulate the operational scenario. In order to validate this code, three different case studies have been considered: ring-length variations due to energy detuning, fast-beam decoherence due to uncorrected chromatic effects and vertical instabilities due to bunch-to-bunch wakefield effects. The first two effects have been measured during the last run and the predictions have been validated. The instability has been compared with previous studies. The results are presented and discussed.

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MOPJE068

PLACET2: A Novel Code for Beam Dynamics in Recirculating Machines

linac, dipole, lattice, operation

465

D. Pellegrini, A. Latina, D. Schulte
CERN, Geneva, Switzerland

Efforts have been taken to enable the simulation of recirculating machines in PLACET. The new version, PLACET2, allows handling multiple interconnected beamlines in order to obtain a realistic model of a machine. Two new elements, injectors and dumps, have been introduced and are active components of any working machine. Trains of bunches are routed through beamlines and tracked simultaneously in a parallel manner. Tracking through time-dependent elements is possible, and care is made to preserve the correct time-structure of the beam in case of beam recombination. This allows straightforward computations of multi-bunch effects arising with high-charge and shortly spaced bunch trains, even with variable train structure. The main features of the code are presented together with its working principles and its key ideas. Two case studies are introduced: LHeC and the CTF3 combiner ring.

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MOPJE069

General Functionality for Turn-Dependent Element Properties in SixTrack

cavity, HOM, collimation, optics

468

K.N. Sjobak, H. Burkhardt, R. De Maria, A. Mereghetti, A. Santamaría García
CERN, Geneva, Switzerland

In order to facilitate studies of how dynamically changing element attributes affect the dynamics of the beam and beam losses, the functionality for dynamic kicks (DYNK) of SixTrack has been significantly extended. This functionality can be used for the simulation of dynamic scenarios, such as when crab cavities are switched on, orbit bumps are applied, optics are changed, or failures occur. The functionality has been extended with a more general and flexible implementation, such that arbitrary time-dependent functions can be defined and applied to different attributes of families or individual elements, directly from the user input files. This removes the need for source code manipulation, and it is compatible with LHC@Home which offers substantial computing resources from volunteers. In this paper, the functionality and implementation of DYNK is discussed, along with examples of application to the HL-LHC crab cavities.

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MOPJE075

Tracking Through Analytic Quadrupole Fringe Fields With GPT

quadrupole, space-charge, interface, multipole

489

S.B. van der Geer, M.J. de Loos
Pulsar Physics, Eindhoven, The Netherlands
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

In the early design stages it is customary to work with a highly simplified analytic model to describe the beam line. Dipoles and quadrupoles are often based on hard-edged approximations. This is not only unrealistic, it also significantly slows down time-domain spacecharge tracking codes such as the General Particle Tracer (GPT) code. The underlying reason for the poor performance is that despite the fact that the simple hard-edged field equations are fast to evaluate, they force the integration process to use excessively small step sizes near the fields discontinuities in order to achieve the desired accuracy. In other worlds, the apparently simple equations turn out to be the most difficult ones to evaluate numerically. An obvious solution is to switch to field-maps, but this is not practical in the early design stages. In this contribution we show a new solution implemented in the GPT code based on analytical expressions for the fringes where the transverse size of the magnet is properly taken into account. In addition to producing more realistic results, the smooth fields increase tracking speed by over an order of magnitude for typical test cases.

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MOPJE077

Progress on Simulation of Fixed Field Alternating Gradient Accelerators

closed-orbit, betatron, experiment, acceleration

495

S.L. Sheehy
JAI, Oxford, United Kingdom
A. Adelmann
PSI, Villigen PSI, Switzerland
M. Haj Tahar, F. Méot
BNL, Upton, Long Island, New York, USA
Y. Ishi, Y. Kuriyama, Y. Mori, M. Sakamoto, T. Uesugi
Kyoto University, Research Reactor Institute, Osaka, Japan
D.J. Kelliher, S. Machida, C.R. Prior, C.T. Rogers
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

Fixed Field Alternating Gradient accelerators have been realised in recent decades thanks partly to computational power, enabling detailed design and simulation prior to construction. We review the specific challenges of these machines and the range of different codes used to model them including ZGOUBI, OPAL and a number of in-house codes from different institutes. The current status of benchmarking between codes is presented and compared to the results of recent characterisation experiments with a 150 MeV FFAG at KURRI in Japan. Finally, we outline plans toward ever more realistic simulations including space charge, material interactions and more detailed models of various components.

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MOPJE078

Beam Delivery Simulation - Recent Developments and Optimization

collider, background, toolkit, linear-collider

499

J. Snuverink, S.T. Boogert, H. Garcia Morales, S.M. Gibson, R. Kwee-Hinzmann, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
L.C. Deacon
UCL, London, United Kingdom

Funding: Research supported by FP7 HiLumi LHC - grant agreement 284404 and by the STFC via the JAI3 grant
Beam Delivery Simulation (BDSIM) is a particle tracking code that simulates the passage of particles through both the magnetic accelerator lattice as well as their interaction with the material of the accelerator itself. The Geant4 toolkit is used to give a full range of physics processes needed to simulate both the interaction of primary particles and the production and subsequent propagation of secondaries. BDSIM has already been used to simulate linear accelerators such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC), but it has recently been adapted to simulate circular accelerators as well, producing loss maps for the Large Hadron Collider (LHC). In this paper the most recent developments, which extend BDSIM's functionality as well as improve its efficiency are presented. Improvement and refactorisation of the tracking algorithms are presented alongside improved automatic geometry construction for increased particle tracking speed.

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MOPJE084

Particle-in-cell Simulations of a Plasma Lens at Daresbury Laboratory

plasma, focusing, emittance, experiment

518

K. Hanahoe, O. Mete, G.X. Xia
UMAN, Manchester, United Kingdom
D. Angal-Kalinin, J.K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.D.A. Smith
TXUK, Warrington, United Kingdom

Feasibility of a focusing element using the transverse fields provided by a plasma cell was studied numerically. In this paper, an experimental set up is proposed for various beam parameters available from the VELA and CLARA beam lines at Daresbury Laboratory. 2D simulation results from VSim, and expected results from planned measurement stations are presented. Field properties and the advantages and disadvantages of such an instrument compared to conventional focusing elements are discussed.

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MOPMA001

Comparison of Measurements and Simulations for Single Bunch Instabilities at Diamond

impedance, wakefield, radiation, synchrotron

521

M. Atay, R. Bartolini
JAI, Oxford, United Kingdom
R. Bartolini, R.T. Fielder, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

The single bunch dynamics in the Diamond storage ring has been analysed with a multiparticle tracking code and compared with the results of a wealth of diagnostics, including streak camera, Schottky diodes and FTIR spectra. The interplay of various wakefield sources has been studied and it has been found that the THz spectrum can be reproduced in many cases with simple impedance models, both below and above the bursting threshold.

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MOPMA004

Numerical Optimization of Accelerators within oPAC

network, lattice, controls, quadrupole

533

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

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.
Powerful simulation tools are required for every accelerator and light source to study the motion of charged particles through electromagnetic fields during the accelerator design process, to optimize the performance of machine diagnostics and to assess beam stability and non-linear effects. The Optimization of Particle Accelerators (oPAC) Project is funded by the EU within the 7th Framework Programme and currently supports 23 Fellows that are based at institutions across Europe. This large network carries out R&D that closely links beam physics studies with the development of diagnostics and beyond state-of-the-art simulation tools. This contribution presents selected research outcomes from oPAC, including the numerical optimization of beam loss monitor locations along the European Spallation Source’s 5 MW proton linac, results from tracking studies for the LHeC lattice that allow beam stability to be assessed, and multi-objective optimization of the linear and non-linear beam dynamics of the synchrotron SOLEIL. In addition, an overview of recent and future oPAC events is also given.

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MOPMA007

Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade

cavity, feedback, timing, impedance

543

M. Borland, T.G. Berenc, R.R. Lindberg, A. Xiao
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.

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MOPMA008

Simulation of Gas-Scattering Lifetime using Position- and Species-Dependent Pressure and Aperture Profiles

scattering, vacuum, storage-ring, photon

546

M. Borland, J.A. Carter, H. Cease, B.K. Stillwell
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
When computing gas-scattering lifetime for storage rings, it is common to use the average pressure, even though it is known that the pressure varies with location in the ring and varies differently for different gas species. In addition, other simplifications are commonly made, such as assuming that the apertures in the horizontal and vertical planes are independent and assuming that the momentum acceptance can be characterized by a single value. In this paper, we describe computation of the elastic- and bremsstrahlung-scattering lifetimes that includes species-specific gas pressure profiles computed with VACCALC and MOLFLOW. In addition, the computations make use of the detailed shape of the dynamic acceptance and the position-dependent momentum acceptance. Comparisons are made to simpler methods for the Advanced Photon Source storage ring and the multi-bend achromat upgrade lattice.

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MOPMA009

Improvements in Modeling of Collective Effects in ELEGANT

cavity, collective-effects, lattice, impedance

549

M. Borland, R.R. Lindberg, A. Xiao
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.

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MOPMA010

Commissioning Simulations for the APS Upgrade Lattice

lattice, coupling, quadrupole, closed-orbit

553

V. Sajaev, M. Borland
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A hybrid seven-bend-achromat lattice has been proposed for the APS upgrade that will feature very strong focusing elements and relatively small vacuum chamber. Achieving design lattice parameters during commissioning will need to be accomplished in a short period of time to minimize dark time for APS users. We describe here start-to-end simulation of the machine commissioning beginning from first-turn trajectory correction, performing orbit and lattice correction, and finally evaluating nonlinear performance of the corrected lattice in terms of dynamic aperture and lifetime.

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MOPMA012

Intra-Beam and Touschek Scattering Computations for Beam with Non-Gaussian Longitudinal Distributions

scattering, emittance, distributed, lattice

559

A. Xiao, M. Borland
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Both intra-beam scattering (IBS) and the Touschek effect become prominent for multi-bend-achromat- (MBA-) based ultra-low-emittance storage rings. To mitigate the transverse emittance degradation and obtain a reasonably long beam lifetime, a higher harmonic rf cavity (HHC) is often proposed to lengthen the bunch. The use of such a cavity results in a non-gaussian longitudinal distribution. However, common methods for computing IBS and Touschek scattering assume Gaussian distributions. Modifications have been made to several simulation codes that are part of the {\tt elegant} toolkit to allow these computations for arbitrary longitudinal distributions. After describing these modifications, we review the results of detailed simulations for the proposed hybrid seven-bend-achromat (H7BA) upgrade lattice for the Advanced Photon Source.

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MOPMA015

Applications of an MPI Enhanced Simulated Annealing Algorithm on nuSTORM and 6D Muon Cooling

sextupole, lattice, storage-ring, emittance

568

A. Liu
Fermilab, Batavia, Illinois, USA

The nuSTORM decay ring is a compact racetrack storage ring with a circumference ∼ 480 m using large aperture (∅=60 cm) magnets. The design goal of the ring is to achieve a momentum acceptance of 3.8±10\% GeV/c and a phase space acceptance of 2000 μm·rad. The design has many challenges because the acceptance will be affected by many nonlinearity terms with large particle emittance and/or large momentum offset. In this paper, we present the application of a meta-heuristic optimization algorithm to the sextupole correction in the ring. The algorithm is capable of finding a balanced compromise among corrections of the nonlinearity terms, and finding the largest acceptance. This technique can be applied to the design of similar storage rings that store beams with wide transverse phase space and momentum spectra. We also present the recent study on the application of this algorithm to a part of the 6D muon cooling channel. The technique and the cooling concept will be applied to design a cooling channel for the extracted muon beam at nuSTORM in the future study.

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MOPMA017

Numerical simulations of transverse modes in Gaussian bunches with space charge

space-charge, damping, lattice, synchrotron

575

A. Macridin, J.F. Amundson, E.G. Stern
Fermilab, Batavia, Illinois, USA

The transverse modes and the intrinsic Landau damping in Gaussian bunched beams with space charge are numerically investigated. The evolution of the phase space density is calculated with the Synergia accelerator modeling package and analyzed with Dynamic Mode Decomposition (DMD) method. DMD is a relatively new technique used to calculate mode dynamics in both linear and nonlinear systems. The properties of the first three space charge modes, including their shape, damping rates and tune shifts are calculated over the entire range of the space charge interaction.

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MOPMA018

Simulation of Multipacting in SC Low Beta Cavities at FNAL

cavity, niobium, operation, linac

579

G.V. Romanov, P. Berrutti, T.N. Khabiboulline
Fermilab, Batavia, Illinois, USA

Proton Improvement Plan-II at Fermilab is a plan for improvements to the accelerator complex aimed at providing a beam power capability of at least 1 MW on target at the initiation of LBNE (Long Base Neutrino Experiment) operations. The central element of the PIP-II is a new 800 MeV superconducting linac, injecting into the existing Booster. Multipacting affects superconducting RF cavities in the entire range from high energy elliptical cavities to coaxial resonators for low-beta applications. This work is focused on multipacting study in the low-beta 325 MHz spoke cavities; namely SSR1 and SSR2, which are especially susceptible to the phenomena. The extensive simulations of multipacting in the cavities with updated material properties and comparison of the results with experimental data helped us to improve overall reliability and accuracy of these simulations. Our practical approach to the simulations is described in details. For SSR2, which has a high multipacting barrier right at the operating power level, some changes of the cavity shape to mitigate this harmful phenomenon are proposed.

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MOPMA019

Simulations of the Fermilab Recycler for Losses and Collimation

space-charge, collimation, proton, target

582

E.G. Stern, R. Ainsworth, J.F. Amundson, B.C. Brown
Fermilab, Batavia, Illinois, USA

Fermilab has recently completed an upgrade to the com- plex with the goal of delivering 700 kW of beam power as 120 GeV protons to the NuMI target. A major part of boost- ing beam power is to shorten the beam cycle by accumulating up to 12 bunches of 0.5 × 10 11 protons in the Recycler ring through slip-stacking during the Main Injector ramp. This introduces much higher intensities into the Recycler than it has had before. Meeting radiation safety requirements with high intensity operations requires understanding the ef- fects of space charge induced tune spreads and resulting halo formation, and aperture restrictions in the real machine to de- velop a collimation strategy. We report on initial simulations of slip-stacking in the Recycler performed with Synergia.

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MOPMA024

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

emittance, electron, 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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MOPMA025

CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs

impedance, dipole, lattice, damping

596

C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
D. Douglas, R. Li, C. Tennant
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.

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MOPMA029

Experiences Simulating Nonlinear Integrable Optics

lattice, optics, diagnostics, emittance

611

S.D. Webb, D.L. Bruhwiler
RadiaSoft LLC, Boulder, Colorado, USA
V.V. Danilov
ORNL, Oak Ridge, Tennessee, USA
R.A. Kishek
UMD, College Park, Maryland, USA
S. Nagaitsev, A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011340.
With increasing interest in the nonlinear integrable optics, it is important that early experiences with simulating the lattices be shared to save time and point out potential difficulties in the simulations. We present here some details of simulating the nonlinear integrable lattices. We discuss correctly implementing and testing the elliptic element kicks, and the limits of the thin lens approximation. We also discuss generating a properly matched bunch in the transverse phase space, and how to analyze the resulting computational data from simulations.

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MOPMA030

Multisymplectic Integrators for Accelerator Tracking Codes

space-charge, plasma, storage-ring, DTL

614

S.D. Webb, D.L. Bruhwiler
RadiaSoft LLC, Boulder, Colorado, USA

It has been long understood that long time single particle tracking requires symplectic integrators to keep the simulations stable. In contrast, space charge has been added to tracking codes without much regard for this. Indeed, multisymplectic integrators are a promising new field which may lead to more stable and accurate simulations of intense beams. We present here the basic concept, through a spectral electrostatic field solve which is suitable for adapting into existing tracking codes. We also discuss the limitations of current algorithms, and suggest directions for future development for the next generations of high intensity accelerators.

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MOPMA031

Simulations of Diamond Detectors with Schottky Contacts

electron, 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

electron, 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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MOPMA035

Current Status of the GPU-accelerated ELEGANT

GPU, acceleration, collective-effects, lattice

623

I.V. Pogorelov, J.R. King
Tech-X, Boulder, Colorado, USA
K.M. Amyx
Sierra Nevada Corporation, Centennial, USA
M. Borland, R. Soliday
ANL, Argonne, Ilinois, USA

Funding: Work supported by the DOE Office of Science, Office of BES grant No. DE-SC0004585, and by Tech-X Corporation. This research used resources of the OLCF, supported under Contract DE-AC05-00OR22725.
Efficient implementation of general-purpose particle tracking on GPUs can bring significant performance benefits to large-scale tracking simulations and direct (tracking-based) accelerator optimization techniques. This presentation is an update on the current status of our work on accelerating Argonne National Lab’s particle accelerator simulation code ELEGANT [*] using CUDA-enabled GPU. We summarize the performance of beamline elements ported to GPU, and discuss optimization techniques for some important collective effects kernels. We also outline briefly our testing and code validation infrastructure within ELEGANT and present the latest results of scaling studies with realistic lattices of the GPU-accelerated version of the code.
* M. Borland, ‘‘elegant: A Flexible SDDS-compliant Code for Accelerator Simulation", APS LS-287, September 2000

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MOPMA037

Electron Cloud Buildup and Dissipation Models For PIP-II

electron, 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

electron, 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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MOPMA044

Barrier Shock Compression with Longitudinal Space Charge

space-charge, emittance, electron, 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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MOPMA045

Conceptual Difficulties of a Thermodynamics Description of Charged-Particle Beams

emittance, space-charge, focusing, beam-transport

649

S. Bernal
UMD, College Park, Maryland, USA

Funding: This work is funded by the US Dept. of Energy
We review the existing phenomenological theories of emittance growth with and without entropy terms and re-examine the condition for thermal equipartitioning in an unbunched charged-particle beam. The model incorporates linear space charge and a uniform-focusing lattice. Because of non-extensitivity of the transverse ("thermal") energy and the absence of a classical heat bath, we conclude that a rigorous classical thermodynamics treatment of charged-particle beams is not possible. In particular, the postulated relationships between the rms emittance and temperature and entropy must be qualified.

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MOPMA050

Smooth Fast Multipole Method for Space Charge Tracking: An Alternate to Particle-In-Cell

multipole, space-charge, framework, emittance

663

A.J. Gee, B. Erdelyi
Northern Illinois University, DeKalb, Illinois, USA
B. Erdelyi
ANL, Argonne, USA

The fast multipole method (FMM) algorithm was developed by Greengard and Rokhlin in 1987 *. As one of the top ten algorithms of the 20th century, it has been applied in a wide range of fields. The FMM complexity is O(N), where N is the number of articles, allowing for large-scale simulations. However, it includes all the two-body collisional forces, in contrast to other methods such as the popular particle in-cell (PIC) methods. While collisionality can be very important, many applications require only the mean field effects. PIC is frequently used in this regime. Due to recent concerns of unphysical effects of grids, interpolation and other approximations in PIC codes, an alternative based on different underlying assumptions would prove enlightening. For these cases, a smoothed or softened FMM using a Plummer-like smoothing parameter holds much promise. Unfortunately, the original FMM based on analytic expansions of the 1/r-like potentials does not allow for Plummer softening. We present our new soft-FMM employing differential algebras (DA) to obtain the modified expansions. We also compare the performance of the smoothed DA-FMM with examples from PIC simulations.
* L. Greengard and V. Rokhlin. “A fast algorithm for particle simulations".

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MOPMA051

Generation of Modulated Bunch Using a Masked Chicane for Beam-Driven Acceleration Experiments at ASTA

bunching, dipole, space-charge, emittance

666

Y.-M. Shin, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.R. Broemmelsiek, D.J. Crawford, A.H. Lumpkin
Fermilab, Batavia, Illinois, USA
A.T. Green
Northern Illinois Univerity, Dekalb, Illinois, USA

Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Longitudinal density modulations on electron beams can improve machine performance of beam-driven accelerators and FELs with resonance beam-wave coupling *. The sub-ps beam modulation has been studied with a masked chicane ** *** by the analytic model and simulations with the beam parameters of the Advanced Superconducting Test Accelerator (ASTA) in Fermilab. With the nominal 50 MeV chicane parameters and 3 ps bunch length, the analytic model showed that a slit-mask with slit period 900 um and aperture width 300 μm generates about 100-um modulation periodicity with 2.4% correlated energy spread. With the designed slit mask and a 3 ps bunch, particle-in-cell simulations (CST-PS), including nonlinear energy distributions, space charge force, and coherent synchrotron radiation (CSR) effect, also result in ~ 100 um of longitudinal modulation. The beam modulation has been extensively examined with three different beam conditions, 0.25, 1 , and 3.2 nC, by extended 3D tracking simulations (Elegant). The modulated bunch generation will be tested by a slit-mask installed at the chicane of the ASTA 50-MeV-injector beamline for beam-driven acceleration experiments.
* E. Kallos, Southern California 2008
** D. C. Nguyen, B. E. Carlston, NIMA 375, 597 (1996)
*** P. Muggli, V. Yakimenko, M. Babzien, E. Kallos, and K. P. Kusche, PRL 101, 054801 (2008)

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MOPMA052

Implementation of Quadrupole-scan Emittance Measurement at Fermilab's Advanced Superconducting Test Accelerator (ASTA)

emittance, quadrupole, controls, monitoring

669

A.T. Green
Northern Illinois Univerity, Dekalb, Illinois, USA
Y.-M. Shin
Fermilab, Batavia, Illinois, USA
Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Transverse-emittance measurements based on the quadrupole-scan technique * ** ***, have been widely used to characterize the beam phase-space parameters in linear accelerators. This paper discusses the implementation of the technique at the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. We plan on deploying a flexible implementation that permits an operator to select the quadrupole associated analysing screen to measure the beam emittance. Our implementation utilizes Python scripts combined with Fermilab’s control system ACNet and ELEGANT quadrupole-scan method at 50 MeV given the range of operating charge (20 pC to 3.2 nC) available at ASTA. Some preliminary measurements will also be presented.
* B.E. Carlsten, et al, Nucl. Instrum. Methods Phys. Res. Sect. A 331, 791 (1993)
** C. Eckman et al, IPAC 2012
*** K. Poorrezaei, et al, Phys. Rev. ST-AB 16, 082801 (2013)

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MOPMA054

Start-to-end Simulation of Free-electron Lasers

FEL, wiggler, linac, electron

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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MOPMA055

MuSim, a Graphical User Interface for Multiple Simulation Programs

interface, detector, storage-ring, target

678

T.J. Roberts
Muons, Inc, Illinois, USA
P.L. Gueye
Hampton University, Hampton, Virginia, USA

MuSim is a new user-friendly program designed to interface to many different particle simulation codes, regardless of their data formats or geometry descriptions. It presents the user with a compelling graphical user interface that includes a flexible 3-D view of the simulated world plus powerful editing and drag-and-drop capabilities. All aspects of the design can be parametrized so that parameter scans and optimizations are easy. It is simple to create plots and display events in the 3-D viewer (with a slider to vary the transparency of solids), allowing for an effortless comparison of different simulation codes. Simulation codes: G4beamline, MAD-X, and MCNP; more coming. Many accelerator design tools and beam optics codes were written long ago, with primitive user interfaces by today’s standards. MuSim is specifically designed to make it easy to interface to such codes, providing a common user experience for all, and permitting the construction and exploration of models with very little overhead. For today’s technology-driven students, graphical interfaces meet their expectations far better than text-based tools, and education in accelerator physics is one of our primary goals.

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MOPMA056

Measurement and Modeling of Single Bunch Wake Field Effects in CESR

emittance, impedance, wakefield, storage-ring

681

J.R. Calvey, M.G. Billing, W. Hartung, J.D. Perrin, D. L. Rubin, D. Sagan, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF PHY-1416318 and NSF DMR 1332208. This research used the National Energy Research Scientific Computing Center, which is supported by DOE Contract No. DE-AC02-05CH11231.
Short-range wake fields have been incorporated into a Bmad-based particle tracking code in order to assess their contribution to current-dependent emittance growth, tune shift, and single bunch instabilities. The wakes are computed for CESR vacuum components using the T3P modeling software. Simulation results are compared with measurements of bunch length, vertical beam size, and coherent tune shift. Additionally, we use insertable scrapers to vary the transverse wake and measure the effect on the beam. We show that a vertical emittance increase at high current may be due to a transverse monopole wake, originating in the lump pump slots throughout CESR.

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MOPMA057

Space Charge Neutralization of 750 keV Proton Beam in LANSCE Injector Line

emittance, space-charge, proton, beam-transport

685

Y.K. Batygin
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396
The 750-keV low-energy beam transport of the Los Alamos Neutron Science Center (LANSCE) linac consists of two independent beam lines for simultaneous injection of H⁺ and H⁻ beams into the linear accelerator. Space charge effects play an important role in the beam transport therein. A series of experiments were performed to determine the level of proton beam space charge neutralization by residual gas ionization, and time required for neutralization. Study was performed as emittance scans between pair of emittance measurement stations. The value of compensated space charge was determined through comparison of results of measurements and simulations using macroparticle method and envelope code. Obtained results provide new setup for beam tuning in transport beamline.

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MOPMA058

Effect of Spherical Aberration on Beam Emittance Growth

emittance, focusing, space-charge, proton

688

Y.K. Batygin
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396
Spherical aberration in axial-symmetric magnetic focusing lenses results in S-shape figure of beam emittance. Filamentation of beam emittance in phase space is a fundamental property of a beam affected by aberrations. Analytical expression for effective beam emittance growth due to spherical aberration as a function of lens aberraion coefficient, initial beam emittance, beam radius, and focal lens of the focusing lens is obtained. Analysis is extended for beam space charge aberrations. Analytical results are confirmed by numerical calculations.

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MOPMA059

Lorentz boosted frame simulation of Laser wakefield acceleration using hybrid Yee-fft solver in quasi-3d geometry

plasma, laser, wakefield, acceleration

691

P. Yu, A.W. Davidson, V.K. Decyk, W.B. Mori, A. Tableman, F.S. Tsung
UCLA, Los Angeles, California, USA
F. Fiuza, L.O. Silva, J. Vieira
IPFN, Lisbon, Portugal
R.A. Fonseca
ISCTE - IUL, Lisboa, Portugal
W. Lu, X.L. Xu
TUB, Beijing, People's Republic of China

We present results from a preliminary study on modeling Laser wakefield acceleration (LWFA) with OSIRIS in a Lorentz boosted frame using a quasi-3D algorithm. In the quasi-3D algorithm, the fields and currents are expanded into azimuthal harmonics and only a limited number of harmonics are kept. Field equations in (r,z) space are solved for a desired number of harmonics in φ. To suppress the numerical Cerenkov instability (NCI) that inevitably arises due to the relativistic plasma drift in the simulation, we use a hybrid Yee-FFT solver in which the field equations are solved in (k_z, r) space, where \hat{z} is the drifting direction. Preliminary results show that high fidelity LWFA boosted frame simulations can be carried out with no evidence of the NCI. Good agreement is found when comparing LWFA boosted frame simulations in the full 3D geometry against those in the quasi-3D geometry. In addition, we discuss how the moving window can be combined with the hybrid Yee-FFT solver to further speed up the simulation. The results indicate that unprecedented speed ups for LWFA simulations can be achieved when combining the Lorentz boosted frame technique, the quasi-3D algorithm, and a moving window.

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MOPMN002

Advances in Parallel Finite Element Code Suite ACE3P

cavity, radiation, SRF, electron

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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MOPMN008

Space Charge Studies in FFAG Using the Tracking Code Zgoubi

space-charge, emittance, betatron, damping

717

M. Haj Tahar, F. Méot, 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.
A method is implemented in Zgoubi that allows the computation of space charge effects in 2D distributions and with some restrictions in 3D distributions. It relies on decomposiing field maps or analytical elements into slices and applying a space charge kick to the particles. The aim of this study is to investigate the accuracy of this technique, its limitations/advantages by comparisons with other linear/nonlinear computation methods and codes, and to apply it to high power fixed field ring design studies.

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MOPMN009

Cross-platform and Cloud-based Access to Multiple Particle Accelerator Codes via Application Containers

Linux, radiation, software, FEL

720

D.L. Bruhwiler, G. Andonian, M.A. Harrison, S. Seung
RadiaBeam, Santa Monica, California, USA
D.L. Bruhwiler, R. Nagler, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA
P. Moeller
Bivio Software Inc., Boulder, USA
T.V. Shaftan
BNL, Upton, Long Island, New York, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0006284.
Particle accelerator and radiation modeling codes focus on specific problems, rely on complicated command-line interfaces, are sometimes limited to a small number of computing platforms, and can be difficult to install. There is also a growing need to use two or more codes together for end-to-end design or for complicated sub-systems. RadTrack is a lightweight cross-platform GUI for such codes, based on the Qt framework and PyQt bindings for Python. RadTrack is designed to support multiple codes, placing no burden on the corresponding development teams. Elegant and the Synchrotron Radiation Workshop (SRW) are supported now in a pre-beta stage, and support for GENESIS 1.3 is under development. These codes are being containerized via the open source Docker platform for use in the cloud. The open source Vagrant and Virtual Box are used for MacOS and Windows. We discuss RadTrack and our vision for cloud computing.

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MOPMN012

SPACE Code for Beam-Plasma Interaction

plasma, ion, electron, 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, cavity, electron

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, electron, 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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MOPMN021

NSLS-II Storage Ring BPM Button Development

vacuum, impedance, multipole, storage-ring

748

A. Blednykh, B. Bacha, G. Bassi, W.X. Cheng, C. Hetzel, B.N. Kosciuk, D. Padrazo, O. Singh
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract DE-AC02-98CH10886
The NSLS-II BPM Button design and its development process have been described. Subjects discussed include BPM Button impedance optimization, design and construction, production, BPM Button selection and a first temperature measurements at 200mA average current within 1200 bunches.

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MOPMN028

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

emittance, electron, dipole, 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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MOPHA007

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

electron, space-charge, detector, 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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MOPHA014

Magnetic Field Parametrization for Efficient Spin Tracking with POLE

lattice, resonance, closed-orbit, quadrupole

808

J.F. Schmidt, W. Hillert
ELSA, Bonn, Germany

Funding: BMBF
The new spin dynamics simulation suite pole is designed to perform systematic studies of beam depolarization in circular accelerators with short storage times or fast energy ramps. It is based on spin tracking using a Runge-Kutta algorithm with adaptive step width. pole can approximate the magnetic fields of the accelerator with a Fourier series to reduce computing time. Therefore, the magnetic field distribution is simplified with frequency filters by a C++ library before the spin tracking. The versatile library deals with import and export of lattices and particle trajectories from MAD-X and Elegant. The derived magnetic field distributions can be interpolated, Fourier transformed and accessed easily by applications. This contribution discusses advantages and disadvantages of the frquency filtering concept.

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MOPHA038

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

laser, wakefield, operation, electron

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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MOPHA054

Interaction Point Orbit Feedback System at SuperKEKB

feedback, luminosity, quadrupole, vacuum

921

Y. Funakoshi, H. Fukuma, T. Kawamoto, M. Masuzawa, T. Oki, S. Uehara, H. Yamaoka
KEK, Ibaraki, Japan
S.D. Anderson, S.M. Gierman, M. Kosovsky, J.T. Seeman, C.M. Spencer, M.K. Sullivan, O. Turgut, U. Wienands
SLAC, Menlo Park, California, USA
P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, C. Rimbault
LAL, Orsay, France

In order to maintain an optimum beam collision condition in a double ring collider such as SuperKEKB it is essential to have an orbit feedback system at the interaction point (IP). We have designed such a system based on experiences at KEKB and PEP-II. For the vertical offset and crossing angle, we will rely on the system based on the beam orbit measurement similar to that used at KEKB. For the horizontal offset, however, we will utilize the dithering system which was successfully used at PEP-II, because the horizontal beam-beam kick is very weak with the "nano-beam scheme". Some hardware devices have been already fabricated and others are in preparation. The present status of the development is reported.

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MOPHA058

Beam Based Gain Calibration for Beam Position Monitor at J-PARC Main Ring

operation, synchrotron, proton, closed-orbit

927

H. Kuboki, J. Takano, M. Tejima, T. Toyama
KEK, Ibaraki, Japan
S. Hatakeyama
JAEA/J-PARC, Tokai-mura, Japan

Funding: MEXT KAKENHI Grant Number 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled "Unification and Development of the Neutrino Science Frontier"
Beam Position Monitor (BPM) is one of the essential elements in a synchrotron facility. It provides the accurate beam positions, which are used to correct the closed orbit distortion. Each BPM is installed with the electronics which enable to acquire the data of the turn-by-turn beam positions. Here, we define the "gain" as the proportionality coefficient between the signal detected at the ADC and the ideal signal without any errors. The signal strength from a BPM electrode varies depending on 1) transmission characteristics of a long cable, 2) processing circuit, and 3) contact resistance at the connected parts. These are the origin of the gain deviations. In order to correct the deviations, a Beam Based Gain Calibration (BBGC) method has been proposed *. Development of a new method for adequate gain calibration is required because any calibration method for routine operation has not been established for BPMs with diagonal-cut electrodes used at J-PARC Main Ring. The results of analysis will be presented using the Total Least Square fitting as an adequate method for the BBGC with sufficient accuracy within 0.6% in one standard deviation.
* M. Tejima et al., DIPAC2011 (2011).

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MOPTY015

Beam Compression Dynamics and Associated Measurement Methods in Superconducting THz Source

controls, space-charge, gun, electron

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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MOPTY019

Precise Position Measurement by Analyzing the Correlation Between Electrodes of a Single Bpm

pick-up, hardware, synchrotron, impedance

975

Z.C. Chen
SSRF, Shanghai, People's Republic of China
L.W. Lai, Y.B. Leng, Y.B. Yan
SINAP, Shanghai, People's Republic of China

Beam position is one of the most important parameters in a particle accelerator. The more accurate and precise the measurement system is, the more features of the beam dynamics could be revealed. A method called model-independent analysis (MIA) takes advantage of multiple beam position monitors (BPM) on the storage ring to obtain the actual beam positions by removing the random noise of each BPM. Inspired by MIA, the original voltage waveforms obtained from the electrodes of a single BPM can also be decomposed to get the beam position information. This article discusses the results of the experiments and the evaluation of the performance of the BPM at the Shanghai Institute of Applied Physics.

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MOPTY021

Measurement of Clock Jitter in Beam Diagnostic System

diagnostics, beam-diagnostic, extraction, injection

981

Y. Yang, Y.B. Leng, Y.B. Yan
SSRF, Shanghai, People's Republic of China

Low clock jitter can improve the performance of beam diagnostic system. This paper presents a procedure for the direct measurement of low-level clock jitter. High resolution spectrum analyzer or broadband high sampling rate oscilloscope is not demanded by using this method. Simulation will be introduced.

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MOPTY033

Fast Kicker

kicker, impedance, vacuum, magnet-design

1001

V.V. Gambaryan, A.A. Starostenko
BINP SB RAS, Novosibirsk, Russia

Pulsed deflecting magnet project was worked out in BINP. The kicker design task is: impulsive force value is 1 mT*m, pulse edge is 5 ns, and impulse duration is about 200 ns. The unconventional approach to kicker design was offered. The possibility for set of wires using instead of plates using is considered. This approach allows us to reduce the effective plate surface. In this case we can decrease effects related to induced charges and currents. In the result of modelling optimal construction was developed. It includes 6 wires. The magnet aperture is about 5 cm. Calculated field rise time (about 1.5 ns) satisfies the conditions. Induced current effect reducing idea was confirmed. For configuration with 3 wires pair (with cross section of 2 mm) induced current in one wire is about 10% and in the wall is about 40%. However for design with plates current is about 40% and 20% respectively. Obtained magnet construction allows controlling of high field homogeneity by changing currents magnitudes in wires. In general we demonstrated the method of field optimization. Optimal kicker design was obtained. Wires using idea was substantiated.

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MOPTY047

ESS Cold LINAC BLM Locations Determination

detector, linac, quadrupole, proton

1039

M. Jarosz, A. Jansson, J.C. Kazantzidis, T.J. Shea, L. Tchelidze
ESS, Lund, Sweden

Funding: This project (oPAC) is funded by the European Union under contract PITN-GA-2011-289485.
The linear accelerator of ESS will produce a 5 MW proton beam. Beam of this power must be strictly monitored by a specialized Beam Loss Monitoring (BLM) System to detect any abnormal losses and to ensure that operational losses do not lead to excessive activation. A long series of beam loss simulations was performed using MARS Monte Carlo code system in order to optimize the number and setting mounting locations of the detectors for best coverage, distinguishability and sensitivity. Simulations anticipated multiple possible beam loss scenarios resulting in different loss patterns. The results of energy deposition in air in the linac tunnel in multiple locations were analysed in several different ways. Incorporated methods varied from simple brute force approach to more sophisticated singular value decomposition based algorithms, all resulting in detector layout proposals. Locations selected for BLMs were evaluated for all methods.

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MOPTY052

Experimental and Simulation Studies of Hydrodynamic Tunneling of Ultra-Relativistic Protons

target, proton, experiment, cavity

1048

F. Burkart, R. Schmidt, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
A.R. Piriz
Universidad de Castilla-La Mancha, Ciudad Real, Spain
A. Shutov
IPCP, Chernogolovka, Moscow region, Russia
N.A. Tahir
GSI, Darmstadt, Germany

The expected damage due to the release of the full LHC beam energy at a single aperture bottleneck has been studied. These studies have shown that the range of the 7 TeV LHC proton beam is significantly extended compared to that of a single proton due to hydrodynamic tunneling effect. For instance, it was evaluated that the protons and their showers will penetrate up to a length of 25 m in solid carbon compared to a static range of around 3 m. To check the validity of these simulations, beam- target heating experiments using the 440 GeV proton beam generated by the SPS were performed at the HiRadMat test facility at CERN *. Solid copper targets were facially irradiated by the beam and measurements confirmed hydrodynamic tunneling of the protons and their showers. Simulations have been done by running the energy deposition code FLUKA and the 2D hydrodynamic code, BIG2, iteratively. Very good agreement has been found between the simulations and the experimental results ** providing confidence in the validity of the studies for the LHC. This paper presents the simulation studies, the results of a benchmarking experiment, and the detailed target investigations.
* N.A. Tahir et al., Phys. Rev. Special Topics Accel. Beams 15 (2012) 051003.
** R. Schmidt et al., Phys. Plasmas 21 (2014) 080701.

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MOPTY053

Electromagnetic Design and Optimization of Directivity of Stripline Beam Position Monitors for the High Luminosity Large Hadron Collider

luminosity, impedance, hadron, collider

1051

D. Draskovic, C.B. Boccard, O.R. Jones, T. Lefèvre, M. Wendt
CERN, Geneva, Switzerland

This paper presents the preliminary electromagnetic design of a stripline Beam Position Monitor (BPM) for the High Luminosity program of the Large Hadron Collider (HL-LHC) at CERN. The design is fitted into a new octagonal shielded Beam Screen for the low-beta triplets and is optimized for high directivity. It also includes internal Tungsten absorbers, required to reduce the energy deposition in the superconducting magnets. The achieved broadband directivity in wakefield solver simulations presents significant improvement over the directivity of the current stripline BPMs installed in the LHC.

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MOPTY057

Feasibility Study of Monitoring the Population of the CERN-LHC Abort Gap with Diamond Based Particle Detectors

detector, beam-losses, monitoring, kicker

1065

O. Stein, F. Burkart, B. Dehning, R. Schmidt, C.B. Sørensen, D. Wollmann
CERN, Geneva, Switzerland

At the end of a physics fill and in case of a failure, the LHC beams must be extracted and transferred through a 750m long line to the beam dump block. During the rise of the extraction kickers to their full strength a particle-free abort gap, with a length of 3 us in the LHC filling pattern, is required to prevent beam losses that could lead to substantial quenching of magnets, with a risk of damage. Therefore the particle population in the abort gap, which is mainly due to un-bunched beam, is monitored. Above a certain threshold an active cleaning by excitation of betatron oscillations with the transverse feedback system is initiated. This paper describes a novel method of monitoring the abort gap population using diamond particle detectors for detecting the interactions of beam in the abort gap with neon gas, injected in the beam pipe. Two different layouts of the system and the expected interaction and detection rates are discussed.

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MOPWI012

Conceptual Design and Analysis of a Storage Ring Beam Position Monitor for the APS Upgrade

vacuum, operation, alignment, impedance

1170

B.K. Stillwell, R.M. Lill, R.R. Lindberg, M.M. O'Neill, B.G. Rocke, X. Sun
ANL, Argonne, Ilinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Created by UChicago Argonne, LLC, operator of Argonne National Laboratory, a U.S. Department of Energy Office of Science laboratory operated under Contract No. DE-AC02-06CH11357.
A conceptual design has been developed for a radio frequency (rf) pickup-type beam position monitor (BPM) for use in a multi-bend achromat (MBA) storage ring under consideration by the APS Upgrade project (APS-U). Beam feedback systems are expected to require fourteen rf BPMs per sector with exceptional sensitivity and mechanical stability. Simultaneously, BPM insertion length must be minimized to allow lattice designers the greatest freedom in selecting magnet lengths and locations. Envisioned is a conventional four probe arrangement integrated inside of a pair of rf-shielded bellows for mechanical isolation. Basic aspects of the design are presented along with the results of analyses which establish expected mechanical, electronic, and beam physics-related performance measures.

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MOPWI020

Development of Simple Tracking Libraries for ALS-U

lattice, Windows, framework, dynamic-aperture

1192

H. Nishimura, D. Robin, K. Song, C. Steier, C. Sun, W. Wan
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The conceptual lattice design study of a new diffraction-limited light source has become much more computer intensive than that for the 3rd-generation rings. We are in a process of upgrading our existing accelerator modeling and simulation libraries, Goemon* in C++ and a new version Tracy#**, to fulfil such new demand. The C++ version has been actively used on the ALS HPC cluster for multi-objective optimization (MOGA) to optimize the ALS lattice***, and recently for ALS-U****. This time, based on the current version in C#, we extracted its subset and ported it to C and C++. The routines are made thread-safe to enable OpenMP locally, and CPU-time profiling was extensively used to remove redundancies. The new refitting method of quad settings brought smooth switching from 5-dim to 6-dim. The data structure itself is simplified for the use on GPU that is based on our previous effort of tracking particles in GPU*****. Tracy# itself is also upgraded to cooperate with these C/C++ versions. Their use from Python will be also mentioned.
* H. Nishimura, PAC01, 3066-3068.
** H. Nishimura, ICAP09.
*** C. Sun, et. al.,PAC11, 793-795.
**** H. Tarawneh, et. al.,J.Phys.493 012020, 2014.
***** H. Nishimura, et. al.,PAC11, 1764-1766.

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MOPWI024

Accelerator Online Simulation Platform

database, lattice, software, space-charge

1204

C.P. Chu, Y. Zhang
FRIB, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
A platform for accelerator online beam simulation has been established for Facility for Rare Isotope Beams (FRIB). This modeling platform supports multiple simulation codes for different sections of the complex machine which cannot be properly modeled with a single online simulation tool. Model data for the platform is stored in a relational database which is designed to accommodate most simulation data. The stored data is accessible with physics intuitive data API (Application Programming Interface). Presently, the platform is supporting Open XAL, MAD-X and IMPACT simulation codes. In addition to the model data storage and access, tools such as data comparison and simple graphing capability are also included in the platform.

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MOPWI025

Phase and Amplitude Tuning Algorithms for the FRIB Superconducting Cavities

cavity, linac, acceleration, SRF

1207

Y. Zhang, P. Chu, Z.Q. He
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
FRIB driver linac will deliver all heavy ion beams up to uranium with energy above 200 MeV/u, and maximum beam power on target 400 kW for nuclear physics research. Phase and amplitude tuning of the FRIB superconducting cavities – totally about 330 of them, are important to the linac beam commissioning at low power and normal operation at high power. Because relatively low beam energy and high acceleration gradient, beam velocity changes significantly in the cavity RF gaps and the beam bunch cannot preserve perfectly in the further downstream beam diagnostics systems, beam longitudinal tuning algorithms are studied for different FRIB cavities and at different beam energy, which include the acceleration cavities as well as the re-buncher cavities.

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MOPWI026

Transverse Matching of Horizontal-Vertical Coupled Beams for the FRIB Linac

linac, quadrupole, lattice, solenoid

1211

Y. Zhang, P. Chu, Z.Q. He, S.M. Lund, D.G. Maxwell
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
FRIB driver linac will deliver all heavy ion beams up to uranium with energy above 200 MeV/u, and maximum beam power on target 400 kW for nuclear physics research. Strong horizontal-vertical beam coupling exists in the FRIB linac since superconducting solenoids are applied to focus multi charge state beams. Further, the FRIB low beta SRF cavities have raised quadrupole field components. The combined effects make beam transverse matching challenging. In this paper, we study transverse matching of horizontal-vertical coupled beams based on beam profile measurements with multiple wire scanners. There are multiple solutions for the initial linac beams with coupling, and errors of the beam diagnostics and magnet power supplies introduce further complication. Nonetheless, simulation studies show that satisfactory transverse matching can be achieved with proper linac beam tuning.

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MOPWI031

Microwave Modeling for Electron Cloud Density Measurements at CesrTA

resonance, electron, 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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MOPWI034

Adaptive Accelerator Tuning

controls, DTL, feedback, hardware

1237

A. Scheinker
LANL, Los Alamos, New Mexico, USA

We start with an overview of advanced adaptive control schemes in use throughout the accelerator community. We then present a recently developed, novel, model-independent feedback controller*, which is robust to measurement noise, and able to tune an arbitrary number of coupled parameters simultaneously based only on a user-defined cost function. We discuss the possibility of combining virtual beam measurements from simulations with actual diagnostic signals from the accelerator into a single cost function, which takes into account both unknown machine variations and estimates of physically inaccessible beam characteristics. We present recent in-hardware experimental results obtained at the Los Alamos Neutron Science Center** and at the Facility for Advanced Accelerator Tests (FACET)***, demonstrating the scheme’s ability to simultaneously tune many parameters and its robustness to noise and system time-variation.
* A. Scheinker et al., PRSTAB, 16, 102803, 2013.
** A. Scheinker et al., NIMA, 756, pp. 30-38, 2014.
*** A. Scheinker and S. Gessner, Conference on Decision and Control, 2014.

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MOPWI041

Identification of Intra-Bunch Transverse Dynamics for Model Based Wideband Feedback Control at CERN Super Proton Synchrotron

controls, feedback, proton, synchrotron

1249

O. Turgut, J.E. Dusatko, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
W. Höfle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program (LARP).
Multi-input multi-output (MIMO) feedback design techniques can be helpful to stabilize intra-bunch transverse instabilities induced by electron-clouds or transverse mode couplings at the CERN Super Proton Synchrotron (SPS). These MIMO techniques require a reduced order model of intra-bunch dynamics. We estimate a linear reduced order MIMO models for transverse intra-bunch dynamics and use these models to design model based MIMO feedback controllers. The effort is motivated by the plans to increase currents in the SPS as part of the HL-LHC upgrade. Parameters of the reduced order models are estimated based on driven beam SPS measurements. We study different types of controllers. We test the model based designs using macro particle simulation codes (CMAD and HEADTAIL) and compare its performance with FIR filters tested during beam measurements of the feedback system in SPS machine development (MD) studies.

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MOPWI047

Architectural Improvements and New Processing Tools for the Open XAL Online Model

cavity, hardware, software, coupling

1262

C.K. Allen, T.A. Pelaia II
ORNL, Oak Ridge, Tennessee, USA
J.M. Freed
University of South Carolina, Columbia, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
The Open XAL online model is the component of Open XAL* providing accelerator modeling dynamic synchronization to live hardware. Several significant architectural enhancements and feature additions have been made concerning the handling and processing of simulation data. The major structural change is the creation of a single class Trajectory<> that manages all simulation data. Another significant design change was the development of standard tools for processing simulation results. One may obtain machine parameters such as fixed orbit, phase advance, dispersion, etc., or beam-based calculations such as RMS size and centroid location simply by passing simulation results, i.e. a Trajectory<> object, to these computation tools. Finally, the ability to fully create composite modeling elements was implemented in the online model. Specifically, accelerator hardware can be modeled as a collection of constituent modeling elements. This sub-structure capability is extremely useful for modeling RF cavities consisting of coupled RF gaps coupled and drift spaces. We present an overview of the new architecture and how it is used when building applications.
* http://xaldev.sourceforge.net/

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TUAB3

Chromaticity Effects for Space Charge Dominated Beams in the CERN PS Booster

space-charge, resonance, emittance, sextupole

1335

V. Forte
Université Blaise Pascal, Clermont-Ferrand, France
E. Benedetto, F. Schmidt
CERN, Geneva, Switzerland

In view of the LHC Injectors Upgrade (LIU) project, an extensive campaign is on-going in the CERN PS Booster (PSB) to study collective effects for the future operation with the 160 MeV injection from Linac4. In operation, the machine is running with uncorrected natural chromaticity. This paper focuses on the study of the effects of chromaticity on losses and beam blow-up.

Slides TUAB3 [4.887 MB]

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TUAC2

Wideband Vertical Intra-Bunch Feedback At The SPS - 2015 Results And Path Forward

feedback, controls, kicker, optics

1353

C.H. Rivetta, J.E. Dusatko, J.D. Fox, O. Turgut
SLAC, Menlo Park, California, USA
S. De Santis
LBNL, Berkeley, California, USA
W. Höfle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract # DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP)
We present experimental measurements taken from CERN SPS machine development studies with a wideband intra-bunch feedback channel prototype. The demonstration system is a digital processing system with recently installed wideband kicker and amplifier components. This new hardware extends the bandwidth up to 1GHz and allows driving and controlling multiple vertical transverse modes in the bunch. The studies are focused on both driving the bunch with spectrally controlled signals to identify a reduced model of the bunch dynamics and testing model-based feedback controllers to stabilize the bunch dynamics. The measurements are structured to validate reduced MIMO models and macro-particle simulation codes, including the dynamics and limits of the feedback channel. Noise effects and uncertainties in the model are evaluated via SPS measurements to quantify the limits of control techniques applied to stabilize the intrabunch dynamics. The design of controllers for Q26 and Q20 optics are illustrated and future control developments are described.

Slides TUAC2 [30.936 MB]

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TUAC3

Optimization of Beam Loss Monitor Network for Fault Modes

cavity, detector, network, lattice

1356

Z. Liu, Z.Q. He, S.M. Lidia, D. Liu, Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Beam Loss Monitoring (BLM) System is an essential part to protect accelerator from machine faults. Compared with the empirical or uniform BLM arrangement in most accelerators, our new optimization approach proposes a “minimum spatial distribution” for BLM network. In this distribution, BLMs shall be placed at a small set of “critical positions” that can detect all failure / FPS trigger-able events of each fault mode. In additional, to implement a more advanced function of fault diagnosis, BLM should also be placed at “discrimination points” for fault-induced loss pattern recognition. With examples of FRIB failure event simulations, the author demonstrates the proof of concept to locate these “critical positions” and “discrimination points” for the minimum spatial distribution of BLMs.

Slides TUAC3 [2.341 MB]

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TUAD2

Comparison between Measured and Computed Temperatures of the Internal High Energy Beam Dump in the CERN SPS

target, dumping, shielding, kicker

1373

G.E. Steele, R. Folch, V. Kain, I.V. Leitao, R. Losito, C. Maglioni, F. Pasdeloup, A. Perillo-Marcone, F.M. Velotti
CERN, Geneva, Switzerland

The SPS high energy internal dump (TIDVG) is designed to receive beam dumps from 10².2 to 450 GeV. The absorbing core is composed of 2.5m graphite, followed by 1m of aluminium, then 0.5m of copper and finally 0.3m of tungsten, all of which is surrounded by a water cooled copper jacket. An inspection during Long Shutdown 1 revealed significant beam induced damage to the Al section of the dump block. Temperature sensors were installed to monitor the new dump replacing the damaged one. This paper summarises the correlation between the temperature measured as a function of the energy deposited and the same temperatures computed in a numerical model combining FLUKA and ANSYS simulations. The goal of this study is the assessment of the thermal contact quality between the beam absorbing blocks and the copper jacket, by analysing the cooling times observed from the measurements and from the thermo-mechanical simulations. This paper presents an improved method to estimate the efficiency and long term reliability of the cooling of this type of design, with the view of optimising the performance of future dump versions.

Slides TUAD2 [5.768 MB]

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TUBD3

Effects of Accelerating Structures on On-line DFS in the Main Linac of CLIC

wakefield, emittance, linac, dipole

1387

J. Pfingstner, E. Adli
University of Oslo, Oslo, Norway
D. Schulte
CERN, Geneva, Switzerland

Long-term ground motion will create significant dispersion in the time-scale of hours in the main linac of CLIC. To preserve the emittance to an acceptable level, a dispersion correction with on-line dispersion-free steering (DFS) is inevitable. For this on-line technique, the dispersion has to be measured using beam energy variations of only about one per mil in order to not disturb the operation of the accelerator. For such small energy variations, the interaction of the particle beam and the accelerating structures creates large enough additional signals components in the measured dispersion to cause the dispersion correction to not work properly anymore. In this paper, the additional signals are described and their effect on the DFS algorithm is analysed. Finally, methods for the mitigation of the deteriorating signal components are presented and studied via simulations.

Slides TUBD3 [1.697 MB]

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TUPWA005

Comparison of Bunch Compression Schemes for the AXXS FEL

linac, FEL, electron, 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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TUPWA016

Modeling of beam losses at ESRF

vacuum, scattering, electron, 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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TUPWA026

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

laser, electron, polarization, 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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TUPWA030

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

bunching, electron, emittance, 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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TUPWA032

Progress in the Injector Upgrade of the LINAC II at DESY

electron, linac, gun, 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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TUPWA037

Statistical Optimization of FEL Performance

quadrupole, FEL, controls, alignment

1496

I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany
I. Zagorodnov
DESY, Hamburg, Germany

Modern FEL facilities such as the European XFEL will serve large number of users, thus understanding and optimizing their performance parameters such as the output power is important. In this work we describe the statistical approach to such optimization under assumption that the possibility of modelling is limited by uncertainties. We present results of such statistical optimization of SASE radiation power for FLASH and discuss how the results of such empirical tuning can be fed back into the model used in simulations

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TUPWA044

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

cathode, electron, emittance, vacuum

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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TUPWA045

Further Investigations on the MESA injector

coupling, linac, space-charge, experiment

1515

R.G. Heine, K. Aulenbacher, S. Friederich, C. Matejcek, F. Schlander
IKP, Mainz, Germany

Funding: work supported by the German Federal Ministery of Education and Research under the Cluster of Excellence "PRISMA"
The MESA ERL to be build at Mainz in the next years is a multi turn recirculating linac with beam currents of up to 10 mA. The dynamic range of the beam currents demanded by the experiments is of at least two orders of magnitude. This is a special challenge for the layout design of an injector. In this paper we present the current status of the design of the injector linac called MAMBO (MilliAMpereBOoster).

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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, electron, cathode, emittance

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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TUPWA059

Modeling of Photoemission and Electron Spin Polarization from NEA GaAs Photocathodes

electron, scattering, polarization, 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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TUPWA063

FEL Enhancement by Microbuch Structure Made with Phase-Space Rotation

FEL, laser, cavity, bunching

1570

M. Kuriki, Y. Seimiya
HU/AdSM, Higashi-Hiroshima, Japan
S. Chen, K. Ohmi, J. Urakawa
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kato
ISIR, Osaka, Japan

Funding: This work is partly supported by MEXT/JSPS KAKENHI (Grant-in-Aid for scientic research) 25390126, Japan.
FEL is one of the ideal radiation source over the wide range of wavelength region with a high brightness and a high coherence. Many methods to improve FEL gain has been proposed by introducing an active modulation on the bunch charge distribution. The transverse-longitudinal phase-space rotation is one of the promising method to realize the density modulation as the micro-bunch structure. Initially, a beam density modulation in the transverse direction made by a mechanical slit, is properly transformed into the density modulation in the longitudinal direction by the phase-space rotation. The micro-bunch structure made with this method has a large tunability by changing the slit geometry, the beam line design, and the beam dynamics tuning. For FEL, enegy chirp made by the emittance exchange and chromaticity made by this chirp should be properly corrected. Simulation results and possible applications are discussed.

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TUPWA068

Simulation Study of Beam Halo and Loss for KEK Compact ERL

cavity, laser, gun, electron

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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TUPWA069

Simulation Study on Bunch Compression and Decompression for the Compact ERL

sextupole, linac, optics, emittance

1591

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

Generation of THz coherent radiation (THz-CSR) is planned for the near future at the Compact Energy Recovery Linac (cERL) in KEK where the beam recirculation and energy recovery were already achieved in February 2014 and an experiment for generation of laser-Compton scattering X-rays (LCS-X) is being prepared to start in February 2015. To achieve a ultra-short bunch less than 100 fs for generation of the THz-CSR up to 5 THz, we have studied bunch compression and decompression in the cERL mainly by using a simulation code ELEGANT. In this study, off-crest acceleration in the main superconducting linac and non-zero R56 optics in the two arc sections are used and sextupole magnets are introduced into the two arc sections for correcting T566 of the arc sections. In this paper, we will present the simulation results and the requirements for the sextupole magnets including their number and layout.

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TUPWA070

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

radiation, electron, 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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TUPJE014

An X-Band Linac with Tunable Beam Energy

linac, electron, 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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TUPJE019

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

electron, radiation, laser, FEL

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, electron, photon, scattering

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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TUPJE033

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

undulator, radiation, resonance, electron

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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TUPJE048

Orbit Correction and Stability Studies for Ultra-Low Emittance Storage Rings

photon, emittance, dipole, storage-ring

1728

M. Böge, M. Aiba, A. Streun
PSI, Villigen PSI, Switzerland

Ultra-low emittance storage rings exhibit extremely strong focusing and sextupolar chromaticity corrections. The therefore mandatory excellent centering of the closed orbit in the small aperture magnets is a challenging task and necessitates a proper beam diagnostics and correction layout. Correction and stability studies for a possible ultra-low emittance upgrade of the Swiss Light Source are presented.

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TUPJE054

Developments in CLARA Accelerator Design and Simulations

FEL, laser, undulator, linac

1744

P.H. Williams, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom

We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. The layout changes include a dedicated collimator in CLARA front end to provide some control over the dark current, changes to low energy diagnostics section and modifications to FEL modules. The progress in the design simulations mainly focus on injector simulations incorporating wake fields in ASTRA, comparison of using ELEGANT and CSRTRACK for the Variable Bunch Compressor and first considerations of requirement of laser heater for CLARA.

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TUPJE057

Realistic Undulators for Intense Gamma-ray Beams at Future Colliders

undulator, electron, positron, 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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TUPJE060

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

radiation, electron, 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, electron, 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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TUPJE065

Multi-Bunch Stability Analysis of the Advanced Photon Source Upgrade Including the Higher-Harmonic Cavity

HOM, damping, impedance, radiation

1784

L. Emery, T.G. Berenc, M. Borland, R.R. Lindberg
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Multi-bunch stability simulations were done for the very-low-emittance hybrid seven-bend-achromat (H7BA) lattice proposed for the Advanced Photon Source (APS) upgrade. The simulations, performed using tracking code elegant, were meant to determine whether the long-term wakefields of the higher-order modes (HOMs) of the main 352-MHz cavities will produce an instability. The multi-particle simulations include the important effects of the Higher-Harmonic Cavity (HHC) and the longitudinal impedance of the new vacuum chamber. These realistic simulations show that the HHC provides additional damping in the form of the Landau damping. Still, the HOMs may likely produce a multi-bunch instability which can be cured with more effective HOM damping or a longitudinal feedback system.

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TUPJE066

Development of an Abort Kicker at APS to Mitigate Beam Loss-induced Quenches of the Superconducting Undulator

kicker, injection, beam-losses, septum

1787

K.C. Harkay, J.C. Dooling, Y. Ivanyushenkov, R. Laird, F. Lenkszus, C.C. Putnam, V. Sajaev, J. Wang
ANL, Argonne, Ilinois, USA

Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The first superconducting undulator (SCU0) at the Advanced Photon Source (APS) has been delivering 80-100 keV photons for user science since January 2013. SCU0 often quenches during beam dumps triggered by the machine protection system (MPS). SCU0 typically recovers quickly after a quench, but SCU1, a second, longer device to be installed in 2015, may take longer to recover. We tested using injection kickers as an abort system to dump the beam away from SCU0 and the planned location of SCU1. An alternate trigger was tested that fires the kickers with MPS. We demonstrated that controlling the beam dump location with kickers can significantly reduce the beam losses at SCU0, as measured by fiber optic (FO) beam loss monitors (BLMs), and can also prevent a quench. A dedicated abort kicker system has been developed based on elegant simulations. A spare injection kicker was modified to produce the required waveform. Injection kicker tests, simulations, and the abort kicker design are described. Demonstration of this strategy in APS has implications for the APS Upgrade, where more SCUs are planned.

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TUPJE072

Advanced Photon Source Injection Related Simulation and Measurement

injection, lattice, operation, septum

1806

Y. Sun
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Injection efficiency is one of the key factors in ensuring successful operation of storage ring light sources. In this paper, injection simulation and measurement studies at the Advanced Photon Source will be presented. The tracking simulations and measurements are compared in terms of the dynamic aperture and injection efficiency. Injection efficiency is also measured on the betatron tunes space and on different stored beam orbits.
yisun@aps.anl.gov

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TUPJE075

Simulation Study of Injection Performance for the Advanced Photon Source Upgrade

injection, emittance, storage-ring, kicker

1816

A. Xiao, V. Sajaev
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
A vertical on-axis injection scheme has been proposed for the hybrid seven-bend-achromat (H7BA) Advanced Photon Source upgrade (APSU) lattice. In order to evaluate the injection performance, various errors, such as injection beam jitter, optical mismatch and errors, and injection element errors have been investigated and their significance has been discovered. Injection efficiency is then simulated under different error levels. Based on these simulation results, specifications and an error-budget for individual systems have been defined.

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TUPJE076

Design Study of the Higher Harmonic Cavity for Advanced Photon Source Upgrade

cavity, operation, impedance, superconducting-cavity

1819

S.H. Kim, T.G. Berenc, J. Carwardine, G. Decker, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, Illinois, USA

Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
A higher-harmonic cavity is planned for the proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice to increase the bunch length, improve the Touschek lifetime and increase the single-bunch current limit. We have investigated a range of options including 3rd, 4th, and 5th harmonics of the main radio frequency (RF) system, as well as configurations with and without external RF power couplers. The current baseline is a single 4th harmonic superconducting cavity with adjustable RF couplers and a slow tuner which provide the flexibility to operate over a wide range of beam currents. The cavity is designed to provide 0.84 MV at 1408 MHz for the nominal 6 GeV, 200 mA electron beam, and 4.1 MV main RF voltage. In this paper, we discuss the harmonic cavity parameters based on analytical calculations of the equilibrium bunch distribution and make comparisons to other options.

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TUPJE077

Instability Thresholds for the Advanced Photon Source Multi- Bend Achromat Upgrade

impedance, wakefield, injection, collective-effects

1822

R.R. Lindberg
ANL, Argonne, Illinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An important operating mode for the multi-bend achromat (MBA) upgrade at the Advanced Photon Source (APS) calls for 200 mA average current divided evenly over 48 bunches. Ensuring that the desired 4.2 mA single bunch current can be stably stored requires a detailed understanding of the impedance in the MBA ring. We briefly discuss modeling sources of impedance using the electromagnetic codes GdfidL and ECHO, and how we then include both geometric and resistive wall wakefields using the tracking code elegant to predict collective instabilities. We first validate our procedures by comparing APS experimental measurements to tracking predictions using the APS storage ring impedance model. We then discuss the MBA impedance model, for which we find that a chromaticity of 5 units is sufficient to obtain the required 4.2 mA single bunch current. Finally, we mention certain design changes that may reduce the impedance and allow for a reduction in chromaticity.

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TUPJE078

Modeling of Impedance Effects for the APS-MBA Upgrade

impedance, vacuum, wakefield, photon

1825

R.R. Lindberg
ANL, Argonne, Illinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Understanding the sources of impedance is critical to accelerator design, and only becomes more important as vacuum chambers become smaller and closer to the electron beam. The multibend achromat upgrade at the Advanced Photon Source (APS) requires small, 22-mm diameter vacuum chambers and even smaller (6 mm) gaps for the insertion devices, so that both rf heating and wakefield-driven transverse instabilities become important concerns. We discuss modeling the primary sources of geometric impedance using the electromagnetic finite difference codes GdfidL and ECHO, and how these codes are influencing vacuum and accelerator component design.

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TUPMA003

Microbunching Phenomena in LCLS-II

laser, space-charge, bunching, undulator

1843

M. Venturini, C. F. Papadopoulos, J. Qiang
LBNL, Berkeley, California, USA
Y. Ding, P. Emma, Z. Huang, G. Marcus, A. Marinelli, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley
SLAC, Menlo Park, California, USA

Funding: Work supported by DOE, in part under Contract No. DE-AC02-05CH11231 and through the LCLS-II project.
The microbunching instability has long been recognized as a potential limiting factor to the performance of X-ray FELs. It is of particular relevance in LCLS-II due, in part, to a layout that includes a long bypass beamline between the Linac and the undulators. Here we focus on two aspects of the instability that highlight the importance of 3D effects.

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TUPMA004

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

electron, emittance, cathode, laser

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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TUPMA007

Numerical Investigation of a Cascaded Longitudinal Space-Charge Amplifier at the Fermilab's Advanced Superconducting Test Accelerator

space-charge, radiation, bunching, impedance

1850

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

In a cascaded longitudinal space-charge amplifier (LSCA), initial density noise in a relativistic e-beam is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. This type of amplification process was shown to potentially result in large final density modulations * compatible with the production of broadband electromagnetic radiation. The technique was recently demonstrated in the optical domain **. In this paper we investigate, via numerical simulations, the performances of a cascaded LSCA beamline at the Fermilab's Advanced Superconducting Test Accelerator (ASTA). We especially explore the properties of the produced broadband radiation. Our studies have been conducted with an effective three-dimensional space-charge algorithm.
* Dohlus, M. et al. Proc. SPIE 8779. doi:10.1117/12.2017369
** Marinelli, A. et al. Phys. Rev. Lett. 110, 264802 (2013)

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TUPMA008

Numerical Study of Three Dimensional Effects in Longitudinal Space-Charge Impedance

impedance, space-charge, detector, radiation

1853

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Longitudinal space-charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed instabilities. Such "microbunching instabilities" were recently shown to be potentially useful to support the generation of broadband coherent radiation pulses. Therefore there has been an increasing interest in devising accelerator beamlines capable of sustaining this LSC instability as a mechanism to produce a coherent light source. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. In this paper we use a N-body "Barnes-Hut" algorithm * to simulate the 3D space charge force in the beam combined with Elegant ** and explore the limitation of the 1D model often used.
* Barnes, J. & Hut, P., Nature 324, 446-449, 1986.
** Borland, M., Advanced Photon Source LS-287, 2000.

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TUPMA018

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

gun, electron, 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, electron, 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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TUPMA021

Optimization of an Improved SASE (iSASE) FEL

FEL, radiation, lattice, undulator

1881

L. Gupta
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
K. Fang, J. Wu
SLAC, Menlo Park, California, USA

Funding: Supported by US DOE FWP-2013-SLAC-100164 and DOE SULI.
In order to improve free electron laser technology for the future LCLSII at SLAC, a new strategy for creating radiation with increased temporal coherence is under development. The improved Self-Amplified Spontaneous Emission (iSASE) FEL utilizes phase shifters which allow for the spontaneously emitted radiation to interact with and stimulate more electrons to radiate coherently. Five phase shifters were simulated, with 34 normal-conducting undulators and focusing-defocusing quadrupoles as an LCLSII FEL lattice using the FEL software Genesis 1.3. Two general schemes, one providing a total phase shift of arbitrary distribution, the other providing a sequential or distributed phase shift, were simulated and optimized using a simulated annealing algorithm. The results suggest that the phase shifters must provide a total shift comparable to the bunch length, and the shifts must be distributed with one large shift, followed by smaller shifts.
* J. Wu, A. Marinelli, C. Pellegrini, Proc. FEL2012, pp. 237, Japan (2012).
** J. Wu, et al., Proc. IPAC2013, pp. 2068, China (2013).

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TUPMA034

Control of Synchrotron Radiation Effects During Recirculation with Bunch Compression

emittance, controls, recirculation, lattice

1910

D. Douglas, S.V. Benson, R. Li, C. Tennant
JLab, Newport News, Virginia, USA
G.A. Krafft, B. Terzić
ODU, Norfolk, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 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 DE-AC05-06OR23177.
Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction ** and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.***. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects ****.
* D. Douglas et al., these proceedings
** S. Benson et al., these proceedings
*** S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013
**** C.Y. Tsai et al., these proceedings

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TUPMA048

Experimental and Simulational Result of Multipactors in 112 MHz QWR Injector

gun, electron, cavity, cathode

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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TUPTY004

Tracking Simulation for Beam Loss Studies with Application to FCC

lattice, scattering, collider, detector

2004

M. Boscolo
INFN/LNF, Frascati (Roma), Italy
H. Burkhardt
CERN, Geneva, Switzerland

We present an implementation of a tracking simulation tool used to evaluate the main particle loss effects for Flavor Factories with the aim of applying these studies also to FCC. We describe the interface of the Monte Carlo tracking code with MAD-X, showing first simulations of the Touschek effect for the FCC-ee at the Z. We plan to use this approach also for multi-turn simulations of particles scattered by radiative Bhabha, beam-gas and eventually Beamstrahlung effects.

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TUPTY006

Study of Electron Cloud Instabilities in FCC-hh

electron, proton, photon, emittance

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, electron, proton, 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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TUPTY016

Study of Background and MDI Design for CEPC

background, detector, scattering, photon

2028

Y. Yue, Q. Qin
IHEP, Beijing, People's Republic of China

CEPC is a project designed to obtain a large number of Higgs events by keeping e⁺e⁻ collisions at the center-of-mass energy of 240 GeV and deliver peak luminosity above 10³⁴ cm^-2 s^-1 for each interaction point. The super high energy and the pretty high luminosity will bring some special background problems, which will exert difficulty on the MDI design and the detectors protection. In this article, I will show the simulation result of the main background sources at CEPC and give some suggestions on the MDI design and detectors protection.

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TUPTY019

Realistic Beam Halo Model study in the Extraction Line of ATF2

background, optics, electron, 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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TUPTY024

Updated Simulation Studies of Damage Limit of LHC Tertiary Collimators

proton, optics, collimation, kicker

2053

E. Quaranta, A. Bertarelli, R. Bruce, F. Carra, F. Cerutti, P. Gradassi, A. Lechner, S. Redaelli, E. Skordis
CERN, Geneva, Switzerland

The tertiary collimators (TCTs) in the LHC, installed in front of the experiments, in standard operation intercept fractions of 10³ halo particles. However, they risk to be hit by high-intensity primary beams in case of asynchronous beam dump. TCT damage thresholds were initially inferred from results of destructive tests on a TCT jaw, supported by numerical simulations, assuming simplified impact scenarios with one single bunch hitting the jaw with a given impact parameter. In this paper, more realistic failure conditions, including a train of bunches and taking into account the full collimation hierarchy, are used to derive updated damage limits. The results are used to update the margins in the collimation hierarchy and could thus potentially have an influence on the LHC performance.

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TUPTY025

Betatron Cleaning for Heavy Ion Beams with IR7 Dispersion Suppressor Collimators

ion, proton, heavy-ion, collimation

2057

P.D. Hermes, R. Bruce, J.M. Jowett, S. Redaelli
CERN, Geneva, Switzerland

The betatron collimators in IR7 constitute the backbone of the collimation system of the LHC. A fraction of the secondary halo protons or heavy-ion fragments, scattered out of the primary collimator, is not captured by the secondary collimators but hit cold magnets in the IR7 dispersion suppressor (DS) where the dispersion starts to increase. A possible approach to reduce these losses is based on the installation of additional collimators in the DS region. In this paper, simulations of the cleaning efficiency for Pb⁸²⁺ ions are used to evaluate the effect of the additional collimators. The results indicate a significant improvement of the heavy-ion cleaning efficiency.

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TUPTY027

SixTrack Simulations of Beam Cleaning During High-beta Operation in the LHC

background, proton, experiment, collimation

2060

R. Bruce
CERN, Geneva, Switzerland

The 1000 m high-beta run in the LHC provided very clean conditions for observing experimental backgrounds. In ATLAS, a much higher background was observed for Beam 2 than for Beam 1, suspected to be caused by upstream showers from beam losses on collimators or aperture. However, no local beam losses were observed in the vicinity. This paper presents SixTrack simulations of the beam cleaning during the high-beta run. The results demonstrate that, for the special optics and collimator settings used, the highest loss location in IR1 is at the TAS absorber just in front of the ATLAS detector, where no beam loss monitor is installed. Furthermore, the highest losses are seen in Beam 2. The results could thus provide a possible explanation of the ATLAS observations, although detailed shower calculations would be needed for a quantitative comparison.

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TUPTY029

Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials

collimation, scattering, impedance, proton

2068

E. Quaranta, R. Bruce, A. Mereghetti, S. Redaelli, A. Rossi
CERN, Geneva, Switzerland

The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.

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TUPTY031

Tools for Flexible Optimisation of IR Designs with Application to FCC

radiation, synchrotron, synchrotron-radiation, detector

2072

H. Burkhardt
CERN, Geneva, Switzerland
M. Boscolo
INFN/LNF, Frascati (Roma), Italy

The interaction regions of future high-luminosity colliders require well balanced designs, which provide both for a very high luminosity and at the same time keep backgrounds and radiation at tolerable levels. We describe a set of flexible tools, targeted at providing a first evaluation of losses in the interaction region as part of the design studies, and their application to FCC.

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TUPTY035

Beam Dynamics Requirements for the Powering Scheme of the HL-LHC Triplet

quadrupole, controls, optics, dynamic-aperture

2082

M. Fitterer, R. De Maria, S.D. Fartoukh, M. Giovannozzi
CERN, Geneva, Switzerland

Funding: The HiLumi LHC Design Study is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
For the HL-LHC, β^* values as small as 15 cm are envisaged as baseline scenario for the high luminosity insertions IR1 and IR5, thus leading to an increase of the maximum beta-functions in the inner triplet (IT). The larger beta-functions in the IT result in a higher sensitivity of the beam to any linear or non-linear, static or dynamic, field imperfections in the IT region. In this paper, we summarize accordingly the tolerances of the triplet power supplies in terms of current ripple, stability and reproducibility. Both the baseline IT powering scheme and other alternative schemes will be presented, the later reducing the tune shift caused by a current modulation and thus weakening its possible impact on the long term stability.

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TUPTY038

BPM Tolerances for HL-LHC Orbit Correction in the Inner Triplet Area

luminosity, optics, impedance, emittance

2094

M. Fitterer, R. De Maria
CERN, Geneva, Switzerland

Funding: The HiLumi LHC Design Study is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
For the HL-LHC beam spot sizes as small as 7 mum are considered for the high luminosity insertions IR1 and IR5. In addition, the luminosity has to be levelled over several hours by changing β^* resulting in constant changes of the optics and thus orbit changes. The small beam size and the continuous optics changes in general make the alignment of the beams at the IP challenging. In order to avoid continuous luminosity scans for the alignment of the beams at the IP, the orbit correction has to rely on the readings of the BPMs in the IT region. In this paper we review the requirements on resolution and accuracy of the BPMs and compare different options for the placement of the BPMs in the IT region.

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TUPTY042

Non-linear Coupling Studies in the LHC

coupling, octupole, hadron, collider

2105

T. Persson, Y.I. Levinsen, E.H. Maclean, R. Tomás
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom

The amplitude detuning has been observed to decrease significantly as the horizontal and vertical tunes are approaching each other. This effect is potentially harmful since it might cause a loss of Landau damping, hence giving rise to instabilities. The measured tune split (Qx-Qy) versus amplitude is several times bigger than what can be explained with linear coupling. In this paper we present studies performed to identify the dominant sources of the non-linear coupling observed in the LHC.

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TUPTY045

Interactions between Macroparticles and High-Energy Proton Beams

proton, electron, 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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TUPTY046

Impact of Beam Losses in the LHC Collimation Regions

collimation, proton, dipole, coupling

2116

E. Skordis, R. Bruce, F. Cerutti, A. Ferrari, P.D. Hermes, A. Lechner, A. Mereghetti, P.G. Ortega, S. Redaelli, V. Vlachoudis
CERN, Geneva, Switzerland

The upgrade of the LHC energy and brightness, from the 2015 restart at close to design energy until the HL-LHC era with considerable hardware development and layout renewal, poses tight challenges in terms of machine protection. The collimation insertions and especially the one dedicated to betatron cleaning (IR7), where most of the beam halo is intercepted to spare from losses the cold sectors of the ring, will be subject to a significant increase of radiation load, whose leakage to the nearby dispersion suppressors must be kept sustainable. The past LHC run, while displaying a remarkable performance of the collimation system, offered the opportunity for a demanding benchmarking of the complex simulation chain describing the beam losses and the macroscopic effects of the induced particle showers, this way strengthening the confidence in the reliability of its predictions. This paper discusses the adopted calculation strategy and its evolution options, showing the accuracy achieved with respect to Beam Loss Monitor measurements in controlled loss scenarios. Expectations at design energy, including lifetime considerations concerning critical elements, will also be presented.

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TUPTY049

Protection of Superconducting Magnets in Case of Accidental Beam Losses during HL-LHC Injection

injection, vacuum, kicker, shielding

2128

A. Lechner, M.J. Barnes, C. Bracco, B. Goddard, F.L. Maciariello, A. Perillo Marcone, N.V. Shetty, G.E. Steele, J.A. Uythoven, F.M. Velotti
CERN, Geneva, Switzerland
F.M. Velotti
EPFL, Lausanne, Switzerland

Funding: Research supported by the High Luminosity LHC project.
The LHC injection regions accommodate a system of beam-intercepting devices which protect superconducting magnets and other accelerator components in case of mis-steered injected beam or accidentally kicked stored beam, e.g. due to injection kicker or timing malfunctions. The brightness and intensity increase required by the High Luminosity (HL) upgrade of the LHC necessitates a redesign of some devices to improve their robustness and to reduce the leakage of secondary particle showers to downstream magnets. In this paper, we review possible failure scenarios and we quantify the energy deposition in superconducting coils by means of FLUKA shower calculations. Conceptual design studies for the new protection system are presented, with the main focus on the primary injection protection absorber (TDI) and the adjacent mask (TCDD).

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TUPTY051

Injection Protection Upgrade for the HL-LHC

injection, impedance, kicker, proton

2136

J.A. Uythoven, N. Biancacci, C. Bracco, L. Gentini, B. Goddard, A. Lechner, F.L. Maciariello, A. Perillo Marcone, B. Salvant, N.V. Shetty, G.E. Steele, F.M. Velotti
CERN, Geneva, Switzerland
O. Frasciello, M. Zobov
INFN/LNF, Frascati (Roma), Italy

The injector complex of the LHC is undergoing important changes in the light of the LIU project to provide brighter beams to the LHC. For this reason and as part of the High Luminosity LHC project the injection protection system of the LHC will be upgraded in the Long Shutdown 2 (2018 - 2019) to be able to protect downstream elements against injection failures with the high brightness, high intensity HL-LHC beams. The upgraded LHC injection protection system will consist of a segmented injection protection absorber TDIS, and auxiliary collimators and masks. The layout modifications are described, and the machine element protection and absorber jaw robustness studies are presented for the new systems.

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TUPTY054

RF Design of the CLIC Structure Prototype Optimized for Manufacturing from Two Halves

linac, multipole, wakefield, collider

2147

H. Zha, A. Grudiev
CERN, Geneva, Switzerland
V.A. Dolgashev
SLAC, Menlo Park, California, USA

We present the RF design of a 12GHz Compact Linear Collider (CLIC) main linac accelerating structure prototype. The structure is made from two longitudinally symmetric halves. The main manufacturing process of each half is precision milling. The structure uses the same iris dimensions as the CLIC-G structure but the cell shape is optimized for milling. The geometry is optimized to reduce the surface electric and magnetic fields and the modified Poynting vector. This design can potentially reduce fabrication cost.

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TUPTY055

Optimization of the RF Design of the CLIC Main Linac Accelerating Structure

wakefield, linac, collider, cavity

2150

H. Zha, A. Grudiev
CERN, Geneva, Switzerland

We present a new optimized design of the accelerating structure for the main linac of CLIC (Compact Linear Collider). The new structure has lower surface magnetic fields and a significantly smaller transverse size compared to the baseline design described in the CLIC Concept Design Report (CDR). This new design should reach higher accelerating gradients and have a reduced manufacturing cost. The details of the RF design procedure and the obtained results are presented in this paper.

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TUPTY063

FCC-ee: Energy Calibration

polarization, wiggler, storage-ring, electron

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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TUPTY067

Beam Induced Background Simulation Studies at IR1 with New High Luminosity LHC Layout

optics, background, collimation, luminosity

2184

R. Kwee-Hinzmann, S.M. Gibson
JAI, Egham, Surrey, United Kingdom
R. Bruce, F. Cerutti, L.S. Esposito, A. Lechner
CERN, Geneva, Switzerland
S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom

Funding: Research supported by FP7 HiLumi LHC – Grant agreement 284404
In the High Luminosity LHC (HL-LHC), the collimation system will be upgraded in the high-luminosity experimental regions. Additional protection is planned for the Q4 and Q5 magnets that are located further upstream of the tertiary collimators that protect the inner triplet magnets. We evaluate the effect of this proposed collimation layout for the incoming beam 1 on machine-induced background in the experimental area of IR1 (ATLAS). The main scenario is the round optics with β∗ of 15 cm, but a flat scenario is also briefly discussed.

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TUPTY069

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

electron, collimation, proton, betatron

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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TUPTY070

Strong-Strong Simulations of Beta star Levelling for Flat and Round Beams

luminosity, emittance, resonance, detector

2192

M.P. Crouch, R.B. Appleby
UMAN, Manchester, United Kingdom
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: STFC HL-LHC
The HL-LHC project aims to reach larger peak luminosities, however this can lead to a high pile up in the detectors. To control the pile up, luminosity levelling has been suggested. One proposed method is β*-luminosity levelling, in which beams collide at a larger than nominal β*. The β* is then reduced in steps as the beam intensity decays. This allows the luminosity to be kept constant over part of a physics fill. The use of round or flat optics will change the beam-beam effect of the head on collisions as well as the long range interactions. Here simulations of β* levelling are presented for the case of flat and round beam optics and the difference in terms of the beam-beam effect is highlighted.

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TUPTY073

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

luminosity, optics, beam-beam-effects, electron

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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TUPTY074

Muon Beam Emittance Evolution in the Helical Ionization Cooling Channel for Bright Muon Sources

plasma, emittance, collider, space-charge

2203

K. Yonehara, C.Y. Yoshikawa
Fermilab, Batavia, Illinois, USA
C.M. Ankenbrandt, R.P. Johnson, S.A. Kahn
Muons, Inc, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
Y.S. Derbenev, A.V. Sy
JLab, Newport News, Virginia, USA
B.T. Freemire
IIT, Chicago, Illinois, USA

The six-dimensional ionization cooling is essential to design a bright muon source. A geometry constraint is a challenge issue in a compact helical cooling channel (HCC). Especially, the HCC requires a large bore helical magnet and a compact helical RF system to incorporate the RF into the magnet chamber. A new emittance evolution has been designed to mitigate the geometry constraint. The HCC was functionally separated into three parts sections. The lattice at the initial section provides a large transverse acceptance by using a strong helical focus magnet. Once the transverse beam size is small enough to get into the compact RF the HCC lattice in the middle section generates a large longitudinal beta tune to dominate the longitudinal cooling. Consequently, the longitudinal emittance becomes smaller than the transverse one at the end of middle section. In the final section, the magnetic field strength is gradually reduced to match out the helical channel to the straight solenoid. As a result, the emittance exchange takes place and the final transverse emittance becomes smaller than the longitudinal one. The new emittance evolution scenario will be discussed in this presentation.

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TUPTY076

Beam-Beam Simulation of Crab Cavity White Noise for LHC Upgrade

luminosity, cavity, emittance, beam-beam-effects

2206

J. Qiang
LBNL, Berkeley, California, USA
J. Barranco García
EPFL, Lausanne, Switzerland
K. Ohmi
KEK, Ibaraki, Japan
T. Pieloni
CERN, Geneva, Switzerland

High luminosity LHC upgrade will improve the luminosity of the current LHC operation by an order of magnitude. Crab cavity as a critical component for compensating luminosity loss from large crossing angle collision and also providing luminosity leveling for the LHC upgrade is being actively pursued. In this paper, we will report on the study of potential effects of the crab cavity noise on the beam luminosity lifetime based on strong-strong beam-beam simulations.

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TUPTY077

Strong-Strong Beam-Beam Simulation of Bunch Length Splitting at the LHC

emittance, synchrotron, resonance, beam-beam-effects

2210

J. Qiang, S. Paret
LBNL, Berkeley, California, USA
K. Ohmi
KEK, Ibaraki, Japan
T. Pieloni
CERN, Geneva, Switzerland

Longitudinal bunch length splitting was observed for some LHC beams. In this paper, we will report on the study of the observation using strong-strong beam-beam simulations. We explore a variety of factors including initial momentum deviation, collision crossing angle, synchroton tune, chromaticity, working points and bunch intensity that contribute to the beam particle loss and the bunch length splitting, and try to understand the underlying mechanism of the observed phenomena.

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TUPWI007

Algorithm of Reconstructing Particle Distribution in N-dimensional Phase Space from Profile in Beam Transport

beam-transport, quadrupole, induction, emittance

2256

T. Aoki
Hitachi Ltd., Ibaraki-ken, Japan

In particle beam therapy, it is demanded to improve measurement of beam extracted from accelerator in order to realize more conformal irradiation. We developed a method of reconstructing particle distribution from measured profile in beam transport. In this method, particle distribution is obtained by solving a following equation: I=Dρ, where I is a counted number of particles at a single channel of the profile monitor, D is a matrix representing relation between I and ρ, and ρ is number of particles included in a single n-dimensional voxel of phase space at start point of the beam transport. D is a n×m matrix, where n is number of data which obtained under multiple conditions of beam transport, and m is number of voxels of phase space to be reconstructed. We succeeded formulation of D matrix from transportation matrix of the beam transport R, and discovered that D is formulated as piecewise-polynomials of elements of R. By this method, it is enable to reconstruct the particle distribution in arbitrary dimensional phase space. We show details of the formulation of D and results of simulations of reconstruction of particle distribution in phase space by this method.

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TUPWI022

GEM*STAR Accelerator-Driven Subcritical System for Improved Safety, Waste Management, and Plutonium Disposition

neutron, target, proton, operation

2289

R.P. Johnson, R.J. Abrams, M.A.C. Cummings, G. Flanagan, T.J. Roberts
Muons, Inc, Illinois, USA
C. Bowman
ADNA, Los Alamos, New Mexico, USA
R.B. Vogelaar
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Operation of high-power SRF particle accelerators at two US national laboratories allows us to consider a less-expensive nuclear reactor that operates without the need for a critical core, fuel enrichment, or reprocessing. A multipurpose reactor design that takes advantage of this new accelerator capability includes an internal spallation neutron target and high-temperature molten-salt fuel with continuous purging of volatile radioactive fission products. The reactor contains less than a critical mass and almost a million times fewer volatile radioactive fission products than conventional reactors like those at Fukushima. We describe GEM*STAR *, a reactor that without redesign will burn spent nuclear fuel, natural uranium, thorium, or surplus weapons material. A first application is to burn 34 tonnes of excess weapons grade plutonium as an important step in nuclear disarmament under the 2000 Plutonium Management and Disposition Agreement **. The process heat generated by this W-Pu can be used for the Fischer-Tropsch conversion of natural gas and renewable carbon into 42 billion gallons of low-CO2-footprint, drop-in, synthetic diesel fuel for the DOD.
* Charles D. Bowman, R. Bruce Vogelaar, et al., Handbook of Nuclear Engineering, Springer Science+Business Media LLC (2010).
** http://www.state.gov/r/pa/prs/ps/2010/04/140097.htm

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TUPWI033

Matching into the Helical Bunch Coalescing Channel for a High Luminosity Muon Collider

emittance, acceleration, luminosity, collider

2315

A.V. Sy, Y.S. Derbenev, V.S. Morozov
JLab, Newport News, Virginia, USA
C.M. Ankenbrandt, R.P. Johnson
Muons, Inc, Illinois, USA
D.V. Neuffer, K. Yonehara, C.Y. Yoshikawa
Fermilab, Batavia, Illinois, USA

Funding: This work was supported in part by U.S. DOE STTR Grant DE-SC0007634. This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For high luminosity in a muon collider, muon bunches that have been cooled in the six-dimensional helical cooling channel (HCC) must be merged into a single bunch and further cooled in preparation for acceleration and transport to the collider ring. The helical bunch coalescing channel has been previously simulated [*, **] and provides the most natural match from helical upstream and downstream subsystems. This work focuses on the matching from the exit of the multiple bunch HCC into the start of the helical bunch coalescing channel. The simulated helical matching section simultaneously matches the helical spatial period λ in addition to providing the necessary acceleration for efficient bunch coalescing. Previous studies assumed that the acceleration of muon bunches from p=209.15 MeV/c to 286.816 MeV/c and matching of λ from 0.5 m to 1.0 m could be accomplished with zero particle losses and zero emittance growth in the individual bunches. This study demonstrates nonzero values for both particle loss and emittance growth, and provides considerations for reducing these adverse effects to best preserve high luminosity.
*C. Yoshikawa, et al., “Bunch Coalescing in a Helical Channel,” MAP-doc-4302-v2.
**C. Yoshikawa, et al., “Bunch Coalescing in a Helical Channel,” IPAC12 TUPPD013, New Orleans, Louisiana, USA.

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TUPWI040

End-to-End Simulation of Bunch Merging for a Muon Collider

solenoid, kicker, collider, emittance

2336

Y. Bao, G.G. Hanson
UCR, Riverside, California, USA
R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA

Muon accelerator beams are commonly produced indirectly through pion decay by interaction of a charged particle beam with a target. Efficient muon capture requires the muons to be first phase-rotated by rf cavities into a train of 21 bunches with much reduced energy spread. Since luminosity is proportional to the square of the number of muons per bunch, it is crucial for a Muon Collider to use relatively few bunches with many muons per bunch. In this paper we will describe a bunch merging scheme that should achieve this goal. We present for the first time a complete end-to-end simulation of a 6D bunch merger for a Muon Collider. The 21 bunches arising from the phase-rotator, after some initial cooling, are merged in longitudinal phase space into 7 bunches, which then go through 7 paths with different lengths and reach at the final collecting ”funnel” at the same time. The final single bunch has a transverse and a longitudinal emittance that matches well with the subsequent 6D rectilinear cooling scheme.

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TUPWI042

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

electron, gun, 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

quadrupole, lattice, optics, electron

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, electron, 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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TUPWI053

Polarization Simulations in the RHIC Run 15 Lattice

resonance, optics, polarization, lattice

2372

F. Méot, H. Huang, Y. Luo, V.H. Ranjbar, G. Robert-Demolaize
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.
RHIC polarized proton Run 15 uses a new acceleration ramp optics, compared to RHIC Run~14 and earlier runs, in relation with electron-lens beam-beam compensation developments. The new optics induces different strengths in the depolarizing snake resonance sequence, from injection to top energy. As a consequence, polarization transport along the new ramp has been investigated, based on spin tracking simulations. Sample results are reported and discussed.

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TUPWI055

Chromatic Effects and Orbit Correction in eRHIC Arcs

emittance, linac, lattice, quadrupole

2378

F. Méot, C. Liu
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.
In the FFAG version of the electron energy recovery recirculator of the eRHIC electron-ion collider project, natural chromaticity is important and not corrected. Tracking simulations illustrate various aspects of its effects on 6-D bunch dynamics over the 16 turn recirculation from 1.3 to 21.2GeV collision energy, and back down to injection energy. These effects can be mitigated via orbit control, the methodology for that is described and its effectiveness illustrated via a series of ad hoc numerical simulations. Because polarization is paramount in the eRHIC NP program, its careful monitoring is part of the simulations.

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WEXB2

Measurement and Analysis of Electron Cloud Induced Emittance Growth at CesrTA

electron, 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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WEYB1

Benchmarking and Application of Space Charge Codes for Rings

space-charge, resonance, lattice, experiment

2402

S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

This presentation should present an overview of efforts for benchmarking and application of space charge codes for rings. After briefly recalling the historical background of the simulation efforts of space charge effects in rings, we will overview the present benchmarking efforts against experimental results.

Slides WEYB1 [6.541 MB]

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WEXC2

Advances in Proton Linac Online Modeling

linac, GPU, space-charge, operation

2423

X. Pang
LANL, Los Alamos, New Mexico, USA

This talk will review current online modeling tools used for proton linacs and then focus on a new approach that marries multi-particle beam dynamics with modern GPU technology to provide pseudo real-time beam information in a control room setting. Benefits to be discussed will include fast turnaround, accurate beam quality prediction, cost efficiency, test bed for new control and operation scheme development and operator training.

Slides WEXC2 [4.292 MB]

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WEAB2

Beam and Spin Dynamics for Storage Ring Based EDM Search

dipole, storage-ring, resonance, experiment

2454

A. Lehrach
FZJ, Jülich, Germany

Funding: On behalf of the JEDI collaboration and JARA-FAME (Jülich Aachen Research Alliance)
Permanent EDMs (electric dipole moment) of fundamental particles violate both time invariance T and parity P. Assuming the CPT theorem this implies CP violation. The Standard Model (SM) predicts non-vanishing EDMs, their magnitudes, however, are expected to be unobservably small with current techniques. Hence, the discovery of a non-zero EDM would be a signal for “new physics”. As a first step towards EDM searches of charged particles in storage rings, R&D work at the Cooler Synchrotron COSY is pursued. On a longer time scale, the design and construction of a dedicated storage ring will be carried out. Spin-tracking simulations are absolutely crucial to explore the feasibility of the planned storage ring EDM experiments and to investigate systematic limitations. For a detailed study during the storage and buildup of the EDM signal, one needs to track a large sample of particles for billions of turns. Benchmarking experiments are performed at the Cooler Synchrotron COSY to check and to further improve the simulation tools and prototype accelerator components are tested. Finally, the layout of a dedicated storage ring has to be optimized by a full simulation of spin motion.

Slides WEAB2 [1.459 MB]

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WEAB3

Intra-beam Scattering Effects in ELENA

antiproton, emittance, electron, scattering

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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WEPWA005

Simulations Study for Self-Modulation Experiment at PITZ

plasma, electron, wakefield, 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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WEPWA012

Design of a Microwave Frequency Sweep Interferometer for Plasma Density Measurements in ECR Ion Sources

plasma, ion, diagnostics, ion-source

2512

G. Torrisi, R. Agnello, G. Castro, L. Celona, V. Finocchiaro, S. Gammino, D. Mascali, L. Neri, S. Passarello
INFN/LNS, Catania, Italy
T. Isernia, G. Torrisi
Universitá Mediterranea di Reggio Calabria, Reggio Calabria, Italy
G. Sorbello
University of Catania, Catania, Italy

Electron Cyclotron Resonance Ion Sources (ECRIS) are among the candidates to support the growing request of intense beams of multicharged ions. Their further development is related to the availability of new diagnostic tools, nowadays consisting of few types only of devices designed on purpose for such compact machines. Microwave Interferometry is a non-invasive method for plasma diagnostics and represents the best candidate for the whole plasma density measurements. Interferometry in ECR Ion Sources is a challenging task due to their compact size. The typical density range of ECR plasmas (10¹¹-10¹² cm^-3) causes the probing beam wavelength to be in the order of few centimetres, which is comparable to the chamber radius. The paper describes the design of a new microwave interferometer based on the so-called "frequency sweep" method: the density is here derived by the frequency shift of a beating signal obtained during the fast sweep of both probing and reference microwave signals; inner cavity multipaths contributions can thereby be suppressed by cleaning the spurious frequencies from the beating signal spectrum.

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WEPWA013

A Transport Beamline Solution for Laser-Driven Proton Beams

laser, proton, dipole, quadrupole

2515

A. Tramontana, G. Candiano, G.A.P. Cirrone, M. Costa, G. Cuttone, G. Gallo, R. Leanza, R. Manna, V. Marchese, G. Milluzzo, G. Petringa, D. Rizzo, F. Romano, S. Salamone, F. Schillaci, V. Scuderi
INFN/LNS, Catania, Italy
M. Maggiore
INFN/LNL, Legnaro (PD), Italy
V. Scuderi
ELI-BEAMS, Prague, Czech Republic

Laser-target interaction represents a very promising field in several potential applications, from nuclear physics to medicine. On the other hand optically accelerated particle beams are characterized by some extreme features, often not suitable for several applications, as an high peak current, a poor shot-to-shot reproducibility and a wide energy and angular distribution. Therefore many efforts are currently ongoing for the development of specific beam transport devices in order to obtain controlled and reproducible output beams. In this framework, this work want to report about a transport beamline solution dedicated to laser-driven beams and made of two main sections: a quadrupole-focusing device and an energy selector system. A test beam-line consisting of prototypes has been realised at INFN-LNS (National Institute of Physics-South National Laboratories, Ct, I) and partially tested with conventional accelerated proton beams. Moreover, some of these prototypes have been already tested with laser-driven beams.\ Several simulations have been also performed using the Geant4 Monte Carlo toolkit, in order to best exploit the beamline potentiality. Preliminary simulations of a transported beamline to select 5 MeV and 24 MeV proton beams are here reported.

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WEPWA015

RF Input Coupler for 20 K Cooled C-band 2.6-cell Photocathode RF Gun

cavity, gun, resonance, network

2522

T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan
T.S. Shintomi
Nihon University, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
For future use in a compact linac-driven X-ray source, a cryo-cooled C-band photocathode RF gun is under development. The RF experiment on the basic 2.6-cell test cavity has shown that the unloaded Q-value of the cavity at 20 K can be explained by the surface resistance based on the anomalous skin effect. Since the cavity was intended for preliminary experiments of the low temperature RF properties*, a new test cavity with an RF input coupler has been designed. The basic structure of the accelerating cells has not been changed from the previous cavity. Avoiding an element with a low cooling efficiency such as the inner electrode in a coaxial coupler, a simpler cylindrical input coupler has been designed. The coupler consists of a cylindrical TM01 mode waveguide and a mode converter from a rectangular TE10 mode, with both elements placed on the accelerating axis. The structure and the dimensions of the coupler have been determined using the 3-D simulation code CST Studio so that the resonant frequency of the whole system and the coupling coefficient of the coupler meet the specifications of the RF gun. The new test cavity will be completed early in 2015 at KEK.
* T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf
/IPAC2014/papers/mopri030.pdf

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WEPWA026

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

plasma, electron, proton, 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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WEPWA028

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

emittance, electron, 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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WEPWA032

CsK2Sb Growth Studies: Towards High Quantum Efficiency and Smooth Surfaces

cathode, emittance, detector, experiment

2566

S.G. Schubert, M. Gaowei, J. Sinsheimer, J. Smedley
BNL, Upton, Long Island, New York, USA
Z. Ding, E.M. Muller
SBU, Stony Brook, New York, USA
J. Kühn
HZB, Berlin, Germany
H.A. Padmore, J.J. Wong
LBNL, Berkeley, California, USA
J. Xie
ANL, Argonne, Illinois, USA

Funding: This work was supported by the US DOE, under Contracts DE-AC02-05CH11231, DE-AC02-98CH10886, KC0407-ALSJNT-I0013, DE-FG02-12ER41837 and the German BMBF, Helmholtz-Association and Land Berlin.
The properties of CsK2Sb, make this material an ideal candidate as photocathode for electron injector use. Producing photocathodes with quantum efficiencies with 7% and greater at 532 nm poses no challenge, nevertheless the traditional growth mechanisms, which are based on a sequential deposition of Antimony, Potassium and Cesium at a temperature gradient yield a rough surface with a rms roughness in the range of 25 nm. Surface roughness’s in this region impacts the emittance. At an accelerating field of 3 MV/m an rms surface roughness of 25 nm is the dominant effect on emittance and will limit injector performance. Studies are performed to optimize roughness. Various growth procedures are exploited and the surface roughness compared.

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WEPWA034

High-charge-short-bunch Operation Possibility at Argonne Wakefield Accelerator Facility

emittance, linac, wakefield, dipole

2572

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Gai, G. Ha, K.-J. Kim, J.G. Power
ANL, Argonne, Illinois, USA

Originally the drive beam line at Argonne Wakefield Accelerator (AWA) Facility was designed to generate the high charge bunch train. However, we recently installed the double dog-leg type emittance exchange beam line which have two identical dog-leg structures. With this beam line, it is possible to compress the bunch by introducing the chicane or using single dog-leg. Simulation studies have been carried out to confirm the minimum bunch length for each charge and the emittance growth by the coherent synchrotron radiation. We present GPT simulation results to show high-charge-short-bunch operation possibility at AWA facility.

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WEPWA035

Initial EEX-based Bunch Shaping Experiment Results at the Argonne Wakefield Accelerator Facility

experiment, dipole, cavity, emittance

2575

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Funding: This work is partly supported by POSTECH BK²¹⁺ and Argonne National Laboratory
A program is under development at Argonne National Laboratory to use an emittance exchange (EEX) beamline to perform longitudinal bunch shaping (LBS). The double dog-leg EEX beamline was recently installed at the Argonne Wakefield Accelerator (AWA) and the goals of the proof-of-principle experiment are to demonstrate LBS and characterize its deformations from the ideal shape due to higher-order and collective effects. The LBS beamline at the AWA consists of insert-able transverse masks mounted on an actuator and four quadrupoles (to manipulate the transverse phase space) before the EEX beamline, which consists of two identical dog-legs and a deflecting cavity. The mask and input beam parameters are varied during the experiment to explore the shaping capability and clarify the deformation sources and their mitigation. Progress on the commissioning of the LBS beamline, initial experimental data and benchmarks to GPT simulations will be presented.

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WEPWA045

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

plasma, electron, dipole, proton

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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WEPWA046

Time Domain Simulations of Detuned Accelerating Cavities for Two Beam Applications

cavity, impedance, accelerating-gradient, cathode

2605

R.M. Jones, L.R. Carver
UMAN, Manchester, United Kingdom

A multi-harmonic accelerating cavity that has its fundamental and harmonic mode frequency detuned away from the bunch repetition frequency could provide the basis for a beam driven wakefield accelerator with high transformer ratios. The excitation of multiple harmonic eigenmodes will allow high gradients to be achieved without encouraging the onset of rf breakdown or pulsed surface heating. This accelerating cavity will be introduced, and time domain simulations verifying the theory will be shown.

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WEPWA051

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

acceleration, electron, laser, 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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WEPWA057

Design Concepts for Muon-Based Accelerators

collider, factory, target, proton

2633

R.D. Ryne
LBNL, Berkeley, California, USA
Y.I. Alexahin, A.D. Bross, K. E. Gollwitzer, N.V. Mokhov, D.V. Neuffer, M.A. Palmer, K. Yonehara
Fermilab, Batavia, Illinois, USA
J.S. Berg, H.G. Kirk, R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA
S.A. Bogacz
JLab, Newport News, Virginia, USA
J.-P. Delahaye
SLAC, Menlo Park, California, USA
T.J. Roberts
Muons, Inc, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Muon-based accelerators have the potential to enable facilities at both the Intensity and the Energy Frontiers. Muon storage rings can serve as high precision neutrino sources, and a muon collider is an ideal technology for a TeV or multi-TeV collider. Progress in muon accelerator designs has advanced steadily in recent years. In regard to 6D muon cooling, detailed and realistic designs now exist that provide more than 5 order-of-magnitude emittance reduction. Furthermore, detector performance studies indicate that with suitable pixelation and timing resolution, backgrounds in the collider detectors can be significantly reduced thus enabling high quality physics results. Thanks to these and other advances in design & simulation of muon systems, technology development, and systems demonstrations, muon storage-ring-based neutrino sources and a muon collider appear more feasible than ever before. A muon collider is now arguably among the most compelling approaches to a multi-TeV lepton collider. This paper summarizes the current status of design concepts for muon-based accelerators for neutrino factories and a muon collider.

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WEPWA059

RF Plasma-Based Ion Source Modeling on Unstructured Meshes

ion, ion-source, plasma, electron

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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WEPWA062

Design and High-Power Testing of a Hybrid Photonic Band-Gap (PBG) Accelerator Structure at 17 GHz

cavity, lattice, coupling, flattop

2646

J.X. Zhang, A.M. Cook, B.J. Munroe, M.A. Shapiro, R.J. Temkin, H. Xu
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics under Award Number DE-SC0010075.
An overmoded hybrid Photonic Band Gap (HPBG) structure used as an accelerator cavity has been theoretically designed and high power tested at 17.1 GHz. The HPBG structure consists of a triangular lattice of dielectric (sapphire) and metallic (copper) rods. Due to the frequency selectivity, the hybrid PBG cavity can be operated in a TM02 mode. The maximum surface fields are on the triple point of the innermost row of the sapphire rods. The relatively high value of the surface fields resulted in a high breakdown rate (BDR) at a low gradient in the HPBG structure. Breakdown damage on the triple point edge and the metallization of copper onto the sapphire surface have been observed in the post-testing images. An improved HPBG design, that reduces the peak fields, has been developed. It will be built and tested in an effort to improve the HPBG performance.

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WEPWA063

Beam-Plasma Effects in Muon Ionization Cooling Lattices

plasma, electron, 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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WEPWA064

Ionization Cooling Channels in COSY Infinity

emittance, space-charge, multipole, solenoid

2652

B.T. Loseth, M. Berz
MSU, East Lansing, Michigan, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Ionization cooling is a method to reduce the emittance of a beam through the use of absorbers, rf cavities, and strong solenoids for focusing, arranged into a condensed lattice. By tuning lattice parameters, it is possible to construct a staged cooling channel in which the beam emittance is always considerably greater than the minimum value. In the late stages of the cooling channel, space charge effects can become a significant obstacle to further emittance reduction once the beam becomes sufficiently condensed. A method has been implemented in COSY Infinity, a beam dynamics simulation and analysis code, which efficiently and accurately calculates the self-fields of all particles on each other based on a variant of the Fast Multipole Method (FMM). In this paper, we present simulations of a muon ionization cooling channel performed in COSY, utilizing the FMM, benchmarked against G4beamline, a standard code for muon beam analysis, in order to investigate the significance of space charge effects.

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WEPWA066

The Advancement of Cooling Absorbers in COSY Infinity

scattering, electron, 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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WEPWA067

Acoustic Breakdown Localization in RF Cavities

cavity, experiment, timing, diagnostics

2658

P.G. Lane, P. Snopok, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA
E. Behnke, I.Y. Levine
Indiana University South Bend, South Bend, USA
D.W. Peterson
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy
Current designs for muon cooling channels require high-gradient RF cavities to be placed in solenoidal magnetic fields in order to contain muons with large transverse emittances. It has been found that doing so reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields it would be helpful to have a diagnostic tool which can detect breakdown and localize the source of the breakdown inside the cavity. We report here on acoustic simulations and comparisons with experimental acoustic data of breakdown from several RF cavities. Included in this analysis are our most recent results from attempting to localize breakdown using these data.

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WEPWA068

Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas

plasma, radiation, laser, vacuum

2661

C.M. Miao, T.M. Antonsen
UMD, College Park, Maryland, USA
J. Palastro
Icarus Research, Inc., Bethesda, Maryland, USA

Intense, short laser pulses propagating through inhomogeneous plasma can ponderomotively drive THz radiation. Here we consider a transition radiation mechanism (TRM) for THz generation as a laser pulse crosses a plasma boundary. Full format PIC simulations and theoretical analysis are conducted demonstrating that TRM results in low frequency, broad band, coherent THz radiation. The effect of a density ramp is also considered and shown to enhance the radiated energy.

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WEPWA072

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

acceleration, plasma, electron, wakefield

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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WEPJE007

Simulation Studies of BBU Suppression Methods and Acceptable Tolerances in Dielectric Wakefield Accelerators

wakefield, quadrupole, lattice, dipole

2685

D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
A. Zholents
ANL, Argonne, Illinois, 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.
The advantage of dielectric wakefield accelerators (DWAs) is the ability to achieve accelerating gradients well above the limits of conventional accelerators. However DWAs will also produce high transverse wakefields if the beam propagates off-center, which grow even faster than the accelerating gradient when the width of the beam channel is decreased.* It is highly important to suppress single beam breakup (BBU) instability in order for the beam to propagate long enough so that a reasonable amount of energy (e.g., 80%) from the drive bunch is extracted. In addition bending of the dielectric channel has a similar effect to off-center steering of the beam with the required tolerances on the channel straightness typically in a few micron range. For both rectangular and circular dielectric lined waveguides we use a FODO lattice with a tapered strength for suppression of BBU. We impose initial energy chirp on the drive beam to make use of the BNS damping. We change rectangular waveguide orientation by 90 degrees with a small step to make use of the quadrupole wakefield focusing. These and other techniques and tolerance requirements are discussed and simulation results are presented in this presentation.
* C. Li, W. Gai, C. Jing, J.G. Power, C.X. Tang, and A. Zholents, High gradient limits due to single bunch beam breakup in a collinear dielectric wakefield accelerator, PRSTAB 17, 091302 (2014).

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WEPJE012

Design and Optimisation of Dielectric Laser Deflecting Structures

laser, electron, acceleration, undulator

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, electron

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, electron, 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

electron, laser, acceleration, vacuum

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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WEPJE024

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

electron, plasma, laser, 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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WEPJE025

Phase Space Density as a Measure of Cooling Performance for the International Muon Ionization Cooling Experiment

emittance, luminosity, experiment, scattering

2726

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.
The International Muon Ionization Cooling Experiment (MICE)* is an experiment to demonstrate ionization cooling of a muon beam in a beamline that shares characteristics with one that might be used for a muon collider or neutrino factory. I describe a way to quantify cooling performance by examining the phase space density of muons, and determining how much that density increases. This contrasts with the more common methods that rely on the covariance matrix and compute emittances from that. I discuss why a direct measure of phase space density might be preferable to a covariance matrix method. I apply this technique to an early proposal for the MICE final step beamline. I discuss how matching impacts the measured performance.
* http://mice.iit.edu/ I am not a MICE collaboration member, and nothing herein should be construed as representing the work or views of the collaboration.

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WEPJE026

Conceptual Design of a Quadrupole Magnet for eRHIC

quadrupole, permanent-magnet, target, electron

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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WEPJE027

Partial Return Yoke for MICE Step IV and Final Step

solenoid, shielding, experiment, instrumentation

2732

H. Witte, J.S. Berg, S.R. Plate
BNL, Upton, Long Island, New York, USA
A.D. Bross
Fermilab, Batavia, Illinois, USA
J.S. Tarrant
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This paper reports on the progress of the design and construction of a retro-fitted return yoke for the international Muon Ionization Cooling Experiment (MICE). MICE is a proof-of-principle experiment aiming to demonstrate ionization cooling experimentally. In earlier studies we outlined how a partial return yoke can be used to mitigate stray magnetic field in the experimental hall; we report on the progress of the construction of the partial return yoke for MICE Step IV. We also discuss an extension of the Partial Return Yoke for the final step of MICE; we show simulation results of the expected performance.

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WEPMA008

RF Design of a High Gradient S-Band Travelling Wave Accelerating Structure for Thomx Linac

accelerating-gradient, impedance, linac, vacuum

2757

M. El Khaldi, L. Garolfi
LAL, Orsay, France

There is growing demand from the industrial and research communities for high gradient, compact RF accelerating structures. The Thomx high gradient structure (HGS) is travelling wave (TW), quasi constant gradient section and will operate at 2998.55 MHz (30°C in vacuum) in the 2π/3 mode. The optimization of the cell shape (Electromagnetic design) has been carried out with the codes HFSS and CST MWS, in order to improve the main RF characteristics of the cavity such as shunt impedance, accelerating gradient, group velocity, modified Poynting vector, surface fields, etc. Prototypes with a reduced number of cells have been designed. For an input power of about 20 MW, EM simulation results show that an average accelerating gradient of 28 MV/m is achieved which corresponds to a peak accelerating gradient of 35 MV/m, a peak surface gradient of 44 MV/m and peak modified Poynting vector S_cmax of 0.24 MW/mm².

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WEPMA009

3 GHz Single Cell Cavity Optimization Design

accelerating-gradient, linac, cavity, electron

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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WEPMA012

High-Q Cavity Operation: Study on the Thermoelectrically Induced Contribution to RF Surface Resistance

cavity, shielding, niobium, operation

2771

J.M. Köszegi, J. Knobloch, O. Kugeler, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

We present a study concerning the operation of a superconducting RF cavity (non-doped niobium) in horizontal testing with the focus on understanding the thermoelectrically induced contribution to the surface resistance. Starting in 2009, we suggested a means of reducing the residual resistance by warming up a cavity after initial cooldown to about 20K and cooling it down again. In subsequent studies we used this technique to manipulate the residual resistance by more than a factor of 2. We postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Since several questions remained open, we present here a more extensive study including measurement of two additional passband modes of the 9-cell cavity that confirms the effect. We also discuss simulations that substantiate the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters result in a non-symmetric current distribution. Hence a significant amount of magnetic flux can be generated at the RF surface resulting in an increased surface resistance.

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WEPMA017

Alvarez DTL Cavity Design for the UNLAC Upgrade

cavity, electron, DTL, impedance

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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WEPMA020

SIS100 Dipole Field Harmonics and Dynamic Aperture Calculations

dipole, multipole, quadrupole, synchrotron

2795

C. Omet, E.S. Fischer, G. Franchetti, V. Kornilov, A. Mierau, C. Roux, P. Schnizer, D. Schäfer, S. Sorge, P.J. Spiller, K. Sugita
GSI, Darmstadt, Germany

During the acceptance test of the First of Series (FoS) SIS100 super-ferric dipole, detailed field measurements have been done. The harmonic coefficients have been extracted from these and dynamic aperture simulations have been done which are presented here. Furthermore, geometric precision measurement tools for the magnet have been developed to track down the field errors to geometric errors. Finally, mitigation actions have been taken to reduce these errors during manufacturing to ensure the design beam survival rate in SIS100.

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WEPMA021

Efficient Pulsed Quadrupole

quadrupole, damping, pulsed-power, operation

2799

I.J. Petzenhauser, U. Blell, P.J. Spiller
GSI, Darmstadt, Germany
C. Tenholt
IAP, Frankfurt am Main, Germany

Funding: Work supported by EuCARD-2-WP03-EnEfficient. EuCARD-2 is co-funded by the partners and the European Commission under Capacities 7th Framework Programme, Grant Agreement 312453
In order to raise the focusing gradient in case of bunched beam lines, an alternative, iron free, pulsed quadrupole was designed. The transfer channels between synchrotrons as well as the final focusing for the production of secondary beams are possible applications. The quadrupole is running in a pulsed mode, which means an immense saving of energy by avoiding standby operation. Still the high gradients demand high currents. Hence a circuit had to be developed which is able to recover a significant amount of the pulsing energy for following shots. The basic design of the electrical circuit of the pulsed quadrupole is introduced. Furthermore more energy efficient circuits are presented and the limits of adaptability are considered.

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WEPMA024

System Design for a Deterministic Bunch-to-Bucket Transfer

synchrotron, LLRF, ion, timing

2809

T. Ferrand
TEMF, TU Darmstadt, Darmstadt, Germany
J.N. Bai
IAP, Frankfurt am Main, Germany

Funding: Supported by GSI and the Technical University Darmstadt in the frame of the cooperation for FAIR.
A deterministic bunch to bucket transfer system is currently under development in the frame of the FAIR project at GSI. To achieve our accuracy and stability requirements, a set of hardware modules will be implemented. These hardware modules are expected to provide values such as the relative phase advance between the RF systems of both, the source and the target synchrotron according to an external timing system. These values are exchanged via optical fibers between different supply rooms, and the considered RF signals are re-synthesized locally. These re-synthesized signals are synchronized to enable a precise phase advance control between the synchrotrons’ RF systems. The first step of the development consists in modeling the actual DDS and DSP-based LLRF environment of the SIS18 under Ptolemy-II. Measurements on real devices will be performed concurrently to the simulation. We expect to use this simulation to refine our timing expectations regarding the synchronization process and the inter-module communication protocols and design the synchronization function, which will be implemented on the hardware modules.

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WEPMA029

Design of a Normal Conducting Cavity for Arrival Time Stabilization at FLASH

cavity, wakefield, coupling, HOM

2818

M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany
J. Roßbach
Uni HH, Hamburg, Germany

It has been shown, that beam-based feedback loops stabilize the bunch arrival time in the femtoseconds range. However, further minimizing the bunch arrival time jitter requires a faster actuator that is a normal conducting cavity with higher bandwidth compared to narrow-band superconducting cavities. We present the design of a 4-cell normal conducting cavity that is going to be used in a fast beam-based feedback at free-electron laser FLASH at Hamburg. The input power will be injected to the cavity via a loop coupler from the side of the first cell. The operating frequency of the designed cavity is about 3 GHz with an adjustable bandwidth. The long range longitudinal wakefield calculation results are reported to investigate the cavity performance for multi-beam operation up to 3 MHz bunch repetition rate. The results declare that the influence of the long range wakefield on the arrival time jitter is less than 1 fs.

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WEPMA030

Design and Characterization of Permanent Magnetic Solenoids for REGAE

solenoid, emittance, electron, experiment

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, electron, gun, 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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WEPMA035

Low- and High-Beta SRF Elliptical Cavity Stiffening

cavity, resonance, proton, SRF

2835

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Elliptical SRF cavities are the main accelerating structures in many accelerators worldwide. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape. Also mechanical eigen resonances of cavities are the main source of the microphonics. To withstand any kind of external loads on the resonator walls different schemes of the cavity stiffening were applied. In the paper we report the basic investigations of the cavity stiffening using FNAL 650 MHz β=0.92 and 0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.

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WEPMA036

Double-Cell Notch Filter for SRF Gun Investigations

gun, cathode, SRF, cavity

2838

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
J. Knobloch, A. Neumann
HZB, Berlin, Germany
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that results in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with a zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine-tuning during operation. To eliminate the problems of the choke filter fine-tuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double-cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modifications.

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WEPMA040

Magnet Studies for the Accelerator FLUTE at KIT

dipole, experiment, linac, multipole

2849

S. Hillenbrand, A. Bernhard, A.-S. Müller, M.J. Nasse, R. Rossmanith, R. Ruprecht, M. Sauter, S. Schott, M. Schuh, S. Schulz, M. Weber, P. Wesolowski, C. Widmann
KIT, Karlsruhe, Germany

At KIT we are currently constructing the compact linear accelerator FLUTE (Ferninfrarot Linac Und Test Experiment). This 41 MeV machine is aimed at accelerator physics and synchrotron radiation research, using ultra-short electron bunches. The electrons are generated at a photo-cathode using picosecond long UV laser pulses. A magnetic chicane is used to compress the bunches longitudinally to a few femtoseconds. This contribution describes both the magnet design, in particular the optimization of the chicane dipoles based on finite element method (FEM) simulations, as well as the implementation of a magnet measurement system.

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WEPMA045

Energy Deposition and DPA in the Superconducting Links for the HiLumi LHC project at the LHC Interaction Points

neutron, photon, luminosity, radiation

2865

F. Broggi, A. Bignami, C. Santini
INFN/LASA, Segrate (MI), Italy
A. Ballarino, F. Cerutti, L.S. Esposito
CERN, Geneva, Switzerland

Funding: The work is part of HiLumi LHC Design Study, partly funded by the European Commission, GA 284404, and included in the High Luminosity LHC project.
In the framework of the upgrade of the LHC machine, the powering of the LHC magnets foresees the removal of the power converters and distribution feedboxes from the tunnel and its location at the surface[1]. The Magnesium Diboride (MgB2) connecting lines in the tunnel will be exposed to the debris from 7+7 TeV p-p interaction. The Superconducting (SC) Links will arrive from the surface to the tunnel near the separation dipole, at about 80 m from the Interaction Point at IP1 and IP5. The Connection Box (where the cables of the SC Links are connected to the NbTi bus bar) will be close to the beam pipe. The debris and its effect on the MgB2 SC links in the connection box (energy deposition and displacement per atom) are presented. The effect of thermal neutrons on the Boron consumption and the contribution of the lithium nucleus and the alpha particle on the DPA are evaluated. The results are normalized to an integrated luminosity of 3000 fb-1, value that represents the LHC High Luminosity lifetime. The dose delivered to the SC Links is found to be below the damage limit. Further studies are necessary to correlate the induced displacement per atom to the superconducting properties.

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WEPMA050

Permanent Dipole Magnet R&D for SPring-8-II

dipole, quadrupole, permanent-magnet, shielding

2883

T. Taniuchi, T. Aoki, K. Fukami, S. Takano, T. Watanabe
JASRI/SPring-8, Hyogo-ken, Japan

Permanent magnets are promising for future light source machines with its compactness, small power consumption. We have proposed a variable-field permanent dipole magnet and demonstrated its performance*. Following the result, a prototype magnet with a longitudinal field gradient and a magnetic shunt circuit was designed and fabricated. The longitudinal field gradient enables a lower beam emittance and the magnetic shunt circuit improves a temperature stability of the magnetic field strength. Simulation studies and measurement results are presented in this report. The interference of magnetic fields between neighboring magnets was also investigated.
* T. Watanabe et al., Proc. of IPAC 2014.

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WEPMA053

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

cavity, electron, 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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WEPMN010

Analysis of the Electromagnetic Field in the Coupler of Normal Temperature Travelling-Wave Accelerating Tube

coupling, cavity, electromagnetic-fields, emittance

2934

X. He, M. Hou
IHEP, Beijing, People's Republic of China
S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

With the developed requirement of the beam quality in modern accelerators, rapid development of all kinds of accelerating structures with different frequencies and materials have been achieved. However, the normal temperature travelling-wave (TW) accelerating structures which are widely used in Free Electron Laser (FEL) are still indispensable. For reducing the beam emittance, it is very important to optimize the symmetry of the high-order electromagnetic field in the coupler of such accelerating structures. In this paper, the symmetry of the electromagnetic field in TW accelerator couplers using different coupling mechanisms was analysed. A lot of design optimization as well as the result analysis work has been done for the three kinds of commonly used waveguide-coupled TW accelerating structures: single-feed electrical-coupling, dual-feed electrical-coupling using magic tee in feeding waveguide and dual-feed magnetic-coupling using J-type feeding waveguide. Finally, basing on lots of simulation results and the performances during the fabrication, measurement and RF conditioning of these three kinds of structures, the J-type racetrack coupler type is regarded as the best choice.

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WEPMN011

RF Modulation Studies on the S-Band Pulse Compressor

coupling, cavity, flattop, klystron

2937

S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
F. Zhao
IHEP, Beijing, People's Republic of China

An S band SLED-type pulse compressor has been manufactured by IHEP to challenge the 100 MW maximum input power, which means the peak power around the coupling irises is about 500 MW at the phase reversal time. In order to deal with the breakdown problem, the dual side-wall coupling irises model was used. To further improve the reliability at very high power, RF phase modulation (PM) with flat-top output is considered. By using the CST Microwave Studio (MWS) transient solver, a new method was developed to simulate the time response of the pulse compressor. In addition, the theoretical and experimental results of the PM theory are also presented in this paper.

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WEPMN014

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

cavity, electron, 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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WEPMN016

Observation of Dark Current Dependence on Stored Energy in an L-Band RF Gun

cathode, gun, solenoid, experiment

2956

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

A pin cathode has been installed into an L-band photocathode gun to study the influence of stored energy on field emission. The stored energy was varied by tuning the recess of the cathode in order to have the same E-field on the cathode tip. We have observed 5 times difference of dark current level at the same E-field, while by varying the stored energy by three fold. Dynamics study reveals the difference is not caused by transmission, but by emission process itself. We'll present experiment results and discuss possible mechanisms about the phenomena.

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WEPMN017

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

wakefield, electron, 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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WEPMN018

Measurement of Cell-Cell Coupling Coefficient in Photocathode RF Gun

gun, coupling, laser, cathode

2963

P. Wang, H.B. Chen, Q. Gao, J. Shi, L. Zhang
TUB, Beijing, People's Republic of China

A photocathode RF gun is under cold rest in Tsinghua University. We measured the single cavity frequency and the cell-cell coupling coefficient by the detuning method with high accuracy. We use a simplified model to illustrate the whole process of the measurement. The data obtained in the cold test seem to accord with that from the model very well.

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WEPMN019

Calorimetric Power Measurements in X-band High Power RF

klystron, experiment, operation, linac

2967

X.W. Wu, H.B. Chen, L. Zhang
TUB, Beijing, People's Republic of China
N. Catalán Lasheras, B.J. Woolley, W. Wuensch
CERN, Geneva, Switzerland

With the aim to test prototype accelerating structures for CLIC at high-gradient, new klystron-based, X-band high power test stands are being built at CERN. These tests stands are referred to as Xboxes with Xbox1 and Xbox2 being already operational. Stainless steel loads are placed in the end of the Xbox-1 system to absorb the remaining power which comes out of the accelerating structure. Power information is important and needs to be measured precisely. A new power measuring method based on calorimetry is proposed independent from RF measurements subject to frequent calibration. The principles of the method and simulations are presented and the results of actual experimentation are used to validate the method. The results show calorimetric measurement is feasible method and have a good precision at this power level.

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WEPMN022

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

electron, vacuum, cathode, 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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WEPMN026

Development of Non-resonant Perturbing Method for Tuning Traveling Wave Deflecting Structures

cavity, network, higher-order-mode, dipole

2985

J.H. Tan, W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D.C. Tong
TUB, Beijing, People's Republic of China

For traveling wave accelerating structures, the tuning method assisted by bead pull technique based on non-resonant perturbation field distribution measurement has been widely used. Long periodic traveling wave deflecting structure, which operating at HEM11 mode, is difficult to use non-resonant perturbation method, and a improved method has been developed for measuring and tuning by "cage" type perturbing object at SINAP. The measurements on x-band traveling wave deflecting structure are presented in this paper.

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WEPMN028

Preliminary Mechanical Design of Ceramic Pipe Film Coating Equipment at Hefei Light Source II

cathode, vacuum, injection, experiment

2988

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

Ceramic vacuum chambers are important components of the injection chamber at Hefei Light Source II (HLS II). The length of each Ceramic vacuum chamber is 350 mm and their inner surface is coated with TiN thin film whose properties are low secondary electron yield (SEY), good electrical conductivity, stability of performance, ability to block hydrogen permeation. Considering that the cross section of Ceramic pipe is racetrack structure, Ti plate was chose as the cathode to improve TiN thin film deposition rate. Meanwhile, the authors designed a motor drive magnetron sputtering film coating equipment to obtain uniform TiN film.

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WEPMN045

IOT Use as a Power Source for a Linear Accelerating Structure

cavity, coupling, klystron, proton

3027

E.A. Savin, S.V. Matsievskiy, N.P. Sobenin, I.D. Sokolov
MEPhI, Moscow, Russia
A.A. Zavadtsev
Nano, Moscow, Russia

Nowadays the interest of using compact and high efficiency power sources called Inductive Output Tubes (IOT) [1] for feeding accelerating structures with the required pulsed power around 1MW is increasing. In this article results of the beam dynamics and geometry calculations for the L-band IOT S-band IOT and accelerator-generator hybrid module are presented. Different concepts of the cavity have been proposed, but the most efficient has been chosen. The layout of the generator cell with biperiodic bunсher cells has been investigated. The hybrid structure composed from the generator cell and the compact SW accelerating section is proposed.
IOT, linear accelerator, power supply, klystrons

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WEPMN050

A Pinger Magnet System for the ALBA Synchrotron Light Source

storage-ring, kicker, electron, high-voltage

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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WEPMN057

Calculation and Design of a RF Cavity for a Novel Compact Superconducting Cyclotron for Radioisotope Production

cavity, cyclotron, focusing, ion

3055

D. Gavela, J. Calero, L. García-Tabarés, A. Guirao, D. Obradors-Campos, C. Oliver, J.M. Pérez Morales, I. Podadera, F. Toral
CIEMAT, Madrid, Spain

Funding: Work partially funded by CDTI and the Spanish Ministry of Economy and Competitiveness, under the subprogram CENIT, project AMIT, reference CEN-20101014
The AMIT cyclotron will be a 8.5 MeV, 10 microAmp, CW, H⁻ accelerator for the purpose of radioisotope production. It includes a superconducting, weak focusing, 4 T magnet, which allows for a low extraction radius and a compact design. The RF cavity design has to deal with challenging requirements: high electric fields created by the required accelerating voltage (60 kV – 70 kV) on a small gap, a small aperture of the magnet leading to high capacitances and thermal losses, and a requirement for a low overall size of the cavity. A quarter wave resonator with one dee (two acceleration gaps) design was chosen. Calculations with HFSS have been performed to compute the resonant frequency, tuners sensitivity, S-parameters, power losses and geometry for input coupler and pickup. A structural Ansys model has been used to analyze the stresses and the deformations of the cavity. A thermal Ansys model was used for the design of the cooling circuits and the calculation of the temperature distribution. Finally, the fluid dynamics of the cooling circuits have been carefully studied. The results of these calculations and the consequent design decisions are presented in this paper.

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WEPMN058

Transverse Impedance Measurements and DC Breakdown Tests on the First Stripline Kicker Prototype for the CLIC Damping Rings

impedance, coupling, kicker, extraction

3058

C. Belver-Aguilar, A. Faus-Golfe
IFIC, Valencia, Spain
M.J. Barnes, H.A. Day
CERN, Geneva, Switzerland
A. Faus-Golfe
LAL, Orsay, France
F. Toral
CIEMAT, Madrid, Spain

A first stripline kicker prototype for beam extraction from the CLIC Damping Rings (DRs) has been designed at IFIC and CIEMAT, with excellent field homogeneity, good power transmission and low beam coupling impedance. The prototype has been built by the company Trinos Va\-cuum Projects, and laboratory tests and measurements have been carried out at CERN to characterize, without beam, the electromagnetic response of the striplines. In this paper, we present the measurements of the transverse beam coupling impedance, using the coaxial wire method, and a comparison with simulations. Furthermore, results of DC breakdown tests, using High Vol\-ta\-ge (HV) power supplies, are also reported.

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WEPMN059

Design Study and Construction of a Transverse Beam Halo Collimation System for ATF2

wakefield, collimation, dipole, background

3062

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
I. Podadera, F. Toral
CIEMAT, Madrid, Spain

Funding: Work supported by IDC-20121074, FPA2013-47883-C2-1-P and ANR-11-IDEX-0003-02
The feasibility and efficiency of a transverse beam halo collimation system for reducing the background in the ATF2 beamline has been studied in simulations. In this paper the design and construction of a retractable transverse beam halo collimator device is presented. The wakefield induced-impact of a realistic mechanical prototype has been studied with CST PS, as well as the wakefield beam dynamics impact by using the tracking code PLACET.

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WEPHA002

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

impedance, damping, network, electron

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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WEPHA003

Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown

vacuum, collider, injection, hadron

3100

V. Bencini, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, C. Yin Vallgren
CERN, Geneva, Switzerland

During the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+.

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WEPHA007

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

electron, cryogenics, vacuum, 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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WEPHA009

Propagation of Radioactive Contaminants Along the Isolde Beamline

vacuum, target, ion, proton

3115

R. Kersevan, M. Ady, A. Dorsival, A. Gottberg, M. Maietta, G. Vandoni
CERN, Geneva, Switzerland

The vacuum system of RIB facilities is entirely hermetical, with storage of effluents and controlled release to atmosphere after a decay time. In Isolde, distributed primary pumping is sectorized in three parts, but all effluents are conveyed together in a unique tank. Thus, highly contaminated gas from the target and front end may be mixed with less contaminated gas from the beam transfer lines. This study aims at analysing and quantifying the distribution and propagation of neutral rare gas radioactive isotopes along the Isolde beam-line by numerical simulation (steady-state and time resolved Test-Particle Monte-Carlo, Molflow+) and experimental means. The time-resolved Monte-Carlo integrates decay time for the propagating species. To measure the distribution of contaminants, sampling filters are installed at the exhaust of the vacuum turbo-molecular pumps. Comparison between simulation and experiment shows excellent agreement, confirming the pertinence of the Monte-Carlo tool to radioactive species propagation. The filtering effect of magnetic sectors, the RFQ Cooler, and Buncher on the propagating neutral isotopes are quantified.

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WEPHA016

Experimental Setups to Determine the Damage Limit of Superconducting Magnets for Instantaneous Beam Losses

proton, superconducting-magnet, injection, experiment

3138

V. Raginel, B. Auchmann, R. Schmidt, D. Schoerling, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland

The damage mechanism of superconducting magnets due to the direct impact of high intensity particle beams is not well understood. Obvious candidates for upper bounds on the damage limit are overheating of insulation, and melting of the conductor. Lower bounds are obtained by the limits of elasticity in the conductor, taking into account dynamic effects (elastic stress waves). The plastic regime in between these two bounds will lead to differential thermal stress between the superconductor and stabilizer, which may lead to a permanent degradation of the magnet. An improved understanding of these mechanisms is required especially in view of the planned increase in brightness of the beams injected into the LHC and of the future High Luminosity-LHC [2] and Future Circular Collider (FCC). In this paper the plans for room temperature damage tests on critical parts of superconducting magnets and the strategy to test their damage levels at 4.3 K in the HiRadMat facility at CERN , using a 440 GeV proton beam generated by the Super Proton Synchrotron (SPS), is presented. Moreover the status of numerical simulations using FLUKA and multi-physics FEM code (ANSYS) to assess the different effect and the irradiation of the proposed experimental setup in preparation of the test is shown.

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WEPHA023

Ferrite-tuner Development for 80 MHz Single-Cell RF-Cavity Using Orthogonally Biased Garnets

cavity, coupling, resonance, operation

3159

C. Vollinger, F. Caspers
CERN, Geneva, Switzerland

In the frame of the LHC Injector Upgrade program involving the existing 80 MHz cavities in the CERN PS accelerator, an orthogonally biased ferrite tuner is foreseen to complement the current motor-driven piston tuner. This ferrite tuner shall provide the possibility of a fast frequency shift of about 200 kHz on the fundamental mode, to allow a fast switching between proton and ion frequencies. In order to avoid water cooling and related issues, the challenge was to bring magnetic losses in the tuner to a minimum such that a forced air cooling scheme will be sufficient. The tuner was first designed with simulation tools, a prototype was built and low-power RF testing was performed on the tuner-cavity combination to evaluate tuning range, bandwidth, and stability. These tests were carried out on a single-cell copper RF cavity mock-up with a resonance frequency of 88 MHz, where the ferrite tuner is connected via a tuning loop and the perpendicular magnetic bias for ferrite tuner is provided by a DC bias supply. Simulations and test data will be presented.

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WEPHA024

Preliminary Design of a Perpendicular Biased Ferrite Loaded Accelerating Cavity

cavity, resonance, operation, factory

3163

J. Eberhardt, F. Caspers, C. Vollinger
CERN, Geneva, Switzerland

A ferrite loaded accelerating cavity with a frequency sweep of 18 to 40 MHz is studied for a possible upgrade of the CERN accelerator complex. The resonance frequency of a ferrite loaded cavity shifts by applying an external magnetic bias field to the ferrite material by means of changing the relative permeability. We present the electromagnetic design of such a cavity with a special emphasis on the modeling of the nonlinear, anisotropic and dispersive characteristics of the ferrite’s relative permeability above magnetic saturation. For experimental crosscheck, a ferrite loaded resonant test setup was built which provides results for the material performance in a magnetic bias field. A comparison of numerical simulations and experimental measurements is shown and calculations are benchmarked by measurement data. Based on this study a preliminary design of a ferrite loaded accelerating cavity is described.

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WEPHA039

Inrush Current Suppression Scheme of Hot Swap Power Modules

power-supply, controls, synchrotron, photon

3200

Y.T. Li, C.Y. Liu, K.-B. Liu
NSRRC, Hsinchu, Taiwan

The corrected magnet power supplies apply modular designed for Taiwan Photon Source synchrotron project (TPS). If the module is damaged in the chassis, it must to be replaced without interrupting the power. However, the modular is a shared DC bus. If there is no good design and planning, it will cause the protection circuit into action. In this article the theoretical derivation and implementation are used to prove the feasibility and necessity of the soft-start circuit. In the actual signal measurements it could be clearly seen the inrush currents is refrained and improved. Finally, the soft-start circuit is implemented applications in correction magnet power supply modular of Taiwan Photon Source synchrotron project (TPS).

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WEPHA041

ALGORITHM AND CIRCUIT TO IMPROVE ZERO-CROSSING STABILITY OF BIPOLAR TPS TRIM COIL POWER SUPPLY

controls, feedback, FPGA, interface

3206

B.S. Wang, Y.-C. Chien, P.C. Chiu, K.T. Hsu, C.Y. Liu, K.-B. Liu, Y.S. Wong, C.Y. Wu
NSRRC, Hsinchu, Taiwan

In TPS (Taiwan Photon Source) project, 58 home-built small form factor bipolar power supplies are used to fine-tune the trim coil of booster ring bending dipole magnets. With the preliminary analog PI control loop design version, current output will tend to behave with poor linearity around zero current. By employing DSP chip, a full digital PI control loop design together with optimal MOSFT switching algorithm and 13bits PWM output capability is capable of improving the output current performance around zero current. Before the final realization, MATLAB SIMULINK is utilized to find out the optimal MOSFT switching algorithm, and then physical circuit is implemented and tested. The result and design will be demonstrated in this paper to show significant improvement around zero current.

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WEPHA042

Commissioning of the TPS Cooling System: Testing, Adjusting, Balancing and Numerical Simulation

controls, storage-ring, monitoring, status

3209

Z.-D. Tsai, W.S. Chan, Y.C. Chang, C.S. Chen, Y.-C. Chung, C.W. Hsu, C.Y. Liu
NSRRC, Hsinchu, Taiwan

The civil construction and utility systems of the 3-GeV Taiwan Photon Source (TPS) at NSRRC are ready for machine commissioning in 2014. To achieve a highly precise control of temperature, the thermal load must be carefully controlled and balanced. On analysis of the characteristics between the water pipes and the balance valves, a specified control philosophy can effectively adjust the pressure load on the branch pipes to balance the water flow. With regard to the air flow, we use a damper, baffle plant or variable air-volume (VAV) box to balance the air flow of each diffuser. Here we discuss the mechanism through a numerical simulation of the hydrodynamics and verify the practical influences of the testing, adjusting and balancing (TAB) for de-ionized water and the heating, ventilation and air-conditioning (HVAC) system.

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WEPHA060

5MW Power Upgrade Studies of the ISIS TS1 Target

target, neutron, proton, scattering

3253

C. Bungau, A. Bungau, R. Cywinski, T.R. Edgecock
University of Huddersfield, Huddersfield, United Kingdom
C.N. Booth, L. Zang
Sheffield University, Sheffield, United Kingdom

The increasing demand for neutron production at the ISIS neutron spallation source has motivated a study of an upgrade of the production target TS1. This study focuses on a 5 MW power upgrade and complete redesign of the ISIS TS1 spallation target, reflector and neutron moderators. The optimisation of the target-moderator arrangement was done in order to obtain the maximum neutron output per unit input power. In addition, at each step of this optimisation study, the heat load and thermal stresses were calculated to ensure the target can sustain the increase in the beam power.

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WEPTY004

Mathematical Modeling and Analysis of a Wide Bandwidth Bipolar Power Supply for the Fast Correctors in the APS Upgrade Controller

power-supply, controls, feedback, operation

3264

B. Song, J. Wang
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The APS Upgrade requires a fast bipolar power supply for the fast correction magnets. The performance requirement of the power supply includes a -3dB at 10 kHz small-signal bandwidth for the output current. This requirement presents a technical challenge to the design of the power circuit and the power supply regulator because the magnet load may have a significant inductance and make it difficult to achieve a high bandwidth for the current. In order to meet the requirement, different circuit topologies and regulators are being investigated. One of the candidate designs combines a standard H-bridge pulse-width modulation (PWM) circuit and a linear power amplifier to provide a ±15A DC current and an AC component up to 1% of the full scale with the required bandwidth. An appropriate feedback control loop and a current regulator are being designed. The mathematical modeling and simulation of the power circuit and the control loop are being conducted to prove the concept of the design. This paper presents the design of the circuit, mathematical modeling, and the simulation results.

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WEPTY012

Multiple Scattering Effects of a Thin Beryllium Window on a Short, 2 nC, 60 MeV Bunched Electron Beam

scattering, vacuum, experiment, emittance

3280

E.E. Wisniewski, M.E. Conde, W. Gai, G. Ha, J.G. Power
ANL, Argonne, Illinois, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: U.S. Dept of Energy Office of Science under contract number DE-AC02-06CH11357.
The Argonne Wakefield Accelerator 75 MeV drive beamline at Argonne National Laboratory has as its electron source a Cesium telluride photocathode gun with a vacuum requirement on the order of 10^-10 torr. In conflict with this, the experimental program at AWA sometimes requires beamline installation of experimental structures which due to materials and/or construction cannot meet the stringent vacuum requirement. One solution is to sequester these types of structures inside a separate vacuum chamber and inject the beam through a thin Beryllium window. The downside is that multiple scattering effects degrade the beam quality to some degree which is not well-known. This study was done in an effort to better understand and predict the multiple scattering effects of the Be thin window, particularly on the beam transverse size. The results of measurements are compared with GEANT4 Monte Carlo simulations via G4beamline and analytical calculations via GPT.

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WEPTY014

Development of Fast Kickers for the APS MBA Upgrade

kicker, impedance, high-voltage, injection

3286

C. Yao, J. Carwardine, A.R. Cours, F. Lenkszus, R.R. Lindberg, L.H. Morrison, X. Sun, J. Wang, F. Westferro, A. Xiao
ANL, Argonne, Illinois, USA

Funding: *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS multi-bend achromat (MBA) upgrade storage ring will support two bunch fill patterns: a 48-singlets and a 324-singlets. A “swap out” injection scheme is adopted. In order to minimize the beam loss and residual oscillation of injected beam and to minimize the perturbation of stored beam during a swap-on injection, the rise, fall, and flat-top parts of the kicker pulse must be held within a 22.8-ns interval. Traditional ferrite-core-type kickers can’t meet the timing requirements; therefore, we decided to use stripline-type kickers. We have completed a preliminary design of a prototype kicker geometry. Procurement of the pulser supply and other components of an evaluation system is under way. We report the specification and design of the fast kicker and current status.

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WEPTY016

RF Modeling of a Helical Kicker for Fast Chopping

kicker, impedance, experiment, linac

3293

M.H. Awida, A.Z. Chen, T.N. Khabiboulline, G.W. Saewert, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

High intensity proton particle accelerators that supports several simultaneous physics experiments requires sharing the beam. A bunch by bunch beam chopper system located after the Radio Frequency Quadrupole (RFQ) is required in this case to structure the beam in the proper bunch format required by the several experiments. The unused beam will need to be kicked out of the beam path and is disposed in a beam dumb. In this paper, we report on the RF modeling results of a proposed helical kicker. Two beam kickers constitutes the proposed chopper. The beam sequence is formed by kicking in or out the beam bunches from the streamline. The chopper was developed for Project X Injection Experiment (PXIE).

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WEPTY037

A Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

cavity, booster, solenoid, TRIUMF

3358

C.-Y. Tan, J.E. Dey, R.L. Madrak, W. Pellico, G.V. Romanov, D. Sun, I. Terechkine
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A perpendicular biased 2nd harmonic cavity is currently being designed for the Fermilab Booster. Its purpose cavity is to flatten the bucket at injection and thus change the longitudinal beam distribution so that space charge effects are decreased. It can also work at transition to help beam cross it. The choice of perpendicular biasing over parallel biasing is that the Q of the cavity is much higher and thus allows the accelerating voltage to be a factor of 2 higher than a similar parallel biased cavity. This cavity will also provide a higher accelerating voltage per meter than the present folded transmission line cavity. However, this type of cavity presents technical challenges that need to be addressed. The two major issues are cooling of the garnet material from the effects of the RF and the cavity itself from eddy current heating because of the 15 Hz bias field ramp. This paper will address the technical challenge of preventing the garnet from overheating.

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WEPTY044

Phase Transients in the Higher-Harmonic RF Systems For the ALS-U Proposal

experiment, impedance, beam-loading, synchrotron

3372

J.M. Byrd, S. De Santis, T.H. Luo, C. Steier
LBNL, Berkeley, California, USA

Funding: This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231.
The ALS upgrade proposal (ALS-U) requires lengthening the bunch by a factor of at least four in order to increase the beam lifetime to acceptable values. Due to the presence of gaps in the fill pattern, required by the injection/extraction kicker system, the beam-induced voltage in the passive, normal-conducting, cavities which we plan to use is not constant over the length of a bunch train. We present our result on the optimal tuning of the harmonic cavities to obtain the best lifetime increase, including the effects of strongly non-gaussian bunch shapes and wakefield distortions of the potential well.

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WEPTY046

Progress on the MICE 201 MHz Cavities at LBNL

cavity, Windows, coupling, network

3378

T.H. Luo, A.J. DeMello, A.R. Lambert, D. Li, S. Prestemon, S.P. Virostek
LBNL, Berkeley, California, USA

The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of amuon beam by ionization in energy absorbers. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity used to compensate the longitudinal energy loss in the absorbers. The LBNL team has designed and fabricated all MICE RF cavities. The cavities will be post-processed and RF measured before being installed in the RF modules. We present the recent progress on this work, including the low level RF measurement on cavity body and Be windows, the electro-polishing (EP) on the cavity surface, the numerical simulation on cavity Be window detuning, and the ongoing mechanical designing work of cavity components.

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WEPTY047

Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel

cavity, Windows, collider, emittance

3381

T.H. Luo, D. Li, S.P. Virostek
LBNL, Berkeley, California, USA
D.L. Bowring
Fermilab, Batavia, Illinois, USA
R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed within thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.

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WEPTY050

Low Powered RF Measurements of Dielectric Materials for use in High Pressure Gas Filled RF Cavities

cavity, radio-frequency, factory, collider

3387

B.T. Freemire
IIT, Chicago, Illinois, USA
G. Arriaga
Northern Illinois Univerity, Dekalb, Illinois, USA
D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
H.D. Phan
McDaniel College, Westminster, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

The Helical Cooling Channel scheme envisioned for a Muon Collider or Neutrino Factory requires high pressure gas filled radio frequency cavities to operate in superconducting magnets. One method to shrink the radii of the cavities is to load them with a dielectric material. The dielectric constant, loss tangent, and dielectric strength are important in determining the most suitable material. Low powered RF measurements of the dielectric constant and loss tangent were taken for multiple purities of alumina and magnesium calcium titanate, as well as cordierite, forsterite, and aluminum nitride. Measurements of alumina were consistent with previously reported results. The results were used to design an insert for a high powered RF test that included sending beam through the cavity.

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WEPTY056

Novel High Power Sources for the Physics of Ionospheric Modification

gun, cathode, electron, 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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WEPTY059

Alternative Methods for Field Corrections in Helical Solenoids

dipole, solenoid, beam-cooling, emittance

3409

K.E. Melconian
Texas A&M University, College Station, Texas, USA
G. Flanagan, S.A. Kahn
Muons, Inc, Illinois, USA
S. Krave, M.L. Lopes, J.C. Tompkins, K. Yonehara
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance under DOE Contract DE-AC02-07CH11359
Helical cooling channels have been proposed for highly efficient 6D muon cooling. Helical solenoids produce solenoidal, helical dipole, and helical gradient field components. Previous studies explored the geometric tunability limits on these main field components. In this paper we present two alternative correction schemes, tilting the solenoids and the addition of helical lines, to reduce the required strength of the anti-solenoid and add an additional tuning knob.

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WEPTY062

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

multipactoring, electron, 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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WEPTY065

Quadrupole Magnet for a Rapid Cycling Synchrotron

quadrupole, dipole, synchrotron, acceleration

3428

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.
Rapid Cycling Synchrotrons (RCS) feature interleaved warm and cold dipole magnets; the field of the warm magnets is used to modulate the average bending field depending on the particle energy. It has been shown that RCS can be an attractive option for fast acceleration of particles, for example muons which decay quickly. In previous studies it was demonstrated that in principle warm dipole magnets can be designed which can provide the required ramp rates, which are equivalent to frequencies of about 1 kHz. To reduce the losses it is beneficial to employ two separate materials for the yoke; it was also shown that by employing an optimized excitation coil geometry the eddy current losses are acceptable. In this paper we show that the same principles can be applied to quadrupole magnets targeting 30 T/m with a repetition rate of 1kHz and good field quality.

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WEPTY067

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

electron, niobium, 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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WEPTY068

Asymmetric Thermo-currents Diminishing SRF Cavity Performance

cavity, niobium, SRF, superconducting-cavity

3437

R.G. Eichhorn, J. May-Mann
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Over the past years it became evident that the quality factor of a superconducting cavity is not only determined by its surface preparation procedure, but is also influenced by the way the cavity is cooled down. In this paper we will present results from numerical field calculations of magnetic fields produced by thermo-currents, driven by temperature gradients and material transitions. We will show how they can impact the quality factor of a cavity by producing a magnetic field at the RF surface of the cavity.

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WEPTY071

Time Resolved Cryogenic Cooling Analysis of the Cornell Injector Cryomodule

HOM, cryogenics, operation, impedance

3443

R.G. Eichhorn, S.R. Markham, P. Quigley, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Managing parallel cryogenic flows has become a key challenge in designing efficient and smart cryo-modules for particle accelerators. In analyzing the heating dynamics of the cornell high current injector module a power-full computational tool has been set-up allowing time resolved analysis and optimization. We will describe the computational methods and data sets we have used, report the results and compare them to measured data from the module being in good agreement. Mitigation strategies developed on basis of this model have helped pushing the operational limitations.

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WEPTY077

On Quench Propagation, Quench Detection, and Second Sound in SRF Cavities

niobium, cavity, SRF, radio-frequency

3464

S.R. Markham, R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The detection of a second sound wave, excited by a quench, has become a valuable tool in diagnosing hot spots and performance limitations of superconducting cavities. Several years ago, Cornell developed an oscillating super-leak transducer (OST) for these waves that nowadays are used world-wide. In a usual set-up, several OSTs surround the cavity, and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a small remaining mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. We will present a model based on numerical quench propagation simulations and analytic geometrical calculations that help explain the discrepancy.

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WEPWI005

Novel Approach to Variable Voltage Substation Protection

operation, controls, monitoring, pick-up

3496

M.Y. Mehtabuddin, C. Jach, S. Olek
SLAC, Menlo Park, California, USA

Conventional electrical system protection of variable voltage substations(medium voltage rated) of using fuses and phase overcurrent and/or phase time overcurrent protection is not adequate. This was evident from the recent variable voltage substation (VVS) electrical fire at SLAC. Using information obtained from the fire investigation, ETAP simulations, and event reports of the faults which led to the fire, SLAC put into action a fast, feasible, and economical relay protection plan into adequately protecting VVS until long term plan of replacements is implemented. The plan utilizes the existing microprocessor protection relays on the upstream vacuum breakers and included the following adjustments: Adjusting the long time overcurrent according to the de-rated cable ampacities, dual-fed arc flash fault protection, adding negative sequence settings and relay control logic to allow for two sets of settings for inrush mode and normal mode.

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WEPWI007

TTF3 Power Coupler Thermal Analysis for LCLS-II CW Operation

operation, cavity, SRF, resonance

3503

L. Xiao, C. Adolphsen, Z. Li, C.D. Nantista, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
I.V. Gonin, N. Solyak
Fermilab, Batavia, Illinois, USA

The TESLA 9-cell SRF cavity design has been adopted for use in the LCLS-II SRF Linac. Its TTF3 coaxial Fundamental Power Coupler (FPC), developed for pulsed operation in the European XFEL and ILC, requires modest changes to make it suitable for LCLS-II CW operation, in which it must be able to handle up to 7 kW of average power with the maximum temperature rise not to exceed 150 C. In order to improve TTF3 FPC cooling, an increased copper plating thickness will be used on the inner and outer conductor stainless steel RF surfaces. Fully 3D FPC thermal analysis with copper plating was performed using the SLAC developed parallel finite element code suite ACE3P with integrated electromagnetic, thermal and mechanical multi-physics simulation capabilities. In this paper, we present TTF3 FPC thermal analysis simulation results obtained using ACE3P as well as a comparison with measurement results.

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WEPWI016

Investigation of Differential Surface Removal due to Electropolishing at JLab

cavity, cathode, radio-frequency, SRF

3525

F. Marhauser, J. Follkie, C.E. Reece
JLab, Newport News, Virginia, USA

Surface chemistry carried out for Superconducting Radio Frequency (SRF) cavities such as Buffered Chemical Polishing (BCP) and Electropolishing (EP) aims to uniformly remove the internal surface of a cavity along the entire structure and within each cell from equator to iris in order to obtain an equally etched surface. A uniform removal however is not readily achievable due to the complex fluid flow and varying temperatures of the acid mixture, which can lead to differential etching. This needs to be considered when envisaging a certain surface damage removal throughout the interior. The process-specific differential etching influences the target frequency set at the manufacturing stage as well as the field flatness and length of the as-built cavity. We report on analyses of JLab's present EP system using experimental data for six nine-cell cavities that have been processed recently in the frame of the LCLS-II high-Q development plan. In conjunction with numerical simulations, the differential etching and the impact on field flatness is assessed.

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WEPWI029

Cavity Design, Fabrication and Test Performance of 750 MHz, 4-Rod Separators for CEBAF 4-Hall Beam Delivery System

cavity, coupling, hardware, target

3548

H. Wang, G. Cheng, L. Turlington, M.J. Wissmann
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A short version of the original CEBAF normal conducting 4-rod separator cavity has been developed into a 750MHz one * since the concept of simultaneous 4-hall operation for CEBAF is introduced **. This work has been advanced further based on the EM design optimization, bench measurement and by conducting RF-thermal coupled simulation using CST and ANSYS to confirm the cavity tuning and thermal performance. The cavity fabrication used matured technology like copper plating and machining. The cavity flanges, couplers, tuners and cooling channels adopted consistent/compatible hardware with the existing 500MHz cavities. The electromagnetic and thermal design simulations have greatly reduced the prototyping and bench tuning time of the first prototype. Four production cavities have reached a typical 1.94MV kick voltage or 3.0kW wall loss on each cavity after a minor multipactoring or no processing, 7.5% overhead power than the design specification.
* R. Kazimi et al., IPAC2013, Shanghai, China, pp 2896-2898.
** R. Kazimi, IPAC2013, Shanghai, China, pp 3502-3504.

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WEPWI061

Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

cavity, impedance, resonance, electron

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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THPF001

Tomography of Horizontal Phase Space Distribution of a Slow Extracted Proton Beam in the MedAustron High Energy Beam Transfer Line

extraction, proton, software, synchrotron

3673

A. Wastl
ATI, Vienna, Austria
M. Benedikt
CERN, Geneva, Switzerland
A. Garonna
EBG MedAustron, Wr. Neustadt, Austria

Funding: EBG MedAustron Marie Curie Strasse 5 A-2700 Wiener Neustadt www.medaustron.at
MedAustron is a synchrotron based hadron therapy and research center in Wiener Neustadt, Austria, which currently is under commissioning for the first patient treatment. The High Energy Beam Transfer Line (HEBT) consists of mul- tiple functional modules amongst which the phase-shifter- stepper PSS* is the most important module located where the dispersion from the synchrotron is zero and upstream of the switching magnet to the first irradiation room. The PSS is used to control the beam size for the downstream modules and for this scope rotates the beam in horizontal phase space by adjusting the phase advance. This functionality is used in this study to measure beam profiles for multiple phase space angles which act as input for a tomographic reconstruction. Simulation and measurement results are presented.
* M. Benedikt et al, A new concept for the control of a slow-extracted beam in a line with rotational optics, Nuclear Instruments and Methods in Physics Research Section A, Vol 430, Issues 2–3, 1999

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THPF009

Pumping Properties of Cryogenic Surfaces in SIS100

cryogenics, vacuum, operation, background

3696

L.H.J. Bozyk, O.K. Kester, P.J. Spiller
GSI, Darmstadt, Germany
F. Chill, O.K. Kester
IAP, Frankfurt am Main, Germany

Funding: Work supported by Hic4Fair and BMBF (FKZ:05P12RDRBK).
The synchrotron SIS100 of the planned FAIR facility will provide heavy ion beams of highest intensities. The required low charge states are subject to enhanced charge exchange processes in collisions with residual gas molecules. Therefore, highest vacuum quality is crucial for a reliable operation and minimal beam loss. The generation of the required low gas densities relies on the pumping capabilities of the cryogenic beam pipe walls. Most typical gas components in ultra high vacuum are bound by cryocondensation at LHe temperatures, resulting in ultimate low pressures with almost infinite pumping capacity. Hydrogen can not be crycondensated to acceptable low pressures. But if the surface coverage is sufficiently low, it can get bound by cryoadsorption. The pumping capabilities of cryogenic walls for Hydrogen have been investigated for SIS100-like conditions. The measurement results have been used in dynamic vacuum simulations at heavy ion operation. The simulation results are presented.

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THPF010

Simulation and Experimental Investigation of Heavy Ion Induced Desorption from Cryogenic Targets

target, cryogenics, ion, experiment

3699

Ch. Maurer, D.H.H. Hoffmann
TU Darmstadt, Darmstadt, Germany
L.H.J. Bozyk, H. Kollmus, Ch. Maurer, P.J. Spiller
GSI, Darmstadt, Germany

Funding: Bundesministerium für Bildung und Forschung FKZ 06DA7031
Heavy-ion impact induced gas desorption is the key process that drives beam intensity limiting dynamic vacuum losses. Minimizing this effect, by providing low desorption yield surfaces, is an important issue for maintaining a stable ultra high vacuum during operation with medium charge state heavy ions. For room temperature targets, investigation shows a scaling of the desorption yield with the beam's near-surface electronic energy loss, i.e. a decrease with increasing energy*,**. An optimized material for a room temperature ion-catcher has been found. But for the planned superconducting heavy-ion synchrotron SIS100 at the FAIR accelerator complex, the ion catcher system has to work in a cryogenic environment. Desorption measurements with the prototype cryocatcher for SIS100 showed an unexpected energy scaling***, which needs to be explained. Understanding this scaling might lead to a better suited choice of material, resulting in a lower desorption yield. Here, new experimental results will be presented along with insights gained from gas dynamics simulations.
* H. Kollmus et al., AIP Conf. Proc. 773, 207 (2005))
** E. Mahner et al., Phys. Rev. ST Accel. Beams 14, 050102 (2011)
*** L.H.J. Bozyk, H. Kollmus, P.J. Spiller, Proc. of IPAC 2012, p. 3239

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THPF014

325 MHz High Power RF Coupler for the CH-Cavities of the FAIR p-LINAC

coupling, cavity, linac, proton

3712

F. Maimone, R. M. Brodhage, M. Kaiser, W. Vinzenz, M. Vossberg
GSI, Darmstadt, Germany

In order to supply the input RF power to the Cross-bar H-mode (CH) cavities of the p-LINAC for FAIR an inductive RF coupler has been studied. The designed RF coupler, and its water cooled inductive loop, has to withstand up to a 3 MW pulsed power (at 325 MHz). At GSI a prototype has been manufactured and tests were performed. The prototype of the designed high power RF coupler is presented together with the results of the coupling measurements at the CH-prototype cavity.

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THPF017

Design Studies for the Proton-Linac RFQ for FAIR

rfq, proton, linac, acceleration

3718

M. Vossberg, R. M. Brodhage, M. Kaiser, F. Maimone, W. Vinzenz, S. Yaramyshev
GSI, Darmstadt, Germany

The planned 27 m long Proton-Linac (P-LINAC) for FAIR (Facility for Antiproton and Ion Research) comprises a RFQ (Radio-Frequency Quadrupole) and 6 CH-cavities to accelerate a 70 mA proton beam up to 70 MeV. The FAIR Proton-Linac starts with a 325.2 MHz, from 95keV to 3 MeV RFQ accelerator. The main RFQ for this Proton-Linac will be a 4-Vane RFQ. RF analytics with varying and constant transverse focusing strengt for the electrode parameters will be used. CST simulations will help to find cavity parameters for the working frequency. This paper presents the main cavity designs concepts and CST simulation results.

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THPF020

Upgrade of the HSI-RFQ at GSI to Fulfill the FAIR Requirements

rfq, multipole, linac, brilliance

3727

M. Baschke, H. Podlech
IAP, Frankfurt am Main, Germany
W.A. Barth
GSI, Darmstadt, Germany

In Darmstadt/Germany the existing accelerator facility GSI is expanding to one of the biggest joint research projects worldwide: FAIR, a new antiproton and ion research facility with so far unmatched intensities and quality. The existing accelerators will be used as pre-accelerators and therefor need to be upgraded. In a first step the 36 MHz-HSI-RFQ for high current beams will get new electrodes to fulfill the FAIR requirements. First simulation results for capacity and multipole momentums will be presented.

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THPF021

Structural, Mechanical and RF Measurements on the Superconducting 217 MHz CH Cavity for the CW Demonstrator at GSI

cavity, resonance, niobium, operation

3730

F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: Work supported by HIM, GSI, BMBF Contr. No. 05P12RFRBL
Together with the new horizontal cryomodule and two superconducting (sc) 9.5 T solenoids the sc 217 MHz Crossbar-H-mode (CH) cavity represents the continuous wave (cw) demonstrator and brings sc rf technology to GSI. A reliable operability of the sc CH cavity is one major goal of the demonstrator project. Furthermore, the successful beam operation of the demonstrator will be a milestone on the way to a new sc cw linac at GSI for a competitive production of Super Heavy Elements (SHE) in the future. The production of the cryomodule and the solenoids is almost finished while the cavity has been completed except for the helium vessel. In this paper structural mechanical as well as related rf measurements on the sc 217 MHz CH cavity are presented.

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THPF022

Design of the 325 MHz 4-Rod RFQ for the FAIR Proton Linac

rfq, dipole, operation, higher-order-mode

3733

B. Koubek, H. Podlech, A. Schempp
IAP, Frankfurt am Main, Germany

Investigations on the 325 MHz 4-rod RFQ prototype for the FAIR proton linac have confirmed the feasibility of a 4-rod RFQ to work at frequencies above 300 MHz. This RFQ will accelerate protons from 95 keV to 3 MeV within a length of 3.3 m and will be powered by a 2.5 MW klystron. The mechanical and rf design of this RFQ are presented in this paper.

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THPF026

Development of a 325 MHz Ladder-RFQ of the 4-Rod Type

rfq, proton, linac, cavity

3745

M. Schütt, U. Ratzinger
IAP, Frankfurt am Main, Germany
R. M. Brodhage
GSI, Darmstadt, Germany

For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. In the low energy section, between the Ion Source and the main linac an RFQ will be used. The 325 MHz RFQ will accelerate protons from 95 keV to 3.0 MeV. This particular high frequency for an RFQ creates difficulties, which are challenging in developing this cavity. In order to define a satisfactory geometrical configuration for this resonator, both from the RF and the mechanical point of view, different designs have been examined and compared. Very promising results have been reached with a ladder type RFQ, which has been investigated since 2013. We present recent 3D simulations of the general layout and of a complete cavity demonstrating the power of a ladder type RFQ as well as measurements of a 0,8 m prototype RFQ, which was manufactured in late 2014 and designed for RF power and vacuum tests. We will outline a possible RF layout for the RFQ within the new FAIR proton injector and highlight the mechanical advantages.

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THPF027

Ten Gap Model of a New Alvarez DTL Cavity at GSI

cavity, ion, DTL, impedance

3748

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

In order to meet the challenges of the FAIR project at GSI requiring highest beam intensities an upgrade of the existing Universal Linear Accelerator (UNILAC) is planned. The 10⁸ MHz cavities will be replaced by new rf-structures of the same frequency. Simulations are done to improve the rf-properties. The geometry of the drift tubes is to be changed to a smoother curvature to reach a homogeneous surface field distribution and higher shunt impedances. To check the necessity of cooling channels, simulations on the temperature distribution at the drift tubes and stems are conducted. A test bench for low power rf-measurements with a 10 gap aluminum model (scale 1:3) is under construction. The modular mechanical design of the model will allow probing experimentally a wide range of drift tube and stem geometries. With the bead pull method the electrical field distribution will be measured as well as the field stability with respect to parasitic modes. Additionally, appropriate locations along the cavity to place fixed and dynamic rf-frequency tuners will be determined.

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THPF028

Conceptual Design of a Novel RFQ for Medical Accelerators

rfq, ion, alignment, ion-source

3751

R. Cee, E. Feldmeier, Th. Haberer, A. Peters, T.W. Winkelmann
HIT, Heidelberg, Germany

At the Heidelberg Ion Beam Therapy Centre HIT we operate a 4-rod RFQ as first stage of a 7 MeV/u injector linac followed by an IH-DTL. During the first years of patient treatment the injector performance was perfectly adequate, even though the transmission of the linac remained below the theoretical expectations. New developments in dose delivery technology already realised or to come in the future increase the demand on higher beam intensities which will finally result in shorter irradiation times. As measurements performed at our test bench have confirmed that there is a margin for higher transmissions especially for the RFQ we are currently preparing for a new RFQ design. While keeping the original design parameters, the new RFQ should be optimised with respect to the transmission of beams from different ion sources such as electron cyclotron resonance or electron beam ion sources. All parts of the RFQ will be put up for discussion including electrodes, stems, tank and the integrated rebuncher. The design work will profit from new concepts that have evolved at our own and other medical heavy ion facilities in operation and from the progress modern simulation tools have run through.

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THPF038

RIB Transport and Selection for the SPES Project

rfq, emittance, ion, target

3782

M. Comunian, L. Bellan, A. Pisent
INFN/LNL, Legnaro (PD), Italy
A.D. Russo
INFN/LNS, Catania, Italy

The SPES project, at Legnaro National Laboratories (LNL) in Italy, is a RIB ISOL facility for the production and acceleration of “neutron-rich” radioactive ion beams. The beam dynamics of the re-accelerator part is presented with the focus on the preselection and transfer to the charge breeder device and from this device to the CW RFQ used as injector to the LNL linac ALPI.

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THPF039

Stability Studies for J-PARC Linac Upgrade to 50 mA/400 MeV

linac, lattice, emittance, operation

3785

Y. Liu, T. Maruta
KEK/JAEA, Ibaraki-Ken, Japan
K. Futatsukawa, T. Miyao
KEK, Ibaraki, Japan
M. Ikegami
FRIB, East Lansing, Michigan, USA
A. Miura
JAEA/J-PARC, Tokai-mura, Japan

J-PARC linac applies the Equi-partitioning (EP) setting as the base-line design. And it is the first machine to adopt this approach at the design stage. EP condition is a natural solution for avoiding emittance exchange between transverse and longitudinal planes. At J-PARC linac it is also possible to explore off-EP settings. One of the motivations could be a lattice with relaxed envelope for mitigating the intra-beam stripping (IBSt) effects in high current H⁻ beam. During and after the energy upgrade in Jan., 2014 and beam current upgrade in Oct., 2014, experiments were carried out to study the stability and emittance evolution for the EP and off-EP settings with high current H⁻ beam at J-PARC linac for better choices of lattice and better understanding.

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THPF040

Recent Progress of the Beam Commissioning in J-PARC Linac

DTL, linac, rfq, emittance

3789

T. Maruta, Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan
K. Futatsukawa, T. Miyao
KEK, Ibaraki, Japan
M. Ikegami
FRIB, East Lansing, Michigan, USA
A. Miura
JAEA/J-PARC, Tokai-mura, Japan

J-PARC linac iis replaced the front-end in the summer shutdown in year 2014 to extend the maximum peak current to 50 mA from 30 mA. By the combination with the energy upgrade conducted in year 2013, it becomes possible to achieve the design beam energy of 133 kW, which is corresponding to 1 MW at the extraction of 3 GeV Rapid Cycling Sychrotron (RCS). The beam commissioning after the replacement started at Sep./27, and we can successfully accelerate the beam at peak current of 30 mA and 50 mA. In this presentation, we introduce the resent progress of the beam commissioning of the J-PARC linac.

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THPF042

Rectlinear Cooling Scheme for Bright Muon Sources

emittance, space-charge, lattice, cavity

3792

D. Stratakis
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Contract No, DE-AC02-07CH11359 with the US Department of Energy.
A fast cooling technique is described that simultaneously reduces all six phase-space dimensions of a charged particle beam. In this process, cooling is accomplished by reducing the beam momentum through ionization energy loss in absorbers and replenishing the momentum loss only in the longitudinal direction rf cavities. In this work we describe its main features and describe the main results.

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THPF045

Simulation Study of Muon Acceleration using RFQ for a New Muon g-2 Experiment at J-PARC

rfq, acceleration, experiment, emittance

3801

Y. Kondo, K. Hasegawa
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
T. Mibe, M. Otani, N. Saito
KEK, Tsukuba, Japan

A new muon g-2 experiment is planning at J-PARC. In this experiment, ultra cold muons will be generated and accelerated using a linear accelerator. As the first accelerating structure, an RFQ will be used. We are planning to use a spare RFQ of the J-PARC linac for the first acceleration test. We present simulation studies of this acceleration test. A design study of a muon dedicated RFQ is also shown.

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THPF051

Beam-based Alignment Simulation on Transport Line of CSNS

quadrupole, alignment, controls, proton

3818

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

The China Spallation Neutron Source (CSNS) is a high beam power proton machine which needs high precise alignment. Compared to traditional optical alignment, the beam-based alignment (BBA) technique can implement higher precise alignment. This technique with two implementations is applied to the transport line of CSNS to get the transverse misalignments of beam position monitor (BPM) and quadrupole magnet by measuring BPM data under different conditions. The corresponding control system application programs were developed based on CSNS/XAL platform. The result shows the fitted result is consistent with the input result.

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THPF054

XAL Development for CSNS/RCS Commissioning

quadrupole, framework, controls, dipole

3821

Y.W. An, L. Huang, W.B. Liu, Y.D. Liu, S. Wang, Y. Wei
IHEP, Beijing, People's Republic of China

Funding: Work supported by the National Natural Science Fund Committee, contract 11405189.
As a key component of the China Spallation Neutron Source (CSNS) Project, the Rapid Cycling Synchrotron (RCS) accumulates and accelerates the proton beam from 80MeV to 1.6GeV for extracting and striking the target with a repetition rate of 25Hz. A high level application programming framework code called XAL, based on Java Language with a well-performance online model, initially developed at the Spallation Neutron Source (SNS), has been installed as a part of control system via connection to EPICS for CSNS. Much of the applications have been initially established such as Tune Scan, Tune Monitor, Orbit Response Matrix Measurement, RCS Orbit Display, and Beta Function Measurement for preparing CSNS/RCS commissioning are showed in this paper.

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THPF057

Beam Commissioning of C-ADS Injector-I RFQ Accelerator

rfq, emittance, proton, linac

3827

C. Meng, J.S. Cao, Y.Y. Du, H. Geng, T.M. Huang, R.L. Liu, H.F. Ouyang, W.M. Pan, S. Pei, H. Shi, Y.F. Sui, J.L. Wang, S.C. Wang, F. Yan, Q. Ye, L. Yu, Y. Zhao
IHEP, Beijing, People's Republic of China

The C-ADS accelerator is a CW (Continuous-Wave) proton linac with 1.5 GeV in beam energy, 10 mA in beam current, and 15 MW in beam power. C-ADS Injector-I accelerator is a 10-mA 10-MeV CW proton linac, which uses a 3.2-MeV normal conducting 4-Vane RFQ and superconducting single-spoke cavities for accelerating. The frequency of RFQ accelerator is 325 MHz. The test stand composed of an ECR ion source, LEBT, RFQ, MEBT and beam dump have been installed and the first stage of beam commissioning have been finished at IHEP in 2014 mid-year. At 90% duty factor, we got 11 mA proton beam at RFQ exit with 90% beam transmission efficiency, while 95% beam transmission efficiency at 70% duty factor. The energy after RFQ was measured by TOF method with FCTs. The transverse emittance measured by double-slits emittance meter was 0.135 π mm-mrad, which of detailed data analysis will be presented in this paper.

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THPF060

The Simulation Study of Space Charge Effects for CSNS Linac

emittance, space-charge, DTL, focusing

3833

Y. Yuan, L. Huang, J. Peng, S. Wang
IHEP, Beijing, People's Republic of China

China Spallation Neutron Source (CSNS) is a high intensity accelerator based facility. Its accelerator consists of an H⁻ injector and a proton Rapid Cycling Synchrotron. The injector includes the front end and linac. The RFQ accelerates the beam to 3MeV, and then DTL accelerates it to 80MeV. The space charge effect is the most important cause of emittance growth and beam loss due to the low beam energy and the high peak current. The paper performed simulation studies on the space charge effects at the LINAC by using three-dimensional code IMPACT-Z. The emittance evolution is studied in the point of view of the singe-particle dynamics and multi-particle dynamics with different peak beam current. The effect of mismatch is studied by simulation, and the emittance growth with different mismatch factor are given.

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THPF070

Prototyping Progress of SSR1 Single Spoke Resonator for RAON

cavity, target, vacuum, ion

3842

H.J. Cha, H. Kim, H.J. Kim, W.K. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea

The fabrication of prototypes for four different types of superconducting cavities (QWR, HWR, SSR1, and SSR2) for the Korean heavy ion accelerator, “RAON” is in progress. In this presentation, we report the current status of the SSR1 cavity (β=0.3 and f=325 MHz) prototype fabrication based on the technical designs. The simulation results on the target frequency determination for the clamp-up test of the prototype are also given.

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THPF072

Beam Optics of RISP Linac using Dynac Code

linac, rfq, cavity, target

3845

J.-H. Jang, I.S. Hong, H. Jang, D. Jeon, H. Jin, H.J. Kim
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the Rare Isotope Science Project of Institute for Basic Science funded by Ministry of Science, ICT and Future Planning.
The RISP (Rare Isotope Science Project) is developing a superconducting linac which accelerates uranium beams up to 200MeV/u with the beam power of 400kW. The linac consists of an injector which includes an ECR ion source and an RFQ, and superconducting cavities which include QWR (Quarter Wave Resonator), HWR (Half Wave Resonator), and SSR (Single Spoke Resonator). Up to HWR, two charge state beams will be accelerated to achieve the required beam current and then five charge state beams will be used to obtain the higher acceleration efficiency. In this work, we performed the beam optics calculation by using a beam dynamics code DYNAC in order to study a possibility of the code as an online model. We compared the results with the calculation in the baseline design by TRACK code.

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THPF076

Thermal and Structural Analysis of the 72.75 MHz LINCE RFQ

rfq, cavity, software, controls

3857

A.K. Orduz, A. Berjillos, C. Bonțoiu, J.A. Dueñas, I. Martel
University of Huelva, Huelva, Spain
A. Garbayo
AVS, Elgoibar, Spain

Funding: Work partially supported by the Spanish Government (MINECO-CDTI) under program FEDER INTERCONNECTA.
The 72.75 MHz LINCE RFQ is designed to function at room temperature. Effective operation of the RFQ cavity requires efficient water cooling in order to dissipate significant resistive power non-uniformly distributed on the copper walls and vanes. This amounts to about 10 kWfor one 0.5m long RFQ section. Cylindrical cooling channels have been designed and optimized by varying their diameter and position in order to minimize the frequency shift generated by thermal displacements. The article reports results of power loss simulations coupled with electromagnetic modelling studies and their consequences on the RFQ performance in terms of resonant frequency and thermal deformations.

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THPF077

Proposal for a 72.75 MHz RFQ for the LINCE Accelerator Complex

rfq, cavity, pick-up, Windows

3861

A.K. Orduz, A. Berjillos, C. Bonțoiu, J.A. Dueñas, I. Martel
University of Huelva, Huelva, Spain
A. Garbayo
AVS, Elgoibar, Spain

Funding: Work partially supported by the Spanish Government (MINECO-CDTI) under program FEDER INTERCONNECTA
The low-energy part of the LINCE facility can be based on a 72.75MHz normal-conducting RFQ designed to give a 450 keV/u boost for A/Q=7 ions in about 5m length. The vanes have been electromagnetically designed to accommodate dedicated RF windows producing effective separation of the RFQ modes in an octagonal-shaped resonance chamber. This article outlines the optimization of the quality factor of the cavity by using numerical methods for electromagnetic calculations. Experimental results of RF test carried out on a prototype are also discussed.

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THPF083

Painting Schemes for CERN PS Booster H⁻ Injection

injection, emittance, linac, booster

3879

J.L. Abelleira, W. Bartmann, E. Benedetto, C. Bracco, G.P. Di Giovanni, V. Forte, M. Kowalska, M. Meddahi, B. Mikulec, G. Rumolo
CERN, Geneva, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France
M. Kowalska
EPFL, Lausanne, Switzerland

The present 50-MeV proton injection into the PS Booster will be replaced by a H⁻ charge exchange injection at 160 MeV to be provided by Linac 4. The higher energy will allow producing beams at higher brightness. A set of kicker magnets (KSW) will move the beam across the stripping foil to perform phase space painting in the horizontal plane to reduce space charge effects. The PSB must satisfy the different users with very different beams in terms of emittance and intensity. Therefore, the KSW waveforms must be adapted for each case to meet the beam characteristics while minimizing beam losses. Here we present the results of the simulations performed to optimise the injection system. A detailed analysis of the different painting schemes is discussed, including the effect of the working point on the painted beam, and variations in the offset of the injected beam.

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THPF087

New Shaving Scheme for Low-Intensity Beams in the CERN PS Booster and Feasibility at 160 MeV

emittance, booster, closed-orbit, operation

3893

M. Kowalska, E. Benedetto, V. Forte, B. Mikulec, G. Rumolo
CERN, Geneva, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France
M. Kowalska
EPFL, Lausanne, Switzerland

The PS Booster is the first synchrotron in the CERN proton accelerator chain, serving all downstream machines. As part of the LHC Injector Upgrade Project, the PSB injection energy will increase from 50 MeV to 160 MeV and a new H⁻ charge-exchange injection scheme will be implemented. Beam losses are a concern due to the increased injection energy, and mitigation scenarios are under investigation. On the other hand it is desirable for low-intensity beams to have the possibility to precisely tailor sub-micron beam emittances through controlled scraping (transverse shaving process) towards a suitable aperture restriction. Challenges are the higher activation potential of the beam and the smaller transverse beam sizes around 160 MeV as compared to 63 MeV, at which the shaving is presently done. This paper describes the proposal of a new shaving scheme, more robust with respect to the steering errors and the choice of the working point, which localizes the scraping losses on the main PS Booster aperture restriction. The robustness of the new method, together with the results of simulations and measurements are discussed for the current (50 MeV) and future (160 MeV) situation.

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THPF088

CERN PS Booster Upgrade and LHC Beams Emittance

emittance, injection, space-charge, booster

3897

E. Benedetto, J.L. Abelleira, C. Bracco, V. Forte, B. Mikulec, G. Rumolo
CERN, Geneva, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France

By increasing the CERN PS Booster injection energy from 50 MeV to 160 MeV, the LHC Injector Upgrade Project aims at producing twice as brighter beams for the LHC. Previous measurements showed a linear dependence of the transverse emittance with the beam intensity and space-charge simulations confirmed the linear scaling. This paper is discussing in detail the dependence on the longitudinal emittance and on the choice of the working point, with a special attention to the H⁻ injection process and to the beam dynamics in the first 5 ms, during the fall of the injection chicane bump.

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THPF095

Limits on Failure Scenarios for Crab Cavities in the HL-LHC

luminosity, optics, collimation, beam-losses

3923

A. Santamaría García, H. Burkhardt, A. Macpherson, K.N. Sjobak, D. Wollmann, B. Yee-Rendón
CERN, Geneva, Switzerland
K. Hernandez-Chahin
DCI-UG, León, Mexico
B. Yee-Rendón
CINVESTAV, Mexico City, Mexico

The High Luminosity (HL) LHC upgrade aims for a tenfold increase in integrated luminosity compared to the nominal LHC, and for operation at a levelled luminosity of 5 10³⁴ cm^-2.s^-1, which is five times higher than the nominal LHC peak luminosity. Crab Cavities (CCs) are planned to compensate the geometric luminosity loss created by the increased crossing angle by rotating the bunch, allowing quasi head-on collisions at the Interaction Points (IP). The CCs work by creating transverse kicks, and their failure may have short time constants comparable to the reaction time of the Machine Protection System (MPS), producing significant coherent betatron oscillations and fast emittance growth. Simulations of CC failure modes have been carried out with the tracking code SIXTRACK, using the newly added functionality called DYNK, which allows to dynamically change the attributes of the CCs. We describe these simulations and discuss early, preliminary results.

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THPF096

Origin of the Damage to the Internal High Energy Beam Dump in the CERN SPS

proton, vacuum, kicker, dumping

3927

V. Kain, K. Cornelis, B. Goddard, M. Lamont, I.V. Leitao, R. Losito, C. Maglioni, M. Meddahi, F. Pasdeloup, G.E. Steele, F.M. Velotti
CERN, Geneva, Switzerland

The high energy beam dump in the SPS has to deal with beams from 10⁵ to 450 GeV/c and intensities of up to 4 ×10¹³ protons. An inspection during the last shutdown revealed significant damage to the Al section of the dump block. This paper summarizes the results of the analysis revealing the most likely cause of the damage to the beam dump. The implications for future SPS operation will also be briefly discussed, together with the short-term solution put in place.

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THPF098

SPS-to-LHC Transfer Lines Loss Map Generation Using PyCollimate

collimation, scattering, proton, injection

3934

F.M. Velotti
EPFL, Lausanne, Switzerland
W. Bartmann, C. Bracco, M.A. Fraser, B. Goddard, V. Kain, M. Meddahi, F.M. Velotti
CERN, Geneva, Switzerland

The Transfer Lines (TL) linking the Super Proton Synchrotron (SPS) to the Large Hadron Collider (LHC) are both equipped with a complete collimation system to protect the LHC against mis-steered beams. During the setting up of these collimators, their gaps are positioned to nominal values and the phase-space coverage of the whole system is checked using a manual validation procedure. In order to perform this setting-up more efficiently and more reliably, the simulated loss maps of the TLs will be used to validate the collimator positions and settings. In this paper, the simulation procedure for the generation of TL loss maps is described, and a detailed overview of the new scattering routine (pycollimate) is given. Finally, the results of simulations benchmark with another scattering routine are presented.

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THPF099

Upgrade of the SPS Ion Injection System

ion, injection, emittance, kicker

3938

J.A. Uythoven, J. Borburgh, E. Bravin, S. Burger, E. Carlier, J.-M. Cravero, L. Ducimetière, S.S. Gilardoni, B. Goddard, J. Hansen, E.B. Holzer, M. Hourican, T. Kramer, F.L. Maciariello, D. Manglunki, F.-X. Nuiry, A. Perillo Marcone, G.E. Steele, F.M. Velotti, H. Vincke
CERN, Geneva, Switzerland

As part of the LHC Injectors Upgrade Project (LIU) the injection system into the SPS will be upgraded for the use with ions. The changes will include the addition of a Pulse Forming Line parallel to the existing PFN to power the kicker magnets MKP-S. With the PFL a reduced magnetic field rise time of 100 ns should be reached. The missing deflection strength will be given by two new septum magnets MSI-V, to be installed between the existing septum MSI and the kickers MKP-S. A dedicated ion dump will be installed downstream of the injection elements. The parameter lists of the elements and studies concerning emittance blow-up coming from the injection system are presented. The feasibility of the 100 ns kicker rise time and the small ripple of the septum power converter are presented. Material studies of the ion dump are presented together with the radiation impact.

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THPF101

Design of a Proton Travelling Wave Linac with a Novel Tracking Code

linac, proton, quadrupole, lattice

3945

S. Benedetti
EPFL, Lausanne, Switzerland
U. Amaldi
TERA, Novara, Italy
A. Grudiev, A. Latina
CERN, Geneva, Switzerland

A non-relativistic proton linac based on high gradient backward travelling wave accelerating structures was designed using a novel dedicated 3D particle tracking code. Together with the specific RF design approach adopted, the choice of a 2.9985 GHz backward travelling wave (BTW) structure with 150° RF phase advance per cell was driven by the goal of reaching an accelerating gradient of 50 MV/m, which is more than twice that achieved so far. This choice dictated the need to develop a new code for tracking charged particles through travelling wave structures which were never used before in proton linacs. Nevertheless, the new code has the capability of tracking particles through any kind of accelerating structure, given its real and imaginary electromagnetic field map. This project opens a completely new field in the design of compact linacs for proton therapy, possibly leading to cost-effective and widespread single room facilities for cancer treatment.

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THPF102

Verification of the Neutron Mirror Capabilities in MCNPX via Gold Foil Measurements at the EIGER Instrument Beamline at the Swiss Spallation Neutron Source (SINQ)

neutron, target, proton, scattering

3949

R.M. Bergmann, U. Filges, S.H. Forss, E. Rantsiou, D. Reggiani, T. Reiss, U. Stuhr, V. Talanov, M. Wohlmuther
PSI, Villigen PSI, Switzerland

The EIGER triple-axis thermal neutron spectrometer beamline contains “supermirror” neutron guides, which preferentially reflect low-energy neutrons toward the EIGER spectrometer that come from the ambient temperature, light water neutron source in SINQ. Gold foil measurements have been performed at the EIGER beamline in 2013. This process can be modeled from incident proton to thermal neutron exiting the EIGER beamline by using the neutron mirror capabilities of MCNPX, which should be more accurate than simulations with simplified neutron source distributions and geometry representations. The supermirror reflectivity parameters have been measured previously and are used in MCNPX 2.7.0 to reproduce the activity measured from the gold foil irradiation, verifying the neutron mirror modeling capabilities in MCNPX 2.7.0.

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THPF103

Current Status of the SANAEM RFQ Accelerator Beamline

rfq, plasma, proton, cavity

3952

G. Turemen, B. Yasatekin
Ankara University, Faculty of Sciences, Ankara, Turkey
Y. Akgun, A.S. Bolukdemir
TAEK, Ankara, Turkey
A. Alacakir
SNRTC, Ankara, Turkey
A. Bozbey, A. Sahin
TOBB ETU, Ankara, Turkey
S. Erhan
UCLA, Los Angeles, California, USA
Ö. Mete
UMAN, Manchester, United Kingdom
S. Ogur, V. Yildiz
Bogazici University, Bebek / Istanbul, Turkey
S. Oz, A. Ozbey, H. Yildiz
Istanbul University, Istanbul, Turkey
G. Unel
UCI, Irvine, California, USA
F. Yaman
IZTECH, Izmir, Turkey

The design and production of the proton beamline of SPP, which aims to educate accelerator physicists and serve as particle accelerator technologies test bench, continues at TAEK-SANAEM as a multi-phase project. For the first phase, the 20 keV protons will be accelerated to 1.3 MeV by a single piece RFQ. Currently, the beam current and stability tests are ongoing for the Inductively Coupled Plasma ion source and the measured magnetic field maps of the Low Energy Beam Transport solenoids are being matched to the RFQ acceptance with various beam configurations of the ion source by using computer simulations. The production of the RFQ cavity was started by using high grade aluminum material which will be subsequently coated by Copper to reduce the RF losses. The installation of the low energy diagnostics box was also completed. On the RF side, the development of the hybrid power supply based on solid state and tetrode amplifiers continues. All RF transmission components are already produced with the exception of the circulator and the power coupling antenna which are in the manufacture and design phases, respectively. The acceptance tests of the produced RF components are ongoing. This work summarizes the design, production and test phases of the above mentioned SPP proton beamline components.

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THPF104

Design of a Scaled High Duty Factor High Current Negative Penning Surface Plasma Source

plasma, cathode, ion, electron

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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THPF107

Quality and Stability Studies of the Beams in the ELENA Ring Transfer Lines

quadrupole, antiproton, lattice, experiment

3966

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

Funding: Work supported by the EU under Grant Agreement 624854 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
The Extra Low ENergy Antiproton (ELENA) ring will provide seven different experiments at CERN with cooled beams of low energy (~100 keV) antiprotons. As a result, a system of transfer lines is being designed to ensure that each experiment receives a beam with its required properties. In this contribution, particle tracking simulations using MADX are performed to explore the effects on the beam quality and orbit stability of different lattice imperfections, such as element misalignment, electric field and matching errors. The tolerances on the actual values of these quantities are obtained as a guide for the construction of the transfer lines.

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THPF108

EBIS Charge Breeder at ANL and its Integration into ATLAS

ion, beam-transport, dipole, electron

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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THPF112

A New Beam Injection Scheme for the Fermilab Booster

injection, booster, emittance, acceleration

3976

C.M. Bhat
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Here we present an improved beam injection scheme for the Fermilab Booster. The beam is injected on the deceleration part of the standard sinusoidal magnetic ramp and beam capture takes place almost immediately after the injection process, before the beam is fully de-bunched. During the entire capture process we impose in a changing field with changing from negative to zero to positive values. Our simulations clearly showed that this method of beam capture is more efficient to preserve longitudinal beam emittance at the early part of the acceleration cycle and helps to keep the required rf voltage to an optimal value of 15% lower than the current operational values. As a result of the reduced emittance growth at the early part of the Booster cycle we observe reduced required rf power on a typical Booster cycle by ~30%, which is quite important from the point of rf power requirements during the Booster operation. Further, we investigate snap bunch rotation at extraction to provide beam with lower to the MI/RR to improve the proton beam slip-stacking efficiency.

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THPF113

Energy Spread of the Proton Beam in the Fermilab Booster at Its Injection Energy

booster, injection, cavity, proton

3979

C.M. Bhat, B.E. Chase, S. Chaurize, F.G. Garcia, W. Pellico, K. Seiya, T. Sullivan, A.K. Triplett
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
We have measured the total energy spread (99% energy spread) of the Booster beam at its injection energy of 400 MeV by three different methods - 1) creating a notch of about 40 nsec wide in the beam immediately after multiple turn injection and measuring the slippage time required for high and low momentum particles for a grazing touch in line-charge distribution, 2) injecting partial turn beam and letting it to debunch, and 3) comparing the beam profile monitor data with predictions from MAD simulations for the 400 MeV injection beam line. The measurements are repeated under varieties of conditions of RF systems in the ring and in the beam transfer line.

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THPF121

Out of Time Beam Extinction in the Mu2e Experiment

dipole, experiment, proton, extraction

3996

E. Prebys, S.J. Werkema
Fermilab, Batavia, Illinois, USA

Funding: This project is supported by the US Department of Energy under contract No. De-AC02-07CH11359 .
The Mu2e Experiment at Fermilab will search for the conversion of a muon to an electron in the field of an atomic nucleus with unprecedented sensitivity. The experiment requires a beam consisting of proton bunches approximately 200ns FW long, separated by 1.7 microseconds, with no out-of-time protons at the 10^-10 fractional level. Satisfying this "extinction" requirement is very challenging. Simulations show that the formation of the bunches will result in an extinction of roughly 10^-5. The remaining extinction will be accomplished by a system of resonant magnets and collimators, configured such that only in-time beam is delivered to the experiment.

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THPF125

MARS Tracking Simulations for the Mu2e Slow Extracted Proton Beam

extraction, scattering, septum, beam-losses

4010

V.P. Nagaslaev, I.L. Rakhno
Fermilab, Batavia, Illinois, USA

Particle tracking taking into account interactions with fields and materials is necessary for proper evaluation of the resonant extraction losses and geometry optimization for the extraction beam line. This paper describes the tracking simulations for the Mu2e Resonant Extraction and discusses the geometry choices made based on these simulations.

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THPF126

PXIE Low Energy Beam Transport Commissioning

solenoid, ion, emittance, ion-source

4013

L.R. Prost, M.L. Alvarez, R. Andrews, J.-P. Carneiro, R.T.P. D'Arcy, B.M. Hanna, V.E. Scarpine, A.V. Shemyakin
Fermilab, Batavia, Illinois, USA
R.T.P. D'Arcy
UCL, London, United Kingdom
C. Wiesner
IAP, Frankfurt am Main, Germany

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the United States Department of Energy
The Proton Improvement Plan II at Fermilab is a program of upgrades to the injection complex [1]. At its core is the design and construction of a CW-compatible, pulsed H⁻ superconducting RF linac. To validate the concept of the front-end of such machine, a test accelerator (a.k.a. PXIE) is under construction [2]. It includes a 10 mA DC, 30 keV H⁻ ion source, a 2m-long LEBT, a 2.1 MeV CW RFQ, followed by a MEBT that feeds the first of 2 cryomodules taking the beam energy to ~25 MeV, and a High Energy Beam Transport section (HEBT) that takes the beam to a dump. The ion source and LEBT, which includes 3 solenoids, several clearing electrodes/collimators and a chopping system, have been built, installed, and commissioned to full specification parameters. This report presents the outcome of our commissioning activities, including phase-space measurements at the end of the beam line under various neutralization schemes obtained by changing the electrodes’ biases and chopper parameters.

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THPF131

Beam Studies for the Proton Improvement Plan (PIP) - Reducing Beam Loss at the Fermilab Booster

booster, injection, proton, lattice

4027

K. Seiya, C.M. Bhat, D.E. Johnson, V.V. Kapin, W. Pellico, C.-Y. Tan, R. Tesarek
Fermilab, Batavia, Illinois, USA

The Fermilab Booster is being upgraded under the Proton Improvement Plan (PIP) to be capable of providing a proton flux of 2.25·10¹⁷ protons per hour. The intensity per cycle will remain at the present operational 4.3·10¹² protons per pulse, however the Booster beam cycle rate is going to be increased from 7.5 Hz to 15 Hz. One of the biggest challenges is to maintain the present beam loss power while the doubling the beam flux. Under PIP, there has been a large effort in beam studies and simulations to better understand the mechanisms of the beam loss. The goal is to reduce it by half by correcting and controlling the beam dynamics and by improving operational systems through hardware upgrades. This paper is going to present the recent beam study results and status of the Booster operations.

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THPF149

Electromagnetic Modeling of 4-Rod RFQ Tuning

rfq, vacuum, quadrupole, linac

4076

S.S. Kurennoy, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Modern codes make possible detailed 3D electromagnetic modeling of RFQ accelerators. We have recently analyzed two 201.25-MHz 4-rod RFQs – one commissioned at FNAL and a new design for LANL – with CST Studio using imported manufacturer CAD files*. The RFQ electromagnetic analysis with MicroWave Studio (MWS) was followed by beam dynamics modeling with Particle Studio as well as other multi-particle codes. Here we apply a similar approach to study the process of RFQ tuning in 3D CST models. In particular, the results will be used to better understand tuning the voltage flatness along the new LANL 4-rod RFQ.
* S.S. Kurennoy, LINAC14, Geneva, Switzerland, 2014, THPP097.

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THPF150

3D Electromagnetic and Beam Dynamics Modeling of the LANSCE Drift-Tube Linac

DTL, beam-losses, linac, rfq

4079

S.S. Kurennoy, Y.K. Batygin
LANL, Los Alamos, New Mexico, USA

The LANSCE drift-tube linac (DTL) accelerates the proton or H⁻ beam to 100 MeV. It consists of four tanks containing tens of drift tubes and post-couplers; for example, tank 2 is almost 20 m long and has 66 cells. We have developed 3D models of full tanks [1] in the DTL with CST Studio to accurately calculate the tank modes, their sensitivity to post-coupler positions and tilts, tuner effects, and RF-coupler influence. Electromagnetic analysis of the DTL tank models is performed using MicroWave Studio (MWS). The full-tank analysis allows tuning the field profile of the operating mode and adjusting the frequencies of the neighboring modes within a realistic CST model. Beam dynamics is modeled with Particle Studio for bunch trains with realistic initial beam distributions using the MWS-calculated and tuned RF fields and quadrupole magnetic fields to determine the output beam parameters and locations of particle losses.
* S.S. Kurennoy, LINAC14, Geneva, Switzerland, 2014, MOPP106.

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