FEL2014 - List of Keywords (gun)

Paper	Title	Other Keywords	Page
MOP021	Commissioning of a Dual-sweep Streak Camera with Applications to the ASTA Photoinjector Drive Laser	laser, timing, controls, cavity	66
	A.H. Lumpkin, D.R. Edstrom, J. Ruan, J.K. Santucci Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The high-power electron beams for the Advanced Superconducting Test Accelerator (ASTA) facility will be generated in a photoinjector based on a UV drive laser and the L-band rf photocathode (PC) gun cavity. The initial objectives of these studies were: 1) the evaluation of the amplified UV component’s bunch length and phase stability and 2) the commissioning of the laser room Hamamatsu C5680 streak camera system. We used a new readout camera based on the Prosilica GC1380 digital CCD with Gig-E readout that was compatible with our image processing tools. We observed a longer than expected UV bunch length of 4 ps σ and an unexpected peak multiplicity (with spacing of about 70 ps) in the synchronous sum of 5 UV micropulses. We have now systematically investigated the issues of whether the multiplicity was with each micropulse of the 3-MHz pulse train. We describe our extensive investigations that indicated both issues originated in the multi-pass amplifier. We have replaced the MPA with three single-pass devices, measured 3.5-ps bunch lengths without the multiplicity, and generated photoelectrons from the gun successfully.

MOP053	SASE FEL Performance at the SwissFEL Injector Test Facility	FEL, undulator, electron, simulation	144
	S. Reiche PSI, Villigen PSI, Switzerland
	A 4 m long prototype of the SwissFEL undulator module with an undulator period length of 15 mm was installed at the SwissFEL Injector Test Facility and tested with a 200 MeV electron beam in the beginning of 2014. We observed FEL lasing in SASE mode in the wavelength range from 70 to 800 nm, tuning the wavelength by energy and gap. The measurements of the FEL performance are reported. on behalf of the SwissFEL Team

TUA03	A GaAs Photoemission DC Gun for CAEP High-average-power THz FEL	cathode, vacuum, high-voltage, FEL	318
	H. Wang, K. Li, M. Li, D. Wu, D.X. Xiao, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	FEL-THz plays an important role in THz science and technology research, for high power output and tunable wavelength, which is indispensable to material, biology, medical research. Now, the construction is underway at China Academy of Engineering Physics (CAEP) on high-average-power FEL THz source, and the demonstration of stable, reliable, high brightness, high power electron source operation is one of key issues. The components of the system were constructed and the performance tests are still on. The lifetime of the Negative Electron Affinity (NEA) surface is about 40 hours, which is limitied mainly by vacuum. Up to now, the gun can supply 5mA beam current and has been employed for preliminary experiments. In this paper, the design considerations and present status are given.
	Slides TUA03 [1.182 MB]

TUP057	Development of Compact THz-FEL System at Kyoto University	undulator, electron, FEL, simulation	501
	S. Suphakul, T. Kii, H. Ohgaki, Y. Tsugamura, H. Zen Kyoto University, Kyoto, Japan Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China
	We are developing a compact accelerator based terahertz (THz) radiation source by free-electron laser (FEL) at the Institute of Advanced Energy, Kyoto University. The system consists of a 1.6 cell BNL type photocathode RF-gun, a focusing solenoid magnet, a magnetic bunch compressor, focusing quadrupoles and an undulator. The system generates an ultra-short electron pulse in a few hundred femtoseconds shorter than radiation wavelength, resulting in super-radiant emission from the undulator. The target radiation wavelength is 100 to 300 μm. A tracking simulation and optimization are performed by using PARMELA and General Particle Tracer (GPT) code. The FEL radiations are analyzed by a 1 dimensional FEL theory. The design parameters, simulation results and status are reported and discussed in this paper.

TUP072	Present Status of Coherent Electron Cooling Proof-of-principle Experiment	electron, cavity, ion, laser	524
	I. Pinayev, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, L. DeSanto, A. Elizarov, C. Folz, D.M. Gassner, H. Hahn, Y. Hao, C. Ho, Y. Huang, R.L. Hulsart, M. Ilardo, J.P. Jamilkowski, Y.C. Jing, F.X. Karl, D. Kayran, R. Kellermann, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, R.J. Michnoff, T.A. Miller, M.G. Minty, P. Orfin, A. Pendzick, F. Randazzo, T. Rao, J. Reich, T. Roser, J. Sandberg, B. Sheehy, J. Skaritka, K.S. Smith, L. Snydstrup, A.N. Steszyn, R. Than, C. Theisen, R.J. Todd, J.E. Tuozzolo, E. Wang, G. Wang, D. Weiss, M. Wilinski, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb Tech-X, Boulder, Colorado, USA C.H. Boulware, T.L. Grimm, R. Jecks, N. Miller Niowave, Inc., Lansing, Michigan, USA M.A. Kholopov, P. Vobly BINP SB RAS, Novosibirsk, Russia V. Litvinenko Stony Brook University, Stony Brook, USA P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work supported by Stony Brook University and by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported

TUP073	High Power Operation of the THz FEL at ISIR, Osaka University	FEL, electron, operation, linac	528
	K. Kawase, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, G. Isoyama, R. Kato, K. Kubo, K. Miyazaki, S. Suemine, A. Tokuchi, R. Tsutsumi, M. Yaguchi ISIR, Osaka, Japan
	The THz FEL at Osaka University is based on the L-band linac that provides a multi-bunch electron beam with an 8 us duration in the energy range from 12.5 to 20 MeV. Although the RF frequency of the linac is 1.3 GHz, the bunch intervals are expanded to 9.2 ns for the FEL using a sub-harmonic buncher system that operates at 10⁸ MHz, to enhance the bunch charge to 1 nC/bunch. The FEL covers the wavelength range from 30 to 150 um, and maximum energies of the macropulse and the micropulse are 3.7 mJ and 11 uJ, respectively, at ~70 um measured at an experimental station. To enhance the FEL power further, the electron beam current cannot be increased simply because the beam loading in the acceleration tube is too high. To solve this problem, we have developed a 27 MHz grid pulser for the thermionic electron gun that makes the bunch intervals 4 times longer and increases charge of the bunch 4 times higher whereas the beam loading is the same as that in the 108 MHz mode. In this new operation mode, where a single FEL pulse lases in the cavity, we have succeeded in obtaining the micropulse energy exceeding 100 uJ at a wavelength of 68 um.

TUP075	Commissioning Status of the ASTA Facility at Fermilab	cryomodule, laser, cavity, diagnostics	537
	A.H. Lumpkin, D.R. Broemmelsiek, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, A. Hocker, J.R. Leibfritz, J. Ruan, J.K. Santucci, G. Stancari, D. Sun, J.C.T. Thangaraj, R.M. Thurman-Keup, A. Warner, J. Zhu 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. Early commissioning results and status of the Advanced Superconducting Test Accelerator (ASTA) at Fermilab will be described. The ASTA facility consists of an L-band rf photocathode (PC) gun, two superconducting L-band rf booster cavities, transport lines, and an 8-cavity TESLA style cryomodule. Early results include first photoelectrons from the Cs2Te photocathode and operations at 3-5 MeV from the rf PC gun. The beam line with one 4-dipole chicane, extensive diagnostics, and 50-MeV spectrometer are being installed. The base beam profile imaging stations have been equipped with both YAG:Ce scintillators and optical transition radiation (OTR) screens, optical transport, and with 5 Mpix digital CCD cameras using Gig-E readout. A set of rf BPMs, wall current monitors, and toroids are also being implemented. Transport of OTR to a C5680 Hamamatsu streak camera is also planned for longitudinal profile information at the picosecond level. Downstream of this location is the 8-cavity cryomodule in which most cavities have been operated at the targeted 31.5 MV/m gradient. Initial beam measurements at 20 MeV and updated cryomodule results will be presented as available.

TUP079	A Swedish Compact Linac-based THz/X-ray Source at FREIA	electron, cavity, radiation, linac	545
	V.A. Goryashko Private Address, Uppsala, Sweden A. Opanasenko NSC/KIPT, Kharkov, Ukraine V. Zhaunerchyk University of Gothenburg, Gothenburg, Sweden
	THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.

TUP080	Towards an X-ray FEL at the MAX IV Laboratory	FEL, linac, electron, laser	549
	S. Werin, F. Curbis, M. Eriksson, C. Quitmann, S. Thorin MAX-lab, Lund, Sweden P. Johnsson Lund University, Lund, Sweden
	The design of the 3 GeV linac for the MAX IV facility was done to provide the ability to host a future FEL in the hard X-ray as well as in the soft X-ray range. The linear accelerator, with its two bunch compressors, is now under commissioning. Through the years increasing details for the actual FEL have been discussed and presented. In parallel a steering group for the science case for a Swedish FEL has worked and engaged a large number of Swedish user groups. These two paths are now converging into a joint project to develop the concept of an FEL at MAX IV. We will report on the paths to FEL performance based on the 3 GeV injector, FEL design considerations, the scientific preparation of the project, the linac commissioning and the strategy and priorities.

TUP091	Developments in the CLARA FEL Test Facility Accelerator Design and Simulations	FEL, linac, cavity, diagnostics	589
	P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn 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. These comprise a revised front-end to ensure integration with the existing VELA line, simulations of a magnetically compressed ultra-short mode and a post-FEL diagnostics section. We also present first considerations on the inclusion of final acceleration using X-band structures.

TUP095	Design of a Compact Light Source Accelerator Facility at IUAC, Delhi	electron, radiation, undulator, laser	596
	S. Ghosh, R.K. Bhandari, G.K. Chaudhari, D. Kanjilal, J. Karmakar, N. Kumar, A. Pandey, P. Patra, A. Rai, B.K. Sahu IUAC, New Delhi, India A.S. Aryshev, J. Urakawa KEK, Ibaraki, Japan A. Deshpande, T.S. Dixit SAMEER, Mumbai, India V. Naik, A. Roy VECC, Kolkata, India
	Funding: * The project is supported jointly by Board of Research in Nuclear Sciences and Inter University Accelerator Center The demand for a light source with high brightness and short pulse length from the researchers in the field of physical, chemical, biological and medical sciences is growing in India. To cater to the experimental needs of multidisciplinary sciences, a project to develop a compact Light Source at Inter University Accelerator Centre (IUAC) has been taken up. In the first phase of the project, prebunched [1] electron beam of ~ 8 MeV will be produced by a photocathode RF gun and coherent THz radiation will be produced by a short undulator magnet. In the second phase, the energy of the electron beam will be increased up to 50 MeV by two sets of superconducting niobium resonators. The coherent IR radiation will be produced by using an undulator magnet (conventional method) and X-rays by Inverse Compton Scattering. To increase the average brightness of the electromagnetic radiation, fabrication of superconducting RF gun is going to be started in a parallel development. In this paper the detailed design of the LSI accelerator complex as well as construction timetable will be presented. The physical principles of THz generation and major accelerator subsystems will be discussed. [1] S. Liu & J.Urakawa, Proc. of FEL 2011, page-92

WEB02	Beam Operation of the PAL-XFEL Injector Test Facility	laser, emittance, electron, cavity	615
	J.H. Han, S.Y. Baek, M.S. Chae, H. J. Choi, T. Ha, J.H. Hong, J. Hu, W.H. Hwang, S.H. Jung, H.-S. Kang, C. Kim, C.H. Kim, I.Y. Kim, J.M. Kim, S.H. Kim, I.S. Ko, H.-S. Lee, J. Lee, S.J. Lee, W.W. Lee, C.-K. Min, G. Mun, D.H. Na, S.S. Park, S.J. Park, Y.J. Park, Y.G. Son, H. Yang PAL, Pohang, Kyungbuk, Republic of Korea
	The Pohang Accelerator Laboratory X-ray Free electron Laser (PAL-XFEL) project was launched in 2011. This project aims at the generation of X-ray FEL radiation in a range of 0.1 to 10 nm for photon users with a bunch repetition rate of 60 Hz. The machine consists of a 10 GeV normal conducting S-band linear accelerator and five undulator beamlines. The linac and two undulator beamlines will be constructed by the end of 2015 and first FEL radiation is expected in 2016. As a part of preparation for the project, an Injector Test Facility was constructed in 2012. Since December 2012, beam commissioning is being carried out to find optimum operating conditions and to test accelerator components including RF, laser, diagnostics, magnet, vacuum and control. We present the status of beam commissioning and components tests at the test facility.
	Slides WEB02 [10.249 MB]

THP004	Start-to-End Error Studies for FLUTE	laser, simulation, linac, timing	682
	M. Weber, A.-S. Müller, S. Naknaimueang, M. Schuh, M. Schwarz, P. Wesolowski KIT, Karlsruhe, Germany
	FLUTE, a new linac based test facility and THz source, is currently under construction at the Karlsruhe Institute of Technology (KIT) in collaboration with DESY and PSI. With a repetition rate of 10 Hz, electron bunches with charges from 1 pC to 3 nC will be accelerated up to 40-50 MeV and then compressed longitudinally in a magnetic chicane to generate intense coherent THz radiation. Since the stability and repeatability of longitudinal bunch profiles are essential for optimum compression and THz radiation properties, simulation-based start-to-end error studies using the tracking code ASTRA have been performed to determine the influence of the machine elements on the bunches. Thus, critical parameters are identified and their respective tolerance ranges defined. In this contribution a summary of the error studies will be given.

THP007	Recent Electron Beam Optimization at PITZ	emittance, electron, laser, cathode	689
	G. Vashchenko, P. Boonpornprasert, J.D. Good, M. Groß, I.I. Isaev, D.K. Kalantaryan, M. Khojoyan, G. Kourkafas, M. Krasilnikov, D. Malyutin, D. Melkumyan, A. Oppelt, M. Otevřel, T. Rublack, F. Stephan DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria G. Pathak Uni HH, Hamburg, Germany D. Richter HZB, Berlin, Germany
	High brightness electron sources for linac based freee-lectron lasers operating at short wavelength such as FLASH and the European XFEL are characterized and optimized at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). In the last few years PITZ mainly was used to condition RF guns for their later operation at FLASH and the European XFEL. Only limited time could be spent for beam characterization. However, recently we have performed emittance measurements and optimization for a reduced gun accelerating gradient which is similar to the usual operation conditions at FLASH. The results of these measurements are presented in this paper.

THP011	Beam Measurement of Photocathode RF-gun for PAL-XFEL	laser, emittance, electron, solenoid	699
	J.H. Hong, M.S. Chae, J.H. Han, H.-S. Kang, C.-K. Min, S.J. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	The Injector Test Facility (ITF) at Pohang Accelerator Laboratory (PAL) was constructed to develop an injector for the PAL X-ray free-electron laser (PAL-XFEL) project. The PAL-XFEL design requires the injector to produce an electron beam with a slice emittance of 0.4 mm-mrad at the charge of 200 pC. A 4-hole type RF-gun has been successfully fabricated and tested at ITF. In this paper we report the recent beam-measurement results using the RF-gun at ITF. Emittance measurements have been carried out by changing laser and RF parameters.

THP013	Slice Emittance Measurement using RF Deflecting Cavity at PAL-XFEL ITF	emittance, quadrupole, cavity, electron	707
	J. Lee POSTECH, Pohang, Kyungbuk, Republic of Korea J.H. Han, J.H. Hong, I.S. Ko, S.J. Park PAL, Pohang, Kyungbuk, Republic of Korea
	One of key characteristic for operating PAL-XFEL is the time-dependent transverse properties of a bunch, slice emittance. To achieve the design FEL performance of PAL-XFEL a slice emittance of 0.4 mm mrad at 0.2 nC is required. An Injector Test Facility (ITF) was constructed to study beam properties. In addition to projected emittance measurement, slice emittance measurement is being done using a transverse RF deflecting cavity. We presents results of slice emittance measurement at ITF and future plan for the optimization of operating condition.

THP024	High-gradient Cathode Testing for MaRIE	cathode, electron, cavity, laser	739
	J.W. Lewellen, F.L. Krawczyk, N.A. Moody LANL, Los Alamos, New Mexico, USA
	X-ray free-electron lasers (X-FELs) provide unprecedented capabilities for characterizing and controlling matter at temporal, spatial and energetic regimes which have been previously inaccessible. The quality of the electron beam is critical to X-FEL performance; a degradation of beam quality by a factor of two, for instance, can prevent the X-FEL from lasing at all, rather than yielding a simple reduction in output power. While conceptual designs for new beam sources exist, they incorporate assumptions about the behavior of the photocathode, under extreme operating conditions. The combined requirements for high bunch charge, short bunch duration, and small emission area, dictate the use of high-efficiency photocathodes operating at electric field gradients of ~140 MV/m. No suitable cathode has been operated at these gradients, however, so the success of next-generation X-FELs rests on a series of untested assumptions. We present our plans to address these knowledge gaps, including the design of a high-gradient RF cavity specifically designed for testing cathodes under MaRIE-relevant conditions.

THP030	Recent Photocathode R&D for the LCLS injector	laser, cathode, emittance, vacuum	769
	F. Zhou, A. Brachmann, W.J. Corbett, M.J. Ferreira, S. Gilevich, E.N. Jongewaard, J.R. Lewandowski, J. Sheppard, T. Vecchione, S. Vetter, S.P. Weathersby SLAC, Menlo Park, California, USA
	Funding: US DOE under contract No. DE-AC02-76SF00515 Systematic studies of the copper photocathodes identical to those used in the LCLS injector gun has been carried out at SLAC’s RF gun test facility. Recent observations at the gun test facility indicate that the pre-cleaning of the cathode prior to the installation in the gun is the major cause of the lower initial QE (~10^-6) in the RF gun. All of four cathodes tested in the gun test facility have reliable higher initial QE, 4-8·10^-5, with removal of pre-cleaning step. All of details will be described in the paper. A robust laser-assisted processing recipe has been developed. With this recipe, QE can be repeatedly evolved to about 1x10^-4 within 3-4 weeks following the laser processing, and within 1-2 days the emittance is recovered to the values as observed prior to the laser processing. When compared to previous recipe used for the present LCLS cathode, the new recipe uses lower laser fluence and provides faster emittance recovery. Laser pointing stability is a key requirement for the success of the technique. This paper presents all details of the studies for four cathodes with over a few tens of laser-assisted spots and compares the results with the present LCLS cathode.

THP036	Benchmark and Simulation Design of a Low Energy Bunch Compressor	simulation, electron, space-charge, focusing	795
	A. He, F.J. Willeke, L. Yang, L.-H. Yu BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	In the electron beam slicing method, a low energy bunch with very short and focused beam size is required to interact with the storage ring bunch. We have designed a low energy bunch compressor with BNL photocathode electron RF-gun by applying simulation code PARMELA. In this paper, in order to increase the repetition rate of the electron beam slicing system, we change the compressor’s RF gun from BNL RF-gun to LBNL’s VHF gun and redesign the compressor by applying IMPACT-T with both space charge effects and CSR effects considered. The benchmark between PARMELA and IMPACT-T has produced excellent agreement. The comparison of the CSR effects also shows the bunch can be compressed and focused to our desired size after optimization using code IMPACT-T with CSR effects turned on. The new compressor with high repetition rate still works in space charge dominated domain and the bunch with a negative energy chirp at the entrance of the chicane is compressed by a chicane with positive R56. After the optimization, we have achieved a low energy bunch with the 128 fs RMS bunch length, 42 μm and 25 μm RMS beam size in the vertical and horizontal directions respectively, at 22 MeV with 200 pC charge.

THP037	Beam Performance of the Photocathode Gun for the Max IV Linac	emittance, laser, cathode, injection	799
	J. Andersson, F. Curbis, D. Kumbaro, F. Lindau, S. Werin MAX-lab, Lund, Sweden
	The MAX IV facility in Lund (Sweden) is under construction and conditioning of the electron guns for the injector is ongoing. There are two guns in the injector, one thermionic gun for storage ring injection and one photocathode gun for the Short Pulse Facility. In this paper we report on the beam performance tests of the photocathode gun. The measurements were performed at the MAX IV electron gun test stand during spring 2014. Parameters that were studied includes quantum efficiency, emittance and emittance compensation. Results from the measurements are also compared to particle simulations done with ASTRA.

THP039	Commissioning of the Photo-Cathode RF Gun at APS	cathode, laser, solenoid, emittance	803
	Y.-E. Sun, J.C. Dooling, R.R. Lindberg, A. Nassiri, S.J. Pasky, H. Shang, T.L. Smith, A. Zholents ANL, Argonne, Ilinois, USA
	A S-band RF gun is recently RF conditioned and commissioned at APS, Argonne. In this paper we report the high-power RF conditioning process of the gun. Dark currents are monitored during the RF conditioning and found to be less than 150pC. Following the RF conditioning, photo-electron beams are generated from the gun and the copper cathode quantum efficiency is monitored. We study the quantum efficiency as gun gradient varies and vacuum condition improves. Photo-electron beam enery and emittance are measured as RF gun gradient and solenoid, as well as drive-laser conditions are varied. Finally we compare our experimental results with numerical simulations. Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

THP042	The LCLS-II Injector Design	cathode, emittance, laser, cavity	815
	J.F. Schmerge, A. Brachmann, D. Dowell, A.R. Fry, R.K. Li, Z. Li, T.O. Raubenheimer, T. Vecchione, F. Zhou SLAC, Menlo Park, California, USA A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA D. Filippetto, R. Huang, C. F. Papadopoulos, G.J. Portmann, J. Qiang, F. Sannibale, S.P. Virostek, R.P. Wells LBNL, Berkeley, California, USA A. Lunin, N. Solyak, A. Vivoli Fermilab, Batavia, Illinois, USA
	The new LCLS-II project will construct a 4 GeV continuous wave (CW) superconducting linear accelerator to simultaneously feed two undulators which will cover the spectral ranges 0.2-1.2 keV and 1-5 keV, respectively. The injector must provide up to 300 pC/bunch with a normalized emittance < 0.6 mm and peak current > 30 A at up to 1 MHz repetition rate. An electron gun with the required brightness at such high repetition rate has not yet been demonstrated. However, several different options have been explored with results that meet or exceed the performance requirements of LCLS-II. The available technologies for high repetition-rate guns, and the need to keep dark current within acceptable values, limit the accelerating gradient in the electron gun. We propose a CW normal conducting low frequency RF gun for the electron source due to a combination of the simplicity of operation and the highest achieved gradient in a CW gun, potentially allowing for lower beam emittances. The high gradient is especially significant at the 300 pC/bunch charge where beam quality can suffer due to space charge. This paper describes the design challenges and presents our solutions for the LCLS-II injector.

THP045	Development of Photocachode Drive Laser System for RF Guns in KU-FEL	laser, FEL, electron, target	828
	H. Zen, T. Kii, H. Ohgaki, S. Suphakul Kyoto University, Kyoto, Japan R. Kuroda, Y. Taira AIST, Tsukuba, Ibaraki, Japan
	Funding: This research was supported by ZE Research Program, IAE, Kyoto University (ZE26A-22). We have been developing an accelerator based infrared light sources at Institute of Advanced Energy, Kyoto University. An MIR-FEL has been developed* and a THz-FEL is under development*. A thermionic RF gun has been used as the electron source of MIR-FEL. A project of photocathode upgrade of the current thermionic RF gun is now undergoing to increase the peak power of the FEL. We need to develop multi-bunch laser for this purpose. On the other hand, the THz-FEL will be a single-pass FEL using an S-band 1.6-cell photocathode RF gun. For this purpose, a single-bunch laser is enough. A photocathode drive laser system for those purposes has been developed. The laser system consists of an Nd:YVO4 mode-locked oscillator with an integrated AOM, a laser pointing stabilizer, two diode pumped Nd:YAG amplifiers, and harmonic generators. In case of single-bunch operation of the laser, the pulse energy of higher than 150 micro-J at 266 nm has been obtained. For multi-bunch operation, 70 micro-J/micro-pulse and 70 pulses have been obtained. Optimization for multi-bunch operation of the laser is under going. In the conference, status of development of the drive laser will be presented. H. Zen, et al., Infrared Physics & Technology, vol. 51, pp.382-385 (2008). **S. Suphakul, et al., in this conference.

THP046	Cu and Cs2Te Cathodes Preparation and QE History at the SwissFEL Injector Test Facility.	cathode, laser, operation, vacuum	832
	J. Bossert, R. Ganter, M. Schaer, T. Schietinger PSI, Villigen PSI, Switzerland
	The installation of a load-lock chamber attached to the SwissFEL gun gives the possibility to carefully prepare the metallic cathodes under vacuum and also to use semiconductor cathodes like Cs2Te cathodes which cannot be transported through air. The paper presents the preparation procedures used for copper (QE>1.e-4) and Cs2Te cathodes (based on a CERN recipe) together with surface analysis results (SEM, EDX, interferometry, microscopy). Finally, the QE evolutions obtained in the SwissFEL Injector test facility as well as in a test stand are discussed for both materials.

THP047	Photoemission Studies of Niobium and Lead Photocathodes Using Picosecond UV Laser	laser, niobium, cathode, SRF	836
	R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany R. Barday HZB, Berlin, Germany
	Funding: We acknowledge the support of Enhanced European Coordination for Accelerator Research & Development (EuCARD2, WP12), and the support of German Federal Ministry of Education and Research grant 05K12CR1. We present the results of our investigations on superconducting photocathodes for supercondcuting rf injectors. Bulk niobium and lead film on niobium have been considered as the best candidates. The quantum efficiency (QE) at room temperature has been measured with 258 nm UV laser pulses of 14 ps duration. A QE of 10^-4 has been obtained for the lead film. In order to improve the photoemission yield of niobium, new treatment methods, like Cs-activation and implantation with alkali metals, have been applied and the results are reported.

THP048	Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment	electron, cavity, experiment, laser	840
	I. Pinayev, D. Kayran, V. Litvinenko BNL, Upton, Long Island, New York, USA
	Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP049	High Power RF Test and Analysis of Dark Current in the SwissFEL-gun	cathode, solenoid, laser, vacuum	843
	P. Craievich, S. Bettoni, M. Bopp, A. Citterio, C. Ozkan, M. Pedrozzi, J.-Y. Raguin, M. Schaer, A. Scherer, T. Schietinger, L. Stingelin PSI, Villigen PSI, Switzerland
	To fulfill the beam quality and operational requirements of the SwissFEL project, currently under construction at the Paul Scherrer Institut, a new RF photocathode gun for the electron source was designed and manufactured in house. A 2.6 cell S-band gun operating with near-perfect rotationally symmetric RF field was designed to operate with a 100MV/m cathode field at a repetition rate of 100Hz with average power dissipation of 0.9kW with pulse duration of 1us. The first SwissFEL-gun is now fabricated and installed in the SwissFEL Injector Test Facility (SITF). The frequency spectrum and field balance, through bead-pulling, have been directly verified in-situ and then the gun has been operated with high-power RF. The results of bead-pull measurements and high-power tests are presented and discussed. In addition the emitted dark current was also measured during the high-power tests and the charge within the RF pulse was measured as a function of the peak cathode field at different pulse durations. Faraday cup data were taken for cathode peak RF fields up to 100MV/m for the case of a diamond-turned polycrystalline copper cathode.

THP053	Steady State Multipacting in a Micro-pulse Electron Gun	electron, cavity, cathode, experiment	851
	K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao PKU, Beijing, People's Republic of China
	Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.
	Poster THP053 [2.525 MB]

THP054	Dark Current Studies at the APEX Photoinjector	cathode, simulation, electron, solenoid	855
	R. Huang USTC/NSRL, Hefei, Anhui, People's Republic of China D. Filippetto, C. F. Papadopoulos, F. Sannibale LBNL, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The increasing scientific demand for a high repetition rate FEL light source is driving the development of electron sources with high beam quality, delivering electron bunches at rates in the MHz range. An ongoing project to develop such a source is the Advanced Photoinjector Experiment (APEX) at LBNL. High brightness electron beams require high fields at the cathode during the electron emission. Such high fields associated with imperfections on the cathode surface area can induce undesired electron field emission (dark current). Excessive dark current can generate quenching of SRF structures and undesired radiation doses activating accelerator components and damaging undulator structures. In the present paper, we discuss the dark current studies performed at APEX. Field emitters in the cathode area have been localized and characterized, and techniques for minimizing dark current emission and to passively remove it have been investigated.

THP057	Longitudinal and Transverse Optimization for a High Repetition Rate Injector	emittance, electron, cavity, brightness	864
	C. F. Papadopoulos, D. Filippetto, R. Huang, G.J. Portmann, H.J. Qian, F. Sannibale, S.P. Virostek, R.P. Wells LBNL, Berkeley, California, USA A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Brachmann, D. Dowell, P. Emma, Z. Li, T.O. Raubenheimer, J.F. Schmerge, T. Vecchione, F. Zhou SLAC, Menlo Park, California, USA A. Vivoli Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The injector is the low energy part of a linac, where space charge and kinematic effects may affect the electron beam quality significantly, and in the case of single pass systems determines the brightness in the downstream components. Following the increasing demand for high repetition rate user facilities, the VHF-gun, a normal conducting, high repetition rate (1 MHz) RF gun operating at 186 MHz has been constructed at LBNL within the APEX project and is under operation. In the current paper, we report on the status of the beam dynamics studies. For this, a multi-objected approach is used, where both the transverse and the longitudinal phase space quality is optimized, as quantified by the transverse emittance and the bunch length and energy spread respectively. We also report on different bunch charge operating modes.

THP061	Commissioning of an Improved Superconducting RF Photo Injector at ELBE	SRF, cavity, solenoid, laser	881
	J. Teichert, A. Arnold, M. Freitag, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang HZDR, Dresden, Germany P. Kneisel JLab, Newport News, Virginia, USA I. Will MBI, Berlin, Germany
	In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in a new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid. The paper presents the results of the first test run with a Cu photocathode.

THP064	High Repetition Rate S-band Photoinjector Design for the CLARA FEL	cavity, linac, FEL, emittance	889
	J.W. McKenzie, L.S. Cowie, P. Goudket, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom V.V. Paramonov RAS/INR, Moscow, Russia
	We present the design of a 1.5cell S-band photoinjector RF gun intended to be operated at repetition rates up to 400 Hz in single bunch mode. This gun is intended for use at the proposed CLARA (Compact Linear Accelerator for Research and Applications) FEL test facility at Daresbury Laboratory in the UK and will first be tested and characterised on VELA (Versatile Electron Linear Accelerator) in 2015. The final cavity design is presented including optimisation for CLARA beam dynamics, and choice of a novel coaxial H-shaped coupler.

THP084	Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector	electron, cavity, laser, experiment	929
	M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio Waseda University, Tokyo, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT. We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THC02	Thermal Emittance Measurements at the SwissFEL Injector Test Facility	emittance, cathode, laser, electron	970
	E. Prat, S. Bettoni, H.-H. Braun, M.C. Divall, R. Ganter, C.P. Hauri, T. Schietinger, A. Trisorio, C. Vicario PSI, Villigen PSI, Switzerland C.P. Hauri EPFL, Lausanne, Switzerland
	In a laser-driven RF-gun the ultimate limit of the beam emittance is the transverse momentum of the electrons as they exit the cathode, the so-called intrinsic or thermal emittance. In this contribution we present measurements of the thermal emittance at the SwissFEL Injector Test Facility for electron beam charges down to a few tens of fC. We have studied the thermal emittance and QE dependence on the laser wavelength, the RF-gun gradient and the cathode material (Cu and Cs2Te).
	Slides THC02 [1.063 MB]

THC04	Beam Simulations of High Brightness Photocathode DC Gun and Injector for High Repetition FEL Light Source	emittance, operation, FEL, cathode	980
	T. Miyajima, Y. Honda, X. Jin, T. Uchiyama, M. Yamamoto KEK, Ibaraki, Japan R. Hajima, R. Nagai, N. Nishimori JAEA, Ibaraki-ken, Japan
	As a next generation FEL light source based on linac, high repetition rate operation to increase average FEL power has been proposed, e.g. LCLS-II project. The injector, which generates high brightness and high average current beam, is one of key components. A photocathode DC gun and superconducting RF cavities, which are developed for ERL light source, can be employed for the high repetition rate injector. For high repetition rate operation of FEL light source, injector simulations were carried out based on ERL injector with demonstrated hardware performance by the cERL beam operation in KEK. The optimization results show that the gun voltage of 500 kV is helpful to achieve low emittance. In addition, to estimate optimum gun voltage and cavity acceleration gradient for the FEL operation, two optimizations with different injector layouts were carried out. The results show that the both different layouts have potential to achieve target emittance for FEL operation. Under the realistic operation condition, the transverse normalized rms emittance of 0.8 mm mrad with the rms bunch length of 3 ps, the bunch charge of 325 pC, and the beam energy of 10 MeV is obtained from the optimizations.
	Slides THC04 [3.796 MB]

Paper

Title

Other Keywords

Page

MOP021

Commissioning of a Dual-sweep Streak Camera with Applications to the ASTA Photoinjector Drive Laser

laser, timing, controls, cavity

66

A.H. Lumpkin, D.R. Edstrom, J. Ruan, J.K. Santucci
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The high-power electron beams for the Advanced Superconducting Test Accelerator (ASTA) facility will be generated in a photoinjector based on a UV drive laser and the L-band rf photocathode (PC) gun cavity. The initial objectives of these studies were: 1) the evaluation of the amplified UV component’s bunch length and phase stability and 2) the commissioning of the laser room Hamamatsu C5680 streak camera system. We used a new readout camera based on the Prosilica GC1380 digital CCD with Gig-E readout that was compatible with our image processing tools. We observed a longer than expected UV bunch length of 4 ps σ and an unexpected peak multiplicity (with spacing of about 70 ps) in the synchronous sum of 5 UV micropulses. We have now systematically investigated the issues of whether the multiplicity was with each micropulse of the 3-MHz pulse train. We describe our extensive investigations that indicated both issues originated in the multi-pass amplifier. We have replaced the MPA with three single-pass devices, measured 3.5-ps bunch lengths without the multiplicity, and generated photoelectrons from the gun successfully.

MOP053

SASE FEL Performance at the SwissFEL Injector Test Facility

FEL, undulator, electron, simulation

144

S. Reiche
PSI, Villigen PSI, Switzerland

A 4 m long prototype of the SwissFEL undulator module with an undulator period length of 15 mm was installed at the SwissFEL Injector Test Facility and tested with a 200 MeV electron beam in the beginning of 2014. We observed FEL lasing in SASE mode in the wavelength range from 70 to 800 nm, tuning the wavelength by energy and gap. The measurements of the FEL performance are reported.
on behalf of the SwissFEL Team

TUA03

A GaAs Photoemission DC Gun for CAEP High-average-power THz FEL

cathode, vacuum, high-voltage, FEL

318

H. Wang, K. Li, M. Li, D. Wu, D.X. Xiao, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

FEL-THz plays an important role in THz science and technology research, for high power output and tunable wavelength, which is indispensable to material, biology, medical research. Now, the construction is underway at China Academy of Engineering Physics (CAEP) on high-average-power FEL THz source, and the demonstration of stable, reliable, high brightness, high power electron source operation is one of key issues. The components of the system were constructed and the performance tests are still on. The lifetime of the Negative Electron Affinity (NEA) surface is about 40 hours, which is limitied mainly by vacuum. Up to now, the gun can supply 5mA beam current and has been employed for preliminary experiments. In this paper, the design considerations and present status are given.

Slides TUA03 [1.182 MB]

TUP057

Development of Compact THz-FEL System at Kyoto University

undulator, electron, FEL, simulation

501

S. Suphakul, T. Kii, H. Ohgaki, Y. Tsugamura, H. Zen
Kyoto University, Kyoto, Japan
Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

We are developing a compact accelerator based terahertz (THz) radiation source by free-electron laser (FEL) at the Institute of Advanced Energy, Kyoto University. The system consists of a 1.6 cell BNL type photocathode RF-gun, a focusing solenoid magnet, a magnetic bunch compressor, focusing quadrupoles and an undulator. The system generates an ultra-short electron pulse in a few hundred femtoseconds shorter than radiation wavelength, resulting in super-radiant emission from the undulator. The target radiation wavelength is 100 to 300 μm. A tracking simulation and optimization are performed by using PARMELA and General Particle Tracer (GPT) code. The FEL radiations are analyzed by a 1 dimensional FEL theory. The design parameters, simulation results and status are reported and discussed in this paper.

TUP072

Present Status of Coherent Electron Cooling Proof-of-principle Experiment

electron, cavity, ion, laser

524

I. Pinayev, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, L. DeSanto, A. Elizarov, C. Folz, D.M. Gassner, H. Hahn, Y. Hao, C. Ho, Y. Huang, R.L. Hulsart, M. Ilardo, J.P. Jamilkowski, Y.C. Jing, F.X. Karl, D. Kayran, R. Kellermann, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, R.J. Michnoff, T.A. Miller, M.G. Minty, P. Orfin, A. Pendzick, F. Randazzo, T. Rao, J. Reich, T. Roser, J. Sandberg, B. Sheehy, J. Skaritka, K.S. Smith, L. Snydstrup, A.N. Steszyn, R. Than, C. Theisen, R.J. Todd, J.E. Tuozzolo, E. Wang, G. Wang, D. Weiss, M. Wilinski, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb
Tech-X, Boulder, Colorado, USA
C.H. Boulware, T.L. Grimm, R. Jecks, N. Miller
Niowave, Inc., Lansing, Michigan, USA
M.A. Kholopov, P. Vobly
BINP SB RAS, Novosibirsk, Russia
V. Litvinenko
Stony Brook University, Stony Brook, USA
P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work supported by Stony Brook University and by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported

TUP073

High Power Operation of the THz FEL at ISIR, Osaka University

FEL, electron, operation, linac

528

K. Kawase, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, G. Isoyama, R. Kato, K. Kubo, K. Miyazaki, S. Suemine, A. Tokuchi, R. Tsutsumi, M. Yaguchi
ISIR, Osaka, Japan

The THz FEL at Osaka University is based on the L-band linac that provides a multi-bunch electron beam with an 8 us duration in the energy range from 12.5 to 20 MeV. Although the RF frequency of the linac is 1.3 GHz, the bunch intervals are expanded to 9.2 ns for the FEL using a sub-harmonic buncher system that operates at 10⁸ MHz, to enhance the bunch charge to 1 nC/bunch. The FEL covers the wavelength range from 30 to 150 um, and maximum energies of the macropulse and the micropulse are 3.7 mJ and 11 uJ, respectively, at ~70 um measured at an experimental station. To enhance the FEL power further, the electron beam current cannot be increased simply because the beam loading in the acceleration tube is too high. To solve this problem, we have developed a 27 MHz grid pulser for the thermionic electron gun that makes the bunch intervals 4 times longer and increases charge of the bunch 4 times higher whereas the beam loading is the same as that in the 108 MHz mode. In this new operation mode, where a single FEL pulse lases in the cavity, we have succeeded in obtaining the micropulse energy exceeding 100 uJ at a wavelength of 68 um.

TUP075

Commissioning Status of the ASTA Facility at Fermilab

cryomodule, laser, cavity, diagnostics

537

A.H. Lumpkin, D.R. Broemmelsiek, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, A. Hocker, J.R. Leibfritz, J. Ruan, J.K. Santucci, G. Stancari, D. Sun, J.C.T. Thangaraj, R.M. Thurman-Keup, A. Warner, J. Zhu
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.
Early commissioning results and status of the Advanced Superconducting Test Accelerator (ASTA) at Fermilab will be described. The ASTA facility consists of an L-band rf photocathode (PC) gun, two superconducting L-band rf booster cavities, transport lines, and an 8-cavity TESLA style cryomodule. Early results include first photoelectrons from the Cs2Te photocathode and operations at 3-5 MeV from the rf PC gun. The beam line with one 4-dipole chicane, extensive diagnostics, and 50-MeV spectrometer are being installed. The base beam profile imaging stations have been equipped with both YAG:Ce scintillators and optical transition radiation (OTR) screens, optical transport, and with 5 Mpix digital CCD cameras using Gig-E readout. A set of rf BPMs, wall current monitors, and toroids are also being implemented. Transport of OTR to a C5680 Hamamatsu streak camera is also planned for longitudinal profile information at the picosecond level. Downstream of this location is the 8-cavity cryomodule in which most cavities have been operated at the targeted 31.5 MV/m gradient. Initial beam measurements at 20 MeV and updated cryomodule results will be presented as available.

TUP079

A Swedish Compact Linac-based THz/X-ray Source at FREIA

electron, cavity, radiation, linac

545

V.A. Goryashko
Private Address, Uppsala, Sweden
A. Opanasenko
NSC/KIPT, Kharkov, Ukraine
V. Zhaunerchyk
University of Gothenburg, Gothenburg, Sweden

THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.

TUP080

Towards an X-ray FEL at the MAX IV Laboratory

FEL, linac, electron, laser

549

S. Werin, F. Curbis, M. Eriksson, C. Quitmann, S. Thorin
MAX-lab, Lund, Sweden
P. Johnsson
Lund University, Lund, Sweden

The design of the 3 GeV linac for the MAX IV facility was done to provide the ability to host a future FEL in the hard X-ray as well as in the soft X-ray range. The linear accelerator, with its two bunch compressors, is now under commissioning. Through the years increasing details for the actual FEL have been discussed and presented. In parallel a steering group for the science case for a Swedish FEL has worked and engaged a large number of Swedish user groups. These two paths are now converging into a joint project to develop the concept of an FEL at MAX IV. We will report on the paths to FEL performance based on the 3 GeV injector, FEL design considerations, the scientific preparation of the project, the linac commissioning and the strategy and priorities.

TUP091

Developments in the CLARA FEL Test Facility Accelerator Design and Simulations

FEL, linac, cavity, diagnostics

589

P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn
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. These comprise a revised front-end to ensure integration with the existing VELA line, simulations of a magnetically compressed ultra-short mode and a post-FEL diagnostics section. We also present first considerations on the inclusion of final acceleration using X-band structures.

TUP095

Design of a Compact Light Source Accelerator Facility at IUAC, Delhi

electron, radiation, undulator, laser

596

S. Ghosh, R.K. Bhandari, G.K. Chaudhari, D. Kanjilal, J. Karmakar, N. Kumar, A. Pandey, P. Patra, A. Rai, B.K. Sahu
IUAC, New Delhi, India
A.S. Aryshev, J. Urakawa
KEK, Ibaraki, Japan
A. Deshpande, T.S. Dixit
SAMEER, Mumbai, India
V. Naik, A. Roy
VECC, Kolkata, India

Funding: * The project is supported jointly by Board of Research in Nuclear Sciences and Inter University Accelerator Center
The demand for a light source with high brightness and short pulse length from the researchers in the field of physical, chemical, biological and medical sciences is growing in India. To cater to the experimental needs of multidisciplinary sciences, a project to develop a compact Light Source at Inter University Accelerator Centre (IUAC) has been taken up. In the first phase of the project, prebunched [1] electron beam of ~ 8 MeV will be produced by a photocathode RF gun and coherent THz radiation will be produced by a short undulator magnet. In the second phase, the energy of the electron beam will be increased up to 50 MeV by two sets of superconducting niobium resonators. The coherent IR radiation will be produced by using an undulator magnet (conventional method) and X-rays by Inverse Compton Scattering. To increase the average brightness of the electromagnetic radiation, fabrication of superconducting RF gun is going to be started in a parallel development. In this paper the detailed design of the LSI accelerator complex as well as construction timetable will be presented. The physical principles of THz generation and major accelerator subsystems will be discussed.
[1] S. Liu & J.Urakawa, Proc. of FEL 2011, page-92

WEB02

Beam Operation of the PAL-XFEL Injector Test Facility

laser, emittance, electron, cavity

615

J.H. Han, S.Y. Baek, M.S. Chae, H. J. Choi, T. Ha, J.H. Hong, J. Hu, W.H. Hwang, S.H. Jung, H.-S. Kang, C. Kim, C.H. Kim, I.Y. Kim, J.M. Kim, S.H. Kim, I.S. Ko, H.-S. Lee, J. Lee, S.J. Lee, W.W. Lee, C.-K. Min, G. Mun, D.H. Na, S.S. Park, S.J. Park, Y.J. Park, Y.G. Son, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

The Pohang Accelerator Laboratory X-ray Free electron Laser (PAL-XFEL) project was launched in 2011. This project aims at the generation of X-ray FEL radiation in a range of 0.1 to 10 nm for photon users with a bunch repetition rate of 60 Hz. The machine consists of a 10 GeV normal conducting S-band linear accelerator and five undulator beamlines. The linac and two undulator beamlines will be constructed by the end of 2015 and first FEL radiation is expected in 2016. As a part of preparation for the project, an Injector Test Facility was constructed in 2012. Since December 2012, beam commissioning is being carried out to find optimum operating conditions and to test accelerator components including RF, laser, diagnostics, magnet, vacuum and control. We present the status of beam commissioning and components tests at the test facility.

Slides WEB02 [10.249 MB]

THP004

Start-to-End Error Studies for FLUTE

laser, simulation, linac, timing

682

M. Weber, A.-S. Müller, S. Naknaimueang, M. Schuh, M. Schwarz, P. Wesolowski
KIT, Karlsruhe, Germany

FLUTE, a new linac based test facility and THz source, is currently under construction at the Karlsruhe Institute of Technology (KIT) in collaboration with DESY and PSI. With a repetition rate of 10 Hz, electron bunches with charges from 1 pC to 3 nC will be accelerated up to 40-50 MeV and then compressed longitudinally in a magnetic chicane to generate intense coherent THz radiation. Since the stability and repeatability of longitudinal bunch profiles are essential for optimum compression and THz radiation properties, simulation-based start-to-end error studies using the tracking code ASTRA have been performed to determine the influence of the machine elements on the bunches. Thus, critical parameters are identified and their respective tolerance ranges defined. In this contribution a summary of the error studies will be given.

THP007

Recent Electron Beam Optimization at PITZ

emittance, electron, laser, cathode

689

G. Vashchenko, P. Boonpornprasert, J.D. Good, M. Groß, I.I. Isaev, D.K. Kalantaryan, M. Khojoyan, G. Kourkafas, M. Krasilnikov, D. Malyutin, D. Melkumyan, A. Oppelt, M. Otevřel, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
G. Pathak
Uni HH, Hamburg, Germany
D. Richter
HZB, Berlin, Germany

High brightness electron sources for linac based freee-lectron lasers operating at short wavelength such as FLASH and the European XFEL are characterized and optimized at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). In the last few years PITZ mainly was used to condition RF guns for their later operation at FLASH and the European XFEL. Only limited time could be spent for beam characterization. However, recently we have performed emittance measurements and optimization for a reduced gun accelerating gradient which is similar to the usual operation conditions at FLASH. The results of these measurements are presented in this paper.

THP011

Beam Measurement of Photocathode RF-gun for PAL-XFEL

laser, emittance, electron, solenoid

699

J.H. Hong, M.S. Chae, J.H. Han, H.-S. Kang, C.-K. Min, S.J. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

The Injector Test Facility (ITF) at Pohang Accelerator Laboratory (PAL) was constructed to develop an injector for the PAL X-ray free-electron laser (PAL-XFEL) project. The PAL-XFEL design requires the injector to produce an electron beam with a slice emittance of 0.4 mm-mrad at the charge of 200 pC. A 4-hole type RF-gun has been successfully fabricated and tested at ITF. In this paper we report the recent beam-measurement results using the RF-gun at ITF. Emittance measurements have been carried out by changing laser and RF parameters.

THP013

Slice Emittance Measurement using RF Deflecting Cavity at PAL-XFEL ITF

emittance, quadrupole, cavity, electron

707

J. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Han, J.H. Hong, I.S. Ko, S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

One of key characteristic for operating PAL-XFEL is the time-dependent transverse properties of a bunch, slice emittance. To achieve the design FEL performance of PAL-XFEL a slice emittance of 0.4 mm mrad at 0.2 nC is required. An Injector Test Facility (ITF) was constructed to study beam properties. In addition to projected emittance measurement, slice emittance measurement is being done using a transverse RF deflecting cavity. We presents results of slice emittance measurement at ITF and future plan for the optimization of operating condition.

THP024

High-gradient Cathode Testing for MaRIE

cathode, electron, cavity, laser

739

J.W. Lewellen, F.L. Krawczyk, N.A. Moody
LANL, Los Alamos, New Mexico, USA

X-ray free-electron lasers (X-FELs) provide unprecedented capabilities for characterizing and controlling matter at temporal, spatial and energetic regimes which have been previously inaccessible. The quality of the electron beam is critical to X-FEL performance; a degradation of beam quality by a factor of two, for instance, can prevent the X-FEL from lasing at all, rather than yielding a simple reduction in output power. While conceptual designs for new beam sources exist, they incorporate assumptions about the behavior of the photocathode, under extreme operating conditions. The combined requirements for high bunch charge, short bunch duration, and small emission area, dictate the use of high-efficiency photocathodes operating at electric field gradients of ~140 MV/m. No suitable cathode has been operated at these gradients, however, so the success of next-generation X-FELs rests on a series of untested assumptions. We present our plans to address these knowledge gaps, including the design of a high-gradient RF cavity specifically designed for testing cathodes under MaRIE-relevant conditions.

THP030

Recent Photocathode R&D for the LCLS injector

laser, cathode, emittance, vacuum

769

F. Zhou, A. Brachmann, W.J. Corbett, M.J. Ferreira, S. Gilevich, E.N. Jongewaard, J.R. Lewandowski, J. Sheppard, T. Vecchione, S. Vetter, S.P. Weathersby
SLAC, Menlo Park, California, USA

Funding: US DOE under contract No. DE-AC02-76SF00515
Systematic studies of the copper photocathodes identical to those used in the LCLS injector gun has been carried out at SLAC’s RF gun test facility. Recent observations at the gun test facility indicate that the pre-cleaning of the cathode prior to the installation in the gun is the major cause of the lower initial QE (~10^-6) in the RF gun. All of four cathodes tested in the gun test facility have reliable higher initial QE, 4-8·10^-5, with removal of pre-cleaning step. All of details will be described in the paper. A robust laser-assisted processing recipe has been developed. With this recipe, QE can be repeatedly evolved to about 1x10^-4 within 3-4 weeks following the laser processing, and within 1-2 days the emittance is recovered to the values as observed prior to the laser processing. When compared to previous recipe used for the present LCLS cathode, the new recipe uses lower laser fluence and provides faster emittance recovery. Laser pointing stability is a key requirement for the success of the technique. This paper presents all details of the studies for four cathodes with over a few tens of laser-assisted spots and compares the results with the present LCLS cathode.

THP036

Benchmark and Simulation Design of a Low Energy Bunch Compressor

simulation, electron, space-charge, focusing

795

A. He, F.J. Willeke, L. Yang, L.-H. Yu
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In the electron beam slicing method, a low energy bunch with very short and focused beam size is required to interact with the storage ring bunch. We have designed a low energy bunch compressor with BNL photocathode electron RF-gun by applying simulation code PARMELA. In this paper, in order to increase the repetition rate of the electron beam slicing system, we change the compressor’s RF gun from BNL RF-gun to LBNL’s VHF gun and redesign the compressor by applying IMPACT-T with both space charge effects and CSR effects considered. The benchmark between PARMELA and IMPACT-T has produced excellent agreement. The comparison of the CSR effects also shows the bunch can be compressed and focused to our desired size after optimization using code IMPACT-T with CSR effects turned on. The new compressor with high repetition rate still works in space charge dominated domain and the bunch with a negative energy chirp at the entrance of the chicane is compressed by a chicane with positive R56. After the optimization, we have achieved a low energy bunch with the 128 fs RMS bunch length, 42 μm and 25 μm RMS beam size in the vertical and horizontal directions respectively, at 22 MeV with 200 pC charge.

THP037

Beam Performance of the Photocathode Gun for the Max IV Linac

emittance, laser, cathode, injection

799

J. Andersson, F. Curbis, D. Kumbaro, F. Lindau, S. Werin
MAX-lab, Lund, Sweden

The MAX IV facility in Lund (Sweden) is under construction and conditioning of the electron guns for the injector is ongoing. There are two guns in the injector, one thermionic gun for storage ring injection and one photocathode gun for the Short Pulse Facility. In this paper we report on the beam performance tests of the photocathode gun. The measurements were performed at the MAX IV electron gun test stand during spring 2014. Parameters that were studied includes quantum efficiency, emittance and emittance compensation. Results from the measurements are also compared to particle simulations done with ASTRA.

THP039

Commissioning of the Photo-Cathode RF Gun at APS

cathode, laser, solenoid, emittance

803

Y.-E. Sun, J.C. Dooling, R.R. Lindberg, A. Nassiri, S.J. Pasky, H. Shang, T.L. Smith, A. Zholents
ANL, Argonne, Ilinois, USA

A S-band RF gun is recently RF conditioned and commissioned at APS, Argonne. In this paper we report the high-power RF conditioning process of the gun. Dark currents are monitored during the RF conditioning and found to be less than 150pC. Following the RF conditioning, photo-electron beams are generated from the gun and the copper cathode quantum efficiency is monitored. We study the quantum efficiency as gun gradient varies and vacuum condition improves. Photo-electron beam enery and emittance are measured as RF gun gradient and solenoid, as well as drive-laser conditions are varied. Finally we compare our experimental results with numerical simulations.
Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

THP042

The LCLS-II Injector Design

cathode, emittance, laser, cavity

815

J.F. Schmerge, A. Brachmann, D. Dowell, A.R. Fry, R.K. Li, Z. Li, T.O. Raubenheimer, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
D. Filippetto, R. Huang, C. F. Papadopoulos, G.J. Portmann, J. Qiang, F. Sannibale, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
A. Lunin, N. Solyak, A. Vivoli
Fermilab, Batavia, Illinois, USA

The new LCLS-II project will construct a 4 GeV continuous wave (CW) superconducting linear accelerator to simultaneously feed two undulators which will cover the spectral ranges 0.2-1.2 keV and 1-5 keV, respectively. The injector must provide up to 300 pC/bunch with a normalized emittance < 0.6 mm and peak current > 30 A at up to 1 MHz repetition rate. An electron gun with the required brightness at such high repetition rate has not yet been demonstrated. However, several different options have been explored with results that meet or exceed the performance requirements of LCLS-II. The available technologies for high repetition-rate guns, and the need to keep dark current within acceptable values, limit the accelerating gradient in the electron gun. We propose a CW normal conducting low frequency RF gun for the electron source due to a combination of the simplicity of operation and the highest achieved gradient in a CW gun, potentially allowing for lower beam emittances. The high gradient is especially significant at the 300 pC/bunch charge where beam quality can suffer due to space charge. This paper describes the design challenges and presents our solutions for the LCLS-II injector.

THP045

Development of Photocachode Drive Laser System for RF Guns in KU-FEL

laser, FEL, electron, target

828

H. Zen, T. Kii, H. Ohgaki, S. Suphakul
Kyoto University, Kyoto, Japan
R. Kuroda, Y. Taira
AIST, Tsukuba, Ibaraki, Japan

Funding: This research was supported by ZE Research Program, IAE, Kyoto University (ZE26A-22).
We have been developing an accelerator based infrared light sources at Institute of Advanced Energy, Kyoto University. An MIR-FEL has been developed* and a THz-FEL is under development**. A thermionic RF gun has been used as the electron source of MIR-FEL. A project of photocathode upgrade of the current thermionic RF gun is now undergoing to increase the peak power of the FEL. We need to develop multi-bunch laser for this purpose. On the other hand, the THz-FEL will be a single-pass FEL using an S-band 1.6-cell photocathode RF gun. For this purpose, a single-bunch laser is enough. A photocathode drive laser system for those purposes has been developed. The laser system consists of an Nd:YVO4 mode-locked oscillator with an integrated AOM, a laser pointing stabilizer, two diode pumped Nd:YAG amplifiers, and harmonic generators. In case of single-bunch operation of the laser, the pulse energy of higher than 150 micro-J at 266 nm has been obtained. For multi-bunch operation, 70 micro-J/micro-pulse and 70 pulses have been obtained. Optimization for multi-bunch operation of the laser is under going. In the conference, status of development of the drive laser will be presented.
*H. Zen, et al., Infrared Physics & Technology, vol. 51, pp.382-385 (2008).
**S. Suphakul, et al., in this conference.

THP046

Cu and Cs2Te Cathodes Preparation and QE History at the SwissFEL Injector Test Facility.

cathode, laser, operation, vacuum

832

J. Bossert, R. Ganter, M. Schaer, T. Schietinger
PSI, Villigen PSI, Switzerland

The installation of a load-lock chamber attached to the SwissFEL gun gives the possibility to carefully prepare the metallic cathodes under vacuum and also to use semiconductor cathodes like Cs2Te cathodes which cannot be transported through air. The paper presents the preparation procedures used for copper (QE>1.e-4) and Cs2Te cathodes (based on a CERN recipe) together with surface analysis results (SEM, EDX, interferometry, microscopy). Finally, the QE evolutions obtained in the SwissFEL Injector test facility as well as in a test stand are discussed for both materials.

THP047

Photoemission Studies of Niobium and Lead Photocathodes Using Picosecond UV Laser

laser, niobium, cathode, SRF

836

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

Funding: We acknowledge the support of Enhanced European Coordination for Accelerator Research & Development (EuCARD2, WP12), and the support of German Federal Ministry of Education and Research grant 05K12CR1.
We present the results of our investigations on superconducting photocathodes for supercondcuting rf injectors. Bulk niobium and lead film on niobium have been considered as the best candidates. The quantum efficiency (QE) at room temperature has been measured with 258 nm UV laser pulses of 14 ps duration. A QE of 10^-4 has been obtained for the lead film. In order to improve the photoemission yield of niobium, new treatment methods, like Cs-activation and implantation with alkali metals, have been applied and the results are reported.

THP048

Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment

electron, cavity, experiment, laser

840

I. Pinayev, D. Kayran, V. Litvinenko
BNL, Upton, Long Island, New York, USA

Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP049

High Power RF Test and Analysis of Dark Current in the SwissFEL-gun

cathode, solenoid, laser, vacuum

843

P. Craievich, S. Bettoni, M. Bopp, A. Citterio, C. Ozkan, M. Pedrozzi, J.-Y. Raguin, M. Schaer, A. Scherer, T. Schietinger, L. Stingelin
PSI, Villigen PSI, Switzerland

To fulfill the beam quality and operational requirements of the SwissFEL project, currently under construction at the Paul Scherrer Institut, a new RF photocathode gun for the electron source was designed and manufactured in house. A 2.6 cell S-band gun operating with near-perfect rotationally symmetric RF field was designed to operate with a 100MV/m cathode field at a repetition rate of 100Hz with average power dissipation of 0.9kW with pulse duration of 1us. The first SwissFEL-gun is now fabricated and installed in the SwissFEL Injector Test Facility (SITF). The frequency spectrum and field balance, through bead-pulling, have been directly verified in-situ and then the gun has been operated with high-power RF. The results of bead-pull measurements and high-power tests are presented and discussed. In addition the emitted dark current was also measured during the high-power tests and the charge within the RF pulse was measured as a function of the peak cathode field at different pulse durations. Faraday cup data were taken for cathode peak RF fields up to 100MV/m for the case of a diamond-turned polycrystalline copper cathode.

THP053

Steady State Multipacting in a Micro-pulse Electron Gun

electron, cavity, cathode, experiment

851

K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.

Poster THP053 [2.525 MB]

THP054

Dark Current Studies at the APEX Photoinjector

cathode, simulation, electron, solenoid

855

R. Huang
USTC/NSRL, Hefei, Anhui, People's Republic of China
D. Filippetto, C. F. Papadopoulos, F. Sannibale
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The increasing scientific demand for a high repetition rate FEL light source is driving the development of electron sources with high beam quality, delivering electron bunches at rates in the MHz range. An ongoing project to develop such a source is the Advanced Photoinjector Experiment (APEX) at LBNL. High brightness electron beams require high fields at the cathode during the electron emission. Such high fields associated with imperfections on the cathode surface area can induce undesired electron field emission (dark current). Excessive dark current can generate quenching of SRF structures and undesired radiation doses activating accelerator components and damaging undulator structures. In the present paper, we discuss the dark current studies performed at APEX. Field emitters in the cathode area have been localized and characterized, and techniques for minimizing dark current emission and to passively remove it have been investigated.

THP057

Longitudinal and Transverse Optimization for a High Repetition Rate Injector

emittance, electron, cavity, brightness

864

C. F. Papadopoulos, D. Filippetto, R. Huang, G.J. Portmann, H.J. Qian, F. Sannibale, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Brachmann, D. Dowell, P. Emma, Z. Li, T.O. Raubenheimer, J.F. Schmerge, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
A. Vivoli
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The injector is the low energy part of a linac, where space charge and kinematic effects may affect the electron beam quality significantly, and in the case of single pass systems determines the brightness in the downstream components. Following the increasing demand for high repetition rate user facilities, the VHF-gun, a normal conducting, high repetition rate (1 MHz) RF gun operating at 186 MHz has been constructed at LBNL within the APEX project and is under operation. In the current paper, we report on the status of the beam dynamics studies. For this, a multi-objected approach is used, where both the transverse and the longitudinal phase space quality is optimized, as quantified by the transverse emittance and the bunch length and energy spread respectively. We also report on different bunch charge operating modes.

THP061

Commissioning of an Improved Superconducting RF Photo Injector at ELBE

SRF, cavity, solenoid, laser

881

J. Teichert, A. Arnold, M. Freitag, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
P. Kneisel
JLab, Newport News, Virginia, USA
I. Will
MBI, Berlin, Germany

In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in a new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid. The paper presents the results of the first test run with a Cu photocathode.

THP064

High Repetition Rate S-band Photoinjector Design for the CLARA FEL

cavity, linac, FEL, emittance

889

J.W. McKenzie, L.S. Cowie, P. Goudket, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
V.V. Paramonov
RAS/INR, Moscow, Russia

We present the design of a 1.5cell S-band photoinjector RF gun intended to be operated at repetition rates up to 400 Hz in single bunch mode. This gun is intended for use at the proposed CLARA (Compact Linear Accelerator for Research and Applications) FEL test facility at Daresbury Laboratory in the UK and will first be tested and characterised on VELA (Versatile Electron Linear Accelerator) in 2015. The final cavity design is presented including optimisation for CLARA beam dynamics, and choice of a novel coaxial H-shaped coupler.

THP084

Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector

electron, cavity, laser, experiment

929

M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio
Waseda University, Tokyo, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT.
We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THC02

Thermal Emittance Measurements at the SwissFEL Injector Test Facility

emittance, cathode, laser, electron

970

E. Prat, S. Bettoni, H.-H. Braun, M.C. Divall, R. Ganter, C.P. Hauri, T. Schietinger, A. Trisorio, C. Vicario
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland

In a laser-driven RF-gun the ultimate limit of the beam emittance is the transverse momentum of the electrons as they exit the cathode, the so-called intrinsic or thermal emittance. In this contribution we present measurements of the thermal emittance at the SwissFEL Injector Test Facility for electron beam charges down to a few tens of fC. We have studied the thermal emittance and QE dependence on the laser wavelength, the RF-gun gradient and the cathode material (Cu and Cs2Te).

Slides THC02 [1.063 MB]

THC04

Beam Simulations of High Brightness Photocathode DC Gun and Injector for High Repetition FEL Light Source

emittance, operation, FEL, cathode

980

T. Miyajima, Y. Honda, X. Jin, T. Uchiyama, M. Yamamoto
KEK, Ibaraki, Japan
R. Hajima, R. Nagai, N. Nishimori
JAEA, Ibaraki-ken, Japan

As a next generation FEL light source based on linac, high repetition rate operation to increase average FEL power has been proposed, e.g. LCLS-II project. The injector, which generates high brightness and high average current beam, is one of key components. A photocathode DC gun and superconducting RF cavities, which are developed for ERL light source, can be employed for the high repetition rate injector. For high repetition rate operation of FEL light source, injector simulations were carried out based on ERL injector with demonstrated hardware performance by the cERL beam operation in KEK. The optimization results show that the gun voltage of 500 kV is helpful to achieve low emittance. In addition, to estimate optimum gun voltage and cavity acceleration gradient for the FEL operation, two optimizations with different injector layouts were carried out. The results show that the both different layouts have potential to achieve target emittance for FEL operation. Under the realistic operation condition, the transverse normalized rms emittance of 0.8 mm mrad with the rms bunch length of 3 ps, the bunch charge of 325 pC, and the beam energy of 10 MeV is obtained from the optimizations.

Slides THC04 [3.796 MB]