IPAC2015 - List of Keywords (laser)

Paper	Title	Other Keywords	Page
MOAC1	Awake: the Proof-of-principle R&D Experiment at CERN	proton, electron, plasma, experiment	34
	P. Muggli MPI, Muenchen, Germany M. Bernardini, T. Bohl, C. Bracco, A.C. Butterworth, S. Cipiccia, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, A.V. Petrenko, J.S. Schmidt, M. Turner, H. Vincke CERN, Geneva, Switzerland
	The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a proof-of-principle R&D experiment at CERN. It is the world’s first proton driven plasma wakefield acceleration experiment, using a high-energy proton bunch to drive a plasma wakefield for electron beam acceleration. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV proton beam bunches from the SPS, which will be sent to a plasma source. An electron beam will be injected into the plasma cell to probe the accelerating wakefield. Challenging modifications in the area and new installations are required for AWAKE. First proton beam to the experiment is expected late 2016. The accelerating electron physics will start late 2017. This paper gives an overview of the project from a physics and engineering point of view, it describes the main activities, the milestones, the organizational set-up for the project management and coordination.
	Slides MOAC1 [21.632 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOAC1
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MOPWA025	Simulation of Laser Cooling of Heavy Ion Beams at High Intensities	synchrotron, ion, scattering, simulation	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA025
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MOPWA040	Virtual Cavity Probe Generation using Calibrated Forward and Reflected Signals	cavity, coupling, controls, flattop	200
	S. Pfeiffer, V. Ayvazyan, J. Branlard, L. Butkowski, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany R. Rybaniec Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	The European X-ray free electron laser requires a high-precision control of accelerating fields to ensure a stable photon generation. Its low level radio frequency system, based on the MicroTCA.4 standard, detects the probe, forward and reflected signals for each cavity. While the probe signal is used to control the accelerating fields, a combination of the forward and reflected signals can be used to compute a virtual probe, whose accuracy is comparable to the directly sampled probe. This requires the removal of cross-coupling effects between the forward and reflected signals. This paper presents the precise generation of a virtual probe using an extended method of least squares. The virtual probe can then be used for precise field control in case the probe signal is missing or corrupted. It can also be used to detect any deviation from the nominal probe profile.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA040
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MOPWA042	Sub-fs Electron Bunch Generation Using Magnetic Compressor at SINBAD	electron, simulation, plasma, acceleration	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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MOPJE008	Suppression of Microbunching Instability via a Transverse Gradient Undulator	electron, linac, simulation, FEL	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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MOPMA043	Longitudinal Bunch Shaping at Picosecond Scales using Alpha-BBO Crystals at the Advanced Superconducting Test Accelerator	gun, electron, linac, space-charge	643
	B. Beaudoin UMD, College Park, Maryland, USA D.R. Edstrom, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Funding: This works is supported by the University Research Association, Inc. Operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy The Integrable Optics Test Accelerator (IOTA) electron injector at Fermilab will enable a broad range of experiments at a national laboratory in order to study and develop solutions to the limitations that prevent the propagation of high intensity beams at picosecond lengths. One of the most significant complications towards increasing short-beam intensity is space-charge, especially in the vicinity of the gun. A few applications that require a longitudinally shaped electron beam at high intensities are for, the generation of THz waves and dielectric wakefields, each of which will encounter the effects of longitudinal space-charge. This paper investigates the effects of longitudinal space-charge on alpha-BBO UV laser shaped electron bunches in the vicinity of the 1½cell 1.3 GHz cylindrically symmetric RF photocathode gun.
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MOPMA049	Development of a Single-pass Amplifier for an Optical Stochastic Cooling Proof-of-principle Experiment at Fermilab's IOTA facility	undulator, experiment, radiation, focusing	659
	M.B. Andorf, P. Piot Northern Illinois University, DeKalb, Illinois, USA V.A. Lebedev, P. Piot Fermilab, Batavia, Illinois, USA
	Optical stochastic cooling (OSC) is a method of beam cooling which is expected to provide cooling rates orders of magnitude larger than ordinary stochastic cooling. Light from an undulator (the pickup) is amplified and fed back onto the particle beam via another undulator (the kicker). Fermilab is currently exploring a possible proof-of-principle experiment of the OSC at the integrable-optics test accelerator (IOTA) ring. To implement effective OSC a good correction of phase distortions in the entire band of the optical amplifier is required. In this contribution we present progress in experimental characterization of phase distortions associated to a Titanium Sapphire crystal laser-gain medium (a possible candidate gain medium for the OSC experiment to be performed at IOTA). We also discuss a possible option for a mid-IR amplifier.
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MOPMA059	Lorentz boosted frame simulation of Laser wakefield acceleration using hybrid Yee-fft solver in quasi-3d geometry	simulation, plasma, 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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MOPHA006	A Slow RF-Laser Feedback for PHIL Photoinjector	feedback, gun, electron, controls	784
	N. ElKamchi, V. Chaumat, V. Soskov LAL, Orsay, France
	PHIL is an electron beam accelerator at LAL. It produces low energy (E<5 MeV) and high current (1 nC/bunch) electrons bunch at a repetition frequency of 5Hz. The stability of the beam charge at PHIL is a key issue for the succeful operation of the physic experiences that use the machine. At PHIL, the beam charge is quite stable, but we often note a slow charge drift on long duration experiences. Two ICTs, and a back-end electronics are used to monitor the stability of the beam charge, with an accuracy of about 1pC. Several types of jitter can impact the stability of the beam charge. The fluctuations of the RF power or the RF-laser relative phase drift could have significant influence, due to temperature variations that produce cables dilataion, and electronic components overheating. To correct the phase drift, we describe a method based on a slow analog-digital feedback loop between the RF wave in the gun (3 GHz) and the synchronisation signal of the laser (75MHz). It allows to maintain the jitter between the laser pulse and the RF wave stable at a very low value. As a result, the electron beam charge is maintained at a stable level, to meet the requirements of the users.
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MOPHA008	Investigation of Beam Halo Using In Vacuum Diamond Sensor at ATF2	electron, pick-up, vacuum, controls	791
	S. Liu, P. Bambade, F. Bogard, P. Cornebise, V. Kubytskyi, C. Sylvia LAL, Orsay, France A. Faus-Golfe, N. Fuster-Martínez IFIC, Valencia, Spain T. Tauchi, N. Terunuma KEK, Ibaraki, Japan T. Tauchi, N. Terunuma Sokendai, Ibaraki, Japan
	Funding: Chinese Scholarship Council, CNRS and P2IO LABEX Beam halo transverse distribution measurements are of great importance for the understanding of background sources of the nano-meter beam size monitor at the interaction point (IPBSM) of ATF2. One of the most critical issues for the beam halo measurement is to reach high dynamic range. Two in vacuum diamond sensor beam halo scanners (DSv) with four strips each have been developed for the investigation of beam halo transverse distributions at ATF2. The first DSv was installed for horizontal beam halo scanning after the interaction point (IP) of ATF2, in Nov. 2014. It aims to measure the beam halo distribution with large dynamic range (~10⁶), and investigate the possibility of probing the Compton recoil electrons produced in the interaction with the IPBSM laser beams. Studies to characterize the DS performance and measurements of horizontal beam halo performed in Nov.-Dec. 2014 are presented.
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MOPHA009	Single-Shot Electro-Optic Sampling Combined With Photonic Time-Stretch: Detailed Results at SOLEIL	synchrotron, detector, storage-ring, real-time	795
	C. Szwaj, C. Evain, E. Roussel PhLAM/CERLA, Villeneuve d'Ascq, France S. Bielawski PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France J.B. Brubach, L. Cassinari, M.-E. Couprie, M. Labat, L. Manceron, J.P. Ricaud, P. Roy, M.-A. Tordeux SOLEIL, Gif-sur-Yvette, France M. Le Parquier CERLA, Villeneuve d'Ascq, France
	Funding: ANR (DYNACO project), FEDER, CEMPI LABEX. Single-shot recording of pulses is possible with high repetition rates (more than 80 MHz), as was demonstrated in the framework of a PhLAM-SOLEIL collaboration * *. This can be achieved by a relatively simple upgrade of existing setups based on spectral encoding. The strategy consists to encode the sub-picosecond information into the time domain, but at a slower scale (nanoseconds), using dispersion in a long optical fiber. Then the information is recorded by a photodiode connected to an oscilloscope. In this poster, we present guidelines for the practical realization of the electro-optical setup, as well as a performance analysis. In particular, we analyze the temporal resolution and compare it to the classical electro-optical sampling setup. E. Roussel et al., Proceedings of IPAC2014, THOBA01. ** E. Roussel et al., arXiv:1410.7048
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MOPHA023	Observation of Coherent Pulses in the Sub-THz Range at DELTA	electron, radiation, detector, synchrotron	823
	C. Mai, F.H. Bahnsen, M. Bolsinger, S. Hilbrich, M. Huck, M. Höner, S. Khan, A. Meyer auf der Heide, R. Molo, H. Rast, G. Shayeganrad, P. Ungelenk DELTA, Dortmund, Germany M. Brosi, B. Kehrer, A.-S. Müller, M.J. Nasse, P. Schönfeldt, P. Schütze, S. Walther KIT, Karlsruhe, Germany H. Huck DESY Zeuthen, Zeuthen, Germany
	Funding: Work supported by the BMBF (05K13PEC). Coherent ultrashort THz pulses induced by a laser-electron interaction are routinely produced and observed at DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund University. The turn-by-turn evolution of the radiation spectrum is known to shift to the sub-THz regime after the initial laser-electron interaction. Recently, an ultrafast YBCO-based THz detector has been permanently installed and a Schottky diode has been tested at the THz beamline. Measurements with these detectors showing the temporal evolution of the coherent signals after several revolutions are presented. Furthermore, the concept of a recently designed Fourier-transform spectrometer optimized for the sub-THz region is shown.
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MOPHA026	Present and Future Optical-to-Microwave Synchronization Systems at REGAE Facility for Electron Diffraction and Plasma Acceleration Experiments	electron, detector, timing, plasma	833
	M. Titberidze, F.J. Grüner, A.R. Maier, B. Zeitler CFEL, Hamburg, Germany S.W. Epp MPSD, Hamburg, Germany M. Felber, K. Flöttmann, T. Lamb, U. Mavrič, J.M. Müller, H. Schlarb, C. Sydlo DESY, Hamburg, Germany F.J. Grüner, A.R. Maier, M. Titberidze Uni HH, Hamburg, Germany E. Janas Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	Relativistic Electron Gun for Atomic Explorations (REGAE) is a Radio Frequency (RF) driven linear accelerator. It uses frequency tripled short photon pulses (~ 35 fs) from the Titanium Sapphire (Ti:Sa.) Laser system in order to generate electron bunches from the photo-cathode. The electron bunches are accelerated up to ~ 5 MeV kinetic energy and compressed down to sub-10 fs using the so called ballistic bunching technique. REGAE currently is used for electron diffraction experiments (by Prof. R.J.D. Miller's Group). In near future within the collaboration of Laboratory for Laser- and beam-driven plasma Acceleration (LAOLA), REGAE will also be employed to externally inject electron bunches into laser driven linear plasma waves. Both experiments require very precise synchronization (sub-50 fs) of the photo-injector laser and RF reference. In this paper we present experimental results of the current and new optical to microwave synchronization systems in comparison. We also address some of the issues related to the current system and give an upper limit in terms of its long-term performance.
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MOPHA029	Operation Experiences with the MICROTCA.4-based LLRF Control System at FLASH	LLRF, operation, electron, radiation	844
	M. Omet, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, M. Hoffmann, F. Ludwig, U. Mavrič, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang DESY, Hamburg, Germany W. Cichalewski, D.R. Makowski TUL-DMCS, Łódź, Poland K. Czuba, K. Oliwa, I. Rutkowski, R. Rybaniec, D. Sikora, W. Wierba, M. Żukociński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland A. Piotrowski FastLogic Sp. z o.o., Łódź, Poland
	The Free-Electron Laser in Hamburg (FLASH) at Deutsches Elektronen-Synchrotron (DESY), Hamburg Germany is a user facility providing ultra-short, femtosecond laser pulses up to the soft X-ray wavelength range. For the precise regulation of the radio frequency (RF) fields within the 60 superconducting cavities, which are organized in 5 RF stations, digital low level RF (LLRF) control systems based on the MTCA.4 standard were implemented in 2013. Until now experiences with failures potentially due to radiation, overheating, and ageing as well as with the general operation of the control systems have been gained. These have a direct impact on the operation and on the performance of FLASH and will allow future improvements. The lessons learned are not only important for FLASH but also in the scope of European X-ray Free-Electron Laser (X-FEL), which will be operated with the same LLRF control system.
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MOPHA032	All-Optical Synchronization of Pulsed Laser Systems at FLASH and XFEL	timing, LLRF, FEL, controls	854
	J.M. Müller, M.K. Czwalinna, M. Felber, M. Schäfer, H. Schlarb, B. Schmidt, S. Schulz, C. Sydlo, F. Zummack DESY, Hamburg, Germany
	The all-optical laser synchronization at FLASH and XFEL provides femtosecond-stable timing of the FEL X-ray photon pulses and associated optical laser pulses (photo-injector laser, seed laser, pump-probe laser, etc.). Based on a two-color balanced optical cross-correlation scheme a high-precision measure of the laser pulse arrival time is delivered, which is used for diagnostic purposes as well as for the active stabilization of the laser systems. In this paper, we present the latest installations of our all-optical synchronization systems at FLASH and the recent developments for the upcoming European XFEL that will ensure a reliable femtosecond-stable timing of FEL and related pulsed laser systems.
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MOPHA034	High Voltage RTM Piezo Driver for XFEL Special Diagnostics	diagnostics, operation, high-voltage, hardware	860
	K.P. Przygoda, M. Felber, C. Gerth, M. Heuer, E. Janas, U. Mavrič, P. Peier, H. Schlarb, B. Steffen, C. Sydlo DESY, Hamburg, Germany T. Kozak, P. Prędki TUL-DMCS, Łódź, Poland
	High voltage RTM Piezo Driver has been developed to support special diagnostic applications foreseen for XFEL facility. The RTM is capable of driving 4 piezo actuators with voltages up to ±80 V. The solid-state power amplifiers are driven using 18-bit DACs and sampling rates of 1 MSPS. The bandwidth of the driver is remotely tunable using programmable low pass filters. The 4-channel Piezo Driver unit provides the information of piezo output voltage and current. Three independent test setups have been built to test 4-channel Piezo Driver performance. In the paper we are presenting EOD laser lock to 1.3 GHz FLASH master oscillator using bipolar piezo stretcher (fine tuning). The piezo motor based course tuning has been applied for the long term laser stability measurements. The unipolar piezo actuator operation has been demonstrated for the Origami Onefive laser locked to 1.3 GHz LAB MO. The preliminary results of active stabilization of 3 km fiber link laboratory setup are shown.
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MOPHA038	Studies for a Wakefield-Optimized Near-Field EO Setup at the ANKA Storage Ring	wakefield, simulation, 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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MOPHA040	First Results of Energy Measurements with a Compact Compton Backscattering Setup at ANKA	electron, photon, detector, storage-ring	876
	C. Chang, E. Bründermann, E. Hertle, N. Hiller, E. Huttel, A.-S. Müller, M.J. Nasse, M. Schuh, J.L. Steinmann KIT, Karlsruhe, Germany H.-W. Hübers, H. Richter DLR, Berlin, Germany
	Funding: This work is funded by the European Union under contract PITN-GA-2011-289191 An electron energy measurement setup based on the detection of Compton backscattered photons, generated by laser light scattered off the relativistic electron beam, has been proposed and developed for operation at the ANKA storage ring of the Karlsruhe Institute of Technology (KIT). In contrast to conventional methods based on head-on collisions, the setup at ANKA is, for the first time, realized in a transverse configuration where the laser beam hits the electron beam at an angle of ~90°. This makes it possible to achieve a relatively low-cost and very compact setup since it only requires a small side-port instead of a straight section. This development could benefit storage rings with restricted space or where no straight sections are available, for example due to interferences with existing beamlines. The setup and the first measurement results are presented in the paper.
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MOPHA041	Laser Wire Based Transverse Emittance Measurement of H⁻ Beam at Spallation Neutron Source	emittance, electron, neutron, dipole	879
	Y. Liu, A.V. Aleksandrov, C.D. Long, A.A. Menshov, A.P. Zhukov ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. A laser wire based transverse emittance measurement system has been developed at the Spallation Neutron Source (SNS). The system enables a nonintrusive measurement of the transverse emittance in both directions on a 925 MeV/1 MW hydrogen ion (H⁻) beam at the high energy beam transport (HEBT) beam line.
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MOPHA060	Feasibility Study on Measurement and Control of Relative Positioning for Nano-beam Collision	controls, alignment, acceleration, superconducting-magnet	933
	H. Matsunaga, H. Yoshioka Takenaka Corporation, Institute of Technology, Chiba, Japan M. Masuzawa, Y. Ohsawa, R. Sugahara, H. Yamaoka KEK, Ibaraki, Japan
	In the SuperKEKB and future International Linear Collider project, it is required to measure and control an offset of very small beams with a precision of several nanometers at the interaction point. This paper is a feasibility study on measuring and controlling nano-order relative position by using a laser interferometer and a piezoelectric stage. The first part shows that the precision of measurement position about a direction of laser radiation is less than or equal to 1 nanometer in frequency region less than 100Hz. The second part is discussed a measurement of relative displacement between two points which are 10 meter away on substructures located at the interaction point in the SuperKEKB. To compare with difference of accelerometers for reference, a relative displacement measurement with a precision of several nanometers by a laser interferometer became clear. The final part is discussed a relative positioning control by using a Piezo-Stage between two points on active vibration isolation tables. We achieved to control a relative displacement below 2 nanometers in frequency region less than 10Hz.
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MOPTY013	Control System for DC-SRF Photo-Injector at Peking University	controls, SRF, LLRF, cryomodule	962
	L.W. Feng, J.K. Hao, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, B.C. Zhang PKU, Beijing, People's Republic of China
	A control system has been designed and constructed to full-fill the operation requirement of the DC-SRF photo injector developed at Peking University. The system includes FPGA based low level radio frequency (LLRF) control system, PLC based machine protection system, VME based magnet power control, and PC based EPICS IOC. All these systems were integrated to support the stable operation of the DC-SRF photo injector and has shown their robustness. The LLRF system was optimized and tuned for 2K CW/Pulse operation and the stability of amplitude and phase achieves 0.1% and 0.1° respectively.
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MOPTY028	Introduction to BINP HLS to Measure Vertical Changes on PAL-XFEL Buildings and Ground	alignment, operation, ground-motion, synchrotron	994
	H. J. Choi, K.H. Gil, H.-S. Kang, S.H. Kim, K.W. Seo PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL is being installed and will be completed by December of 2015 so that users can be supported beginning in 2016. PAL-XFEL equipment should continuously maintain the bunch beam parameter. To this end, PAL-XFEL equipment has to be kept precisely aligned. As a part of the process for installing PAL-XFEL, a surface geodetic network and the installation of a tunnel measurement network inside buildings is in preparation; additionally, the fiducialization of major equipment is underway. After PAL-XFEL equipment is optimized and aligned, if the ground and buildings go through vertical changes during operation, misalignment of equipments will cause errors in the electron beam trajectory, which will lead to changes to the beam parameter. For continuous and systemic measurement of vertical changes in buildings and to monitor ground sinking and uplifting, the BINP Ultrasonic-type Hydrostatic Levelling System (HLS) is to be installed and operated in all sections of PAL-XFEL for linear accelerator, Undulator and beam line. This study will introduce the operation principle, design concept and advantages (self-calibration) of HLS, and will outline its installation plan and operation plan.
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MOPTY079	The Installation and Operation of TPS Laser PSD System in TPS Storage Ring	storage-ring, alignment, operation, electron	1123
	M.L. Chen, J.-R. Chen, P.S.D. Chuang, H.C. Ho, K.H. Hsu, D.-G. Huang, C.K. Kuan, W.Y. Lai, C.J. Lin, S.Y. Perng, T.C. Tseng, H.S. Wang NSRRC, Hsinchu, Taiwan
	24 sets of Laser PSD positioning system are parts of the TPS girder auto¬alignment system. Laser PSD positioning systems are installed in the straight¬ section girders of TPS storage ring. The Laser PSD systems are assembled and calibrated in the Lab beforehand. The Laser and PSDs are assembled on girder and transported to TPS storage ring and Installed. During construction the system deviates from the normal position caused by variant temperature and external influence. For absolute position precision, another laser calibration system should be built to recalibrate the laser PSD system. This paper describes the installation of Laser PSD system in TPS storage ring and the status of the PSD system. A new absolute position calibration method for precision upgrade is also discussed.
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MOPTY084	Design, Testing and Performance Results of a High-resolution, Broad-band, Low-latency Stripline Beam Position Monitor System	electron, operation, collider, FPGA	1136
	P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry JAI, Oxford, United Kingdom D.R. Bett CERN, Geneva, Switzerland
	A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. The fast analogue front-end signal processor is based on a single-stage RF down-mixer. The processor latency is 15.6 ± 0.1 ns. A position resolution below 300 nm has been demonstrated for beam intensities of around 1 nC, with single-pass beam.
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MOPWI003	Laserwire Emittance Scanner at CERN Linac 4	linac, detector, emittance, ion	1146
	K.O. Kruchinin, G.E. Boorman, A. Bosco, S.M. Gibson, P. Karataev Royal Holloway, University of London, Surrey, United Kingdom E. Bravin, T. Hofmann, U. Raich, F. Roncarolo, F. Zocca CERN, Geneva, Switzerland A.P. Letchford STFC/RAL, Chilton, Didcot, Oxon, United Kingdom J.K. Pozimski Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	Linac 4 presently under construction at CERN is designed to replace the existing 50 MeV Linac 2 in the LHC injector chain and will accelerate the beam of high current negative hydrogen ions to 160 MeV. During the commissioning a laserwire emittance scanner has been installed allowing noninvasive measuring of the emittance at 3 MeV and 12 MeV setups. A low power infrared fibre coupled laser was focused in the interaction region down to ~150 um and collided with the ion beam neutralising negative ions. At each transverse laser position with respect to the ion beam the angular distribution of the neutral particle beamlets was recorded by scanning a diamond detector across the beamlet at a certain distance from the IP while the main beam of the H⁻ ions was deflected using dipole magnet installed upstream the detector. Measuring the profile of the beamlet by scanning the laser across the beam allows to directly measure the transverse phase-space distribution and reconstruct the transverse beam emittance. In this report we will describe the analysis of the data collected during the 3 MeV and 12 MeV operation of the Linac 4. We will discuss the hardware status and future plans.
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MOPWI004	Novel Single Shot Bunch Length Diagnostic using Coherent Diffraction Radiation	electron, radiation, experiment, optics	1150
	R.B. Fiorito, C.P. Welsch, H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom A.G. Shkvarunets UMD, College Park, Maryland, USA
	Funding: European Union’s grant agreement no. 624890 and STFC Cockcroft core grant No. ST/G008248/1; US Office of Naval Research and DOD Joint Technology Office. Current beam bunch length monitors which measure the spectral content of beam-associated coherent radiation to determine the longitudinal bunch form factor usually require wide bandwidth detection or Fourier transformation of interferometric data and multiple beam pulses. The data must then be Fourier transformed to obtain the bunch length. In this contribution we discuss progress in the development of a novel single shot method that utilizes the frequency integrated angular distribution (AD) of coherent diffraction radiation (CDR) to measure the RMS bunch length directly. We also present simulation results which show how the AD changes with bunch length for several electron beam linacs, where we are planning to test this new method, our single shot measurement technique and plans for comparison to other bunch length monitors.
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MOPWI016	Development of a Versatile Bunch-length Monitor for Electron Beams at ASTA	radiation, electron, linac, optics	1181
	A.H. Lumpkin, D.J. Crawford, D.R. Edstrom, J. Ruan, J.K. Santucci, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA
	Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the United States Department of Energy. The generation of bright electron beams at the ASTA/IOTA facility at Fermilab includes implementation of a versatile bunch-length monitor located after the 4-dipole chicane bunch compressor for electron beam energies of 20-50 MeV and integrated charges in excess of 10 nC. The station will include both a Hamamatsu C5680 synchroscan streak camera and a Martin-Puplett interferometer (MPI). An Al-coated Si screen will be used to generate both optical transition radiation (OTR) and coherent transition radiation (CTR) during the beam’s interaction with the screen. A chicane bypass beamline will allow the measurement of the initial bunch length at the same downstream beamline location using OTR and the streak camera. The UV component of the drive laser has previously been characterized with a Gaussian fit σ of 3.5 ps, and the uncompressed electron beam is expected to be similar to this value at low charge per micropulse. In addition, OTR will be transported to the streak camera from the focal plane of the downstream spectrometer to provide an E-t distribution within the micropulse time scale. Commissioning of the system and initial results with beam will be presented as available. A.H. Lumpkin et al., Proceedings of FEL14, MOP021, Basel, Switzerland, www. JACoW.org.
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MOPWI029	Electron Bombardment of ZnTe EO Bunch Charge Detector for Signal Lifetime Studies in Radiation Environment	electron, lattice, detector, radiation	1220
	J.E. Williams, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA S.V. Benson, S. Zhang JLab, Newport News, Virginia, USA
	Electro-optic detection of bunch charge distribution utilizing the nonlinear Pockel's and Kerr effect of materials has been implemented at various facilities as a method of passive detection for beam preservation throughout characterization. Most commonly, the inorganic II-VI material ZnTe is employed due to it's strong Pockel's EO effect and relatively high temporal resolution (~90 fs). Despite early exploration of radiation damage on ZnTe in exploration of semi-conductor materials in the 1970's, full characterization of EO response over radiation lifetime has yet to be performed. The following poster presents a method for ZnTe crystal characterization studies throughout radiation exposure at various energies and dosages by analyzing the changes in index of refraction including bulk uniformity, and THz signal response changes.
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TUYC2	Multi-GeV Plasma Acceleration Results at BELLA	plasma, electron, experiment, injection	1319
	A.J. Gonsalves, C. Benedetti, S.S. Bulanov, J. Daniels, E. Esarey, C.G.R. Geddes, H.S. Mao, D.E. Mittelberger, K. Nakamura, C.B. Schroeder, C. Tóth, J. van Tilborg LBNL, Berkeley, California, USA W. Leemans UCB, Berkeley, California, USA
	Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231 Laser-plasma accelerators (LPAs)* are being investigated as a compact driver for light sources and high-energy linear colliders. Recently 2 GeV beams were generated by focusing ≈ 100 J laser pulses onto a gas target. We report here on the generation of beams with energy up to 4.2 GeV using 16 J of laser pulse energy at the BErkeley Lab Laser Accelerator (BELLA). This was achieved by using laser pulses of high spatial and temporal quality coupled to a pre-formed capillary discharge waveguide of length 9 cm. The waveguide (in conjunction with self-guiding) allowed for mitigation of diffraction. High spatial quality (Strehl ratio at focus 0.8±0.1) was achieved using a deformable mirror placed before the focusing optic. The dominant contribution to the non-Gaussian content of the focal spot was the near-field intensity profile. For maximum efficiency high-power femtosecond systems employ super-Gaussian near-field profiles of the form I(r)∝e^-2(r/w^N), where I is the intensity, r is the radial coordinate, w is the spot size, and N is the order. Compared with Gaussian laser pulses where N=2, pulses from the BELLA laser system had N=10. Simulations showed that an increased contribution of self-guiding was required to effectively confine the laser energy for optimum acceleration and mitigation of damage to the capillary waveguide. Through appropriate choice of plasma density electron beams with energy up to 4.2 GeV were observed. In this regime the electron beam angular fluctuations were > 2 mrad rms, caused in part by errors in waveguide alignment and by laser-induced damage to the capillary that introduces plasma asymmetry. Improved alignment of the waveguide and mitigation of capillary damage allowed for reduction in angular fluctuations to 0.6 mrad rms. The electron beams had energy of 2.7±0.1 GeV, charge of 150 pC, and divergence less than 1 mrad. E. Esarey, et al., Rev. Mod. Phys. 81, 1229 (2009) X. Wang, et al., Nat. Communications 4, 1988 (2013) * W. P. Leemans, et al., Phys. Rev. Lett. 113, 245002 (2014)
	Slides TUYC2 [13.023 MB]
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TUYC3	Scaling Down Synchronous Acceleration: Recent Results, Current Status, and Future Plans of a Subrelativistic Dielectric Laser Acceleration Project	electron, acceleration, experiment, focusing	1325
	J.C. McNeur, P. Hommelhoff, M. Kozak, A. Li, N. Schönenberger, A.D. Tafel University of Erlangen-Nuremberg, Erlangen, Germany
	This talk will describe the latest results using laser powered dielectric accelerators. Recent experiments in the US (SLAC) and Europe (MPQ) have fabricated dielectric accelerators powered with optical lasers and used them to accelerate electrons with gradients between 25 and 300 MeV/m. The latest results will be reviewed and prospects and applications for the future will be discussed.
	Slides TUYC3 [21.295 MB]
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TUBC1	Recent Progress and Operational Status of the Compact ERL at KEK	operation, quadrupole, experiment, beam-losses	1359
	S. Sakanaka, M. Adachi, S. Adachi, T. Akagi, M. Akemoto, D.A. Arakawa, S. Araki, S. Asaoka, M. Egi, K. Enami, K. Endo, S. Fukuda, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, K. Hozumi, A. Ishii, X.J. Jin, E. Kako, Y. Kamiya, H. Katagiri, H. Kawata, Y. Kobayashi, Y. Kojima, Y. Kondou, A. Kosuge, T. Kume, T. Matsumoto, H. Matsumura, H. Matsushita, S. Michizono, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, K. Nakao, K.N. Nigorikawa, T. Nogami, S. Noguchi, S. Nozawa, T. Obina, T. Ozaki, F. Qiu, H. Sagehashi, H. Sakai, S. Sasaki, K. Satoh, T. Shidara, M. Shimada, K. Shinoe, T. Shioya, T. Shishido, M. Tadano, T. Tahara, T. Takahashi, R. Takai, H. Takaki, T. Takenaka, O. Tanaka, Y. Tanimoto, N. Terunuma, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, J. Urakawa, K. Watanabe, M. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan R. Hajima, S. Matsuba, M. Mori, R. Nagai, N. Nishimori, M. Sawamura, T. Shizuma JAEA, Ibaraki-ken, Japan J.G. Hwang KNU, Deagu, Republic of Korea M. Kuriki Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan Y. Seimiya HU/AdSM, Higashi-Hiroshima, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program from the MEXT, and by the MEXT grant for promoting technology for nuclear security. The Compact Energy Recovery Linac (cERL) is a superconducting test accelerator aimed at establishing technologies for the ERL-based future light source. After its construction during 2009 to 2013, the first CW beams of 20 MeV were successfully transported through the recirculation loop in February 2014. Then, initial tuning of beams and evaluations of beam properties were carried out. From September to December in 2014, we are constructing a Laser Compton Scattering (LCS) source* which aims at demonstrating technology for the future high-flux quasi-monochromatic gamma-ray source. In the next run of the cERL, which begins at the end of January 2015, we plan such works as an increase in the beam current (from 10 uA to 100 uA), commissioning of the LCS source, and sustained tuning of beams for lower emittance. We will report up-to-date results of these developments. * N. Nakamura et al., IPAC2014, MOPRO110; S. Sakanaka et al., LINAC14, TUPOL01. ** R. Nagai et al., IPAC2014, WEPRO003.
	Slides TUBC1 [2.679 MB]
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TUBC2	Multi-GHz Pulse-Train X-Band Capability for Laser Compton X-Ray and Gamma-Ray Sources	electron, brightness, scattering, photon	1363
	D.J. Gibson, G.G. Anderson, S.G. Anderson, C.P.J. Barty, R.A. Marsh, M. J. Messerly, M.A. Prantil LLNL, Livermore, California, USA
	Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. A wide variety of light-source applications would benefit from increased average brightness, which generally corresponds to increasing average current in the driving accelerator. Presented is an accelerator architecture that is capable of producing hundreds of electron bunches, spaced as close together as every RF cycle, which provides the chance to increase current while maintaining beam quality. This system relies on an X-band photoinjector and a photoinjection drive laser that is driven by the same rf source to ensure synchronization, and an interaction laser system designed to match the duty cycle of the electron pulse train. Results of the photoinjector laser performance and initial experimental measurements of beam quality in accelerated bunch trains are presented, along with a discussion of the impact on the performance of tunable, narrow-bandwidth x-ray and gamma-ray beams based on Compton-scattering.
	Slides TUBC2 [20.256 MB]
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TUBC3	Recent Results from FEL seeding at FLASH	FEL, electron, operation, radiation	1366
	J. Bödewadt, S. Ackermann, R.W. Aßmann, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, R. Ivanov, T. Laarmann, J.M. Müller, T. Tanikawa DESY, Hamburg, Germany S. Ackermann, Ph. Amstutz, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach Uni HH, Hamburg, Germany K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany
	The free-electron laser facility FLASH at DESY operates since several years in SASE mode, delivering high-intensity FEL pulses in the extreme ultra violet and soft x-ray wavelength range for users. In order to get more control of the characteristics of the FEL pulses external FEL seeding has proven to be a reliable method to do so. At FLASH, an experimental setup to test several different external seeding methods has been installed since 2010. After successful demonstration of direct seeding at 38 nm, the setup is now being operated in HGHG and later EEHG mode. Furthermore, other studies on laser induced effects on the electron beam dynamics have been performed. In this contribution, we give an overview of recent experimental results on FEL seeding at FLASH.
	Slides TUBC3 [6.651 MB]
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TUPWA008	Mixing and Space-Charge Effects In Free-Electron Lasers	electron, FEL, radiation, space-charge	1410
	E.A. Peter, A. Endler, F.B. Rizzato IF-UFRGS, Porto Alegre, Brazil A.P.B. Serbeto UFF, Niterói - RJ, Brazil
	Funding: This work was supported by CNPq and FAPERGS, Brazil, and by the Air Force Office of Scientific Research (AFOSR), USA, under the Grant No. FA9550-12-1-0438 Free-electron lasers are devices which efficiently convert the kinetic energy from a relativistic electron beam into electromagnetic radiation, amplifying an initial small sign. The present work revisits the subject of mixing, saturation and space-charge effects in free-electron lasers. Use is made of the compressibility factor, which proves to be a helpful tool in the related systems of charged beams confined by static magnetic fields. The compressibility allows to build a semi-analytical model and to perform analytical estimates of the elapsed time until the onset of mixing, which in turn allows to estimate the saturated amplitude of the radiation field. In addition, the compressibility helps to pinpoint space-charge effects and the corresponding transition from Compton to Raman regimes. The semi-analytical model and the particles simulations are compared, exhibiting a good agreement.* * E. Peter, A. Endler, F. B. Rizzato, and A. Serbeto, Phys. Plasmas 20, 123104 (2013). ** E. Peter, A. Endler, and F. B. Rizzato, Phys. Plasmas 21, 113104 (2014)
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TUPWA011	Progress on the LUNEX5 project	FEL, undulator, electron, operation	1416
	M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, J.D. Bozek, F. Briquez, L. Cassinari, L. Chapuis, J. Da Silva, J. Daillant, Y. Dietrich, M. Diop, J.P. Duval, M.E. El Ajjouri, T.K. El Ajjouri, C. Herbeaux, N. Hubert, M. Khojoyan, M. Labat, P. Lebasque, N. Leclercq, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, F. Marteau, C. Miron, P. Morin, A. Nadji, R. Nagaoka, F. Polack, F. Ribeiro, J.P. Ricaud, P. Rommeluère, P. Roy, G. Sharma, K.T. Tavakoli, M. Thomasset, M. Tilmont, S. Tripathi, M. Valléau, J. Vétéran, W. Yang, D. Zerbib SOLEIL, Gif-sur-Yvette, France S. Bielawski, C. Evain PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France B. Carré, D. Garzella CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France X. Davoine CEA/DAM/DIF, Arpajon, France N. Delerue LAL, Orsay, France G. Devanz, C. Madec, A. Mosnier CEA/IRFU, Gif-sur-Yvette, France A. Dubois, J. Lüning CCPMR, Paris, France G. Lambert, V. Malka, A. Rousse, C. Thaury LOA, Palaiseau, France E. Roussel Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy C. Szwaj PhLAM/CERLA, Villeneuve d'Ascq, France
	LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent Free Electron Laser (FEL) pulses in the 40-4 nm spectral range. It comprises a 400 MeV superconducting Linear Accelerator for high repetition rate operation (10 kHz), multi-FEL lines and adapted for studies of advanced FEL schemes, a 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application, a single undulator line enabling advanced seeding and pilot user applications. Different studies such as on two color FEL and R&D programs have been launched. A test experiment for the demonstration of 180 MeV LWFA based FEL amplification at 200 nm is under preparation in collaboration with the Laboratoire d’Optique Appliquée, thanks to a proper electron beam manipulation. Specific hardware is also under development such as a cryo-ready 3 m long undulator of 15 mm period.
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TUPWA020	BNL ATF II Beamlines Design	experiment, electron, cavity, linac	1445
	M.G. Fedurin, Y.C. Jing, D. Stratakis, C. Swinson BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Brookhaven National Lab. Accelerator Test Facility (BNL ATF) is currently undergoing a major upgrade (ATF-II). Together with a new location and much improved facilities, the ATF will see an upgrade in its major capabilities: electron beam energy and quality and CO2 laser power. The electron beam energy will be increased in stages, first to 100-150 MeV followed by a further increase to 500 MeV. Combined with the planned increase in CO2 laser power (from 1-100 TW), the ATF-II will be a powerful tool for Advanced Accelerator research. A high-brightness electron beam, produced by a photocathode gun, will be accelerated and optionally delivered to multiple beamlines. Besides the energy range (up to a possible 500 MeV in the final stage) the electron beam can be tailored to each experiment with options such as: small transverse beam size (<10 um), flat beam, short bunch length (<100 fs) and, combined short and small bunch options. This report gives a detailed overview of the ATF-II capabilities and beamlines configuration.
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TUPWA021	A New Method to Generate Ultrashort and Coherent Pulses of Short-Wavelength Synchrotron Radiation	electron, radiation, synchrotron, storage-ring	1448
	S. Khan DELTA, Dortmund, Germany
	Funding: Work supported by the BMBF (contract 05K13PE3) A laser-based method to generate ultrashort pulses of synchrotron radiation in electron storage rings is coherent harmonic generation (CHG) using two undulators to produce coherent radiation at harmonics of the initial laser wavelength by microbunching. The bunching factor and thus the pulse intensity, however, decreases exponentially with increasing harmonic order. Echo-enabled harmonic generation (EEHG), proposed in 2009 as FEL seeding scheme, can be used to produce short synchrotron radiation pulses at higher harmonics, but requires three undulators in a straight section. In this paper, a less space-consuming method based on seeding with intensity-modulated laser pulses is introduced, which also has the potential of significant bunching factors at high harmonics. G. Stupakov, PRL 102 (2009), 074801.
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TUPWA022	Characterization and Optimization of Ultrashort and Coherent VUV Pulses at the DELTA Storage Ring	electron, radiation, synchrotron, undulator	1452
	S. Khan, F.H. Bahnsen, M. Bolsinger, S. Hilbrich, M. Huck, M. Höner, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, G. Shayeganrad, P. Ungelenk DELTA, Dortmund, Germany H. Huck DESY Zeuthen, Zeuthen, Germany
	Funding: Work supported by BMBF (05K13PE3 and 05K13PEC), DFG (INST 212/236-1 FUGG) and the Land NRW At DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund University, a source for coherent and ultrashort vacuum-ultraviolet (VUV) and terahertz (THz) pulses is now in operation. The VUV source is based on a laser-induced energy modulation and coherent harmonic generation (CHG). A subsequently developing dip in the longitudinal electron distribution gives rise to coherent THz radiation. Recent results regarding the optimization of the laser-electron interaction and characterization of the CHG pulses are presented.
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TUPWA026	Simulation of Optical Transport Beamlines for High-quality Optical Beams for Accelerator Applications	electron, polarization, simulation, FEL	1462
	J. Bödewadt, N. Ekanayake DESY, Hamburg, Germany
	High-quality optical beams play already an important role in the field of particle accelerators which will most probably become even more prominent in the view of laser-driven particle accelerators. Nowadays, optical transport systems are needed for particle generation in photo injectors, for particle acceleration in laser-driven plasma wakefield accelerators, for particle beam diagnostics such as synchrotron radiation monitoring systems, or for particle manipulation schemes e.g. for external seeding of free-electron lasers. For the latter case, also the photon beam transport to the user end-stations requires dedicated optical transport system. The utilized wavelengths range from the hard x-ray up to the far-infrared spectral range. Parameters like surface quality, polarization effects, damage thresholds in- and out-of-vacuum, mechanical stability, dispersion effect etc. need to be studied for the variaty of applications. Here, we present the simulation results of the optical transport beamline for the seeding setup at FLASH and give a comparision to our measurement results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA026
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TUPWA031	Compression of Train of Bunches with Ramped Intensity Profile at SPARC_LAB	linac, cathode, plasma, electron	1476
	B. Marchetti DESY, Hamburg, Germany A. Bacci Istituto Nazionale di Fisica Nucleare, Milano, Italy E. Chiadroni, M. Ferrario, R. Pompili INFN/LNF, Frascati (Roma), Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy
	The production and acceleration of train of bunches with variable spacing in the ps/sub-ps range having ramped intensity profile are interesting to drive a plasma wave in the so-called resonant Plasma Wake-Fields Acceleration (r-PWFA). At SPARC_LAB trains having a constant intensity profile have been produced for the first time by using a shaped photo-cathode laser combined with the use of the velocity bunching compression technique,,*. If the sub-bunches have ramped intensity, i.e. they have different charge density, the space charge force affects differently the development of the longitudinal phase space of each one of them during the compression. In this paper we present preliminary simulations for the compression of a ramped train of bunches. The differences between the beam dynamics for a train of bunches having constant intensity profile and the ramped train are underlined. We discuss also the possibility of properly tuning the shaping of the photocathode laser to balance the space charge effect. SLAC-PUB-3528 M. Ferrario et al., Phys. Rev. Lett. 104, 054801 (2010). * M. Ferrario et al. NIM A 637, S43-S46 (2011). **** E. Chiadroni et al., Rev. Sci. Instrum. 84, 022703
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TUPWA033	Status of the Soft X-ray Free Electron Laser FLASH	operation, FEL, optics, photon	1482
	M. Vogt, B. Faatz, J. Feldhaus, K. Honkavaara, S. Schreiber, R. Treusch DESY, Hamburg, Germany
	The superconducting free-electron laser FLASH at DESY routinely produces up to several thousand photon pulses per second with wavelengths in the soft X-ray and vacuum UV regime and with energies up to 0.5 mJ per pulse. In 2014 the assembly of a second undulator beamline, FLASH2, was finished. While recommissioning of the FLASH linac and the original FLASH1 beamline was finished already at the end of 2013, the commissioning of FLASH2 could only be started in early February 2014. Only a few weeks have been reserved for dedicated set up of FLASH2, and most of its commissioning has been performed parasitically during the FLASH1 user run. The first beam was extracted through the septum to the FLASH2 beamline on March 4th, 2014, and the first lasing of FLASH2 at a wavelength of about 40 nm was achieved on August 20th, while FLASH1 was lasing simultaneously with 250 bunches at 13.5 nm. We summarize here the status of the FLASH2 commissioning and the FLASH1 operation during its 5th user period.
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TUPWA039	Transverse Gradient Undulator-Based High-Gain-FELs - a Parameter Study	undulator, electron, FEL, resonance	1502
	A. Bernhard, V. Afonso Rodríguez, E. Burkard, A.-S. Müller, C. Widmann KIT, Karlsruhe, Germany
	Transverse gradient undulators (TGU) have recently been discussed as sources for High Gain Free Electron Lasers (FEL) driven by electron beams with an elevated energy spread as for example generated in storage rings or wakefield accelerators. In this contribution we present the results of a parameter study based on the one-dimensional TGU-FEL theory making realistic assumptions on the key parameters achievable for the transverse gradient undulator. We show for which parameter areas LWFA-driven TGU-FELs are virtually technically feasible today and which technical improvements would be required to employ the concept for a laboratory-scale X-Ray FEL.
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TUPWA042	Status of the Accelerator Physics Test Facility FLUTE	electron, gun, linac, diagnostics	1506
	M.J. Nasse, A. Bernhard, I. Birkel, A. Borysenko, A. Böhm, S. Hillenbrand, N. Hiller, S. Höninger, S. Marsching, A.-S. Müller, R. Rossmanith, R. Ruprecht, M. Schuh, M. Schwarz, B. Smit, S. Walther, M. Weber, P. Wesolowski KIT, Karlsruhe, Germany R.W. Aßmann, M. Felber, K. Flöttmann, C. Gerth, M. Hoffmann, P. Peier, H. Schlarb, B. Steffen DESY, Hamburg, Germany R. Ischebeck, B. Keil, V. Schlott, L. Stingelin PSI, Villigen PSI, Switzerland
	A new compact versatile linear accelerator named FLUTE (Ferninfrarot Linac Und Test Experiment) is currently under construction at the Karlsruhe Institute of Technology (KIT). It will serve as an accelerator test facility and allow conducting a variety of accelerator physics studies. In addition, it will be used to generate intense, ultra-short THz pulses for photon science experiments. FLUTE consists of a ~7 MeV photo-injector gun, a ~41 MeV S-band linac and a D-shaped chicane to compress bunches to a few femtoseconds. This contribution presents an overview of the project status and the accompanying simulation studies.
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TUPWA046	Facility Upgrade at PITZ and First Operation Results	gun, plasma, operation, electron	1518
	A. Oppelt, P. Boonpornprasert, A. Donat, J.D. Good, M. Groß, H. Huck, I.I. Isaev, L. Jachmann, D.K. Kalantaryan, M. Khojoyan, W. Köhler, G. Koss, G. Kourkafas, M. Krasilnikov, O. Lishilin, D. Malyutin, J. Meissner, D. Melkumyan, M. Otevřel, M. Penno, B. Petrosyan, S. Philipp, M. Pohl, Y. Renier, T. Rublack, B. Schöneich, J. Schultze, F. Stephan, F. Tonisch, G. Trowitzsch, G. Vashchenko, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. A. Bakr Assiut University, Assiut, Egypt C. Hernandez-Garcia JLab, Newport News, Virginia, USA G. Pathak Uni HH, Hamburg, Germany D. Richter HZB, Berlin, Germany
	The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops, optimizes and characterizes high brightness electron sources for free electron lasers like FLASH and the European XFEL. In the last year, the facility was significantly upgraded by the installation of a new normal conducting radio- frequency (RF) gun cavity with its new waveguide system for the RF feed, which should allow stable and reliable gun operation, as required for the European XFEL. Other relevant additions include beamline modifications for improving the electron beam transport through the PITZ accelerator, extending the beam-based measurement capabilities, and preparing the installation of a plasma cell. Furthermore, the laser hutch was re-arranged in order to be able to house an additional, new photo cathode drive laser system which should be able to produce 3D ellipsoidal laser pulses to further improve the electron beam quality. This paper describes in detail the aforementioned facility upgrades and reports on the first operation experience with the new gun setup.
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TUPWA047	First Results Attained With the Quasi 3-D Ellipsoidal Photo Cathode Laser Pulse System at the High Brightness Photo Injector PITZ	electron, cathode, emittance, simulation	1522
	T. Rublack, J.D. Good, M. Khojoyan, M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky IAP/RAS, Nizhny Novgorod, Russia I. Hartl, S. Schreiber DESY, Hamburg, Germany E. Syresin JINR, Dubna, Moscow Region, Russia
	Funding: Funded by the German Federal Ministry of Education and Research (BMBF) project 05K10CHE in the framework of the German-Russian collaboration "Development and Use of Accelerator-Based Photon Sources". 3-D ellipsoidal photo cathode laser pulses are considered as the next step in optimization of photo injectors required for a successful operation of linac based free electron lasers. Beam dynamics simulations using such laser pulses compared to conventional cylindrical pulses have shown a significant improvement in electron beam emittance. In collaboration with the Institute of Applied Physics (Nizhny Novgorod, Russia) and the Joint Institute of Nuclear Research (Dubna, Russia) such a 3-D ellipsoidal laser pulse system has been developed and afterwards installed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). The pulse shaping is realized using the spatial light modulator technique. This allows very fine amplitude modulation within a laser pulse. The characterization of the shape of the laser pulses can be done by cross-correlation measurements. Using this method the ability to generate and measure quasi ellipsoidal laser pulses has been demonstrated. In this contribution the overall set-up, working principle and first results received with the new photo cathode laser system at PITZ will be reported.
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TUPWA053	Influence of a Non-uniform Longitudinal Heating on High Brightness Electron Beams for FEL	electron, FEL, undulator, linac	1535
	E. Roussel, E. Allaria, M.B. Danailov, G. De Ninno, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Laser-heater systems are essential tools to control and optimize high-gain free electron lasers (FELs), working in the x-ray wavelength range. Indeed, these systems induce a controllable heating of the energy spread of the electron bunch. The heating allows in turn to suppress longitudinal microbunching instabilities limiting the FEL performance. In this communication, we show that a long-wavelength energy modulation of the electron beam induced by the laser heater can persist until the beam entrance in the undulators, affecting the FEL emission process. This non-uniform longitudinal heating can be exploited to investigate the electron-beam microbunching in the linac, as well as to control the FEL spectral properties. Here, we present experimental, analytical and numerical studies carried out at FERMI.
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TUPWA054	The FERMI Seeded FEL Facility: Operational Experience and Future Perspectives	FEL, experiment, electron, operation	1538
	M. Svandrlik, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are now available for users, down to the shortest wavelength of 4 nm. We will report on the completion of the commissioning of the high energy FEL line, FEL-2, and on the operational experience for users, in particular those requiring specific FEL configurations, like two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered by our experience and are aiming to maintain as well as to constantly improve the performance of the facility for our user community.
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TUPWA055	DAΦNE Gamma-Ray Factory	electron, photon, factory, emittance	1542
	D. Alesini, S. Guiducci, C. Milardi, A. Variola, M. Zobov INFN/LNF, Frascati (Roma), Italy I. Chaikovska, Z.F. Zomer LAL, Orsay, France
	Gamma sources with high flux and spectral densities are the main requirements for new nuclear physics experiments to be performed in several worldwide laboratories with dedicated facilities. The presentation is focalized on a proposal of experiment of gamma photons production using Compton collisions between the DAΦNE electron beam and a high average power laser pulse, amplified in a Fabry-Pérot optical resonator. The calculations show that the resulting gamma beam source has extremely interesting properties in terms of spectral density, energy spread and gamma flux comparable (and even better) with the last generation gamma sources. The energy of the gamma beam depends on the adopted laser wavelength and can be tuned changing the energy of the electron ring. In particular we have analyzed the case of a gamma factory tunable in the 2-9 MeV range. The main parameters of this new facility are presented and the perturbation on the transverse and longitudinal electron beam dynamics is discussed. A preliminary accelerator layout to allow experiments with the gamma beam is presented with a first design of the accelerator optics.
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TUPWA063	FEL Enhancement by Microbuch Structure Made with Phase-Space Rotation	FEL, simulation, 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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TUPWA065	Generation of Multi-bunch Beam with Beam Loading Compensation by Using RF Amplitude Modulation in Laser Undulator Compact X-ray (LUCX)	cavity, electron, gun, booster	1576
	M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan K. Sakaue, M. Washio RISE, Tokyo, Japan
	We have developed a compact X-ray source based on inverse Compton scattering between an electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. The accelerator consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. Our aim is to obtain a clear X-ray image in a shorter period of times and the target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth at present. To achieve this target, it is necessary to increase the intensity of an electron beam to 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches with beam-loading compensation by using the delta T method and the amplitude modulation of RF pulse. The bunch-by-bunch energy difference is within 1.3% peak to peak. We will report the results of the multi-bunch beam generation and acceleration in this accelerator. This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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TUPWA066	Development of a High Average Power Laser for High Brightness X-ray Source and Imaging at cERL	cavity, electron, detector, photon	1579
	A. Kosuge, T. Akagi, S. Araki, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan R. Hajima, M. Mori, T. Shizuma JAEA, Ibaraki-ken, Japan R. Nagai JAEA/ERL, Ibaraki, Japan
	Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan. High brightness X-rays via laser-Compton scattering (LCS) of laser photons stored in an optical cavity by a relativistic electron beam is useful for many scientific and industrial applications such as X-ray imaging. The construction of compact Energy Recovery Linac (cERL) is now in progress at KEK to generate low-emittance and high-current electron beams. In order to demonstrate the generation of high brightness LCS X-rays, it is necessary to develop a high average power injection laser and an optical four-mirror ring cavity with two concave mirrors which is used to produce a small spot laser beam inside the cavity. In this presentation, we will show the result of the development of the high average laser system, the LCS X-rays generation, and the X-ray imaging.
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TUPWA068	Simulation Study of Beam Halo and Loss for KEK Compact ERL	simulation, cavity, 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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TUPWA070	CST Simulations of THz Cherenkov Smith-purcell Radiation from Corrugated Capillary	radiation, simulation, electron, polarization	1594
	K. Lekomtsev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan P. Karataev JAI, Egham, Surrey, United Kingdom A. Ponomarenko, A.A. Tishchenko MEPhI, Moscow, Russia
	Recent advances in generation of femtosecond pre-bunched beams have a potential to generate coherent THz radiation occurring via combination of Smith-Purcell radiation (SPR) and Cherenkov radiation (ChR) generated in a corrugated capillary. This mechanism was studied theoretically . LUCX accelerator at High Energy Accelerator Research Organisation (KEK) has been upgraded by introducing fs Ti:Sa laser system and it is currently generating short tens of fs electron bunches . In this report we present EM simulations of Ch.SPR generated in a corrugated channel in infinite dielectric and in a dielectric corrugated capillary. CST PIC solver is used as a simulation tool. It was earlier used for simulation of Transition radiation *. Intensity dependencies of ChR and SPR peaks as functions of the capillary radius and the corrugation depth are compared with the theoretical investigation . Output of THz radiation from the dielectric capillary with a radiation reflector is simulated. * A.A. Ponomarenko et. al, NIMB 309 (2013) 223-226. M. Fukuda et. al, NIMA 637 (2011) S67. * K.V. Lekomtsev et. al, J. Phys.: Conf. Ser. 517, (2014) 012016.
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TUPWA071	Improvements of the Laser System for RF-Gun at SuperKEKB Injector	electron, operation, gun, cryogenics	1598
	R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	For realizing higher charge and low emittance electron and positron beams in SuperKEKB, we have been making improvements in laser system for RF-gun. The difficulty in controlling thermomechanical distortions has been one of the most important factors for preserving high laser conversion efficiency of infrared-to-ultraviolet and operating at higher repetition rate. We demonstrated that efficient removal of waste heat can be realized by adopting Yb:YAG and copper bonding composite via Au-Sn solder. On the other hand, we proposed the novel design of the cascade laser configuration. Base on this, we can improve the quantum efficiency by utilizing other Yb ions doped crystals as active medium which are pumped by 1035 nm Yb:YAG laser. Excellent thermal management and high charge beams have been achieved by improvements of these two aspects. Additionally, in order to employ high duty ratio pump system and realize laser operation at high repetition rate, we investigated the laser operation in cryogenic environment. A perspective towards the next step experiment is also presented in this paper.
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TUPWA072	Coherent Thomson Scattering Radiation Generated by using PEHG	radiation, electron, scattering, undulator	1601
	S. Chen, K. Ohmi, D. Zhou KEK, Ibaraki, Japan S. Huang PKU, Beijing, People's Republic of China
	In this paper, we present the coherent Thomson scattering of a long wavelength laser with ultrashort electron slices. The ultrashort electron slices are generated by the longitudinal bunch density modulation method of PEHG. Coherent radiation with ultrashort pulse length is generated in EUV regime by this method.
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TUPJE002	Demonstration of High-flux Photon Generation from an ERL-based Laser Compton Photon Source	photon, electron, cavity, linac	1607
	R. Nagai, R. Hajima, M. Mori, T. Shizuma JAEA, Ibaraki-ken, Japan T. Akagi, S. Araki, Y. Honda, A. Kosuge, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	A high-flux photon source from the laser Compton scattering (LCS) by an electron beam in an energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear materials. In order to demonstrate accelerator and laser technologies required for a LCS photon generation, a LCS photon source is under construction at the Compact ERL (cERL). The LCS photon source consists of a mode-locked fiber laser and a laser enhancement cavity. Flux monitors and a data aqcuisition system are also under construction. The commissioning of the LCS photon source will be started in February 2015 and LCS photon generation is scheduled in March 2015. The demonstration result of the LCS photon source will be presented in detail.
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TUPJE003	Quasi-Traveling Wave RF Gun and Beam Commissioning for SuperKEKB	gun, cathode, emittance, cavity	1610
	T. Natsui The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun which has two side coupled standing wave field. We call it quasi-traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. This RF gun has been installed in the KEK J-linac. Beam commissioning with the RF gun is in progress.
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TUPJE004	Narrow Band Coherent Edge Radiation at UVSOR-III	radiation, electron, experiment, storage-ring	1613
	M. Hosaka, O. Oodake, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan S. Bielawski, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France M. Katoh, T. Konomi, J. Yamazaki UVSOR, Okazaki, Japan H. Zen Kyoto University, Kyoto, Japan
	Edge radiation can be an interesting new light source because of its property that the radiation is well collimated and is radially polarized. We are developing coherent light sources in the THz region at UVSOR-III storage ring. We have already succeeded in producing a narrow band coherent THz radiation by manipulating the interaction of a relativistic electron bunch with an amplitude modulated laser with. Recently a simplified tentative beamline for detection of the edge radiation is installed at downstream of a short straight section of UVSOR-III. Coherent radiation from electron bunches after the interaction with the amplitude modulated laser is observed. Detailed measurements of polarizations and special distribution of the radiation are underway. The latest status of the study will be reported.
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TUPJE006	Recent Developments of UVSOR-III	undulator, injection, operation, synchrotron	1619
	M. Katoh, K. Hayashi, J. Yamazaki UVSOR, Okazaki, Japan M. Adachi, T. Konomi, N. Yamamoto KEK, Ibaraki, Japan M. Hosaka, Y. Takashima Nagoya University, Nagoya, Japan
	A 750 MeV low energy synchrotron light source, UVSOR, has been operational since 1983. About ten years after the first major upgrade in 2003, the second major upgrade was carried out in 2012, in which all the bending magnets were replaced with combined function ones and a new in-vacuum undulator was installed in the last straight section reserved for undulators. After this upgrade, the light source, UVSOR-III, has been operational with small emittance of 17 nm-rad, with six undulators, and fully with the top-up injection at 300mA. Adding to the present status of the accelerator, most recent progresses in the pulsed sextupole magnet for the beam injection and in the coherent light source development station will be presented.
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TUPJE007	Measurement of Temporal Electric Field of Electron Bunch using Photoconductive Antenna	electron, linac, polarization, radiation	1623
	K. Kan, M. Gohdo, T. Kondoh, I. Nozawa, A. Ogata, T. Toigawa, J. Yang, Y. Yoshida ISIR, Osaka, Japan
	A temporal electric field profile, which is a radially polarized terahertz (THz) pulse from an electron bunch, was measured by a large-aperture photoconductive antenna (PCA) with micro-structured concentric electrodes* for the detection of THz pulses. Photo-induced charge carriers were generated by irradiation of femtosecond laser pulses on semiconductor plane of the electrodes on the PCA. Time-domain measurement of coherent transition radiation (CTR) was conducted by the measurement of electric-field-induced current output from the PCA with sweeping the timing of the laser irradiation. The measurements on femtosecond electron bunches of 32 MeV and >80 pC will be reported. * K. Kan et al., Appl. Phys. Lett. 102, 221118 (2013).
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TUPJE008	Relocation and Improvement Status of the SCSS Test Accelerator to Provide Dual FEL Drivers at SACLA	acceleration, undulator, linac, electron	1626
	Y. Otake RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	To increase user experiment chances at SACLA, Equipping a new beamline and an additional linac as a further FEL driver is effective. For this reason, the SCSS test accelerator as the prototype of SACLA is reused and improved, because of terminating its role. SCSS with an electron beam energy of 250 MeV generated an extreme ultraviolet laser with 50-60 nm. We relocated SCSS into the SACLA undulator hall and improved its performance. Three newly designed C-band accelerator-units for the relocated SCSS accelerator with an acceleration gradient of 47 MeV/m at maximum boost an electron beam energy of up to 420 MeV. By FEL simulation, the EUV-FEL with 30-40 nm and 100 uJ are expected in conditions of the electron energy and 2 modified undulators with 5 m long each. As a further capability, the relocated SCSS accelerator has space to add 9 C-band accelerator units and 2 undulators and the units increase a beam energy of up to 1.4 GeV, as which can generate a soft X-ray FEL. The relocation of the accelerator was finished in the summer of 2014 and its RF conditioning was now started. This paper describes the relocation and improvement status of the modified SCSS accelerator.
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TUPJE009	Study on Frequency Multiplier of a Pulsed Laser Repetition using an Optical Cavity	cavity, gun, electron, cathode	1629
	T. Kobayashi Waseda University, Tokyo, Japan
	We have been studying a compact electron accelerator based on an S-band Cs-Te photo-cathode rf gun at Waseda University. The system is using S-band rf of 2856MHz. When a repetition of the electron bunch is integral multiple of rf, it enables a lot of electron bunch acceleration for the rf gun. The repetition of the electron bunch generated by a photo-cathode rf gun depends on the oscillating frequency of the pulsed mode-locked laser. We have been developing a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation (NLPR). However, its repetition is limited by the fiber length to produce NLPR. Therefore, we have started to develop the external optical cavity which is multiplier of a pulsed laser repetition. It would enable the rf gun to generate high-dose electron beam in a very short time. In this conference, we will report design of the external optical cavity to multiply the pulsed laser repetition, the experimental results of the frequency multiplying of a mode-locked Yb-doped fiber laser, and the future prospects. Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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TUPJE011	Laser-Compton Scattering X-ray Source Based on Normal Conducting Linac and Optical Enhancement Cavity	cavity, electron, linac, photon	1635
	K. Sakaue, M. Washio Waseda University, Tokyo, Japan S. Araki, M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have been developing a compact X-ray source via laser-Compton scattering (LCS) at KEK-LUCX (Laser Undulator Compact X-ray source) facility. The LUCX system is based on S-band normal conducting linac with an energy of 30 MeV and optical enhancement cavity for photon target. As a photon target, we invented a burst mode laser pulse storage technique for a normal conducting linac, which enables to store the high power laser pulses at the timing of electron bunchs. The peak storage power exceeds to more than 250 kW with 357 MHz repetition. Electron linac is under operation with multi-bunch mode, 1000 bunches/train with 600 pC charge in each bunches. We have succeeded to produce 1000 pulse/train LCS X-ray train. Combining high repetition rate electron linac and burst mode optical enhancement cavity, more than 10⁹ ph./sec/10%b.w. flux would be possible. In this conference, the introduction of our test facility LUCX, recent expermental results, and future prospective including normal conducting LCS X-ray source will be presented.
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TUPJE012	Preliminary Result of Photon Counting Acquisition Scheme for Laser Pump/X-ray Probe Experiments	synchrotron, experiment, detector, timing	1638
	J. He, J.S. Cao, G. Gao, Y.F. Sui, Y. Tao, J.H. Yue, Z. Zhang, Y.F. Zhou IHEP, Beijing, People's Republic of China
	Funding: This work is supported by the NSFC under grant No.11305186 R&D project has been initiated for a proposed ultralow emittance (~50pm.rad) synchrotron light source built in Beijing. The R&D includes the development of high repetition rate laser pump/X-ray probe for ultrafast dynamics detection in future source. In a typical laser pump/X-ray probe measurement, the X-ray pulse follows a laser pulse in adjustable delay. We are interested in the difference between laser on and laser off at different delay, which will snapshot dynamic process. To capture this trivial difference, it requires the acquisition system to single out the signal from this special X-ray pulse at adequate S/N ratio. For the R&D of high repetition rate pump-probe, we have set up a prototype counting acquisition system based on NIM modular electronics, which was tested in Beijing Synchrotron Radiation Facility (BSRF). The laser will be synchronized with a camshaft bunch at 124 kHz, a tenth of the revolution frequency. Avalanche Photo Diode (APD) was used to detect the X-ray pulse from this camshaft bunch due to its nanosecond response. Before the laser is delivered, we mimic the 124 kHz laser- on signal. The signals from APD are separated by power dividers into two Constant Fraction Discriminator (CFD) input channels. The signal in laser-on/off channel is gated out at 1.24MHz using the 1.24MHz timing signal divided from 499.8 MHz RF signal, while the mimic laser-on signal gated out at 124 kHz. Multiplied by ten times, the mimic laser-on signal counts should be consistent with the laser-on+off counts, if our counting modular works well. We carried out this test at 1W1B wiggler beam line to measure the Fe fluorescence signal. The performance of our system is demonstrated in the good consistency between mimic laser on and laser on+off signals.
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TUPJE019	Operating Cascaded High-gain Harmonic Generation with Double-pulse Electron Beams	electron, radiation, FEL, simulation	1661
	Z. Wang, C. Feng, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China L. Yu BNL, Upton, Long Island, New York, USA
	Cascaded high gain harmonic generation (HGHG) is the primary candidate for the generation of high power, full temporal coherent radiation at the wavelength of nanometer. However, the experimental results at the existing facility show large fluctuation of the output energy pulse at the second stage of cascading. In this paper, we study the scheme of double-pulse electron beams, which is helpful to increase the stability of pulse energy against the timing jitter. The method to generate double-pulse electron beams is shown in the paper and comparison between double-pulse scheme and standard cascaded HGHG is present base on three-dimensional start-to-end simulation to give a straightforward image on the obviously improvement of the FEL stability.
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TUPJE021	Interaction Chamber Design for a Sub-MeV Laser-compton Gamma-ray Source	electron, photon, scattering, simulation	1665
	H.H. Xu, J.H. Chen, G.T. Fan, D. Wang, H.L. Wu, B.J. Xu SINAP, Shanghai, People's Republic of China
	Previously, fixed angle Laser-Compton Scattering (LCS) experiments have been conducted at the terminal of the 100MeV LINAC of the Shanghai Institute of Applied Physics, using SINAP-I* and SINAP-II facility. Sub-MeV energy continuously tunable laser-Compton light source device (SINAP-Ⅲ) is an updated facility that will allow the collision angle between the laser and electron beam continuously adjustable from 20 to 160 degrees. This new feature will enable convenient control on the peak energy of the generated X/γ ray, especially when the energy of electrons cannot be momentarily adjusted, e.g. on the storage ring. The well control of the status of LCS is necessary. An interaction chamber containing a rotatable structure that holds a series of plane mirrors and convex lens is presented to achieve it. This work is a summary of its design. The simulation of photon production's variation caused by the system errors is performed using a MC code. The accuracies of installation and adjustment of mirrors and lens are given according to the simulation results. The sizes of these optical devices are also optimized to make the chamber as compact as possible due to space limitation. W. Luo et al., Rev. of Sci. Instrum, 81 (2010) 013304 W. Luo et al., Applied Physics B, 101 (2010)761-771 * W. Luo et al., NIM A, 660 (2011), p. 108
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TUPJE039	Recent Results on the Performance of Cs3Sb Photocathodes in the PHIN RF-Gun	cathode, gun, vacuum, operation	1699
	C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, I. Martini, M. Martyanov CERN, Geneva, Switzerland
	For the CLIC drive beam a photoinjector option is under study at CERN as an alternative to the thermionic electron gun in the CLIC baseline design. The CLIC drive beam requires a high bunch charge of 8.4 nC and 0.14 ms long trains with 2 ns bunch spacing, which is challenging for a photoinjector. In particular the required long and high intensity laser pulses cause a degradation of the beam quality during the frequency conversion process, which generates the ultra-violet laser beam needed for standard Cs2Te photocathodes. To overcome this issue Cs3Sb cathodes sensitive to green light have been studied at the high-charge PHIN photoinjector since a few years. In this paper recent measurements of fundamental properties of Cs3Sb photocathodes such as quantum efficiency, cathode lifetime and dark current from summer 2014 will be presented, and compared with previous measurements and with the performance of Cs2Te photocathodes.
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TUPJE040	Surface Characterization at CERN of Photocathodes for Photoinjector Applications	cathode, gun, electron, operation	1703
	I. Martini, E. Chevallay, V. Fedosseev, C. Heßler, H. Neupert, V. Nistor, M. Taborelli CERN, Geneva, Switzerland
	R&D on photocathodes takes place at CERN within the CLIC (Compact Linear Collider) project. Photocathodes are produced as thin films on Oxygen Free copper substrate using a co-deposition technique, and characterized in a dedicated laboratory with a DC photo-electron gun. A new UHV carrier vessel compatible with CERN’s XPS (X-ray Photoelectron Spectroscopy) analysis equipment has been commissioned and is used to transport photocathodes from the production laboratory to perform a systematic study of different compounds used as photoemissive materials. In this paper photocathodes used in a RF photoinjector will be characterized and the correlation of their surface properties with their performance will be investigated.
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TUPJE054	Developments in CLARA Accelerator Design and Simulations	FEL, simulation, 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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TUPJE060	Development of Advanced Fourth Generation Light Sources for the Accelerator Science Laboratory	radiation, electron, simulation, cavity	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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TUPJE074	LCLS Injector Laser Modulation to Improve FEL Operation Efficiency and Performance	electron, optics, FEL, emittance	1813
	S. Li, D.K. Bohler, W.J. Corbett, A.S. Fisher, S. Gilevich, Z. Huang, A. Li, D.F. Ratner, J. Robinson, F. Zhou SLAC, Menlo Park, California, USA R.B. Fiorito, E.J. Montgomery UMD, College Park, Maryland, USA H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom H.D. Zhang The University of Liverpool, Liverpool, United Kingdom
	In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The injector laser strikes a copper photocathode which emits photo-electrons due to photo-electric effect. The emittance of the electron beam is highly related to the transverse shape of the injector laser. Currently the LCLS injector laser has hot spots that degrade the FEL performance. The goal of this project is to use adaptive optics to modulate the transverse shape of the injector laser, in order to produce a desired shape of electron beam. With a more controllable electron transverse profile, we can achieve lower emittance for the FEL, improve the FEL performance and operation reliability. We first present various options for adaptive optics and damage test results. Then we will discuss the shaping process with an iterative algorithm to achieve the desired shape, characterized by Zernike polynomial deconstruction.
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TUPMA003	Microbunching Phenomena in LCLS-II	space-charge, bunching, simulation, 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, simulation	1846
	D.G. Velázquez, R.L. Seibert, L.K. Spentzouris, J. Terry, Z.M. Yusof Illinois Institute of Technology, Chicago, Illinois, USA
	Photocathode emission properties are critical for electron beam applications such as photoinjectors for free electron lasers (FEL) and energy recovery Linacs (ERL). We investigate whether emission properties of photocathodes can be manipulated through the engineering of the surface electronic structure. The multilayers described here have been predicted to have emission properties in correlation with the film thickness. This paper describes how ultra-thin multilayered MgO/Ag/MgO films in the crystallographic orientations (001) and (111) multilayers were synthesized and characterized. Preliminary results of work function measurements are provided. Films were grown by pulsed laser deposition at 130 °C for the (001) orientation and 210 °C for the (111) orientation at a background pressure of ~ 5×10^-9 Torr. Epitaxial growth was monitored in-situ using reflection high-energy electron diffraction, which showed single crystal island growth for each stage of the multilayer formation. Photoelectron spectroscopy was used to track the chemical state transition from Ag to MgO during the deposition of successive layers. The Kelvin probe technique was used to measure the change in contact potential difference, and thus work function, for various MgO layer thicknesses in comparison with bare single crystal Ag(001)and Ag(111) thin films. The work function was observed to reduce with increasing thickness of MgO from 0 to 4 monolayers as much as 0.89 eV and 0.72 eV for the (001) and (111) orientations, respectively. Photoelectron spectra near the Fermi level revealed electron density shifts toward zero binding energy for the multilayered surfaces with respect to the clean Ag surfaces.
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TUPMA017	Pulsed-wire Measurements for Insertion Devices	undulator, electron, detector, FEL	1869
	A. D'Audney, S. Biedron, S.V. Milton, S.A. Stellingwerff CSU, Fort Collins, Colorado, USA
	The performance of a Free Electron Laser (FELs) depends in part on the integrity of the magnetic field in the undulator. The magnetic field on the axis of the undulator is transverse and sinusoidally varying due to the periodic sequence of dipoles. The ideal trajectory of a relativistic electron bunch, inserted along the axis, is sinusoidal in the plane of oscillation. Phase errors are produced when the path of the electron is not the ideal sinusoidal trajectory, due to imperfections in the magnetic field. The result of such phase errors is a reduction of laser gain impacting overall FEL performance. A pulsed-wire method can be used to determine the profile of the magnetic field. This is achieved by sending a square current pulse through the wire, which will induce an interaction with the magnetic field. Measurement of the displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic field. Dispersion in the wire can be corrected using algorithms resulting in higher accuracy. Once the fields are known, magnetic shims are placed where any corrections are needed.
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TUPMA019	Simulation and Analysis of Laser/Electron Beam interaction for use as a Free Electron Laser	undulator, simulation, 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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TUPMA025	X-Band RF Photoinjector for Laser Compton X-Ray and Gamma-Ray Sources	electron, emittance, dipole, gun	1891
	R.A. Marsh, G.G. Anderson, S.G. Anderson, C.P.J. Barty, D.J. Gibson LLNL, Livermore, California, USA
	Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Extremely bright narrow bandwidth gamma-ray sources are expanding the application of accelerator technology and light sources in new directions. An X-band test station has been commissioned at LLNL to develop multi-bunch electron beams. This multi-bunch mode will have stringent requirements for the electron bunch properties including low emittance and energy spread, but across multiple bunches. The test station is a unique facility featuring a 200 MV/m 5.59 cell X-band photogun powered by a SLAC XL4 klystron driven by a Scandinova solid-state modulator. This paper focuses on its current status including the generation and initial characterization of first electron beam. Design and installation of the inverse-Compton scattering interaction region and upgrade paths will be discussed along with future applications.
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TUPMA028	Feasibility Study for an X-ray FEL Oscillator at the LCLS-II	electron, cavity, FEL, undulator	1897
	T.J. Maxwell, J. Arthur, Y. Ding, W.M. Fawley, J.C. Frisch, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus SLAC, Menlo Park, California, USA W.M. Fawley Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy K.-J. Kim, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin ANL, Argonne, Ilinois, USA
	Funding: This work supported in part under US Department of Energy contract DE-AC02-76SF00515. We show that a free-electron laser oscillator generating X-ray pulses with hard X-ray wavelengths of order 0.1 nm is feasible using the presently proposed FEL-quality electron beam within the space of existing LCLS-II infrastructure when combined with a low-loss X-ray crystal cavity. In an oscillator configuration driven by the 4 GeV energy electron beam lasing at the fifth harmonic, output x-ray bandwidths as small as a few meV are possible. The delivered average spectral flux is at least two orders of magnitude greater than present synchrotron-based sources with highly stable, coherent pulses of duration 1 ps or less for applications in Mössbauer spectroscopy and inelastic x-ray scattering.
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TUPMA030	Narrowband Continuously Tunable Radiation in the 5 to 10 Terahertz Range by Inverse Compton Scattering	electron, radiation, photon, scattering	1901
	Z. Wu, K. Fang, M.-H. Wang, J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199. 5 to 10 THz has recently become the frontier of THz radiation sources development, pushed by the growing interests of spectroscopy and pump-probe material study in this frequency range. This spectrum “Gap” lies in between the several THz range covered by Electro-Optical crystal based THz generation, and the tens of THz range covered by the difference frequency generation method. The state-of-the-art EO crystal THz source using tilted pulse front technique has been able to reach ~ 100 MV/m peak field strength, large enough to be used in an inverse Compton scattering process to push these low energy photons to shorter wavelengths of the desired 5-10 THz range. The required electron beam energy is within 1~2 MeV, therefore a compact footprint of the whole system. The process would occur coherently granted the electron beam is bunched to a fraction of the radiation wavelengths (several microns). A system operating at KHz or even MHz repetition rate is possible given the low electron energy and thus low RF acceleration gradient required. This work will explore the scheme with design parameters and simulation results.
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TUPMA031	Dispersive Property of the Pulse Front Tilt of a Short Pulse Optical Undulator	optics, FEL, electron, undulator	1904
	M.-H. Wang, J. Wu, Z. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE No. DE-AC02-76SF00515. A short pulse laser can be used as an optical undulator to achieve a high-gain and high-brightness X-ray free electron laser (FEL) [1]. To extend the interaction duration of electron and laser field, the electron and the laser will propagate toward each other with an small angle. In addition, to maintain the FEL lasing resonant condition, the laser pulse shape need be flattened and the pulse front will be titled. Due to the short pulse duration, the laser pulse has a broad bandwidth. In this paper, we will first describe the method of generalized Gaussian beam propagation using ray matrix. By applying the Gaussian beam ray matrix, we can study the dispersive property after the pulse front of the short laser is tilted. The results of the optics design for the proposal of SLAC Compton scattering FEL are shown as an example in this paper. [1] C. Chang, et al.,“High-brightness X-ray free-electron laser with an optical undulator by pulse shaping”. Optics Express, Vol. 21, Issue 26, pp. 32013-32018 (2013).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA031
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TUPMA033	A Bunch Compression Method for Free Electron Lasers that Avoids Parasitic Compressions	electron, dipole, FEL, acceleration	1907
	S.V. Benson, D. Douglas, C. Tennant, F.G. Wilson JLab, Newport News, Virginia, USA D.C. Nguyen LANL, Los Alamos, New Mexico, USA
	Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences. Virtually all existing high energy (>few MeV) linac-driven FELs compress the electron bunch length though the use of off-crest acceleration on the rising side of the RF waveform followed by transport through a magnetic chicane. This approach has at least three flaws: 1) it is difficult to correct aberrations- particularly RF curvature, 2) rising side acceleration exacerbates space charge-induced distortion of the longitudinal phase space, and 3) all achromatic "negative compaction" compressors create parasitic compression during the final compression process, increasing the CSR-induced emittance growth. One can avoid these deficiencies by using acceleration on the falling side of the RF waveform and a compressor with M56>0. This approach offers multiple advantages: 1) It is readily achieved in beam lines supporting simple schemes for aberration compensation, 2) Longitudinal space charge (LSC)-induced phase space distortion tends, on the falling side of the RF waveform, to enhance the chirp, and 3) Compressors with M56>0 can be configured to avoid spurious over-compression. We will discuss this bunch compression scheme in detail and give results of a successful beam test in April 2012 using the JLab UV Demo FEL
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TUPMA038	Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Brag Reflector	polarization, electron, cathode, vacuum	1923
	S. Zhang, M. Poelker, M.L. Stutzman JLab, Newport News, Virginia, USA Y. Chen, A. Moy SVT Associates, Eden Prairie, Minnesota, USA
	Funding: This project was supported by the U.S. DOE Basic Energy Sciences under contract No. DE-AC05-060R23177. Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.
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TUPTY057	Scenarios for Circular Gamma-Gamma Higgs Factories	collider, luminosity, electron, factory	2156
	F. Zimmermann, Y. Papaphilippou CERN, Geneva, Switzerland R. Aleksan CEA/DSM/IRFU, France A. Apyan NU, Evanston, Illinois, USA
	Funding: The research leading to these results has received partial funding from the European Commission under the FP7 Research Infrastructures project EuCARD-2, grant agreement no.312453. The Higgs boson can be produced directly in gamma-gamma collisions generated by laser Compton back scattering off 80-90 GeV electron or positron beams. We discuss options for realizing a gamma-gamma Higgs factory using a high-energy circular e⁺e⁻ collider, such as FCC-ee or CEPC, and/or its top-up injector ring, and compare the parameters and advantages of such a facility, including the expected performance, with those for a Higgs factory based on a recirculating linac, such as SAPPHiRE.
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TUPWI010	Development of a Pulse Radiolysis System by Ultra-fast Super Continuum Probe at Waseda University	polarization, gun, electron, cathode	2265
	Y. Ito Waseda University, Tokyo, Japan Y. Hosaka, K. Sakaue, M. Washio RISE, Tokyo, Japan

Paper

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MOAC1

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

proton, electron, plasma, experiment

34

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

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

Slides MOAC1 [21.632 MB]

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MOPWA025

Simulation of Laser Cooling of Heavy Ion Beams at High Intensities

synchrotron, ion, scattering, simulation

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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MOPWA040

Virtual Cavity Probe Generation using Calibrated Forward and Reflected Signals

cavity, coupling, controls, flattop

200

S. Pfeiffer, V. Ayvazyan, J. Branlard, L. Butkowski, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
R. Rybaniec
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

The European X-ray free electron laser requires a high-precision control of accelerating fields to ensure a stable photon generation. Its low level radio frequency system, based on the MicroTCA.4 standard, detects the probe, forward and reflected signals for each cavity. While the probe signal is used to control the accelerating fields, a combination of the forward and reflected signals can be used to compute a virtual probe, whose accuracy is comparable to the directly sampled probe. This requires the removal of cross-coupling effects between the forward and reflected signals. This paper presents the precise generation of a virtual probe using an extended method of least squares. The virtual probe can then be used for precise field control in case the probe signal is missing or corrupted. It can also be used to detect any deviation from the nominal probe profile.

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MOPWA042

Sub-fs Electron Bunch Generation Using Magnetic Compressor at SINBAD

electron, simulation, plasma, acceleration

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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MOPJE008

Suppression of Microbunching Instability via a Transverse Gradient Undulator

electron, linac, simulation, FEL

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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MOPMA043

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

gun, electron, linac, space-charge

643

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

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

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MOPMA049

Development of a Single-pass Amplifier for an Optical Stochastic Cooling Proof-of-principle Experiment at Fermilab's IOTA facility

undulator, experiment, radiation, focusing

659

M.B. Andorf, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
V.A. Lebedev, P. Piot
Fermilab, Batavia, Illinois, USA

Optical stochastic cooling (OSC) is a method of beam cooling which is expected to provide cooling rates orders of magnitude larger than ordinary stochastic cooling. Light from an undulator (the pickup) is amplified and fed back onto the particle beam via another undulator (the kicker). Fermilab is currently exploring a possible proof-of-principle experiment of the OSC at the integrable-optics test accelerator (IOTA) ring. To implement effective OSC a good correction of phase distortions in the entire band of the optical amplifier is required. In this contribution we present progress in experimental characterization of phase distortions associated to a Titanium Sapphire crystal laser-gain medium (a possible candidate gain medium for the OSC experiment to be performed at IOTA). We also discuss a possible option for a mid-IR amplifier.

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MOPMA059

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

simulation, plasma, 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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MOPHA006

A Slow RF-Laser Feedback for PHIL Photoinjector

feedback, gun, electron, controls

784

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

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

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MOPHA008

Investigation of Beam Halo Using In Vacuum Diamond Sensor at ATF2

electron, pick-up, vacuum, controls

791

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

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

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MOPHA009

Single-Shot Electro-Optic Sampling Combined With Photonic Time-Stretch: Detailed Results at SOLEIL

synchrotron, detector, storage-ring, real-time

795

C. Szwaj, C. Evain, E. Roussel
PhLAM/CERLA, Villeneuve d'Ascq, France
S. Bielawski
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
J.B. Brubach, L. Cassinari, M.-E. Couprie, M. Labat, L. Manceron, J.P. Ricaud, P. Roy, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France
M. Le Parquier
CERLA, Villeneuve d'Ascq, France

Funding: ANR (DYNACO project), FEDER, CEMPI LABEX.
Single-shot recording of pulses is possible with high repetition rates (more than 80 MHz), as was demonstrated in the framework of a PhLAM-SOLEIL collaboration * **. This can be achieved by a relatively simple upgrade of existing setups based on spectral encoding. The strategy consists to encode the sub-picosecond information into the time domain, but at a slower scale (nanoseconds), using dispersion in a long optical fiber. Then the information is recorded by a photodiode connected to an oscilloscope. In this poster, we present guidelines for the practical realization of the electro-optical setup, as well as a performance analysis. In particular, we analyze the temporal resolution and compare it to the classical electro-optical sampling setup.
* E. Roussel et al., Proceedings of IPAC2014, THOBA01.
** E. Roussel et al., arXiv:1410.7048

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MOPHA023

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

electron, radiation, detector, synchrotron

823

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

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

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MOPHA026

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

electron, detector, timing, plasma

833

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

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

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MOPHA029

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

LLRF, operation, electron, radiation

844

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

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

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MOPHA032

All-Optical Synchronization of Pulsed Laser Systems at FLASH and XFEL

timing, LLRF, FEL, controls

854

J.M. Müller, M.K. Czwalinna, M. Felber, M. Schäfer, H. Schlarb, B. Schmidt, S. Schulz, C. Sydlo, F. Zummack
DESY, Hamburg, Germany

The all-optical laser synchronization at FLASH and XFEL provides femtosecond-stable timing of the FEL X-ray photon pulses and associated optical laser pulses (photo-injector laser, seed laser, pump-probe laser, etc.). Based on a two-color balanced optical cross-correlation scheme a high-precision measure of the laser pulse arrival time is delivered, which is used for diagnostic purposes as well as for the active stabilization of the laser systems. In this paper, we present the latest installations of our all-optical synchronization systems at FLASH and the recent developments for the upcoming European XFEL that will ensure a reliable femtosecond-stable timing of FEL and related pulsed laser systems.

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MOPHA034

High Voltage RTM Piezo Driver for XFEL Special Diagnostics

diagnostics, operation, high-voltage, hardware

860

K.P. Przygoda, M. Felber, C. Gerth, M. Heuer, E. Janas, U. Mavrič, P. Peier, H. Schlarb, B. Steffen, C. Sydlo
DESY, Hamburg, Germany
T. Kozak, P. Prędki
TUL-DMCS, Łódź, Poland

High voltage RTM Piezo Driver has been developed to support special diagnostic applications foreseen for XFEL facility. The RTM is capable of driving 4 piezo actuators with voltages up to ±80 V. The solid-state power amplifiers are driven using 18-bit DACs and sampling rates of 1 MSPS. The bandwidth of the driver is remotely tunable using programmable low pass filters. The 4-channel Piezo Driver unit provides the information of piezo output voltage and current. Three independent test setups have been built to test 4-channel Piezo Driver performance. In the paper we are presenting EOD laser lock to 1.3 GHz FLASH master oscillator using bipolar piezo stretcher (fine tuning). The piezo motor based course tuning has been applied for the long term laser stability measurements. The unipolar piezo actuator operation has been demonstrated for the Origami Onefive laser locked to 1.3 GHz LAB MO. The preliminary results of active stabilization of 3 km fiber link laboratory setup are shown.

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MOPHA038

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

wakefield, simulation, 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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MOPHA040

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

electron, photon, detector, storage-ring

876

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

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

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MOPHA041

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

emittance, electron, neutron, dipole

879

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

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

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MOPHA060

Feasibility Study on Measurement and Control of Relative Positioning for Nano-beam Collision

controls, alignment, acceleration, superconducting-magnet

933

H. Matsunaga, H. Yoshioka
Takenaka Corporation, Institute of Technology, Chiba, Japan
M. Masuzawa, Y. Ohsawa, R. Sugahara, H. Yamaoka
KEK, Ibaraki, Japan

In the SuperKEKB and future International Linear Collider project, it is required to measure and control an offset of very small beams with a precision of several nanometers at the interaction point. This paper is a feasibility study on measuring and controlling nano-order relative position by using a laser interferometer and a piezoelectric stage. The first part shows that the precision of measurement position about a direction of laser radiation is less than or equal to 1 nanometer in frequency region less than 100Hz. The second part is discussed a measurement of relative displacement between two points which are 10 meter away on substructures located at the interaction point in the SuperKEKB. To compare with difference of accelerometers for reference, a relative displacement measurement with a precision of several nanometers by a laser interferometer became clear. The final part is discussed a relative positioning control by using a Piezo-Stage between two points on active vibration isolation tables. We achieved to control a relative displacement below 2 nanometers in frequency region less than 10Hz.

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MOPTY013

Control System for DC-SRF Photo-Injector at Peking University

controls, SRF, LLRF, cryomodule

962

L.W. Feng, J.K. Hao, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, B.C. Zhang
PKU, Beijing, People's Republic of China

A control system has been designed and constructed to full-fill the operation requirement of the DC-SRF photo injector developed at Peking University. The system includes FPGA based low level radio frequency (LLRF) control system, PLC based machine protection system, VME based magnet power control, and PC based EPICS IOC. All these systems were integrated to support the stable operation of the DC-SRF photo injector and has shown their robustness. The LLRF system was optimized and tuned for 2K CW/Pulse operation and the stability of amplitude and phase achieves 0.1% and 0.1° respectively.

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MOPTY028

Introduction to BINP HLS to Measure Vertical Changes on PAL-XFEL Buildings and Ground

alignment, operation, ground-motion, synchrotron

994

H. J. Choi, K.H. Gil, H.-S. Kang, S.H. Kim, K.W. Seo
PAL, Pohang, Kyungbuk, Republic of Korea

PAL-XFEL is being installed and will be completed by December of 2015 so that users can be supported beginning in 2016. PAL-XFEL equipment should continuously maintain the bunch beam parameter. To this end, PAL-XFEL equipment has to be kept precisely aligned. As a part of the process for installing PAL-XFEL, a surface geodetic network and the installation of a tunnel measurement network inside buildings is in preparation; additionally, the fiducialization of major equipment is underway. After PAL-XFEL equipment is optimized and aligned, if the ground and buildings go through vertical changes during operation, misalignment of equipments will cause errors in the electron beam trajectory, which will lead to changes to the beam parameter. For continuous and systemic measurement of vertical changes in buildings and to monitor ground sinking and uplifting, the BINP Ultrasonic-type Hydrostatic Levelling System (HLS) is to be installed and operated in all sections of PAL-XFEL for linear accelerator, Undulator and beam line. This study will introduce the operation principle, design concept and advantages (self-calibration) of HLS, and will outline its installation plan and operation plan.

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MOPTY079

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

storage-ring, alignment, operation, electron

1123

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

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

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MOPTY084

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

electron, operation, collider, FPGA

1136

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

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

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MOPWI003

Laserwire Emittance Scanner at CERN Linac 4

linac, detector, emittance, ion

1146

K.O. Kruchinin, G.E. Boorman, A. Bosco, S.M. Gibson, P. Karataev
Royal Holloway, University of London, Surrey, United Kingdom
E. Bravin, T. Hofmann, U. Raich, F. Roncarolo, F. Zocca
CERN, Geneva, Switzerland
A.P. Letchford
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Linac 4 presently under construction at CERN is designed to replace the existing 50 MeV Linac 2 in the LHC injector chain and will accelerate the beam of high current negative hydrogen ions to 160 MeV. During the commissioning a laserwire emittance scanner has been installed allowing noninvasive measuring of the emittance at 3 MeV and 12 MeV setups. A low power infrared fibre coupled laser was focused in the interaction region down to ~150 um and collided with the ion beam neutralising negative ions. At each transverse laser position with respect to the ion beam the angular distribution of the neutral particle beamlets was recorded by scanning a diamond detector across the beamlet at a certain distance from the IP while the main beam of the H⁻ ions was deflected using dipole magnet installed upstream the detector. Measuring the profile of the beamlet by scanning the laser across the beam allows to directly measure the transverse phase-space distribution and reconstruct the transverse beam emittance. In this report we will describe the analysis of the data collected during the 3 MeV and 12 MeV operation of the Linac 4. We will discuss the hardware status and future plans.

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MOPWI004

Novel Single Shot Bunch Length Diagnostic using Coherent Diffraction Radiation

electron, radiation, experiment, optics

1150

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

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

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MOPWI016

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

radiation, electron, linac, optics

1181

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

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

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MOPWI029

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

electron, lattice, detector, radiation

1220

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

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

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TUYC2

Multi-GeV Plasma Acceleration Results at BELLA

plasma, electron, experiment, injection

1319

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

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

Slides TUYC2 [13.023 MB]

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TUYC3

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

electron, acceleration, experiment, focusing

1325

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

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

Slides TUYC3 [21.295 MB]

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TUBC1

Recent Progress and Operational Status of the Compact ERL at KEK

operation, quadrupole, experiment, beam-losses

1359

S. Sakanaka, M. Adachi, S. Adachi, T. Akagi, M. Akemoto, D.A. Arakawa, S. Araki, S. Asaoka, M. Egi, K. Enami, K. Endo, S. Fukuda, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, K. Hozumi, A. Ishii, X.J. Jin, E. Kako, Y. Kamiya, H. Katagiri, H. Kawata, Y. Kobayashi, Y. Kojima, Y. Kondou, A. Kosuge, T. Kume, T. Matsumoto, H. Matsumura, H. Matsushita, S. Michizono, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, K. Nakao, K.N. Nigorikawa, T. Nogami, S. Noguchi, S. Nozawa, T. Obina, T. Ozaki, F. Qiu, H. Sagehashi, H. Sakai, S. Sasaki, K. Satoh, T. Shidara, M. Shimada, K. Shinoe, T. Shioya, T. Shishido, M. Tadano, T. Tahara, T. Takahashi, R. Takai, H. Takaki, T. Takenaka, O. Tanaka, Y. Tanimoto, N. Terunuma, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, J. Urakawa, K. Watanabe, M. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
R. Hajima, S. Matsuba, M. Mori, R. Nagai, N. Nishimori, M. Sawamura, T. Shizuma
JAEA, Ibaraki-ken, Japan
J.G. Hwang
KNU, Deagu, Republic of Korea
M. Kuriki
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
Y. Seimiya
HU/AdSM, Higashi-Hiroshima, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program from the MEXT, and by the MEXT grant for promoting technology for nuclear security.
The Compact Energy Recovery Linac (cERL) is a superconducting test accelerator aimed at establishing technologies for the ERL-based future light source. After its construction during 2009 to 2013, the first CW beams of 20 MeV were successfully transported through the recirculation loop in February 2014*. Then, initial tuning of beams and evaluations of beam properties were carried out. From September to December in 2014, we are constructing a Laser Compton Scattering (LCS) source** which aims at demonstrating technology for the future high-flux quasi-monochromatic gamma-ray source. In the next run of the cERL, which begins at the end of January 2015, we plan such works as an increase in the beam current (from 10 uA to 100 uA), commissioning of the LCS source, and sustained tuning of beams for lower emittance. We will report up-to-date results of these developments.
* N. Nakamura et al., IPAC2014, MOPRO110; S. Sakanaka et al., LINAC14, TUPOL01.
** R. Nagai et al., IPAC2014, WEPRO003.

Slides TUBC1 [2.679 MB]

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TUBC2

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

electron, brightness, scattering, photon

1363

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

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

Slides TUBC2 [20.256 MB]

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TUBC3

Recent Results from FEL seeding at FLASH

FEL, electron, operation, radiation

1366

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

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

Slides TUBC3 [6.651 MB]

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TUPWA008

Mixing and Space-Charge Effects In Free-Electron Lasers

electron, FEL, radiation, space-charge

1410

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

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

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TUPWA011

Progress on the LUNEX5 project

FEL, undulator, electron, operation

1416

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

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

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TUPWA020

BNL ATF II Beamlines Design

experiment, electron, cavity, linac

1445

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

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

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TUPWA021

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

electron, radiation, synchrotron, storage-ring

1448

S. Khan
DELTA, Dortmund, Germany

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

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TUPWA022

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

electron, radiation, synchrotron, undulator

1452

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

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

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TUPWA026

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

electron, polarization, simulation, FEL

1462

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

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

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TUPWA031

Compression of Train of Bunches with Ramped Intensity Profile at SPARC_LAB

linac, cathode, plasma, electron

1476

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

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

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TUPWA033

Status of the Soft X-ray Free Electron Laser FLASH

operation, FEL, optics, photon

1482

M. Vogt, B. Faatz, J. Feldhaus, K. Honkavaara, S. Schreiber, R. Treusch
DESY, Hamburg, Germany

The superconducting free-electron laser FLASH at DESY routinely produces up to several thousand photon pulses per second with wavelengths in the soft X-ray and vacuum UV regime and with energies up to 0.5 mJ per pulse. In 2014 the assembly of a second undulator beamline, FLASH2, was finished. While recommissioning of the FLASH linac and the original FLASH1 beamline was finished already at the end of 2013, the commissioning of FLASH2 could only be started in early February 2014. Only a few weeks have been reserved for dedicated set up of FLASH2, and most of its commissioning has been performed parasitically during the FLASH1 user run. The first beam was extracted through the septum to the FLASH2 beamline on March 4th, 2014, and the first lasing of FLASH2 at a wavelength of about 40 nm was achieved on August 20th, while FLASH1 was lasing simultaneously with 250 bunches at 13.5 nm. We summarize here the status of the FLASH2 commissioning and the FLASH1 operation during its 5th user period.

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TUPWA039

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

undulator, electron, FEL, resonance

1502

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

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

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TUPWA042

Status of the Accelerator Physics Test Facility FLUTE

electron, gun, linac, diagnostics

1506

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

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

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TUPWA046

Facility Upgrade at PITZ and First Operation Results

gun, plasma, operation, electron

1518

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

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

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TUPWA047

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

electron, cathode, emittance, simulation

1522

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

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

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TUPWA053

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

electron, FEL, undulator, linac

1535

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

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

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TUPWA054

The FERMI Seeded FEL Facility: Operational Experience and Future Perspectives

FEL, experiment, electron, operation

1538

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

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

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TUPWA055

DAΦNE Gamma-Ray Factory

electron, photon, factory, emittance

1542

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

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

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TUPWA063

FEL Enhancement by Microbuch Structure Made with Phase-Space Rotation

FEL, simulation, 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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TUPWA065

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

cavity, electron, gun, booster

1576

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

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

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TUPWA066

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

cavity, electron, detector, photon

1579

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

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

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TUPWA068

Simulation Study of Beam Halo and Loss for KEK Compact ERL

simulation, cavity, 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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TUPWA070

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

radiation, simulation, electron, polarization

1594

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

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

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TUPWA071

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

electron, operation, gun, cryogenics

1598

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

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

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TUPWA072

Coherent Thomson Scattering Radiation Generated by using PEHG

radiation, electron, scattering, undulator

1601

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

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

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TUPJE002

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

photon, electron, cavity, linac

1607

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

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

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TUPJE003

Quasi-Traveling Wave RF Gun and Beam Commissioning for SuperKEKB

gun, cathode, emittance, cavity

1610

T. Natsui
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
Y. Ogawa, M. Yoshida, X. Zhou
KEK, Ibaraki, Japan

We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun which has two side coupled standing wave field. We call it quasi-traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. This RF gun has been installed in the KEK J-linac. Beam commissioning with the RF gun is in progress.

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TUPJE004

Narrow Band Coherent Edge Radiation at UVSOR-III

radiation, electron, experiment, storage-ring

1613

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

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

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TUPJE006

Recent Developments of UVSOR-III

undulator, injection, operation, synchrotron

1619

M. Katoh, K. Hayashi, J. Yamazaki
UVSOR, Okazaki, Japan
M. Adachi, T. Konomi, N. Yamamoto
KEK, Ibaraki, Japan
M. Hosaka, Y. Takashima
Nagoya University, Nagoya, Japan

A 750 MeV low energy synchrotron light source, UVSOR, has been operational since 1983. About ten years after the first major upgrade in 2003, the second major upgrade was carried out in 2012, in which all the bending magnets were replaced with combined function ones and a new in-vacuum undulator was installed in the last straight section reserved for undulators. After this upgrade, the light source, UVSOR-III, has been operational with small emittance of 17 nm-rad, with six undulators, and fully with the top-up injection at 300mA. Adding to the present status of the accelerator, most recent progresses in the pulsed sextupole magnet for the beam injection and in the coherent light source development station will be presented.

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TUPJE007

Measurement of Temporal Electric Field of Electron Bunch using Photoconductive Antenna

electron, linac, polarization, radiation

1623

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

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

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TUPJE008

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

acceleration, undulator, linac, electron

1626

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

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

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TUPJE009

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

cavity, gun, electron, cathode

1629

T. Kobayashi
Waseda University, Tokyo, Japan

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

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TUPJE011

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

cavity, electron, linac, photon

1635

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

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

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TUPJE012

Preliminary Result of Photon Counting Acquisition Scheme for Laser Pump/X-ray Probe Experiments

synchrotron, experiment, detector, timing

1638

J. He, J.S. Cao, G. Gao, Y.F. Sui, Y. Tao, J.H. Yue, Z. Zhang, Y.F. Zhou
IHEP, Beijing, People's Republic of China

Funding: This work is supported by the NSFC under grant No.11305186
R&D project has been initiated for a proposed ultralow emittance (~50pm.rad) synchrotron light source built in Beijing. The R&D includes the development of high repetition rate laser pump/X-ray probe for ultrafast dynamics detection in future source. In a typical laser pump/X-ray probe measurement, the X-ray pulse follows a laser pulse in adjustable delay. We are interested in the difference between laser on and laser off at different delay, which will snapshot dynamic process. To capture this trivial difference, it requires the acquisition system to single out the signal from this special X-ray pulse at adequate S/N ratio. For the R&D of high repetition rate pump-probe, we have set up a prototype counting acquisition system based on NIM modular electronics, which was tested in Beijing Synchrotron Radiation Facility (BSRF). The laser will be synchronized with a camshaft bunch at 124 kHz, a tenth of the revolution frequency. Avalanche Photo Diode (APD) was used to detect the X-ray pulse from this camshaft bunch due to its nanosecond response. Before the laser is delivered, we mimic the 124 kHz laser- on signal. The signals from APD are separated by power dividers into two Constant Fraction Discriminator (CFD) input channels. The signal in laser-on/off channel is gated out at 1.24MHz using the 1.24MHz timing signal divided from 499.8 MHz RF signal, while the mimic laser-on signal gated out at 124 kHz. Multiplied by ten times, the mimic laser-on signal counts should be consistent with the laser-on+off counts, if our counting modular works well. We carried out this test at 1W1B wiggler beam line to measure the Fe fluorescence signal. The performance of our system is demonstrated in the good consistency between mimic laser on and laser on+off signals.

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TUPJE019

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

electron, radiation, FEL, simulation

1661

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

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

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TUPJE021

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

electron, photon, scattering, simulation

1665

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

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

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TUPJE039

Recent Results on the Performance of Cs3Sb Photocathodes in the PHIN RF-Gun

cathode, gun, vacuum, operation

1699

C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, I. Martini, M. Martyanov
CERN, Geneva, Switzerland

For the CLIC drive beam a photoinjector option is under study at CERN as an alternative to the thermionic electron gun in the CLIC baseline design. The CLIC drive beam requires a high bunch charge of 8.4 nC and 0.14 ms long trains with 2 ns bunch spacing, which is challenging for a photoinjector. In particular the required long and high intensity laser pulses cause a degradation of the beam quality during the frequency conversion process, which generates the ultra-violet laser beam needed for standard Cs2Te photocathodes. To overcome this issue Cs3Sb cathodes sensitive to green light have been studied at the high-charge PHIN photoinjector since a few years. In this paper recent measurements of fundamental properties of Cs3Sb photocathodes such as quantum efficiency, cathode lifetime and dark current from summer 2014 will be presented, and compared with previous measurements and with the performance of Cs2Te photocathodes.

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TUPJE040

Surface Characterization at CERN of Photocathodes for Photoinjector Applications

cathode, gun, electron, operation

1703

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

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

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TUPJE054

Developments in CLARA Accelerator Design and Simulations

FEL, simulation, 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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TUPJE060

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

radiation, electron, simulation, cavity

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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TUPJE074

LCLS Injector Laser Modulation to Improve FEL Operation Efficiency and Performance

electron, optics, FEL, emittance

1813

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

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

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TUPMA003

Microbunching Phenomena in LCLS-II

space-charge, bunching, simulation, 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, simulation

1846

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

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

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TUPMA017

Pulsed-wire Measurements for Insertion Devices

undulator, electron, detector, FEL

1869

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

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

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TUPMA019

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

undulator, simulation, 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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TUPMA025

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

electron, emittance, dipole, gun

1891

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

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

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TUPMA028

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

electron, cavity, FEL, undulator

1897

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

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

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TUPMA030

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

electron, radiation, photon, scattering

1901

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

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

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TUPMA031

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

optics, FEL, electron, undulator

1904

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

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

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TUPMA033

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

electron, dipole, FEL, acceleration

1907

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

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

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TUPMA038

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

polarization, electron, cathode, vacuum

1923

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

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

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TUPTY057

Scenarios for Circular Gamma-Gamma Higgs Factories

collider, luminosity, electron, factory

2156

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

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

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TUPWI010

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

polarization, gun, electron, cathode

2265

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

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

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WEAD1

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

wakefield, experiment, electron, acceleration

2472

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

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

Slides WEAD1 [2.091 MB]

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WEAD2

Experimental Results of Carbon NanoTube Cathodes inside RF Environment

cathode, gun, electron, emittance

2475

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

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

Slides WEAD2 [10.445 MB]

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WEAD3

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

electron, gun, polarization, collider

2479

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

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

Slides WEAD3 [3.064 MB]

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WEPWA006

Laser Propagation Effects During Photoionization of Meter Scale Rubidium Vapor Source

plasma, experiment, proton, wakefield

2499

J.T. Moody, F. Batsch, A. Joulaei, P. Muggli, E. Öz
MPI-P, München, Germany
N. Berti, J. Kasparian
University of Geneva, GAP Biophotonics, Carouge, Switzerland

The baseline AWAKE experiment requires a 10 meter long plasma source with a density of 10¹⁵ cm􀀀^-3 and a density uniformity of 0.2%. To produce this plasma, a temperature stabilized rubidium vapor source is photoionized by a terawatt peak power laser pulse. In this paper we describe the laser pulse evolution within the plasma source including the dispersive, diffractive, and photoionization effects on the laser pulse. These calculations will be experimentally investigated in a meter long heat pipe oven using scaled laser parameters.

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WEPWA013

A Transport Beamline Solution for Laser-Driven Proton Beams

proton, simulation, 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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WEPWA016

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

cathode, electron, vacuum, linac

2526

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

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

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WEPWA025

RF Acceleration of Ions Produced by Short Pulse Laser

ion, rfq, experiment, bunching

2548

Y. Fuwa, M. Hashida, Y. Iwashita, S. Sakabe, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
M. Okamura
BNL, Upton, Long Island, New York, USA
A. Yamazaki
Nagoya University, Nagoya, Japan

Funding: This work was supported by Grant-in-Aid for Exploratory Research Number 23654085.
RF acceleration of ions produced by short pulse laser is investigated. An RF cavity is prepared for the acceleration. Some experimental results will be presented.

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WEPWA028

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

simulation, emittance, electron, cathode

2559

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

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

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WEPWA033

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

electron, plasma, target, storage-ring

2569

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

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

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WEPWA051

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

acceleration, electron, simulation, vacuum

2618

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

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

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WEPWA053

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

acceleration, electron, alignment, timing

2624

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

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

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WEPWA068

Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas

plasma, radiation, simulation, 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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WEPWA070

Considerations for an Efficient Terahertz-driven Electron Gun

electron, acceleration, gun, controls

2664

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

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

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WEPWA071

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

electron, acceleration, wakefield, bunching

2667

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

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

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WEPJE012

Design and Optimisation of Dielectric Laser Deflecting Structures

electron, acceleration, undulator, simulation

2698

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

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

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WEPJE013

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

acceleration, coupling, simulation, 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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WEPJE021

Fabrication and Demonstration of a Silicon Buried Grating Accelerator

electron, acceleration, vacuum, simulation

2717

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

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

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WEPJE024

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

electron, plasma, simulation, acceleration

2723

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

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

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WEPMA031

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

electron, gun, simulation, acceleration

2826

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

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

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WEPMA038

Compact In-vacuum Quadrupoles for a Beam Transport System at a Laser Wakefield Accelerator

vacuum, quadrupole, operation, focusing

2845

A. Bernhard, V. Afonso Rodríguez, A.-S. Müller, J. Senger, W. Werner, C. Widmann
KIT, Karlsruhe, Germany

Funding: This work is partially funded by the German Federal Ministry for Education and Research under contract no. 05K10VK2 and 05K10SJ2.
For the transport and matching of electrons generated by a Laser Wakefield Accelerator (LWFA) a beam transport system with strong focusing magnets and a compact design is required. For the realization of such a beam transport system at the LWFA in Jena, Germany, two small series of inexpensive, modular quadrupoles were designed and built. The quadrupoles are iron-dominated electromagnets in order to keep the transport system adaptable to different energies and target parameters. To achieve the required field strength it was necessary to choose a small magnetic aperture. Therefore the magnets were designed for in-vacuum use with water-cooled coils. In this contribution the design, the realization and first field measurements of these quadrupoles are presented.

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WEPMA044

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

gun, cavity, polarization, electron

2862

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

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

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WEPMA053

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

cavity, electron, simulation, multipactoring

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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WEPMN013

Development of DC-SRF Injector at Peking University

SRF, cavity, electron, cathode

2944

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

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

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WEPMN018

Measurement of Cell-Cell Coupling Coefficient in Photocathode RF Gun

gun, coupling, simulation, 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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WEPTY002

Studies into Electron Beam Generation, Acceleration and Diagnostics within LA³NET

network, acceleration, electron, diagnostics

3256

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

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

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WEPTY013

Cs2Te Photocathode Performance in the AWA High-charge High-gradient Drive Gun

cathode, gun, wakefield, space-charge

3283

E.E. Wisniewski, S.P. Antipov, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing, W. Liu, J.G. Power, C. Whiteford
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: U.S. Dept of Energy Office of Science under contract number DE-AC02-06CH11357
The unique high-charge L-band, 1.3 GHz, 1.5 cell gun for the new 75 MeV drive beam is in operation at the Argonne Wakefield Accelerator (AWA) facility (see M.E. Conde, this proceedings.) The high-field (> 80 MV/m) photoinjector has a large area, high QE Cesium telluride photocathode (diameter > 30 mm). The photocathode, a crucial component of the upgraded facility, is fabricated on-site. The photoinjector generates high-charge, short pulse, single bunches (Q > 100 nC) and long bunch-trains (Q > 600 nC) for wakefield experiments. The performance of the photocathode for the AWA drive gun is detailed. Quantum efficiency (QE) measurements indicate long, stable photocathode lifetime under demanding conditions.

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WEPTY028

Fermilab Linac Laser Notcher

linac, booster, cavity, ion

3328

D.E. Johnson, K.L. Duel, M.H. Gardner, T.R. Johnson, V.E. Scarpine, R. Tesarek
Fermilab, Batavia, Illinois, USA

Synchrotrons or storage rings require a small section of their circumference devoid of any beam (i.e. a “notch”) to allow for the rise time of an extraction kicker device. In multi-turn injection schemes, this notch in the beam may be generated either in the linac pulse prior to injection or in the accelerator itself after injection. In the case of the Fermilab Booster, the notch is created in the ring near injection energy by the use of fast kickers, thus depositing the beam in a shielded collimation region within the accelerator tunnel. With increasing beam powers, it is desirable to create this notch at the lowest possible energy to minimize activation. Fermilab has undertaken an R&D project to build a laser system to create the notch within a linac beam pulse, immediately after the RFQ at 750 keV, where activation issues are negligible. We will describe the concept for the laser notcher and discuss our current status and future plans for installation of the device.

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THYB2

The Auto-Alignment Girder System of TPS Storage Ring

alignment, controls, storage-ring, survey

3649

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

To meet the stringent beam dynamic specs of TPS with high brilliance and low emittance characteristics, also to align the girders precisely and quickly with less manpower, the girder system for TPS (Taiwan Photon Source) storage ring is of an auto-tuning design. Each girder can be fine adjusted in 6 axes with 6 motorized cam movers of kinematic mounting design on 3 pedestals. With sensors between each girder, there are 72 girders to make up a whole ring auto-alignment girder system. All the sub-systems were carefully assembled and calibrated in a rented factory outside NSRRC during the civil construction period. Mock-up systems were set up and the auto–alignment processes were examined to modify interferences or mistakes between sub-systems. After the TPS building was nearly completed, the laser tracker alignment network was set up first and then the installation took place. When all the girders and sensors were installed into the tunnel, the auto-alignment procedures were carried out to fine tune all the girders. This paper describes the design, preparation, installation and implementation of this auto-alignment girder system for TPS storage ring.

Slides THYB2 [9.476 MB]

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THPF043

Preliminary Studies of Laser-assisted H⁻ Stripping at 400 MeV

injection, proton, operation, experiment

3795

P.K. Saha, H. Harada, M. Kinsho, T. Maruta, K. Okabe, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T.V. Gorlov
ORNL, Oak Ridge, Tennessee, USA
Y. Irie
KEK, Ibaraki, Japan

Conventional H⁻ stripping injection by using solid stripper foils in high intensity accelerators has many limitations concerning foil scattering beam losses, short lifetime of the foil including unexpected and rapid foil failure due to overheating of the foil. It is not only an issue for reliable machine operation but also for facility maintenance. In the 3-GeV RCS of J-PARC, the residual radiation level is extremely high not only near the injection area but also the used foil itself including the foil holder even at the present operation with one third of the designed 1 MW beam power. As an alternate method, later-assisted stripping of 1 GeV H⁻ beam has been intensively studied at SNS in Oak Ridge. The preparation for the next experiment is underway to demonstrate a three orders of magnitude improvement as compared to the earlier experiment. It is important to extend these studies for the lower H⁻ beam energies. In the same framework as in the SNS, laser stripping for the J-PARC H⁻ beam energy of 400 MeV has been studied in the present work. The real challenges and feasibilities at this lower energy are discussed in this paper.

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THPF144

Analysis of FEL-based CeC Amplification at High Gain Limit

electron, space-charge, FEL, free-electron-laser

4063

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

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
An analysis of CeC amplifier based on 1D FEL theory was previously performed with exact solution of the dispersion relation, assuming electrons having Lorentzian energy distribution *. At high gain limit, the asymptotic behavior of the FEL amplifier can be better understood by Taylor expanding the exact solution of the dispersion relation with respect to the detuning parameter **. In this work, we make quadratic expansion of the dispersion relation for Lorentzian energy distribution * *** and investigate how longitudinal space charge and electrons’ energy spread affect the FEL amplification process.
* G. Wang, PhD Thesis, SUNY Stony Brook, 2008.
** G. Stupakov, M.S. Zolotorev, Comment on “Coherent Electron Cooling”, PRL 110 (2013) 269503.
*** E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, The Physics of Free Electron Lasers, 1999.

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FRXB1

The DOE Long-Term Accelerator R&D Stewardship Program

cyclotron, ion, experiment, controls

4082

E.R. Colby
OHEP/DOE, Germantown, Maryland, USA
M. Farkhondeh
DOE/NP, Germantown, USA
E.S. Lessner
DOE/BES, Germantown, Maryland, USA
M.S. Zisman
US DOE, Washington, USA

Funding: U. S. Department of Energy, Office of Science
Since the Accelerators for America's Future (AfAF) Symposium in 2009, the U. S. Dept. of Energy's Office of High Energy Physics (DOE-HEP) has worked to broaden its accelerator R&D activities beyond supporting only discovery science to include medicine, energy and environment, defense and security, and industry. Accelerators play a key role in many aspects of everyday life, and improving their capabilities will enhance U.S. economic competitiveness and the scientific research that drives it. Funded for the first time in 2014, the DOE Office of Science Accelerator Stewardship Program has launched initiatives to facilitate access to DOE accelerator infrastructure, develop innovative accelerator technologies that solve critical problems, and catalyze new partnerships across the accelerator user community. We will discuss the formulation and evolution of the Accelerator Stewardship program, the current status of initiatives, and plans for engagement with the accelerator and user communities for future stewardship activities.

Slides FRXB1 [3.429 MB]

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