IPAC2011 - List of Keywords (gun)

Paper	Title	Other Keywords	Page
MOPC007	Cold Photocathode RF Gun	cavity, vacuum, cathode, cryogenics	77
	V. Vogel, K. Flöttmann, S. Schreiber DESY, Hamburg, Germany
	Heating and thermal expansion in the normal conductivity RF-photo electron gun, are the main limitations to achieve high accelerating gradient and consequently a low emittance beam. Some pure materials show a significant increase in thermal conductivity with a small coefficient of temperature expansion at temperatures around 20 degrees Kelvin. Possible materials are Molybdenum, Iridium or Tungsten. However, machining of these materials is very difficult. Therefore we propose a simplified shape for an L-band RF gun. We expect to achieve a significant increase in gradient for similar RF powers as used in the present DESY RF-gun. On the other hand, it would also be possible to increase the duty cycle keeping a moderate gradient. In this report we discuss one possible design of an RF-gun using hard metals and present simulations on thermal properties.

MOPC014	RF Processing of L-band RF Gun for KEK-STF	cavity, cathode, laser, solenoid	92
	M. Kuriki, H. Iijima, Y.M. Masumoto HU/AdSM, Higashi-Hiroshima, Japan H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe KEK, Ibaraki, Japan G. Isoyama, R. Kato ISIR, Osaka, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan Y. Takahashi Sokendai, Ibaraki, Japan
	Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie. KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented.

MOPC020	Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac	cavity, booster, linac, electron	110
	T. Aoki, K. Sakaue, M. Washio RISE, Tokyo, Japan A. Deshpande SAMEER, Mumbai, India M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JST Quantum Beam Program We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference.

MOPC022	Development of a Compact C-band Photocathode RF Gun	electron, cathode, injection, emittance	116
	X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang TUB, Beijing, People's Republic of China
	Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program). A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation.

MOPC029	Development of Injector for Compact FEL Tera-hertz Source in CAEP	electron, FEL, booster, simulation	131
	W. Bai, M. Li, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	This paper introducs the development of a injector for compact FEL tera-hertz source at Institute of Applied Electronics in China Academy of Engineering Physics (IAE/CAEP). The injector consist of a main accelerator for energy booster section and a multicavity thermionic-cathode rf gun with low back bombardment, with total length no more than one meter. Numerical simulation result shows that the back bombardment power is less for the thermionic-cathode rf gun of the injector and the main accelerator has a good performance, which can provide high quality electron beam with emittance about 10 pi mm mrad, energy about 7 MeV and energy spread about 1%. At present, the preliminary hot test experiment on the injector has been done. The test results indicate that the mainly tested parameters agree well with the theoretical design ones. The process of the preliminary hot test experiment on the injector is present in this paper.

MOPC033	The Status of a 1.6-cell Photocathode RF Gun at PAL	cavity, klystron, emittance, cathode	142
	M.S. Chae, J.H. Hong, I.S. Ko, Y.W. Parc POSTECH, Pohang, Kyungbuk, Republic of Korea S.J. Park PAL, Pohang, Kyungbuk, Republic of Korea
	The RF power conditioning of the photocathode RF gun with four holes at the side of the full cell named as 'Pohang gun' is in progress. The first goal of the conditioning is the operation of the gun with RF pulse width of 1.5 μm, repetition rate of 30 Hz, field gradient at the cathode of 130 MV/m. We operated the RF gun successfully with the conditions within last few months. It was first operational experience with such conditions in PAL. Now we have a plan to operate RF gun with higher repetition rate up to 60 Hz.

MOPC034	Design of a 0.6-cell Cell Photocathode RF Gun for FED	electron, simulation, cathode, solenoid	145
	Y.W. Parc, M.S. Chae, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.

MOPC081	Pulsed Mode Operation and Longitudinal Parameter Measurement of the Rossendorf SRF Gun	cavity, SRF, cathode, laser	262
	J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P. Michel, P. Murcek, Ch. Schneider, R. Schurig, R. Xiang HZDR, Dresden, Germany T. Kamps, J. Rudolph, M. Schenk HZB, Berlin, Germany I. Will MBI, Berlin, Germany
	Funding: The European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579) the German Federal Ministry of Education and Research grant 05 ES4BR1/8. The Rossendorf SRF gun with a 3 1/2 cell cavity has been operated since 2007. It has produced CW beam with the electron energy of 3 MeV and the average current up to 16 μA. The electron beam of the gun has successfully injected the ELBE superconducting linac since 2010. The Nb cavity has shown constant quality during the operation and for the Cs2Te photocathode life time of months could be obtained. Recently the gun started to run in the pulsed mode with higher gradient. The longitudinal parameters have been measured in this mode. The dark current arose from the high gradient is studied. The main field emission source has been found to be the half cell. Meanwhile, two modified 3+1/2 cell niobium cavities have been fabricated and tested in Jlab. In this paper the new status of the SRF gun will be presented, and the latest results of the beam experiments will be discussed.

MOPC150	High Charge PHIN Photo Injector at CERN with Fast Phase Switching within the Bunch Train for Beam Combination	laser, cathode, vacuum, bunching	430
	M. Divall Csatari, A. Andersson, B. Bolzon, E. Bravin, E. Chevallay, A.E. Dabrowski, S. Döbert, V. Fedosseev, C. Heßler, T. Lefèvre, S. Livesley, R. Losito, O. Mete, M. Olvegård, M. Petrarca, A. Rabiller CERN, Geneva, Switzerland A. Drozdy BUTE, Budapest, Hungary D. Egger EPFL, Lausanne, Switzerland
	The high charge PHIN photo-injector was developed within the frame of the European CARE program to provide an alternative to the drive beam thermionic gun in CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 sub-trains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the scheme. Stability measurements are presented for the phase-coded system. The paper also discusses the latest 8nC charge production and cathode life-time studies on Cs2Te.

MOPC154	RF Photo Gun Stability Measurement at PITZ	laser, feedback, cavity, electron	442
	I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. Hoffmann, H. Schlarb DESY, Hamburg, Germany M.A. Khojoyan YerPhI, Yerevan, Armenia D. Richter HZB, Berlin, Germany A. Shapovalov NRNU MEPHI, Moscow, Russia I.H. Templin, I. Will MBI, Berlin, Germany
	The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPC166	Low RF Control Feedback and IQ Vector Modulator Compensation Functions	controls, linac, feedback, coupling	472
	M.G. Fedurin, R. Malone, V. Yakimenko BNL, Upton, Long Island, New York, USA
	IQ vector modulator is key element of the gun and linac RF control circuits at Accelerator Test Facility at Brookhaven National Laboratory. IQ modulator calibration procedure was developed to find proper compensation functions in the conversion algorithm to minimize phase-amplitude coupling and setting-reading errors: rms(A_set - A_read )= 0.03dB, rms(Phi_set - Phi_read) = 0.3 deg. Since stabilization of the RF phase and amplitude is become critical for many experiments the slow feedback was developed and applied as well to significantly compensate drifts in RF system.

MOPO018	Active Beam Current Stabilization in the Cornell ERL Prototype Injector	laser, feedback, cavity, cathode	523
	F. Löhl, P. Szypryt CLASSE, Ithaca, New York, USA
	In order to operate the Cornell ERL prototype injector at beam currents beyond 10 mA, the beam current has to be highly stable. The reason is that fast beam current fluctuations generate transient effects in the DC gun voltage as well as in the fields of subsequent superconducting cavities, which can lead to excessive beam loss or to trips of subsystems. Therefore, a feedback scheme was developed which uses the signal of a beam current monitor as an input, and applies appropriate corrections to a Pockels cell installed within the laser path of the photo-injector laser. In this paper, high current results achieved with this feedback scheme are presented.

MOPO041	Preliminary Testing of TPS Timing System	controls, linac, booster, EPICS	574
	C.Y. Wu, Y.-T. Chang, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, C.-Y. Liao NSRRC, Hsinchu, Taiwan
	The timing system of Taiwan Photon Source (TPS) provides synchronization for electron gun, modulators of linac, pulse magnet power supplies, booster power supply ramp, bucket addressing of storage ring, diagnostic equipments, beamline gating signal for top-up injection. The timing system utilizes a central event generator to generate events and distribute them over optic fiber network, and decodes them at the event receivers. The system supports uplink functionality which will be used for the fast interlock system to distribute signals like beam dump and post-mortem trigger. The timing system has now been in operation for Linac of TPS. This paper presents prototype for the timing system of TPS.

MOPO043	Applications of Lasers to Accelerator Physics at SSRL	laser, cathode, photon, electron	580
	D.L. Robinson Cal Poly, San Luis Obispo, California, USA W.J. Corbett SLAC, Menlo Park, California, USA
	Recent advances in accelerator physics and SR research have generated the need for high-power lasers in the SPEAR3 accelerator complex. On the injector side, two lasers are being used to test different photocathode materials and to provide photo-assisted emission from the standard dispenser cathode RF gun. For the storage ring, both a TiSa oscillator and a fiber laser locked to the RF master oscillator have been used to characterize short-pulse electron bunches in cross-correlation experiments. These lasers are also used in SR experiments for pump-probe characterization of materials. In this paper we review the laser-based systems, preliminary results and outlook for the future.

MOPS024	Bunch Dynamics through Accelerator Column	space-charge, TRIUMF, electron, cathode	649
	R.A. Baartman TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Funding: TRIUMF research is supported by the National Research Council of Canada. The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived.

MOPS033	Beam Dynamics Studies on the 100 MeV/100 kW Electron Linear Accelerator for NSC KIPT Neutron Source	linac, electron, dipole, simulation	673
	S. Pei, Y.L. Chi, M. Hou, W.B. Liu, G. Pei, S.H. Wang, Z.S. Zhou IHEP Beijing, Beijing, People's Republic of China N. Aizatsky, I.M. Karnaukhov, V.A. Kushnir, V. Mitrochenco, A.Y. Zelinsky NSC/KIPT, Kharkov, Ukraine
	We designed one 100MeV/100kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the base of subcritical assembly. Beam dynamics studies has been conducted to reach the design requirement (E=100MeV, P=100kW, dE/E<1% for 99% particles). In this paper, we will present the progress of the design and dynamics simulation results. For high intensity and long beam pulse linear accelerators, BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced at the downstream of the 1st accelerating section; the unwanted particles will be collimated there.

MOPS035	Energy Spreads by Transient Beam Loading Effect in Pulsed RF Linac	electron, linac, bunching, beam-loading	679
	S.H. Kim, M.-H. Cho, G. Ha, H.R. Yang POSTECH, Pohang, Kyungbuk, Republic of Korea W. Namkung, S.J. Park PAL, Pohang, Kyungbuk, Republic of Korea J.-S. Oh NFRI, Daejon, Republic of Korea
	Funding: Work partly supported by KAPRA and POSTECH Physics BK21 Program RF linacs for high power beams are operated in the fully beam-loaded condition for the power efficiency. In this condition, temporal energy spreads are induced by the transient beam loading effect. Irradiation sources require the beam energy of less than 10 MeV to prevent undesirable neutron production. In order to maximize the beam power and maintain the beam energy in a safe value, we need to suppress the temporal energy spreads. In an L-band traveling-wave linac for irradiation sources, the high energy electrons are suppressed by the beam current modulation with the RF power modulation. As a result, the average beam energy and the corresponding beam power are improved by nearly 60% compared to the case without any modulations.

MOPS042	One-Dimensional Adiabatic Child-Langmuir Flow	simulation, electron, emittance, plasma	694
	C. Chen MIT, Cambridge, Massachusetts, USA R. Pakter, F.B. Rizzato IF-UFRGS, Porto Alegre, Brazil
	Funding: Research supported in part by US Department of Energy, Grant No. DE-FG02-95ER40919, CNPq, FAPERGS, INCTFCx of Brazil, and US Air Force Office of Scientific Research, Grant No. FA9550-09-1-0283. A theory is presented that describes steady-state one-dimensional Child-Langmuir flow at a self-consistent finite temperature distribution. In particular, warm-fluid equations and adiabatic equation of state are used to derive the self-consistent Poisson equation. The profiles of the charged-particle density, the velocity, the electrostatic potential, the pressure and the temperature are computed. Results are compared with self-consistent simulations.

TUODB02	Extreme High Vacuum System of High Brightness Electron Source for ERL	vacuum, electron, ion, cathode	979
	M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama KEK, Ibaraki, Japan H. Akimichi, H. Yoshida AIST, Tsukuba, Japan H. Kurisu Yamaguchi University, Ube-Shi, Japan
	A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10^-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.
	Slides TUODB02 [1.606 MB]

TUPC031	Advanced Research Electron Accelerator Laboratory Based on Photocathode RF Gun	electron, emittance, laser, controls	1066
	B. Grigoryan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, K. Manukyan, I.N. Margaryan, V. Sahakyan, A. Sargsyan, A. Tarloyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan CANDLE, Yerevan, Armenia T. Vardanyan YSU, Yerevan, Armenia
	The low energy sub-picosecond duration electron bunches with extremely small beam emittance have wide applications in advanced research of new accelerator concepts, radiation physics, time-resolved pulse radiolysis and electron diffraction. The conceptual design and experimental program of the Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun are presented. The AREAL design implies single and multibunch operation modes with variable beam energy of 5-20 MeV and 10-100 pC bunch charge. The design is based on 3 GHz 1.6 cells RF gun followed by S-Band accelerating linac.

TUPC032	Beam Phase-Space Study for AREAL RF Photogun Linac	emittance, space-charge, electron, linac	1069
	B. Grigoryan, G.A. Amatuni, I.N. Margaryan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan CANDLE, Yerevan, Armenia
	In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed.

TUPC033	Verifying the Single Bunch Capability of the New Injector at ELSA*	linac, electron, single-bunch, pick-up	1072
	S. Mey, O. Boldt, W. Hillert, N. Hofmann, F. Klarner, D. Krönung, A. Roth, M. Schedler ELSA, Bonn, Germany S. Aderhold DESY, Hamburg, Germany
	Funding: Funded by the DFG within the SFB / TR 16 and the Helmholtz Alliance HA 10¹ "Physics at the Terascale". In order to enhance the operating capabilities of the Bonn University Accelerator Facility, ELSA, a new injector is currently under commissioning. One of its main purpose is to allow a single pulse mode. The injector produces a single electron bunch with 1.5 A pulse current. Design and optimization of the injector have been performed with EGUN, PARMELA and numerical simulations based on the numerical integration of the paraxial equation. A 1 ns long pulse is produced by a thermionic electron source with 90 kV anode - cathode voltage, then compressed and pre-accelerated by a subsequent 500 MHz RF cavity and a four-cell travelling wave buncher. Finally, the bunch will be accelerated to 20 MeV by the main LINAC section. Measurements have been conducted concerning the resulting pulse length and pulse charge to confirm the predictions made by simulations and to investigate the efficiency of the injector system.

TUPC034	Design Studies on 100 MeV/100 kW Electron Linac for NSC KIPT Neutron Source on the Base of Subcritical Assembly Driven by Linac	linac, electron, emittance, target	1075
	Y.L. Chi, J. Cao, X.W. Dai, C.D. Deng, M. Hou, X.C. Kong, R.L. Liu, W.B. Liu, C. Ma, G. Pei, H. Song, S.H. Wang, G. Xu, J. Zhao, Z.S. Zhou IHEP Beijing, Beijing, People's Republic of China M.I. Ayzatskiy, I.M. Karnaukhov, V.A. Kushnir, V.V. Mytrochenko, A.Y. Zelinsky NSC/KIPT, Kharkov, Ukraine S. Pei IHEP Beijng, Beijing, People's Republic of China
	In NSC KIPT, Kharkov, Ukraine, a neutron source on the base of subcritical assembly driven by 100 MeV/100 kW electron linear accelerator is under design and development. To provide neutron flux value of about 1013 neutron/s the electron linear accelerator with 100 MeV beam and average beam power of 100 kW will be used. Construction and manufacture of the linear accelerator of such high beam intensity with low emittance and beam losses is a challenging task. In the report the project of the electron linear accelerator of the required beam energy and intensity is described. The accelerator structure and main technical solutions are presented. To overcome the BBU effect of this high average beam current, several effective measures are adopt, such as using constant gradient structure to spread the HOMs frequencies different cells, larger inner radius and shorter section length make the higher group velocity and optimize the structure geometry to keep the shunt impedance as good as possible. After the beam bunching system, a chicane is followed to chopper the beam to avoid the beam lost in the higher energy part.

TUPC036	S-band ps Pulse Photoinjector for THz Radiation Source	coupling, electromagnetic-fields, electron, acceleration	1078
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia
	S-band photoinjectors with ps pulse are becoming promising as e-guns for high-intensity sub-mm wavelength pulse source. Development of accelerating system for photoinjector with ps bunch is reported. The main aim is to develop a model of accelerating structure that provide top accelerating fields in respect to high electric strength and low RF power uses. The accelerating structures consisting of 1.6 cell of disk-loaded waveguide (DLW), 3 cells and 2 half-cells of DLW, 7 cels and 2 half-cells of DLW and accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW are studying. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics, electric field distribution for all models were acquired. Accelerating structure consisting of 1.6 cells will operate in pi mode of standing wave, all other structures operate in pi/2 mode traveling wave. Accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW has most suitable electrodynamics characteristics and field distribution for sub-mm pulse source according to simulation results.

TUPC038	A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam	linac, electron, bunching, klystron	1081
	J.-Y. Hwang, J.H. Chen, W.K. Lau, A.P. Lee, T.H. Wu NSRRC, Hsinchu, Taiwan N.Y. Huang NTHU, Hsinchu, Taiwan
	A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers.

TUPC043	SEM Field Emission Probe Surface Science Study	cathode, vacuum, electron, laser	1096
	L. Laurent, R.E. Kirby, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This work is supported by Department of Energy Contract No. DE-AC03- 76SF00515. After decades of rf breakdown research, a common acknowledgement among researchers is that a better understanding of what is happening on the surface at a microscopic level needs to be the impetus for future studies. We are designing and fabricating an electron microscope-based high-electric-field current-emission probe to study topographic material features which will enable us to better understand and further advance the technology of high-brightness photocathode rf guns and enable the study of high gradient phenomena. The SEM field emission probe will provide an important diagnostic tool allowing cathodes and high gradient surfaces to be evaluated before and after testing and will help identify and understand the relationship between high field emission locations and vacuum breakdown, non-uniform emission, surface cracking, hotspots, etc. The preliminary results and 2012 goals will be presented.

TUPC057	Femtosecond Photoinjector and Relativistic Electron Microscopy	electron, emittance, laser, cathode	1126
	J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida ISIR, Osaka, Japan J. Urakawa KEK, Ibaraki, Japan
	A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10^-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported.

TUPC058	Design of a Chirping Cell Attached RF Gun for Ultrashort Electron Generation	electron, cavity, laser, radiation	1129
	K. Sakaue, K. Tamai, M. Washio RISE, Tokyo, Japan J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 We have been developing an S-band photocathode rf electron gun at Waseda university. Our rf-gun cavity was firstly designed by BNL and then, modified by our group. In this paper, we will introduce a newly designed rf-gun cavity with energy chirping cell. To generate an energy chirped electron bunch, we attached extra-cell for 1.6cell rf-gun cavity. Cavity design was done by Superfish and particle tracing by PARMELA. By optimizing the chirping cell, we observed linear chirped electron bunch. The front electron have lower energy than rear. Then transporting about 2m, the bunch can be compressed down to 200fsec electron bunch with the charge of 160pC. This ultrashort bunch will be able to use for generating CSR THz radiation, pumping some material to be studied by pulse radiolysis method, and so on. In this conference, the design of chirping cell attached rf-gun, the results of tracing simulation and plan of manufacturing will be presented.

TUPC059	Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun	laser, beam-loading, electron, cavity	1132
	Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto RISE, Tokyo, Japan H. Hayano, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program. At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans.

TUPC060	A Multi-mode RF Photocathode Gun	cathode, cavity, injection, electron	1135
	S.V. Kuzikov, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia J.L. Hirshfield Yale University, Physics Department, New Haven, CT, USA Y. Jiang Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA V. Vogel DESY, Hamburg, Germany
	A photocathode injection gun based on standard emittance compensating techniques and driven by several (N ≥ 2) harmonically related RF sources is considered. Multi-harmonic excitation can provide high-quality flatness in time of the field at the cathode when a bunch is being injected. This allows one to obtain ≥1 nC, 20-40 ps electron bunches with preservation of low emittance. Another advantage is a reduction of Ohmic losses and the required input RF power (for a given cathode field). Preliminary calculations show that input power in a three-mode cavity (0.65 GHz, 1.3 GHz, 2.6 GHz) is nearly half the power needed to feed a single mode with the same cathode field. A further appealing property is the predicted increase of breakdown threshold due to a reduction of surface exposure time to high fields in a symmetric cavity, and due to the so-called anode-cathode effect in a longitudinally asymmetric cavity. These properties may help one to reach bunch energies as high as 3-5 MeV after the first half cell.

TUPC094	Development of High-speed Differential Current-transformer Monitor	electron, bunching, monitoring, status	1227
	S. Matsubara, H. Ego, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan A. Higashiya, S.I. Inoue, Y. Otake RIKEN/SPring-8, Hyogo, Japan H. Maesaka RIKEN Spring-8 Harima, Hyogo, Japan
	The XFEL, which was named SACLA, was constructed in the SPring-8 site. In the SACLA, the bunch length of an electron beam is compressed from 1 ns to 30 fs, and the beam charge is decreased to obtain a genuine electron beam from 1nC to 0.3 nC for lasing. A new current-transformer (CT) monitor, which should measure the charge of the electron beam and make bunch length observation in velocity bunching process, was developed with two advantageous properties. One is differential output signal which suppresses common-mode noise from the thyratron of a klystron modulator by a factor of ten. Another property is high-speed signal output which provides a possibility to measure the bunch length and the time-of-flight (TOF) at the injector part of the SACLA. The output signal has 200 ps rise-time and a pulse width of 400 ps (FWHM) for an impulse beam. We successfully observed the bunch length between 1 ns and 400 ps around a 238 MHz buncher cavity. Moreover, we measured the TOF between two CTs with a few picoseconds resolution for a low-energy beam around 1 MeV. Thus, the new CT performance was confirmed to be sufficient for the SACLA.

TUPC101	Generation of Multimode Quasi-monochromatic Terahertz	electron, linac, radiation, cathode	1248
	K. Kan, T. Kondoh, K. Norizawa, A. Ogata, J. Yang, Y. Yoshida ISIR, Osaka, Japan
	Generation of quasi-monochromatic terahertz (THz) using multimode Coherent Cherenkov Radiation (CCR) on the order of 0.1 THz was investigated. CCR was generated by a hollow dielectric tube covered by a metal and an electron bunch from a photocathode radio-frequency (RF) gun linac. The intensity and frequency of CCR were measured directly by a Michelson interferometer and a bolometer. The frequency spectra measured by the interferometer indicated sharp peaks close to frequencies of 0.09 THz and 0.14 THz, which corresponded to TM03 and TM04 modes, respectively, according to theoretical calculation for a tube with inner and outer radii of 5 mm and 7 mm. The maximum gain of TM03 mode due to the tube length was obtained as 1.5 dB/cm. The other higher modes, e. g. 0.36 THz (TM09) and 0.40 THz (TM010), were also observed from a 150 mm long tube at a bunch charge of 15 pC, which decreased space charge effect and the bunch length. Finally, a new method for bunch diagnostic based on multimode CCR was proposed. The bunch length was estimated to be 0.45 ps at a bunch charge of 5 pC with the intensity ratio of TM03 to TM09 mode.

TUPC102	Measurement of Beam Loss Tracks by Scintillating Fibers at J-PARC Linac	beam-losses, linac, background, simulation	1251
	H. Sako, T. Maruta, A. Miura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	Highest beam loss in the J-PARC linac has been observed that the ACS (Annular-Coupled Structure linac) section. Since the observed beam loss is proportional to the residual gas pressure, the source of the beam loss is considered as H0 produced in an interaction of H⁻ beams with remnant gas. If this assumption is valid, H0 hits the beam duct and changes into H⁺ and escapes from the beam duct. We constructed scintillation fiber hodoscopes to detect H⁺s and eventually identify the particle species as H⁺. The hodoscopes are made of 4 planes of hodoscopes which consists of 16 scintillation fibers of 64mm long and with 4mmx4mm cross section. We installed the hodoscopes at the upstream part of the ACS section and measured beam loss. The results are shown in this paper.

TUPC111	Design of Cavity Beam Monitor at HLS	cavity, quadrupole, emittance, dipole	1278
	Q. Luo, Q.K. Jia, B.G. Sun, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by the Natural Science Foundation of China, National “985 Project”, China Postdoctoral Science Foundation and “the Fundamental Research Funds for the Central Universities” X-FEL requires precious control of beam position and transverse emittance. Non-destructive on-line beam diagnostic methods are required. During the upgrading of HLS a high brightness injector based on photocathode RF electron gun, which can also be used to study FEL, is installed. The cavity beam monitor system designed for the HLS photocathode RF electron gun consists of a cavity beam position monitor and a beam quadrupole moment monitor system. The cavity beam position monitor uses a re-entrant position cavity tuned to TM110 mode as position cavity and cut-through waveguides to suppress the monopole signal. Cold test results showed that position resolution of prototype BPM is better than 3 μm. Beam quadrupole moment monitor system consists of a square pill-box quadrupole moment cavity, a cylindrical pill-box reference cavity, a waveguide coupling network and a superheterodyne receiver used as front-end signal processing system. The whole system works at 5.712 GHz. Strength of quadrupole magnets is adjust to construct a matrix which can be used to work out beam parameters.

TUPC178	Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun	laser, cathode, vacuum, high-voltage	1443
	R.R. Mammei, M. Poelker, R. Suleiman JLAB, Newport News, Virginia, USA J.L. McCarter UVa, Charlottesville, Virginia, USA T. Rao, J. Smedley 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. DOE Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10^-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam.

TUPO007	FLUTE, a Linac Based THz Source	radiation, linac, synchrotron, synchrotron-radiation	1458
	S. Naknaimueang, M. Schwarz Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany R. Abela, H.-H. Braun, R. Ganter, B. Patterson PSI, Villigen, Switzerland A.H. Albert, T. Baumbach, M. Hagelstein, N. Hiller, E. Huttel, V. Judin, B. Kehrer, R. Kubat, S. Marsching, W. Mexner, A.-S. Müller, M.J. Nasse, A. Plech, R. Rossmanith, M. Schuh KIT, Karlsruhe, Germany M.T. Schmelling MPI-K, Heidelberg, Germany
	We propose a versatile THz source named FLUTE (“Ferninfrarot Linac- Und Test-Experiment”) based on a 30 - 50 MeV S-band linac with bunch compressor, that shall not only provide high field THz pulses applications but shall also serve as a test facility to study important accelerator physics issues. This is also of importance in view of the planned utltra-broadband THz to mid infrared user facility TBONE. Special emphasis is put on studies of bunch compression and beam stability as a function of bunch charge (0.1-5 nC) and of different generation mechanisms of coherent radiation (CSR, CER, CTR). This paper describes the design and layout of the proposed FLUTE machine and presents results of beam dynamic calculations with the tracking programs ASTRA and CSRtrack.

TUPO024	Precision X-band Linac Technologies for Nuclear Photonics Gamma-ray Sources	electron, laser, photon, scattering	1491
	F.V. Hartemann, F. Albert, S.G. Anderson, C.P.J. Barty, A.J. Bayramian, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, T.L. Houck, R.A. Marsh, M. J. Messerly, S.S.Q. Wu LLNL, Livermore, California, USA C. Adolphsen, A.E. Candel, T.S. Chu, M.V. Fazio, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou SLAC, Menlo Park, California, USA D. Cutoiu Horia Hulubei National Institute for Physics and Nuclear Engineering, Bucharest, Romania D. Ighigeanu, M. Toma INFLPR, Bucharest - Magurele, Romania V.A. Semenov UCB, Berkeley, California, USA
	Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies.

TUPO026	Developments towards a Full Energy Recovery Linac	cavity, HOM, cathode, SRF	1494
	P. vom Stein, J.H. Hottenbacher, A. Metz RI Research Instruments GmbH, Bergisch Gladbach, Germany
	Energy Recovery Linacs (ERLs) are high potential candidates for driving light sources based on laser Compton scattering with high brilliance photon beams and sub pico second time structure. We report on developments for an advanced ERL design, which allows the recovery of nearly full electron beam energy up to the limits set by the energy width of the beam. This “Full” Energy Recovery Linac (FERL) allows a substantial reduction of the complexity of the accelerator systems resulting into a very compact light source design suitable for industrial and medical applications.

TUPS011	Use of NEG Pumps to Ensure Long Term Performances of High Quantum Efficiency Photocathodes	ion, cathode, vacuum, photon	1539
	L. Monaco, P.M. Michelato, D. Sertore INFN/LASA, Segrate (MI), Italy P. Manini, F. Siviero SAES Getters S.p.A., Lainate, Italy
	Laser triggered photo-cathodes are key components of the electron sources of 4th generation light machines. However, they are very sensitive to the vacuum level and its composition. Photo-cathodes are usually prepared in UHV chamber and then transferred, keeping the extreme vacuum condition, to the operation sites. Since transportation/storage may last from several days to weeks, retaining UHV conditions is a fundamental task to the photocathode usage. In this paper the results obtained using a novel pumping approach are given. This approach is based on coupling a 20 l.s⁻¹ ion getter pump with a Capacitorr® D100 Non Evaporable Getter (NEG) pump. Pressure of 2x10-11 mbar was achieved with the NEG pump after 2 days bake-out, as compared to 8x10-10 mbar achieved with the ion pump alone, after 7 days bake-out. Such pressure values were retained even in absence of power, due to the ability of the NEG to remove gases by chemical reaction. Long term monitoring of cathodes QEs was also carried out at different photon wavelengths over more than 6 months, showing no degradation of the photo-emissive film properties.

TUPS023	Secondary Electron Yield on Cryogenic Surfaces as a Function of Physisorbed Gases	electron, cryogenics, vacuum, insertion	1575
	A. Kuzucan, H. Neupert, M. Taborelli CERN, Geneva, Switzerland H. Stoeri IAP TUW, Wien, Austria
	Electron cloud is a serious limitation for the operation of particle accelerators with intense positively charged beams. It occurs if the secondary electron yield (SEY) of the beam-pipe surface is sufficiently high to induce an electron multiplication. At low surface temperatures, the SEY is strongly influenced by the nature of the physisorbed gases and by the corresponding surface coverage. These conditions occur in many accelerators operating with superconducting magnets and cold vacuum sections such as the LHC and RHIC. In this work, we investigated the variation of the SEY of copper, aluminium and electro-polished copper as a function of physisorbed N2, CO, CO2, CH4, Kr, C2H6 at cryogenic temperatures. The conditioning by electron bombardment of the surface after the physisorption of H2O on electro polished copper will also be presented. The results of the various gases are compared in order to find a rationale for the behaviour of the secondary electrons for the various adsorbates.

TUPS027	Characterization of Carbon Coatings with Low Secondary Electron Yield	electron, vacuum, cryogenics, ion	1587
	C. Yin Vallgren, S. Calatroni, P. Costa Pinto, A. Kuzucan, H. Neupert, M. Taborelli CERN, Geneva, Switzerland
	Amorphous carbon (a-C) coatings can reliably be produced with a maximum secondary electron yield (SEY) close to 1 at room temperature. Measurements at low temperature (LHe) are in progress. Analysis by X-ray Photoemission Spectroscopy (XPS) shows a correlation between the lineshape of C1s spectrum in XPS and maximum SEY of the investigated samples. The initial level of oxygen on the surface of the various samples does not seem to be related to the initial maximum SEY value. However, the increase of the SEY with air exposure time on each individual sample is related to the amount of oxygen containing adsorbates. Storage in different environments has been investigated (static vacuum, aluminum foil, dry nitrogen and desiccators) and shows significant differences in the “aging” behavior. Aging is very moderate when storing samples wrapped in aluminum foil in air. Samples which have undergone aging due to inappropriate storage can be recovered nearly to the initial value of the SEY by typical surface treatments as ion bombardment, annealing under vacuum and conditioning by electron beam. However, an enhanced sensitivity to air exposures is observed for most of these curing methods.

TUPS034	Development and Construction of the Beam Dump for J-PARC Hadron Hall	hadron, proton, status, radiation	1608
	A. Agari, E. Hirose, M. Ieiri, Y. Katoh, M. Minakawa, R. Muto, M. Naruki, Y. Sato, S. Sawada, Y. Shirakabe, Y. Suzuki, H. Takahashi, M. Takasaki, K.H. Tanaka, A. Toyoda, H. Watanabe, Y. Yamanoi KEK, Tsukuba, Japan H. Noumi RCNP, Osaka, Japan
	Funding: This work is supported by Grant-in-Aid (No.22740184) for Young Scientists (B) of the Japan Ministry of Education, Culture, Sports, Science and Technology [MEXT]. A facility of Hadron hall at Japan Proton Accelerator Research Complex (J-PARC) had been constructed in June 2007. Hadron hall is designed to handle intense slow-extraction proton beam from the main accelerator of J-PARC, i.e. 50-GeV-PS. The first transportation of the proton beam to the hall was successfully made in Jan. 2009. A beam dump constructed at the end of the primary proton beam line in Hadron hall is designed to safely absorb 15 μA (=750-kW) proton beam. Its central core of the dump is made of copper with water cooling and is surrounded by iron and concrete for radiation protection. We made thermal and mechanical FEM analysis for investigating heat generation and mechanical stress from energy deposition. We also made cooling experiments for measuring heat transfer coefficient of candidates for new cooling device. As a result, the adopted device has direct cooling paths which are prepared as long holes made by Gun Drill from the outer surface of the copper core. In addition, the beam dump is designed to safely move to 50-m downstream as one body for future expansion of Hadron hall. This paper reports development and construction of the beam dump in Hadron hall.

WEODA02	Collimation Studies with Hollow Electron Beams	electron, collimation, antiproton, proton	1939
	G. Stancari, G. Annala, T.R. Johnson, G.W. Saewert, V.D. Shiltsev, D.A. Still, A. Valishev Fermilab, Batavia, USA
	Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. This work was partially supported by the US LHC Accelerator Research Program (LARP). Recent experimental studies at the Tevatron collider have shown that magnetically confined hollow electron beams can act as a new kind of collimator for high-intensity beams in storage rings. In a hollow electron beam collimator, electrons enclose the circulating beam. Their electric charge kicks halo particles transversely. If their distribution is axially symmetric, the beam core is unaffected. This device is complementary to conventional two-stage collimation systems: the electron beam can be placed arbitrarily close to the circulating beam; and particle removal is smooth, so that the device is a diffusion enhancer rather than a hard aperture limitation. The concept was tested in the Tevatron collider using a hollow electron gun installed in one of the existing electron lenses. We describe some of the technical aspects of hollow-beam scraping and the results of recent measurements.
	Slides WEODA02 [9.049 MB]

WEOAB01	Highly Polarized and High Quantum Efficiency Electron Source Using Transmission-type Photocathode	electron, laser, brightness, polarization	1950
	N. Yamamoto, F. Ichihashi, A. Mano, T. Nakanishi, Y. Takeda, T. Ujihara Nagoya University, Nagoya, Japan X.G. Jin Institute for Advanced Research, Nagoya, Japan
	The GaAs-type semiconductor photocathodes (PCs) with a negative electron affinity surface have been used as a polarized electron source and are expected as electron sources for next generation accelerators, such as Linear Colliders and Energy Recovery Linacs. Recently, we have developed transmission-type photocathodes (T-PCs).　By using T-PCs, polarized electron beam is extracted from the back-side of laser irradiation-side.　This scheme offers great merits in designing electron guns, such as short focusing of the laser light for a high brilliance electron beam and a simple geometrical structure avoiding an interference problem between the laser and the electron beam. The layer structure of the MOVPE-grown superlattice photocathode and the performance of 90% polarization, a super high brilliance, and a high quantum efficiency will be reported.
	Slides WEOAB01 [6.007 MB]

WEPC036	Coherent Synchrotron Radiation Source Based on an Isochronous Accumulator Ring with Femtosecond Electron Bunches	betatron, linac, radiation, lattice	2085
	N.Y. Huang NTHU, Hsinchu, Taiwan H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, F. Miyahara, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan W.K. Lau NSRRC, Hsinchu, Taiwan
	A compact isochronous accumulator ring has been studied as a source of coherent synchrotron radiation (CSR) at a wavelength region from THz to GHz. Since the thermionic rf gun is substantially stable in general, we anticipate a bunch train of very short electron pulses can be provided satisfactorily by means of velocity bunching. Careful numerical simulations show possibility of the bunch length of much less than 100 fs with a bunch charge of 20 pC, which will contain sufficiently large form factor for production of CSR at the wavelengths longer than ~ 0.1 mm. The coherent THz radiation of high average power will be achieved if the short bunches can be circulated in the accumulator ring without bunch lengthening. This paper will describe the optimization of thermionic injector to produce femtosecond bunches in addition to study of the lattice designing of complete isochronous optics for the accumulator ring.

WEPO003	The FERMI@Elettra Magnets	dipole, quadrupole, electron, FEL	2409
	D. Castronovo, R. Fabris, G.L. Loda, D. Zangrando ELETTRA, Basovizza, Italy
	FERMI@Elettra is a single-pass FEL user-facility located next to the third generation synchrotron radiation facility ELETTRA in Trieste, Italy. The linear accelerator contains more than 200 magnets. This paper reports on the design, construction, magnetic measurement and installation.

WEPZ014	Upgrade of the Argonne Wakefield Accelerator Facility (AWA): Commissioning of the RF Gun and Linac Structures for Drive Beam Generation	wakefield, electron, linac, acceleration	2799
	M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof ANL, Argonne, USA S.P. Antipov, C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357. Research at the AWA Facility has been focused on the development of electron beam driven wakefield structures. Accelerating gradients of up to 100 MV/m have been excited in dielectric loaded cylindrical structures operating in the microwave range of frequencies. Several upgrades, presently underway, will enable the facility to explore higher accelerating gradients, and also be able to generate longer RF pulses of higher intensity. The major items included in the upgrade are: (a) a new RF gun with a higher quantum efficiency photocathode will replace the RF gun that has been used to generate the drive bunches; (b) the existing RF gun will be used to generate a witness beam to probe the wakefields; (c) three new L-band RF power stations, each providing 25 MW, will be added to the facility; (d) five linac structures will be added to the drive beamline, bringing the beam energy up from 15 MeV to 75 MeV. The upgraded drive beam will consist of bunch trains of up to 32 bunches spaced by 0.77 ns with up to 100 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.

THYB01	Advanced Beam Manipulation Techniques at SPARC	emittance, linac, simulation, laser	2877
	A. Mostacci, D. Alesini, P. Antici, A. Bacci, M. Bellaveglia, R. Boni, M. Castellano, E. Chiadroni, G. Di Pirro, A. Drago, M. Ferrario, A. Gallo, G. Gatti, A. Ghigo, E. Pace, A.R. Rossi, B. Spataro, C. Vaccarezza INFN/LNF, Frascati (Roma), Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy B. Marchetti INFN-Roma II, Roma, Italy M. Migliorati University of Rome "La Sapienza", Rome, Italy L. Palumbo Rome University La Sapienza, Roma, Italy V. Petrillo, L. Serafini Istituto Nazionale di Fisica Nucleare, Milano, Italy C. Ronsivalle ENEA C.R. Frascati, Frascati (Roma), Italy
	SPARC in Frascati is a high brightness photo-injector used to drive Free Electron Laser experiments and explore advanced beam manipulation techniques. The R&D effort made for the optimization of the beam parameters will be presented here, together with the major experimental results achieved. In particular, we will focus on the generation of sub-picosecond, high brightness electron bunch trains via velocity bunching technique (the so called comb beam). Such bunch trains can be used to drive tunable and narrow band THz sources, FELs and plasma wake field accelerators.
	Slides THYB01 [20.772 MB]

THPC040	Expected Performance Characteristic of Accelerator-based THz Source at Tohoku University	radiation, electron, undulator, focusing	2990
	H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, School of Science, Sendai, Japan N.Y. Huang NTHU, Hsinchu, Taiwan
	Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. Sources of coherent synchrotron radiation at THz wavelength region have been constructed at Tohoku University. Bunch train of extremely shorter electron pulse less than 100 fs will be provided by an injector linac employing thermionic rf gun, where the bunch compression will be performed by means of velocity bunching in an accelerator structure. Radiation source under development are a Halbach type planar undulator and an accumulator isochronous ring. The undulator employs large gap and long period length configuration, so that the resonant frequency of 1 THz is achieved when a lower beam energy of ~ 20 MeV. Since spectrum of coherent synchrotron radiation (CSR) is strongly depending on longitudinal bunch form factor, we have calculated CSR spectra for various conditions of the beam to evaluate the performance of the THz source. Numerical simulation with multi-particle system has been carried out to understand the radiation power and angular distribution as well. The beam transport in the undulator is crucial for quality of the radiation because the beam energy is very much low relative to strong focusing power. Characteristics of THz CSR from the undulator will be discussed.

THPC041	Injector System of Test Accelerator as Coherent Terahertz Source	cavity, electron, cathode, radiation	2993
	S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, School of Science, Sendai, Japan N.Y. Huang NTHU, Hsinchu, Taiwan F. Miyahara KEK, Ibaraki, Japan
	Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. A test accelerator as a coherent terahertz source (t-ACTS) project has been under development at Tohoku University, in which a generation of intense coherent terahertz (THz) radiation from sub-picosecond electron bunch will be demonstrated. We will supply a wide-band coherent radiation from bending magnets in an isochronous ring and a narrow-band coherent THz radiation using an undulator in a linac. Stable generation of very short electron bunch is one of the key issues in the t-ACTS project. The injector system is consists of a thermionic RF gun with two independent cavity cells, an alpha magnet and an accelerating structure. A velocity bunching scheme is employed to produce the very short electron bunch. Components of the t-ACTS injector except the accelerating structure have already been installed and we have started a high power RF processing of the gun cavities. The characteristics of electron bunch extracted from the RF gun are measured by varying phase and amplitude of input RF fields for the gun cavities. The status of t-ACTS project will be presented in the conference.

THPC088	Performance of RF System for XFEL/SPring-8 Injector	cavity, emittance, electron, klystron	3101
	T. Asaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Asaka, H. Ego, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi JASRI/SPring-8, Hyogo-ken, Japan T. Inagaki RIKEN/SPring-8, Hyogo, Japan Y. Otake, T. Shintake, K. Togawa RIKEN Spring-8 Harima, Hyogo, Japan
	In the XFEL/SPring-8 accelerator, the RF processing of an injector for the 8-GeV accelerator were carried out during two months after the installation of all the main components of the accelerator was completed in January 2011. To realize stable bunch compression process without the emittance growth, the injector adopts the combination of an extremely low emittance thermionic gun and multi-stage RF cavities for velocity bunching. In addition, in order to reduce the emittance growth occurring at the transition from the velocity bunching to acceleration, the newly developed L-band APS type accelerating structures and a waveguide system were introduced in the injector. Since an intensity of beam current is affected by the slight variations of RF power and phase of these RF equipment, we have carried out thorough countermeasures to complete highly-stabilized RF systems. Consequently, the stability of RF power and phase in rated operating condition of each RF cavity achieved 20 ppm (std.) and 0.06˚ (std.), respectively. In this paper, we describe the stability performances and RF processing of these RF systems in the injector.

THPC093	Beam Dynamics Simulations for the SwissFEL Injector Test facility	emittance, laser, solenoid, simulation	3107
	S. Bettoni, M. Pedrozzi, S. Reiche, T. Schietinger PSI, Villigen, Switzerland
	The SwissFEL under study at PSI will produce 0.1 nm to 0.7 nm wavelength coherent x-ray. The design of the injector is based on the invariant envelope matching scheme, developed for other photoinjectors in the past years. According to this technique the emittance at the exit of the injector can be minimized if some conditions at the entrance of the booster are satisfied. A campaign of simulations has been carried out to verify the impact of the errors of the machine components (RF and magnetic) and laser shaping (transverse and longitudinal) on the final SwissFEL injector emittance. These results have to be used to define the tolerances on the machine and laser.

THPC095	Commissioning Status of the SwissFEL Injector Test Facility	emittance, laser, solenoid, electron	3110
	T. Schietinger, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, N. Milas, G.L. Orlandi, M. Pedrozzi, E. Prat, S. Reiche, C. Vicario PSI, Villigen, Switzerland
	The SwissFEL injector test facility at the Paul Scherrer Institute has been in operation since August 2010. Its primary goal is the demonstration of a high-brightness electron beam as it will be required to drive the SwissFEL main linac. The injector further serves as a platform for the development and validation of accelerator components needed for the SwissFEL project. We give an overview of recent commissioning activities at about 130 MeV beam energy, with particular emphasis on results from optics matching studies and emittance measurements, the latter obtained with different optics-based methods. A five-cell transverse-deflecting cavity allows studies of the longitudinal bunch charge distribution and slice emittance. Bunch length measurements will become the focus of interest after the installation of a magnetic compression chicane, currently scheduled for the summer of 2011.

THPC106	Commissioning Status of the Fritz Haber Institute THz FEL	electron, FEL, undulator, linac	3137
	A.M.M. Todd, H. Bluem, V. Christina, M.D. Cole, J. Ditta, D. Dowell, K. Jordan, R. Lange, J.H. Park, J. Rathke, T. Schultheiss, L.M. Young AES, Princeton, New Jersey, USA W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, W. Schöllkopf, G. von Helden FHI, Berlin, Germany S.C. Gottschalk STI, Washington, USA
	The THz Free-Electron Laser (FEL) at the Fritz Haber Institute (FHI) of the Max Planck Society in Berlin is designed to deliver radiation from 3 to 300 microns using a single-plane-focusing mid-IR undulator and a two-plane-focusing far-IR undulator that acts as a waveguide for the optical mode. A key aspect of the accelerator performance is the low longitudinal emittance, < 50 keV-psec, that is specified to be delivered at 200 pC bunch charge and 50 MeV from a gridded thermionic electron source. We utilize twin accelerating structures separated by a chicane to deliver the required performance over the < 20 - 50 MeV energy range. The first structure operates at near fixed field while the second structure controls the output energy, which, under some conditions, requires running in a decelerating mode. "First Light" is targeted for the centennial of the sponsor in October 2011 and we will describe progress in the commissioning of this device to achieve this goal. Specifically, the measured performance of the accelerated electron beam will be compared to design simulations and the observed matching of the beam to the mid-IR wiggler will be described.

THPC111	Operation of an L-band RF Gun with Pulses Inside the Burst Mode RF Pulse	cavity, laser, klystron, controls	3146
	V. Vogel, V. Ayvazyan, B. Faatz, K. Flöttmann, D. Lipka, P. Morozov, H. Schlarb, S. Schreiber DESY, Hamburg, Germany
	The Free-Electron Laser in Hamburg (FLASH) is a user facility since 2005, delivering femtosecond short radiation pulses in the wavelength range between 4.1 and 44 nm using the SASE principle. In FLASH, the electron beam is accelerated to 1.25 GeV with L-band superconducting cavities. The electron source is a normal conducting RF-gun photoinjector. The L-band standing wave RF gun has one and a half cells. The gun is operated in burst mode with an RF pulse length of up to 900 microseconds and a repetition rate of 10 Hz. Several hundreds to thousands of bunches are accelerated per second. With 5 MW of pulsed forward power, the dissipated power inside the RF gun is 45 kW. In this paper we propose an operational mode which allows us to reduce the dissipated power to ease operation or to increase the effective duty cycle in the gun by pulsing the gun within one burst. We report on first experimental results at FLASH, where an RF burst of 46μRF-pulses with a length of 10 microseconds separated by 10 microseconds has been successfully generated reducing the dissipated power by a factor of 2.

THPC114	High Brightness Photo Injector Upgrade and Experimental Optimization at PITZ	emittance, laser, electron, booster	3152
	M. Krasilnikov, H.-J. Grabosch, M. Gross, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria L. Hakobyan, M.A. Khojoyan YerPhI, Yerevan, Armenia M. Hoffmann, H. Schlarb DESY, Hamburg, Germany I.I. Isaev, A. Shapovalov MEPhI, Moscow, Russia M.A. Nozdrin JINR, Dubna, Moscow Region, Russia D. Richter HZB, Berlin, Germany I.H. Templin, I. Will MBI, Berlin, Germany
	The photo injector test facility at DESY in Zeuthen (PITZ) develops and optimizes electron sources for linac driven free electron lasers. The main goal of PITZ is to demonstrate a small electron beam emittance by tuning several main parameters of the injector - photo cathode laser pulse, rf gun with solenoids and booster cavity parameters. A slit scan technique is used to measure the transverse phase space of the electron beam and the projected normalized emittance. The photo injector is capable of pulse train production which can be measured with dedicated diagnostics at PITZ. This enables optimization of the beam emittance for a wide range of bunch charges from tens of pC to several nC while keeping high resolution of beam measurements. The results of the experimental optimization will be presented yielding a new benchmark of photo injector performance.

THPC115	Emittance Optimization for Different Bunch Charges with Upgraded Setup at PITZ	emittance, laser, booster, electron	3155
	G. Vashchenko, G. Asova, M. Gross, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, M. Krasilnikov, M. Mahgoub, D. Malyutin, M. Otevřel, B. Petrosyan, S. Rimjaem, A. Shapovalov, F. Stephan, S. Weidinger DESY Zeuthen, Zeuthen, Germany M.A. Nozdrin JINR, Dubna, Moscow Region, Russia D. Richter HZB, Berlin, Germany I.H. Templin, I. Will MBI, Berlin, Germany
	The Photo Injector Test facility at DESY, Zeuthen site, (PITZ) has the aim to develop and optimize high brightness electron sources for Free Electron Lasers like FLASH and the European XFEL. Photo electrons emitted from the Cs2Te cathode are accelerated by a 1.6-cell L-band RF gun cavity operated at 60 MV/m maximum accelerating gradient at the cathode. Cylindrically shaped laser pulses with a flat-top temporal profile of about 20 ps FWHM and 2 ps rise and fall time are used to produce electron beams with extremely low emittance. The PITZ beam line was upgraded in 2010. The new gun cavity (prototype number 4.1) was installed January 2010. The new booster cavity (CDS) with well-defined field distribution was installed in July 2010. The diagnostic system for characterization of the laser hitting the photocathode was upgraded in October 2010. Emittance measurements results for different charges: 2 nC, 1 nC, 0.25 nC, 0.1 nC and 0.02 nC, will be presented. The optimization was done for different parameters, e.g. gun solenoid current, gun phase, laser spot size on the cathode, booster gradient.

THPC120	Experimental Investigation of Photocathode Thermal Emittance Components with a Copper Cathode*	emittance, cathode, laser, electron	3167
	H.J. Qian, Y.-C. Du, Hua, J.F. Hua, W.-H. Huang, C. Li, C.-X. Tang, L.X. Yan TUB, Beijing, People's Republic of China
	With progress of photocathode RF gun technology, thermal emittance has become the primary limitation of electron beam brightness. Extensive efforts have been devoted to study thermal emittance, but experiment results diverge between research groups and few can be well interpreted. One possibility is the undefined online cathode surface conditions, which may cause difference of work functions, field enhancement factor and surface roughness, and lead to thermal emittance divergence. In this paper, we report an experiment of characterizing online photocathode work function, field enhancement factor and surface roughness effect by measuring electric field dependence of photoemission quantum efficiency (QE) and thermal emittance in a Cu-cathode RF gun. Preliminary experiment results reveal huge thermal emittance contributed by surface roughness for the first time, and are in reasonable consistency with theoretical model prediction*. Ivan V. Bazarov et al., Phys. Rev. Lett. 10², 104801(2009) D.H. Dowell et al, Nucl. Instrum. Methods Phys. Res., Sect. A 622, 685 (2010). *D. Xinag et al, PAC’07, 10⁴⁹ (2007)

THPC121	Design and Cold Tests of a Prototype photocathode RF Gun for Shanghai SXFEL Facility	cathode, coupling, vacuum, emittance	3170
	H.J. Qian, H. Chen, Y.-C. Du, W.-H. Huang, C. Li, X.H. Liu, X. H. Lu, C.-X. Tang TUB, Beijing, People's Republic of China
	A soft X-ray (~9 nm) FEL (SXFEL) facility is going to be constructed in Shanghai, China, which requires high charge (>500 pC) electron beam with low transverse emittance (<1.5 mm-mrad) at photoinjector exit. One of the keys to achieve a low emittance with high charge is high gradient on the photocathode, so an S-band photocathode RF gun modified from BNL type gun is designed, which aims running 100 MV/m peak gradient at 10 Hz. By changing the cathode seal technique, removing the insertion RF tuner, and reducing the peak surface field, RF breakdown possibility is reduced. Besides, RF pulse width is also considered to be reduced to lower the RF breakdown possibility. Since zero mode and multipole field degrades the beam emittance, they are also suppressed in the new gun design. Design details and cold testing results are presented in this paper.

THPC123	Injector Layout and Beam Injection into Solaris	injection, linac, storage-ring, klystron	3173
	A.I. Wawrzyniak, C.J. Bocchetta Solaris, Krakow, Poland S.C. Leemann, S. Thorin MAX-lab, Lund, Sweden
	Funding: European Regional Development Fund within the frame of the Innovative Economy Operational Program: POIG.02.01.00-12-213/09 The Solaris synchrotron radiation storage ring to be built in Krakow, Poland is based on the MAX IV 1.5 GeV design. The injector will be a linear accelerator and its components identical to those for the MAX IV project, however, injection is not at full energy and the injector layout is different. The linac and transfer line layout, optics and injection scheme into the storage ring is presented and an analysis of accumulation before energy ramping is discussed.

THPC126	RF Gun Studies for the SwissFEL Injector	laser, emittance, solenoid, cathode	3179
	A. Falone, A. Adelmann, J.-Y. Raguin, L. Stingelin PSI, Villigen, Switzerland
	The Paul Scherrer Institut (PSI) is planning a compact, high brightness hard X-ray free electron laser. For this purpose a new 2.5 cell RF gun has been designed at PSI and is now in production. The RF gun plays an important role in preserving beam emittance, and hence delivers a high quality beam to the injector. We present beam dynamic parametric studies on the effect of cell length variations using two different codes OPAL and ASTRA. Furthermore laser and other RF parameters are scanned to find the best working point of the injector. The simulations are showing that the SwissFEL injector requirements (ϵ<0.4 mm mrad normalized projected emittance) are achievable with a smooth dependence on the geometrical variation of the gun cell lengths confirming a robust RF design of the gun is possible.

THPC127	Recent Results from a Combined Diode-RF Gun	emittance, cathode, electron, laser	3182
	C.H. Gough, S. Ivkovic, M. Paraliev PSI, Villigen, Switzerland
	For the SwissFEL project, a novel combined diode-RF electron gun was tested at PSI, as a possible source for XFELs. Typically, electron bunches of 1-100 pC charge , 1-5 MeV energy and 2-0.3 um-rad emittance were produced and measured. The advantage of the combined gun is that diode geometry and emission surface can be changed readily. An optimum polishing procedure for magnesium photo cathodes was found, and various surfaces such as FEA's were tested in high gradient. Emittance changes for emission surface depression within the cathode, as well as laser spot size and anode hole size, were measured. Finally, the excellent performance of the gun permitted detailed study of the pepperpot EMSY (Emittance Measurement System) behaviour with changing beam parameters.

THPC129	Gallium Arsenide Photocathode Research at Daresbury Laboratory	cathode, electron, laser, vacuum	3185
	L.B. Jones, B.D. Fell, J.W. McKenzie, K.J. Middleman, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R.J. Cash STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom N. Chanlek UMAN, Manchester, United Kingdom
	Significant effort has been expended over several years by ASTeC to optimise procedures for preparing GaAs photocathodes for use as high-current electron sources in accelerators. Having established robust chemical and thermal cleaning processes, and carried out lifetime studies on activated photocathodes by deliberately poisoning them, we present data showing high levels of Quantum Efficiency (QE) for heterostructure photocathodes when activated with Cs-O and Cs-NF3 procedures. We will show that the use of NF3 delivers higher QE, and conveys greater control in that the final QE level can be set more accurately using NF3 than with O. We plan to carry out further experiments on GaAs photocathodes to measure the 2-D energy distribution of the emitted electrons at both room and cryogenic temperatures. We are constructing a retarding-field electron calorimeter which will measure current as a function of retarding voltage. From this, we will establish the 2-D energy distribution in the electron beam, permitting a comparison of these figures for photocathodes at room and low temperatures. The goal is to create an ultra-bright electron source for use with particle accelerators. Proc IPAC ’10, TUPEC018, 1752-1754

THPC130	A 160 keV Photocathode Electron Gun Test Tacility	electron, diagnostics, laser, cathode	3188
	L.B. Jones, B.D. Fell, C. Hill, J.W. McKenzie, K.J. Middleman, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R.J. Cash STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	The ALICE ERL* at Daresbury Laboratory is a prototype 4th generation free-electron laser light source operating at IR wavelengths. An upgrade to the DC photoinjector gun has been designed and partially-constructed, but due to installation postponement, the system will be used for photocathode physics experiments. The re-designed gun will operate at 160 keV. The gun and photocathode preparation facility (PPF) will be assembled with a diagnostic beamline, supporting research towards high-brightness electron beams based on GaAs technology. Combining an external PPF with a load-lock facility allows the rapid exchange of photocathodes, thus permitting the testing of various different photocathode heterostructures, and fine control of the cleaning and activation processes applied during preparation. The diagnostics beamline will include a transverse kicker to study bunch length, and a dipole magnet for beam energy and energy spread measurements. Various horizontal and vertical slit and screen assemblies allow for emittance measurement, so providing full 6-D characterisation of the electron bunches generated. A current transformer and Faraday cups support bunch charge measurements. * Accelerators and Lasers In Combined Experiments electron Energy-Recovery Linac

THPC131	MAX-IV Linac Injector Simulations including Tolerance and Jitter Analysis	linac, emittance, simulation, laser	3191
	J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S. Thorin, S. Werin MAX-lab, Lund, Sweden
	The MAX-IV linac will be used both for injection and top up into two storage rings, and as a high brightness injector for a Short Pulse Facility (SPF) and an FEL (in phase 2). 100 pC bunches of electrons are created from a 1.5 cell S-band photocathode gun and subsequently accelerated up to 3 GeV by S-band linac sections. Simulations of the dynamics of the space-charge dominated beam up to 100 MeV are presented including an analysis of the tolerances required and the effects of jitter sources.

THPC132	A Velocity Bunching Scheme for Creating Sub-picosecond Electron Bunches from an RF Photocathode Gun	cavity, emittance, solenoid, laser	3194
	J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Sub-picosecond electron bunches are in demand for various applications including Free Electron Lasers and electron diffraction experiments. Typically, for Free Electron Lasers, a multiple picosecond scale bunch is produced from a photoinjector with compression achieved via one or more magnetic chicanes by providing an appropriate energy chirp to the bunch in the preceding linac sections. This approach is complex, requiring many components, often including a higher harmonic linac section to linearise the longitudinal phase-space, and careful tuning in order to minimise emittance blow-up due to coherent synchrotron radiation. We present a scheme to deliver sub-picosecond electron bunches, based on a normal conducting RF gun and two short linac sections, one for providing velocity bunching and the second to capture the compressed bunch and accelerate to tens of MeV where the beam properties are then essentially frozen.

THPC134	LCLS RF Gun Copper Cathode Performance	cathode, laser, emittance, electron	3200
	A. Brachmann, F.-J. Decker, P. Emma, R.H. Iverson, P. Stefan, J.L. Turner, F. Zhou SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC03-76SF00515 We report on the performance and the operational experience of the LCLS RF gun copper photocathodes used during the LCLS run I, II, III and IV. We discuss the problems of cathode surface contamination and our experience with methods to remove such contamination. Techniques to obtain high quantum efficiency (QE) while preserving the low emittance quality are discussed. Furthermore, we will present the current status of the installed cathode, its quantum efficiency and the typical injector emittances of the extracted beam.

THPC135	Optimal Parameters of the Photocathode Gun Space Charge to Improve Beam Quality	laser, cathode, electron, space-charge	3203
	M.G. Fedurin, C. Swinson, V. Yakimenko BNL, Upton, Long Island, New York, USA
	Accelerator Test Facility at Brookhaven National Laboratory operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space charge affecting on the own bunch length and transverse profile. Optimal beam loading parameters of the space charge in the photocathode RF gun could be found and used to improve bunch length and emittance. Simple model and experimental results on the Accelerator Test Facility at Brookhaven national Laboratory will be described

THPC142	Burst Pulse Superimposed Electron Beam Acceleration in LEBRA FEL Linac	electron, FEL, acceleration, linac	3218
	T. Tanaka, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, N. Sato LEBRA, Funabashi, Japan S. Aizawa, Y. Arisumi, K. Shinohara Nihon Koshuha Co. Ltd, Yokohama, Japan I. Sato Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi, Japan
	The electron beam for free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University had been extracted from a conventional DC triode electron gun system. In conjunction with the renewal of the gun high voltage terminal a Kentech high-speed grid pulser was installed in addition to the conventional grid pulser. The 89.25MHz sine wave frequency-divided from the 2856MHz accelerating RF has been applied to the high-speed grid pulser, generating 64 or 128 frequency-divided grid pulses synchronous with the round-trip time in the FEL optical resonator. The high-speed grid pulses have been applied to the EIMAC Y646B cathode simultaneously with the conventional macropulse through the pulse coupling strip-line circuit; the resultant beam has been the short pulse beam superimposed on the macropulse beam. By reducing the macropulse voltage, only the train of the burst beam with 0.6ns width has been extracted. The peak burst beam current roughly 6 times higher than the conventional macropulse beam has been obtained with the Farady cup at the end of the FEL beamline. The FEL lasing experiment with the burst beam is underway.

THPO008	Klystron and Modulator System for the PEFP 20 MeV Proton Linac	klystron, linac, rfq, proton	3352
	D.I. Kim, Y.-S. Cho, H.S. Kim, H.-J. Kwon KAERI, Daejon, Republic of Korea
	Funding: This work is supported by the Ministry of Science and Technology of the Korean government. A modulator developed for the 100 MeV proton linear accelerator is operating in the 20 MeV proton linac. The voltage and current of the modulator are -105 kV, 50 A with 1.5 ms pulse width, 60 Hz repetition rate. The modulator drives two klystrons simultaneously, one for the RFQ, the other for the DTL. The typical operation parameters of the modulator are 85 kV of the peak voltage, 34 A of the peak current, 1 ms of the pulse width, 4 Hz of the pulse repetition. The specifications of the klystron are 350 MHz of the frequency, 1.1 MW of the maximum average RF power, less than 95 kV of the beam voltage, triode type electron gun with mod-anode. The mod-anode voltage was supplied by the voltage dividing resistors which were located inside the klystron oil tank. In this paper, the operation performance of the klystron and modulator system for the PEFP 20 MeV proton linac is presented.

THPS026	Surface Plasma H⁻ Ion Source with Saddle RF Antenna Plasma Generator	plasma, ion, extraction, ion-source	3475
	V.G. Dudnikov, R.P. Johnson Muons, Inc, Batavia, USA S.N. Murray, T.R. Pennisi, M. Santana, M.P. Stockli, R.F. Welton ORNL, Oak Ridge, Tennessee, USA
	Funding: *Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0002690. In this project is developed a prototype RF H⁻ surface plasma source (SPS) with saddle (SA) RF antenna which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with a small AlN test chamber and different antennas and magnetic field configurations were tested in the SNS ion source Test Stand. A prototype SA SPS was installed in the Test Stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency of 1.6 mA/kW. Control experiments with H⁻ beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma source (TPS) has been designed. A Saddle antenna SPS with water cooling is being fabricated for high duty factor testing.

THPS064	Application of X-band 3.95 MeV Linac X-ray Source for On-site Bridge Inspection	linac, site, target, electron	3571
	H.F. Jin, K. Demachi, K. Dobashi, T. Fujiwara, M. Uesaka, H. Zhu The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
	We developed an X-ray non-destructive (NDT) system for on-site bridge inspection. A portable X-band (9.3-12 GHz) 3.95MeV linear accelerator (linac) has been developed for this system. The system consists of X-ray of 62kg without the target collimeter of 80kg, the RF power source of 62kg and other utility box of 116kg. For the onsite investigation, a flexible waveguide is used for this linac. And the linac is a point X-ray source. For X-ray detection, we chose 8-inch square size scintillation type flat panel detector. The spatial resolution of the detector is as high as 0.2mm, which is manufactured by Perkin Elmer Co. Cd2O2S:Tb is used for the scintillator crystal. The capable radiation energy range is 40keV to 15MeV. In order to realize quick inspection for a bridge, remote control robot which handles and compact X-ray source and detector are desired. Therefore, we developed 3D location system for this robot. The locating system is realized with image processing with its camera. For the operation, stereoscopic radiographic image is taken and analyzed, and computed tomography (CT) image analysis is taken for detailed inspection. Non-destructive test (NDT) , X-ray Source, X-band, Linac, Detector, Computed Tomography (CT).

THPS090	Development of the Pulse Radiolysis System with a Supercontinuum Radiation using Photonic Crystal Fiber	laser, radiation, electron, optics	3645
	K.B. Ogata, R. Betto, Y. Hosaka, Y. Kawauchi, K. Sakaue, T. Suzuki, M. Washio RISE, Tokyo, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 In usage of radiation, it is important to study the process of chemical effects of ionizing radiation in a material. Pulse radiolysis is a method to trace these rapid initial chemical reactions by ionizing radiation. As a pump beam, we are using 5MeV electron beam produced from the S-band photo cathode RF-Gun. In nanosecond timescale pulse radiolysis, it is required the stable probe light of a broad spectrum. And especially in picosecond timescale pulse radiolysis, probe light should have short pulse width to use stroboscopic method. Therefore, in order to develop a wide range of timescale experimental system, we have been developing a Supercontinuum (SC) light as a probe light, which is generated by nonlinear optical process of short pulse IR laser in photonic crystal fiber (PCF). As a result, the SC light spectrum is broad enough to use as a probe light. Then we tried to measure the absorption spectrum of hydrated electron by SC light, we successfully observed good signal-noise ratio data both nanosecond and picosecond experiment with unified pulse　radiolysis system. In this conference, we will report details of these results and future prospects.

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MOPC007

Cold Photocathode RF Gun

cavity, vacuum, cathode, cryogenics

77

V. Vogel, K. Flöttmann, S. Schreiber
DESY, Hamburg, Germany

Heating and thermal expansion in the normal conductivity RF-photo electron gun, are the main limitations to achieve high accelerating gradient and consequently a low emittance beam. Some pure materials show a significant increase in thermal conductivity with a small coefficient of temperature expansion at temperatures around 20 degrees Kelvin. Possible materials are Molybdenum, Iridium or Tungsten. However, machining of these materials is very difficult. Therefore we propose a simplified shape for an L-band RF gun. We expect to achieve a significant increase in gradient for similar RF powers as used in the present DESY RF-gun. On the other hand, it would also be possible to increase the duty cycle keeping a moderate gradient. In this report we discuss one possible design of an RF-gun using hard metals and present simulations on thermal properties.

MOPC014

RF Processing of L-band RF Gun for KEK-STF

cavity, cathode, laser, solenoid

92

M. Kuriki, H. Iijima, Y.M. Masumoto
HU/AdSM, Higashi-Hiroshima, Japan
H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe
KEK, Ibaraki, Japan
G. Isoyama, R. Kato
ISIR, Osaka, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
Y. Takahashi
Sokendai, Ibaraki, Japan

Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie.
KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented.

MOPC020

Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac

cavity, booster, linac, electron

110

T. Aoki, K. Sakaue, M. Washio
RISE, Tokyo, Japan
A. Deshpande
SAMEER, Mumbai, India
M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by JST Quantum Beam Program
We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference.

MOPC022

Development of a Compact C-band Photocathode RF Gun

electron, cathode, injection, emittance

116

X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang
TUB, Beijing, People's Republic of China

Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program).
A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation.

MOPC029

Development of Injector for Compact FEL Tera-hertz Source in CAEP

electron, FEL, booster, simulation

131

W. Bai, M. Li, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

This paper introducs the development of a injector for compact FEL tera-hertz source at Institute of Applied Electronics in China Academy of Engineering Physics (IAE/CAEP). The injector consist of a main accelerator for energy booster section and a multicavity thermionic-cathode rf gun with low back bombardment, with total length no more than one meter. Numerical simulation result shows that the back bombardment power is less for the thermionic-cathode rf gun of the injector and the main accelerator has a good performance, which can provide high quality electron beam with emittance about 10 pi mm mrad, energy about 7 MeV and energy spread about 1%. At present, the preliminary hot test experiment on the injector has been done. The test results indicate that the mainly tested parameters agree well with the theoretical design ones. The process of the preliminary hot test experiment on the injector is present in this paper.

MOPC033

The Status of a 1.6-cell Photocathode RF Gun at PAL

cavity, klystron, emittance, cathode

142

M.S. Chae, J.H. Hong, I.S. Ko, Y.W. Parc
POSTECH, Pohang, Kyungbuk, Republic of Korea
S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

The RF power conditioning of the photocathode RF gun with four holes at the side of the full cell named as 'Pohang gun' is in progress. The first goal of the conditioning is the operation of the gun with RF pulse width of 1.5 μm, repetition rate of 30 Hz, field gradient at the cathode of 130 MV/m. We operated the RF gun successfully with the conditions within last few months. It was first operational experience with such conditions in PAL. Now we have a plan to operate RF gun with higher repetition rate up to 60 Hz.

MOPC034

Design of a 0.6-cell Cell Photocathode RF Gun for FED

electron, simulation, cathode, solenoid

145

Y.W. Parc, M.S. Chae, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.

MOPC081

Pulsed Mode Operation and Longitudinal Parameter Measurement of the Rossendorf SRF Gun

cavity, SRF, cathode, laser

262

J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P. Michel, P. Murcek, Ch. Schneider, R. Schurig, R. Xiang
HZDR, Dresden, Germany
T. Kamps, J. Rudolph, M. Schenk
HZB, Berlin, Germany
I. Will
MBI, Berlin, Germany

Funding: The European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579) the German Federal Ministry of Education and Research grant 05 ES4BR1/8.
The Rossendorf SRF gun with a 3 1/2 cell cavity has been operated since 2007. It has produced CW beam with the electron energy of 3 MeV and the average current up to 16 μA. The electron beam of the gun has successfully injected the ELBE superconducting linac since 2010. The Nb cavity has shown constant quality during the operation and for the Cs2Te photocathode life time of months could be obtained. Recently the gun started to run in the pulsed mode with higher gradient. The longitudinal parameters have been measured in this mode. The dark current arose from the high gradient is studied. The main field emission source has been found to be the half cell. Meanwhile, two modified 3+1/2 cell niobium cavities have been fabricated and tested in Jlab. In this paper the new status of the SRF gun will be presented, and the latest results of the beam experiments will be discussed.

MOPC150

High Charge PHIN Photo Injector at CERN with Fast Phase Switching within the Bunch Train for Beam Combination

laser, cathode, vacuum, bunching

430

M. Divall Csatari, A. Andersson, B. Bolzon, E. Bravin, E. Chevallay, A.E. Dabrowski, S. Döbert, V. Fedosseev, C. Heßler, T. Lefèvre, S. Livesley, R. Losito, O. Mete, M. Olvegård, M. Petrarca, A. Rabiller
CERN, Geneva, Switzerland
A. Drozdy
BUTE, Budapest, Hungary
D. Egger
EPFL, Lausanne, Switzerland

The high charge PHIN photo-injector was developed within the frame of the European CARE program to provide an alternative to the drive beam thermionic gun in CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 sub-trains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the scheme. Stability measurements are presented for the phase-coded system. The paper also discusses the latest 8nC charge production and cathode life-time studies on Cs2Te.

MOPC154

RF Photo Gun Stability Measurement at PITZ

laser, feedback, cavity, electron

442

I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Khojoyan
YerPhI, Yerevan, Armenia
D. Richter
HZB, Berlin, Germany
A. Shapovalov
NRNU MEPHI, Moscow, Russia
I.H. Templin, I. Will
MBI, Berlin, Germany

The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPC166

Low RF Control Feedback and IQ Vector Modulator Compensation Functions

controls, linac, feedback, coupling

472

M.G. Fedurin, R. Malone, V. Yakimenko
BNL, Upton, Long Island, New York, USA

IQ vector modulator is key element of the gun and linac RF control circuits at Accelerator Test Facility at Brookhaven National Laboratory. IQ modulator calibration procedure was developed to find proper compensation functions in the conversion algorithm to minimize phase-amplitude coupling and setting-reading errors: rms(A_set - A_read )= 0.03dB, rms(Phi_set - Phi_read) = 0.3 deg. Since stabilization of the RF phase and amplitude is become critical for many experiments the slow feedback was developed and applied as well to significantly compensate drifts in RF system.

MOPO018

Active Beam Current Stabilization in the Cornell ERL Prototype Injector

laser, feedback, cavity, cathode

523

F. Löhl, P. Szypryt
CLASSE, Ithaca, New York, USA

In order to operate the Cornell ERL prototype injector at beam currents beyond 10 mA, the beam current has to be highly stable. The reason is that fast beam current fluctuations generate transient effects in the DC gun voltage as well as in the fields of subsequent superconducting cavities, which can lead to excessive beam loss or to trips of subsystems. Therefore, a feedback scheme was developed which uses the signal of a beam current monitor as an input, and applies appropriate corrections to a Pockels cell installed within the laser path of the photo-injector laser. In this paper, high current results achieved with this feedback scheme are presented.

MOPO041

Preliminary Testing of TPS Timing System

controls, linac, booster, EPICS

574

C.Y. Wu, Y.-T. Chang, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, C.-Y. Liao
NSRRC, Hsinchu, Taiwan

The timing system of Taiwan Photon Source (TPS) provides synchronization for electron gun, modulators of linac, pulse magnet power supplies, booster power supply ramp, bucket addressing of storage ring, diagnostic equipments, beamline gating signal for top-up injection. The timing system utilizes a central event generator to generate events and distribute them over optic fiber network, and decodes them at the event receivers. The system supports uplink functionality which will be used for the fast interlock system to distribute signals like beam dump and post-mortem trigger. The timing system has now been in operation for Linac of TPS. This paper presents prototype for the timing system of TPS.

MOPO043

Applications of Lasers to Accelerator Physics at SSRL

laser, cathode, photon, electron

580

D.L. Robinson
Cal Poly, San Luis Obispo, California, USA
W.J. Corbett
SLAC, Menlo Park, California, USA

Recent advances in accelerator physics and SR research have generated the need for high-power lasers in the SPEAR3 accelerator complex. On the injector side, two lasers are being used to test different photocathode materials and to provide photo-assisted emission from the standard dispenser cathode RF gun. For the storage ring, both a TiSa oscillator and a fiber laser locked to the RF master oscillator have been used to characterize short-pulse electron bunches in cross-correlation experiments. These lasers are also used in SR experiments for pump-probe characterization of materials. In this paper we review the laser-based systems, preliminary results and outlook for the future.

MOPS024

Bunch Dynamics through Accelerator Column

space-charge, TRIUMF, electron, cathode

649

R.A. Baartman
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: TRIUMF research is supported by the National Research Council of Canada.
The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived.

MOPS033

Beam Dynamics Studies on the 100 MeV/100 kW Electron Linear Accelerator for NSC KIPT Neutron Source

linac, electron, dipole, simulation

673

S. Pei, Y.L. Chi, M. Hou, W.B. Liu, G. Pei, S.H. Wang, Z.S. Zhou
IHEP Beijing, Beijing, People's Republic of China
N. Aizatsky, I.M. Karnaukhov, V.A. Kushnir, V. Mitrochenco, A.Y. Zelinsky
NSC/KIPT, Kharkov, Ukraine

We designed one 100MeV/100kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the base of subcritical assembly. Beam dynamics studies has been conducted to reach the design requirement (E=100MeV, P=100kW, dE/E<1% for 99% particles). In this paper, we will present the progress of the design and dynamics simulation results. For high intensity and long beam pulse linear accelerators, BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced at the downstream of the 1st accelerating section; the unwanted particles will be collimated there.

MOPS035

Energy Spreads by Transient Beam Loading Effect in Pulsed RF Linac

electron, linac, bunching, beam-loading

679

S.H. Kim, M.-H. Cho, G. Ha, H.R. Yang
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Namkung, S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
J.-S. Oh
NFRI, Daejon, Republic of Korea

Funding: Work partly supported by KAPRA and POSTECH Physics BK21 Program
RF linacs for high power beams are operated in the fully beam-loaded condition for the power efficiency. In this condition, temporal energy spreads are induced by the transient beam loading effect. Irradiation sources require the beam energy of less than 10 MeV to prevent undesirable neutron production. In order to maximize the beam power and maintain the beam energy in a safe value, we need to suppress the temporal energy spreads. In an L-band traveling-wave linac for irradiation sources, the high energy electrons are suppressed by the beam current modulation with the RF power modulation. As a result, the average beam energy and the corresponding beam power are improved by nearly 60% compared to the case without any modulations.

MOPS042

One-Dimensional Adiabatic Child-Langmuir Flow

simulation, electron, emittance, plasma

694

C. Chen
MIT, Cambridge, Massachusetts, USA
R. Pakter, F.B. Rizzato
IF-UFRGS, Porto Alegre, Brazil

Funding: Research supported in part by US Department of Energy, Grant No. DE-FG02-95ER40919, CNPq, FAPERGS, INCTFCx of Brazil, and US Air Force Office of Scientific Research, Grant No. FA9550-09-1-0283.
A theory is presented that describes steady-state one-dimensional Child-Langmuir flow at a self-consistent finite temperature distribution. In particular, warm-fluid equations and adiabatic equation of state are used to derive the self-consistent Poisson equation. The profiles of the charged-particle density, the velocity, the electrostatic potential, the pressure and the temperature are computed. Results are compared with self-consistent simulations.

TUODB02

Extreme High Vacuum System of High Brightness Electron Source for ERL

vacuum, electron, ion, cathode

979

M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama
KEK, Ibaraki, Japan
H. Akimichi, H. Yoshida
AIST, Tsukuba, Japan
H. Kurisu
Yamaguchi University, Ube-Shi, Japan

A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10^-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.

Slides TUODB02 [1.606 MB]

TUPC031

Advanced Research Electron Accelerator Laboratory Based on Photocathode RF Gun

electron, emittance, laser, controls

1066

B. Grigoryan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, K. Manukyan, I.N. Margaryan, V. Sahakyan, A. Sargsyan, A. Tarloyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan
CANDLE, Yerevan, Armenia
T. Vardanyan
YSU, Yerevan, Armenia

The low energy sub-picosecond duration electron bunches with extremely small beam emittance have wide applications in advanced research of new accelerator concepts, radiation physics, time-resolved pulse radiolysis and electron diffraction. The conceptual design and experimental program of the Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun are presented. The AREAL design implies single and multibunch operation modes with variable beam energy of 5-20 MeV and 10-100 pC bunch charge. The design is based on 3 GHz 1.6 cells RF gun followed by S-Band accelerating linac.

TUPC032

Beam Phase-Space Study for AREAL RF Photogun Linac

emittance, space-charge, electron, linac

1069

B. Grigoryan, G.A. Amatuni, I.N. Margaryan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan
CANDLE, Yerevan, Armenia

In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed.

TUPC033

Verifying the Single Bunch Capability of the New Injector at ELSA*

linac, electron, single-bunch, pick-up

1072

S. Mey, O. Boldt, W. Hillert, N. Hofmann, F. Klarner, D. Krönung, A. Roth, M. Schedler
ELSA, Bonn, Germany
S. Aderhold
DESY, Hamburg, Germany

Funding: Funded by the DFG within the SFB / TR 16 and the Helmholtz Alliance HA 10¹ "Physics at the Terascale".
In order to enhance the operating capabilities of the Bonn University Accelerator Facility, ELSA, a new injector is currently under commissioning. One of its main purpose is to allow a single pulse mode. The injector produces a single electron bunch with 1.5 A pulse current. Design and optimization of the injector have been performed with EGUN, PARMELA and numerical simulations based on the numerical integration of the paraxial equation. A 1 ns long pulse is produced by a thermionic electron source with 90 kV anode - cathode voltage, then compressed and pre-accelerated by a subsequent 500 MHz RF cavity and a four-cell travelling wave buncher. Finally, the bunch will be accelerated to 20 MeV by the main LINAC section. Measurements have been conducted concerning the resulting pulse length and pulse charge to confirm the predictions made by simulations and to investigate the efficiency of the injector system.

TUPC034

Design Studies on 100 MeV/100 kW Electron Linac for NSC KIPT Neutron Source on the Base of Subcritical Assembly Driven by Linac

linac, electron, emittance, target

1075

Y.L. Chi, J. Cao, X.W. Dai, C.D. Deng, M. Hou, X.C. Kong, R.L. Liu, W.B. Liu, C. Ma, G. Pei, H. Song, S.H. Wang, G. Xu, J. Zhao, Z.S. Zhou
IHEP Beijing, Beijing, People's Republic of China
M.I. Ayzatskiy, I.M. Karnaukhov, V.A. Kushnir, V.V. Mytrochenko, A.Y. Zelinsky
NSC/KIPT, Kharkov, Ukraine
S. Pei
IHEP Beijng, Beijing, People's Republic of China

In NSC KIPT, Kharkov, Ukraine, a neutron source on the base of subcritical assembly driven by 100 MeV/100 kW electron linear accelerator is under design and development. To provide neutron flux value of about 1013 neutron/s the electron linear accelerator with 100 MeV beam and average beam power of 100 kW will be used. Construction and manufacture of the linear accelerator of such high beam intensity with low emittance and beam losses is a challenging task. In the report the project of the electron linear accelerator of the required beam energy and intensity is described. The accelerator structure and main technical solutions are presented. To overcome the BBU effect of this high average beam current, several effective measures are adopt, such as using constant gradient structure to spread the HOMs frequencies different cells, larger inner radius and shorter section length make the higher group velocity and optimize the structure geometry to keep the shunt impedance as good as possible. After the beam bunching system, a chicane is followed to chopper the beam to avoid the beam lost in the higher energy part.

TUPC036

S-band ps Pulse Photoinjector for THz Radiation Source

coupling, electromagnetic-fields, electron, acceleration

1078

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia

S-band photoinjectors with ps pulse are becoming promising as e-guns for high-intensity sub-mm wavelength pulse source. Development of accelerating system for photoinjector with ps bunch is reported. The main aim is to develop a model of accelerating structure that provide top accelerating fields in respect to high electric strength and low RF power uses. The accelerating structures consisting of 1.6 cell of disk-loaded waveguide (DLW), 3 cells and 2 half-cells of DLW, 7 cels and 2 half-cells of DLW and accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW are studying. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics, electric field distribution for all models were acquired. Accelerating structure consisting of 1.6 cells will operate in pi mode of standing wave, all other structures operate in pi/2 mode traveling wave. Accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW has most suitable electrodynamics characteristics and field distribution for sub-mm pulse source according to simulation results.

TUPC038

A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam

linac, electron, bunching, klystron

1081

J.-Y. Hwang, J.H. Chen, W.K. Lau, A.P. Lee, T.H. Wu
NSRRC, Hsinchu, Taiwan
N.Y. Huang
NTHU, Hsinchu, Taiwan

A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers.

TUPC043

SEM Field Emission Probe Surface Science Study

cathode, vacuum, electron, laser

1096

L. Laurent, R.E. Kirby, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is supported by Department of Energy Contract No. DE-AC03- 76SF00515.
After decades of rf breakdown research, a common acknowledgement among researchers is that a better understanding of what is happening on the surface at a microscopic level needs to be the impetus for future studies. We are designing and fabricating an electron microscope-based high-electric-field current-emission probe to study topographic material features which will enable us to better understand and further advance the technology of high-brightness photocathode rf guns and enable the study of high gradient phenomena. The SEM field emission probe will provide an important diagnostic tool allowing cathodes and high gradient surfaces to be evaluated before and after testing and will help identify and understand the relationship between high field emission locations and vacuum breakdown, non-uniform emission, surface cracking, hotspots, etc. The preliminary results and 2012 goals will be presented.

TUPC057

Femtosecond Photoinjector and Relativistic Electron Microscopy

electron, emittance, laser, cathode

1126

J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida
ISIR, Osaka, Japan
J. Urakawa
KEK, Ibaraki, Japan

A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10^-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported.

TUPC058

Design of a Chirping Cell Attached RF Gun for Ultrashort Electron Generation

electron, cavity, laser, radiation

1129

K. Sakaue, K. Tamai, M. Washio
RISE, Tokyo, Japan
J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690
We have been developing an S-band photocathode rf electron gun at Waseda university. Our rf-gun cavity was firstly designed by BNL and then, modified by our group. In this paper, we will introduce a newly designed rf-gun cavity with energy chirping cell. To generate an energy chirped electron bunch, we attached extra-cell for 1.6cell rf-gun cavity. Cavity design was done by Superfish and particle tracing by PARMELA. By optimizing the chirping cell, we observed linear chirped electron bunch. The front electron have lower energy than rear. Then transporting about 2m, the bunch can be compressed down to 200fsec electron bunch with the charge of 160pC. This ultrashort bunch will be able to use for generating CSR THz radiation, pumping some material to be studied by pulse radiolysis method, and so on. In this conference, the design of chirping cell attached rf-gun, the results of tracing simulation and plan of manufacturing will be presented.

TUPC059

Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun

laser, beam-loading, electron, cavity

1132

Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto
RISE, Tokyo, Japan
H. Hayano, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program.
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans.

TUPC060

A Multi-mode RF Photocathode Gun

cathode, cavity, injection, electron

1135

S.V. Kuzikov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
J.L. Hirshfield
Yale University, Physics Department, New Haven, CT, USA
Y. Jiang
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
V. Vogel
DESY, Hamburg, Germany

A photocathode injection gun based on standard emittance compensating techniques and driven by several (N ≥ 2) harmonically related RF sources is considered. Multi-harmonic excitation can provide high-quality flatness in time of the field at the cathode when a bunch is being injected. This allows one to obtain ≥1 nC, 20-40 ps electron bunches with preservation of low emittance. Another advantage is a reduction of Ohmic losses and the required input RF power (for a given cathode field). Preliminary calculations show that input power in a three-mode cavity (0.65 GHz, 1.3 GHz, 2.6 GHz) is nearly half the power needed to feed a single mode with the same cathode field. A further appealing property is the predicted increase of breakdown threshold due to a reduction of surface exposure time to high fields in a symmetric cavity, and due to the so-called anode-cathode effect in a longitudinally asymmetric cavity. These properties may help one to reach bunch energies as high as 3-5 MeV after the first half cell.

TUPC094

Development of High-speed Differential Current-transformer Monitor

electron, bunching, monitoring, status

1227

S. Matsubara, H. Ego, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
A. Higashiya, S.I. Inoue, Y. Otake
RIKEN/SPring-8, Hyogo, Japan
H. Maesaka
RIKEN Spring-8 Harima, Hyogo, Japan

The XFEL, which was named SACLA, was constructed in the SPring-8 site. In the SACLA, the bunch length of an electron beam is compressed from 1 ns to 30 fs, and the beam charge is decreased to obtain a genuine electron beam from 1nC to 0.3 nC for lasing. A new current-transformer (CT) monitor, which should measure the charge of the electron beam and make bunch length observation in velocity bunching process, was developed with two advantageous properties. One is differential output signal which suppresses common-mode noise from the thyratron of a klystron modulator by a factor of ten. Another property is high-speed signal output which provides a possibility to measure the bunch length and the time-of-flight (TOF) at the injector part of the SACLA. The output signal has 200 ps rise-time and a pulse width of 400 ps (FWHM) for an impulse beam. We successfully observed the bunch length between 1 ns and 400 ps around a 238 MHz buncher cavity. Moreover, we measured the TOF between two CTs with a few picoseconds resolution for a low-energy beam around 1 MeV. Thus, the new CT performance was confirmed to be sufficient for the SACLA.

TUPC101

Generation of Multimode Quasi-monochromatic Terahertz

electron, linac, radiation, cathode

1248

K. Kan, T. Kondoh, K. Norizawa, A. Ogata, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

Generation of quasi-monochromatic terahertz (THz) using multimode Coherent Cherenkov Radiation (CCR) on the order of 0.1 THz was investigated. CCR was generated by a hollow dielectric tube covered by a metal and an electron bunch from a photocathode radio-frequency (RF) gun linac. The intensity and frequency of CCR were measured directly by a Michelson interferometer and a bolometer. The frequency spectra measured by the interferometer indicated sharp peaks close to frequencies of 0.09 THz and 0.14 THz, which corresponded to TM03 and TM04 modes, respectively, according to theoretical calculation for a tube with inner and outer radii of 5 mm and 7 mm. The maximum gain of TM03 mode due to the tube length was obtained as 1.5 dB/cm. The other higher modes, e. g. 0.36 THz (TM09) and 0.40 THz (TM010), were also observed from a 150 mm long tube at a bunch charge of 15 pC, which decreased space charge effect and the bunch length. Finally, a new method for bunch diagnostic based on multimode CCR was proposed. The bunch length was estimated to be 0.45 ps at a bunch charge of 5 pC with the intensity ratio of TM03 to TM09 mode.

TUPC102

Measurement of Beam Loss Tracks by Scintillating Fibers at J-PARC Linac

beam-losses, linac, background, simulation

1251

H. Sako, T. Maruta, A. Miura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

Highest beam loss in the J-PARC linac has been observed that the ACS (Annular-Coupled Structure linac) section. Since the observed beam loss is proportional to the residual gas pressure, the source of the beam loss is considered as H0 produced in an interaction of H⁻ beams with remnant gas. If this assumption is valid, H0 hits the beam duct and changes into H⁺ and escapes from the beam duct. We constructed scintillation fiber hodoscopes to detect H⁺s and eventually identify the particle species as H⁺. The hodoscopes are made of 4 planes of hodoscopes which consists of 16 scintillation fibers of 64mm long and with 4mmx4mm cross section. We installed the hodoscopes at the upstream part of the ACS section and measured beam loss. The results are shown in this paper.

TUPC111

Design of Cavity Beam Monitor at HLS

cavity, quadrupole, emittance, dipole

1278

Q. Luo, Q.K. Jia, B.G. Sun, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by the Natural Science Foundation of China, National “985 Project”, China Postdoctoral Science Foundation and “the Fundamental Research Funds for the Central Universities”
X-FEL requires precious control of beam position and transverse emittance. Non-destructive on-line beam diagnostic methods are required. During the upgrading of HLS a high brightness injector based on photocathode RF electron gun, which can also be used to study FEL, is installed. The cavity beam monitor system designed for the HLS photocathode RF electron gun consists of a cavity beam position monitor and a beam quadrupole moment monitor system. The cavity beam position monitor uses a re-entrant position cavity tuned to TM110 mode as position cavity and cut-through waveguides to suppress the monopole signal. Cold test results showed that position resolution of prototype BPM is better than 3 μm. Beam quadrupole moment monitor system consists of a square pill-box quadrupole moment cavity, a cylindrical pill-box reference cavity, a waveguide coupling network and a superheterodyne receiver used as front-end signal processing system. The whole system works at 5.712 GHz. Strength of quadrupole magnets is adjust to construct a matrix which can be used to work out beam parameters.

TUPC178

Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun

laser, cathode, vacuum, high-voltage

1443

R.R. Mammei, M. Poelker, R. Suleiman
JLAB, Newport News, Virginia, USA
J.L. McCarter
UVa, Charlottesville, Virginia, USA
T. Rao, J. Smedley
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. DOE
Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10^-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam.

TUPO007

FLUTE, a Linac Based THz Source

radiation, linac, synchrotron, synchrotron-radiation

1458

S. Naknaimueang, M. Schwarz
Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
R. Abela, H.-H. Braun, R. Ganter, B. Patterson
PSI, Villigen, Switzerland
A.H. Albert, T. Baumbach, M. Hagelstein, N. Hiller, E. Huttel, V. Judin, B. Kehrer, R. Kubat, S. Marsching, W. Mexner, A.-S. Müller, M.J. Nasse, A. Plech, R. Rossmanith, M. Schuh
KIT, Karlsruhe, Germany
M.T. Schmelling
MPI-K, Heidelberg, Germany

We propose a versatile THz source named FLUTE (“Ferninfrarot Linac- Und Test-Experiment”) based on a 30 - 50 MeV S-band linac with bunch compressor, that shall not only provide high field THz pulses applications but shall also serve as a test facility to study important accelerator physics issues. This is also of importance in view of the planned utltra-broadband THz to mid infrared user facility TBONE. Special emphasis is put on studies of bunch compression and beam stability as a function of bunch charge (0.1-5 nC) and of different generation mechanisms of coherent radiation (CSR, CER, CTR). This paper describes the design and layout of the proposed FLUTE machine and presents results of beam dynamic calculations with the tracking programs ASTRA and CSRtrack.

TUPO024

Precision X-band Linac Technologies for Nuclear Photonics Gamma-ray Sources

electron, laser, photon, scattering

1491

F.V. Hartemann, F. Albert, S.G. Anderson, C.P.J. Barty, A.J. Bayramian, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, T.L. Houck, R.A. Marsh, M. J. Messerly, S.S.Q. Wu
LLNL, Livermore, California, USA
C. Adolphsen, A.E. Candel, T.S. Chu, M.V. Fazio, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
SLAC, Menlo Park, California, USA
D. Cutoiu
Horia Hulubei National Institute for Physics and Nuclear Engineering, Bucharest, Romania
D. Ighigeanu, M. Toma
INFLPR, Bucharest - Magurele, Romania
V.A. Semenov
UCB, Berkeley, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies.

TUPO026

Developments towards a Full Energy Recovery Linac

cavity, HOM, cathode, SRF

1494

P. vom Stein, J.H. Hottenbacher, A. Metz
RI Research Instruments GmbH, Bergisch Gladbach, Germany

Energy Recovery Linacs (ERLs) are high potential candidates for driving light sources based on laser Compton scattering with high brilliance photon beams and sub pico second time structure. We report on developments for an advanced ERL design, which allows the recovery of nearly full electron beam energy up to the limits set by the energy width of the beam. This “Full” Energy Recovery Linac (FERL) allows a substantial reduction of the complexity of the accelerator systems resulting into a very compact light source design suitable for industrial and medical applications.

TUPS011

Use of NEG Pumps to Ensure Long Term Performances of High Quantum Efficiency Photocathodes

ion, cathode, vacuum, photon

1539

L. Monaco, P.M. Michelato, D. Sertore
INFN/LASA, Segrate (MI), Italy
P. Manini, F. Siviero
SAES Getters S.p.A., Lainate, Italy

Laser triggered photo-cathodes are key components of the electron sources of 4th generation light machines. However, they are very sensitive to the vacuum level and its composition. Photo-cathodes are usually prepared in UHV chamber and then transferred, keeping the extreme vacuum condition, to the operation sites. Since transportation/storage may last from several days to weeks, retaining UHV conditions is a fundamental task to the photocathode usage. In this paper the results obtained using a novel pumping approach are given. This approach is based on coupling a 20 l.s⁻¹ ion getter pump with a Capacitorr® D100 Non Evaporable Getter (NEG) pump. Pressure of 2x10-11 mbar was achieved with the NEG pump after 2 days bake-out, as compared to 8x10-10 mbar achieved with the ion pump alone, after 7 days bake-out. Such pressure values were retained even in absence of power, due to the ability of the NEG to remove gases by chemical reaction. Long term monitoring of cathodes QEs was also carried out at different photon wavelengths over more than 6 months, showing no degradation of the photo-emissive film properties.

TUPS023

Secondary Electron Yield on Cryogenic Surfaces as a Function of Physisorbed Gases

electron, cryogenics, vacuum, insertion

1575

A. Kuzucan, H. Neupert, M. Taborelli
CERN, Geneva, Switzerland
H. Stoeri
IAP TUW, Wien, Austria

Electron cloud is a serious limitation for the operation of particle accelerators with intense positively charged beams. It occurs if the secondary electron yield (SEY) of the beam-pipe surface is sufficiently high to induce an electron multiplication. At low surface temperatures, the SEY is strongly influenced by the nature of the physisorbed gases and by the corresponding surface coverage. These conditions occur in many accelerators operating with superconducting magnets and cold vacuum sections such as the LHC and RHIC. In this work, we investigated the variation of the SEY of copper, aluminium and electro-polished copper as a function of physisorbed N2, CO, CO2, CH4, Kr, C2H6 at cryogenic temperatures. The conditioning by electron bombardment of the surface after the physisorption of H2O on electro polished copper will also be presented. The results of the various gases are compared in order to find a rationale for the behaviour of the secondary electrons for the various adsorbates.

TUPS027

Characterization of Carbon Coatings with Low Secondary Electron Yield

electron, vacuum, cryogenics, ion

1587

C. Yin Vallgren, S. Calatroni, P. Costa Pinto, A. Kuzucan, H. Neupert, M. Taborelli
CERN, Geneva, Switzerland

Amorphous carbon (a-C) coatings can reliably be produced with a maximum secondary electron yield (SEY) close to 1 at room temperature. Measurements at low temperature (LHe) are in progress. Analysis by X-ray Photoemission Spectroscopy (XPS) shows a correlation between the lineshape of C1s spectrum in XPS and maximum SEY of the investigated samples. The initial level of oxygen on the surface of the various samples does not seem to be related to the initial maximum SEY value. However, the increase of the SEY with air exposure time on each individual sample is related to the amount of oxygen containing adsorbates. Storage in different environments has been investigated (static vacuum, aluminum foil, dry nitrogen and desiccators) and shows significant differences in the “aging” behavior. Aging is very moderate when storing samples wrapped in aluminum foil in air. Samples which have undergone aging due to inappropriate storage can be recovered nearly to the initial value of the SEY by typical surface treatments as ion bombardment, annealing under vacuum and conditioning by electron beam. However, an enhanced sensitivity to air exposures is observed for most of these curing methods.

TUPS034

Development and Construction of the Beam Dump for J-PARC Hadron Hall

hadron, proton, status, radiation

1608

A. Agari, E. Hirose, M. Ieiri, Y. Katoh, M. Minakawa, R. Muto, M. Naruki, Y. Sato, S. Sawada, Y. Shirakabe, Y. Suzuki, H. Takahashi, M. Takasaki, K.H. Tanaka, A. Toyoda, H. Watanabe, Y. Yamanoi
KEK, Tsukuba, Japan
H. Noumi
RCNP, Osaka, Japan

Funding: This work is supported by Grant-in-Aid (No.22740184) for Young Scientists (B) of the Japan Ministry of Education, Culture, Sports, Science and Technology [MEXT].
A facility of Hadron hall at Japan Proton Accelerator Research Complex (J-PARC) had been constructed in June 2007. Hadron hall is designed to handle intense slow-extraction proton beam from the main accelerator of J-PARC, i.e. 50-GeV-PS. The first transportation of the proton beam to the hall was successfully made in Jan. 2009. A beam dump constructed at the end of the primary proton beam line in Hadron hall is designed to safely absorb 15 μA (=750-kW) proton beam. Its central core of the dump is made of copper with water cooling and is surrounded by iron and concrete for radiation protection. We made thermal and mechanical FEM analysis for investigating heat generation and mechanical stress from energy deposition. We also made cooling experiments for measuring heat transfer coefficient of candidates for new cooling device. As a result, the adopted device has direct cooling paths which are prepared as long holes made by Gun Drill from the outer surface of the copper core. In addition, the beam dump is designed to safely move to 50-m downstream as one body for future expansion of Hadron hall. This paper reports development and construction of the beam dump in Hadron hall.

WEODA02

Collimation Studies with Hollow Electron Beams

electron, collimation, antiproton, proton

1939

G. Stancari, G. Annala, T.R. Johnson, G.W. Saewert, V.D. Shiltsev, D.A. Still, A. Valishev
Fermilab, Batavia, USA

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. This work was partially supported by the US LHC Accelerator Research Program (LARP).
Recent experimental studies at the Tevatron collider have shown that magnetically confined hollow electron beams can act as a new kind of collimator for high-intensity beams in storage rings. In a hollow electron beam collimator, electrons enclose the circulating beam. Their electric charge kicks halo particles transversely. If their distribution is axially symmetric, the beam core is unaffected. This device is complementary to conventional two-stage collimation systems: the electron beam can be placed arbitrarily close to the circulating beam; and particle removal is smooth, so that the device is a diffusion enhancer rather than a hard aperture limitation. The concept was tested in the Tevatron collider using a hollow electron gun installed in one of the existing electron lenses. We describe some of the technical aspects of hollow-beam scraping and the results of recent measurements.

Slides WEODA02 [9.049 MB]

WEOAB01

Highly Polarized and High Quantum Efficiency Electron Source Using Transmission-type Photocathode

electron, laser, brightness, polarization

1950

N. Yamamoto, F. Ichihashi, A. Mano, T. Nakanishi, Y. Takeda, T. Ujihara
Nagoya University, Nagoya, Japan
X.G. Jin
Institute for Advanced Research, Nagoya, Japan

The GaAs-type semiconductor photocathodes (PCs) with a negative electron affinity surface have been used as a polarized electron source and are expected as electron sources for next generation accelerators, such as Linear Colliders and Energy Recovery Linacs. Recently, we have developed transmission-type photocathodes (T-PCs).　By using T-PCs, polarized electron beam is extracted from the back-side of laser irradiation-side.　This scheme offers great merits in designing electron guns, such as short focusing of the laser light for a high brilliance electron beam and a simple geometrical structure avoiding an interference problem between the laser and the electron beam. The layer structure of the MOVPE-grown superlattice photocathode and the performance of 90% polarization, a super high brilliance, and a high quantum efficiency will be reported.

Slides WEOAB01 [6.007 MB]

WEPC036

Coherent Synchrotron Radiation Source Based on an Isochronous Accumulator Ring with Femtosecond Electron Bunches

betatron, linac, radiation, lattice

2085

N.Y. Huang
NTHU, Hsinchu, Taiwan
H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, F. Miyahara, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
W.K. Lau
NSRRC, Hsinchu, Taiwan

A compact isochronous accumulator ring has been studied as a source of coherent synchrotron radiation (CSR) at a wavelength region from THz to GHz. Since the thermionic rf gun is substantially stable in general, we anticipate a bunch train of very short electron pulses can be provided satisfactorily by means of velocity bunching. Careful numerical simulations show possibility of the bunch length of much less than 100 fs with a bunch charge of 20 pC, which will contain sufficiently large form factor for production of CSR at the wavelengths longer than ~ 0.1 mm. The coherent THz radiation of high average power will be achieved if the short bunches can be circulated in the accumulator ring without bunch lengthening. This paper will describe the optimization of thermionic injector to produce femtosecond bunches in addition to study of the lattice designing of complete isochronous optics for the accumulator ring.

WEPO003

The FERMI@Elettra Magnets

dipole, quadrupole, electron, FEL

2409

D. Castronovo, R. Fabris, G.L. Loda, D. Zangrando
ELETTRA, Basovizza, Italy

FERMI@Elettra is a single-pass FEL user-facility located next to the third generation synchrotron radiation facility ELETTRA in Trieste, Italy. The linear accelerator contains more than 200 magnets. This paper reports on the design, construction, magnetic measurement and installation.

WEPZ014

Upgrade of the Argonne Wakefield Accelerator Facility (AWA): Commissioning of the RF Gun and Linac Structures for Drive Beam Generation

wakefield, electron, linac, acceleration

2799

M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
ANL, Argonne, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Research at the AWA Facility has been focused on the development of electron beam driven wakefield structures. Accelerating gradients of up to 100 MV/m have been excited in dielectric loaded cylindrical structures operating in the microwave range of frequencies. Several upgrades, presently underway, will enable the facility to explore higher accelerating gradients, and also be able to generate longer RF pulses of higher intensity. The major items included in the upgrade are: (a) a new RF gun with a higher quantum efficiency photocathode will replace the RF gun that has been used to generate the drive bunches; (b) the existing RF gun will be used to generate a witness beam to probe the wakefields; (c) three new L-band RF power stations, each providing 25 MW, will be added to the facility; (d) five linac structures will be added to the drive beamline, bringing the beam energy up from 15 MeV to 75 MeV. The upgraded drive beam will consist of bunch trains of up to 32 bunches spaced by 0.77 ns with up to 100 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.

THYB01

Advanced Beam Manipulation Techniques at SPARC

emittance, linac, simulation, laser

2877

A. Mostacci, D. Alesini, P. Antici, A. Bacci, M. Bellaveglia, R. Boni, M. Castellano, E. Chiadroni, G. Di Pirro, A. Drago, M. Ferrario, A. Gallo, G. Gatti, A. Ghigo, E. Pace, A.R. Rossi, B. Spataro, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
B. Marchetti
INFN-Roma II, Roma, Italy
M. Migliorati
University of Rome "La Sapienza", Rome, Italy
L. Palumbo
Rome University La Sapienza, Roma, Italy
V. Petrillo, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
C. Ronsivalle
ENEA C.R. Frascati, Frascati (Roma), Italy

SPARC in Frascati is a high brightness photo-injector used to drive Free Electron Laser experiments and explore advanced beam manipulation techniques. The R&D effort made for the optimization of the beam parameters will be presented here, together with the major experimental results achieved. In particular, we will focus on the generation of sub-picosecond, high brightness electron bunch trains via velocity bunching technique (the so called comb beam). Such bunch trains can be used to drive tunable and narrow band THz sources, FELs and plasma wake field accelerators.

Slides THYB01 [20.772 MB]

THPC040

Expected Performance Characteristic of Accelerator-based THz Source at Tohoku University

radiation, electron, undulator, focusing

2990

H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
N.Y. Huang
NTHU, Hsinchu, Taiwan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
Sources of coherent synchrotron radiation at THz wavelength region have been constructed at Tohoku University. Bunch train of extremely shorter electron pulse less than 100 fs will be provided by an injector linac employing thermionic rf gun, where the bunch compression will be performed by means of velocity bunching in an accelerator structure. Radiation source under development are a Halbach type planar undulator and an accumulator isochronous ring. The undulator employs large gap and long period length configuration, so that the resonant frequency of 1 THz is achieved when a lower beam energy of ~ 20 MeV. Since spectrum of coherent synchrotron radiation (CSR) is strongly depending on longitudinal bunch form factor, we have calculated CSR spectra for various conditions of the beam to evaluate the performance of the THz source. Numerical simulation with multi-particle system has been carried out to understand the radiation power and angular distribution as well. The beam transport in the undulator is crucial for quality of the radiation because the beam energy is very much low relative to strong focusing power. Characteristics of THz CSR from the undulator will be discussed.

THPC041

Injector System of Test Accelerator as Coherent Terahertz Source

cavity, electron, cathode, radiation

2993

S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
N.Y. Huang
NTHU, Hsinchu, Taiwan
F. Miyahara
KEK, Ibaraki, Japan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
A test accelerator as a coherent terahertz source (t-ACTS) project has been under development at Tohoku University, in which a generation of intense coherent terahertz (THz) radiation from sub-picosecond electron bunch will be demonstrated. We will supply a wide-band coherent radiation from bending magnets in an isochronous ring and a narrow-band coherent THz radiation using an undulator in a linac. Stable generation of very short electron bunch is one of the key issues in the t-ACTS project. The injector system is consists of a thermionic RF gun with two independent cavity cells, an alpha magnet and an accelerating structure. A velocity bunching scheme is employed to produce the very short electron bunch. Components of the t-ACTS injector except the accelerating structure have already been installed and we have started a high power RF processing of the gun cavities. The characteristics of electron bunch extracted from the RF gun are measured by varying phase and amplitude of input RF fields for the gun cavities. The status of t-ACTS project will be presented in the conference.

THPC088

Performance of RF System for XFEL/SPring-8 Injector

cavity, emittance, electron, klystron

3101

T. Asaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Asaka, H. Ego, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi
JASRI/SPring-8, Hyogo-ken, Japan
T. Inagaki
RIKEN/SPring-8, Hyogo, Japan
Y. Otake, T. Shintake, K. Togawa
RIKEN Spring-8 Harima, Hyogo, Japan

In the XFEL/SPring-8 accelerator, the RF processing of an injector for the 8-GeV accelerator were carried out during two months after the installation of all the main components of the accelerator was completed in January 2011. To realize stable bunch compression process without the emittance growth, the injector adopts the combination of an extremely low emittance thermionic gun and multi-stage RF cavities for velocity bunching. In addition, in order to reduce the emittance growth occurring at the transition from the velocity bunching to acceleration, the newly developed L-band APS type accelerating structures and a waveguide system were introduced in the injector. Since an intensity of beam current is affected by the slight variations of RF power and phase of these RF equipment, we have carried out thorough countermeasures to complete highly-stabilized RF systems. Consequently, the stability of RF power and phase in rated operating condition of each RF cavity achieved 20 ppm (std.) and 0.06˚ (std.), respectively. In this paper, we describe the stability performances and RF processing of these RF systems in the injector.

THPC093

Beam Dynamics Simulations for the SwissFEL Injector Test facility

emittance, laser, solenoid, simulation

3107

S. Bettoni, M. Pedrozzi, S. Reiche, T. Schietinger
PSI, Villigen, Switzerland

The SwissFEL under study at PSI will produce 0.1 nm to 0.7 nm wavelength coherent x-ray. The design of the injector is based on the invariant envelope matching scheme, developed for other photoinjectors in the past years. According to this technique the emittance at the exit of the injector can be minimized if some conditions at the entrance of the booster are satisfied. A campaign of simulations has been carried out to verify the impact of the errors of the machine components (RF and magnetic) and laser shaping (transverse and longitudinal) on the final SwissFEL injector emittance. These results have to be used to define the tolerances on the machine and laser.

THPC095

Commissioning Status of the SwissFEL Injector Test Facility

emittance, laser, solenoid, electron

3110

T. Schietinger, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, N. Milas, G.L. Orlandi, M. Pedrozzi, E. Prat, S. Reiche, C. Vicario
PSI, Villigen, Switzerland

The SwissFEL injector test facility at the Paul Scherrer Institute has been in operation since August 2010. Its primary goal is the demonstration of a high-brightness electron beam as it will be required to drive the SwissFEL main linac. The injector further serves as a platform for the development and validation of accelerator components needed for the SwissFEL project. We give an overview of recent commissioning activities at about 130 MeV beam energy, with particular emphasis on results from optics matching studies and emittance measurements, the latter obtained with different optics-based methods. A five-cell transverse-deflecting cavity allows studies of the longitudinal bunch charge distribution and slice emittance. Bunch length measurements will become the focus of interest after the installation of a magnetic compression chicane, currently scheduled for the summer of 2011.

THPC106

Commissioning Status of the Fritz Haber Institute THz FEL

electron, FEL, undulator, linac

3137

A.M.M. Todd, H. Bluem, V. Christina, M.D. Cole, J. Ditta, D. Dowell, K. Jordan, R. Lange, J.H. Park, J. Rathke, T. Schultheiss, L.M. Young
AES, Princeton, New Jersey, USA
W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, W. Schöllkopf, G. von Helden
FHI, Berlin, Germany
S.C. Gottschalk
STI, Washington, USA

The THz Free-Electron Laser (FEL) at the Fritz Haber Institute (FHI) of the Max Planck Society in Berlin is designed to deliver radiation from 3 to 300 microns using a single-plane-focusing mid-IR undulator and a two-plane-focusing far-IR undulator that acts as a waveguide for the optical mode. A key aspect of the accelerator performance is the low longitudinal emittance, < 50 keV-psec, that is specified to be delivered at 200 pC bunch charge and 50 MeV from a gridded thermionic electron source. We utilize twin accelerating structures separated by a chicane to deliver the required performance over the < 20 - 50 MeV energy range. The first structure operates at near fixed field while the second structure controls the output energy, which, under some conditions, requires running in a decelerating mode. "First Light" is targeted for the centennial of the sponsor in October 2011 and we will describe progress in the commissioning of this device to achieve this goal. Specifically, the measured performance of the accelerated electron beam will be compared to design simulations and the observed matching of the beam to the mid-IR wiggler will be described.

THPC111

Operation of an L-band RF Gun with Pulses Inside the Burst Mode RF Pulse

cavity, laser, klystron, controls

3146

V. Vogel, V. Ayvazyan, B. Faatz, K. Flöttmann, D. Lipka, P. Morozov, H. Schlarb, S. Schreiber
DESY, Hamburg, Germany

The Free-Electron Laser in Hamburg (FLASH) is a user facility since 2005, delivering femtosecond short radiation pulses in the wavelength range between 4.1 and 44 nm using the SASE principle. In FLASH, the electron beam is accelerated to 1.25 GeV with L-band superconducting cavities. The electron source is a normal conducting RF-gun photoinjector. The L-band standing wave RF gun has one and a half cells. The gun is operated in burst mode with an RF pulse length of up to 900 microseconds and a repetition rate of 10 Hz. Several hundreds to thousands of bunches are accelerated per second. With 5 MW of pulsed forward power, the dissipated power inside the RF gun is 45 kW. In this paper we propose an operational mode which allows us to reduce the dissipated power to ease operation or to increase the effective duty cycle in the gun by pulsing the gun within one burst. We report on first experimental results at FLASH, where an RF burst of 46μRF-pulses with a length of 10 microseconds separated by 10 microseconds has been successfully generated reducing the dissipated power by a factor of 2.

THPC114

High Brightness Photo Injector Upgrade and Experimental Optimization at PITZ

emittance, laser, electron, booster

3152

M. Krasilnikov, H.-J. Grabosch, M. Gross, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
L. Hakobyan, M.A. Khojoyan
YerPhI, Yerevan, Armenia
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
I.I. Isaev, A. Shapovalov
MEPhI, Moscow, Russia
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
D. Richter
HZB, Berlin, Germany
I.H. Templin, I. Will
MBI, Berlin, Germany

The photo injector test facility at DESY in Zeuthen (PITZ) develops and optimizes electron sources for linac driven free electron lasers. The main goal of PITZ is to demonstrate a small electron beam emittance by tuning several main parameters of the injector - photo cathode laser pulse, rf gun with solenoids and booster cavity parameters. A slit scan technique is used to measure the transverse phase space of the electron beam and the projected normalized emittance. The photo injector is capable of pulse train production which can be measured with dedicated diagnostics at PITZ. This enables optimization of the beam emittance for a wide range of bunch charges from tens of pC to several nC while keeping high resolution of beam measurements. The results of the experimental optimization will be presented yielding a new benchmark of photo injector performance.

THPC115

Emittance Optimization for Different Bunch Charges with Upgraded Setup at PITZ

emittance, laser, booster, electron

3155

G. Vashchenko, G. Asova, M. Gross, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, M. Krasilnikov, M. Mahgoub, D. Malyutin, M. Otevřel, B. Petrosyan, S. Rimjaem, A. Shapovalov, F. Stephan, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
D. Richter
HZB, Berlin, Germany
I.H. Templin, I. Will
MBI, Berlin, Germany

The Photo Injector Test facility at DESY, Zeuthen site, (PITZ) has the aim to develop and optimize high brightness electron sources for Free Electron Lasers like FLASH and the European XFEL. Photo electrons emitted from the Cs2Te cathode are accelerated by a 1.6-cell L-band RF gun cavity operated at 60 MV/m maximum accelerating gradient at the cathode. Cylindrically shaped laser pulses with a flat-top temporal profile of about 20 ps FWHM and 2 ps rise and fall time are used to produce electron beams with extremely low emittance. The PITZ beam line was upgraded in 2010. The new gun cavity (prototype number 4.1) was installed January 2010. The new booster cavity (CDS) with well-defined field distribution was installed in July 2010. The diagnostic system for characterization of the laser hitting the photocathode was upgraded in October 2010. Emittance measurements results for different charges: 2 nC, 1 nC, 0.25 nC, 0.1 nC and 0.02 nC, will be presented. The optimization was done for different parameters, e.g. gun solenoid current, gun phase, laser spot size on the cathode, booster gradient.

THPC120

Experimental Investigation of Photocathode Thermal Emittance Components with a Copper Cathode*

emittance, cathode, laser, electron

3167

H.J. Qian, Y.-C. Du, Hua, J.F. Hua, W.-H. Huang, C. Li, C.-X. Tang, L.X. Yan
TUB, Beijing, People's Republic of China

With progress of photocathode RF gun technology, thermal emittance has become the primary limitation of electron beam brightness*. Extensive efforts have been devoted to study thermal emittance, but experiment results diverge between research groups and few can be well interpreted**. One possibility is the undefined online cathode surface conditions, which may cause difference of work functions, field enhancement factor and surface roughness, and lead to thermal emittance divergence. In this paper, we report an experiment of characterizing online photocathode work function, field enhancement factor and surface roughness effect by measuring electric field dependence of photoemission quantum efficiency (QE) and thermal emittance in a Cu-cathode RF gun. Preliminary experiment results reveal huge thermal emittance contributed by surface roughness for the first time, and are in reasonable consistency with theoretical model prediction***.
*Ivan V. Bazarov et al., Phys. Rev. Lett. 10², 104801(2009)
** D.H. Dowell et al, Nucl. Instrum. Methods Phys. Res., Sect. A 622, 685 (2010).
***D. Xinag et al, PAC’07, 10⁴⁹ (2007)

THPC121

Design and Cold Tests of a Prototype photocathode RF Gun for Shanghai SXFEL Facility

cathode, coupling, vacuum, emittance

3170

H.J. Qian, H. Chen, Y.-C. Du, W.-H. Huang, C. Li, X.H. Liu, X. H. Lu, C.-X. Tang
TUB, Beijing, People's Republic of China

A soft X-ray (~9 nm) FEL (SXFEL) facility is going to be constructed in Shanghai, China, which requires high charge (>500 pC) electron beam with low transverse emittance (<1.5 mm-mrad) at photoinjector exit. One of the keys to achieve a low emittance with high charge is high gradient on the photocathode, so an S-band photocathode RF gun modified from BNL type gun is designed, which aims running 100 MV/m peak gradient at 10 Hz. By changing the cathode seal technique, removing the insertion RF tuner, and reducing the peak surface field, RF breakdown possibility is reduced. Besides, RF pulse width is also considered to be reduced to lower the RF breakdown possibility. Since zero mode and multipole field degrades the beam emittance, they are also suppressed in the new gun design. Design details and cold testing results are presented in this paper.

THPC123

Injector Layout and Beam Injection into Solaris

injection, linac, storage-ring, klystron

3173

A.I. Wawrzyniak, C.J. Bocchetta
Solaris, Krakow, Poland
S.C. Leemann, S. Thorin
MAX-lab, Lund, Sweden

Funding: European Regional Development Fund within the frame of the Innovative Economy Operational Program: POIG.02.01.00-12-213/09
The Solaris synchrotron radiation storage ring to be built in Krakow, Poland is based on the MAX IV 1.5 GeV design. The injector will be a linear accelerator and its components identical to those for the MAX IV project, however, injection is not at full energy and the injector layout is different. The linac and transfer line layout, optics and injection scheme into the storage ring is presented and an analysis of accumulation before energy ramping is discussed.

THPC126

RF Gun Studies for the SwissFEL Injector

laser, emittance, solenoid, cathode

3179

A. Falone, A. Adelmann, J.-Y. Raguin, L. Stingelin
PSI, Villigen, Switzerland

The Paul Scherrer Institut (PSI) is planning a compact, high brightness hard X-ray free electron laser. For this purpose a new 2.5 cell RF gun has been designed at PSI and is now in production. The RF gun plays an important role in preserving beam emittance, and hence delivers a high quality beam to the injector. We present beam dynamic parametric studies on the effect of cell length variations using two different codes OPAL and ASTRA. Furthermore laser and other RF parameters are scanned to find the best working point of the injector. The simulations are showing that the SwissFEL injector requirements (ϵ<0.4 mm mrad normalized projected emittance) are achievable with a smooth dependence on the geometrical variation of the gun cell lengths confirming a robust RF design of the gun is possible.

THPC127

Recent Results from a Combined Diode-RF Gun

emittance, cathode, electron, laser

3182

C.H. Gough, S. Ivkovic, M. Paraliev
PSI, Villigen, Switzerland

For the SwissFEL project, a novel combined diode-RF electron gun was tested at PSI, as a possible source for XFELs. Typically, electron bunches of 1-100 pC charge , 1-5 MeV energy and 2-0.3 um-rad emittance were produced and measured. The advantage of the combined gun is that diode geometry and emission surface can be changed readily. An optimum polishing procedure for magnesium photo cathodes was found, and various surfaces such as FEA's were tested in high gradient. Emittance changes for emission surface depression within the cathode, as well as laser spot size and anode hole size, were measured. Finally, the excellent performance of the gun permitted detailed study of the pepperpot EMSY (Emittance Measurement System) behaviour with changing beam parameters.

THPC129

Gallium Arsenide Photocathode Research at Daresbury Laboratory

cathode, electron, laser, vacuum

3185

L.B. Jones, B.D. Fell, J.W. McKenzie, K.J. Middleman, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.J. Cash
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
N. Chanlek
UMAN, Manchester, United Kingdom

Significant effort has been expended over several years by ASTeC to optimise procedures for preparing GaAs photocathodes for use as high-current electron sources in accelerators. Having established robust chemical and thermal cleaning processes, and carried out lifetime studies on activated photocathodes by deliberately poisoning them*, we present data showing high levels of Quantum Efficiency (QE) for heterostructure photocathodes when activated with Cs-O and Cs-NF3 procedures. We will show that the use of NF3 delivers higher QE, and conveys greater control in that the final QE level can be set more accurately using NF3 than with O. We plan to carry out further experiments on GaAs photocathodes to measure the 2-D energy distribution of the emitted electrons at both room and cryogenic temperatures. We are constructing a retarding-field electron calorimeter which will measure current as a function of retarding voltage. From this, we will establish the 2-D energy distribution in the electron beam, permitting a comparison of these figures for photocathodes at room and low temperatures. The goal is to create an ultra-bright electron source for use with particle accelerators.
* Proc IPAC ’10, TUPEC018, 1752-1754

THPC130

A 160 keV Photocathode Electron Gun Test Tacility

electron, diagnostics, laser, cathode

3188

L.B. Jones, B.D. Fell, C. Hill, J.W. McKenzie, K.J. Middleman, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.J. Cash
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The ALICE ERL* at Daresbury Laboratory is a prototype 4th generation free-electron laser light source operating at IR wavelengths. An upgrade to the DC photoinjector gun has been designed and partially-constructed, but due to installation postponement, the system will be used for photocathode physics experiments. The re-designed gun will operate at 160 keV. The gun and photocathode preparation facility (PPF) will be assembled with a diagnostic beamline, supporting research towards high-brightness electron beams based on GaAs technology. Combining an external PPF with a load-lock facility allows the rapid exchange of photocathodes, thus permitting the testing of various different photocathode heterostructures, and fine control of the cleaning and activation processes applied during preparation. The diagnostics beamline will include a transverse kicker to study bunch length, and a dipole magnet for beam energy and energy spread measurements. Various horizontal and vertical slit and screen assemblies allow for emittance measurement, so providing full 6-D characterisation of the electron bunches generated. A current transformer and Faraday cups support bunch charge measurements.
* Accelerators and Lasers In Combined Experiments electron Energy-Recovery Linac

THPC131

MAX-IV Linac Injector Simulations including Tolerance and Jitter Analysis

linac, emittance, simulation, laser

3191

J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Thorin, S. Werin
MAX-lab, Lund, Sweden

The MAX-IV linac will be used both for injection and top up into two storage rings, and as a high brightness injector for a Short Pulse Facility (SPF) and an FEL (in phase 2). 100 pC bunches of electrons are created from a 1.5 cell S-band photocathode gun and subsequently accelerated up to 3 GeV by S-band linac sections. Simulations of the dynamics of the space-charge dominated beam up to 100 MeV are presented including an analysis of the tolerances required and the effects of jitter sources.

THPC132

A Velocity Bunching Scheme for Creating Sub-picosecond Electron Bunches from an RF Photocathode Gun

cavity, emittance, solenoid, laser

3194

J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Sub-picosecond electron bunches are in demand for various applications including Free Electron Lasers and electron diffraction experiments. Typically, for Free Electron Lasers, a multiple picosecond scale bunch is produced from a photoinjector with compression achieved via one or more magnetic chicanes by providing an appropriate energy chirp to the bunch in the preceding linac sections. This approach is complex, requiring many components, often including a higher harmonic linac section to linearise the longitudinal phase-space, and careful tuning in order to minimise emittance blow-up due to coherent synchrotron radiation. We present a scheme to deliver sub-picosecond electron bunches, based on a normal conducting RF gun and two short linac sections, one for providing velocity bunching and the second to capture the compressed bunch and accelerate to tens of MeV where the beam properties are then essentially frozen.

THPC134

LCLS RF Gun Copper Cathode Performance

cathode, laser, emittance, electron

3200

A. Brachmann, F.-J. Decker, P. Emma, R.H. Iverson, P. Stefan, J.L. Turner, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC03-76SF00515
We report on the performance and the operational experience of the LCLS RF gun copper photocathodes used during the LCLS run I, II, III and IV. We discuss the problems of cathode surface contamination and our experience with methods to remove such contamination. Techniques to obtain high quantum efficiency (QE) while preserving the low emittance quality are discussed. Furthermore, we will present the current status of the installed cathode, its quantum efficiency and the typical injector emittances of the extracted beam.

THPC135

Optimal Parameters of the Photocathode Gun Space Charge to Improve Beam Quality

laser, cathode, electron, space-charge

3203

M.G. Fedurin, C. Swinson, V. Yakimenko
BNL, Upton, Long Island, New York, USA

Accelerator Test Facility at Brookhaven National Laboratory operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space charge affecting on the own bunch length and transverse profile. Optimal beam loading parameters of the space charge in the photocathode RF gun could be found and used to improve bunch length and emittance. Simple model and experimental results on the Accelerator Test Facility at Brookhaven national Laboratory will be described

THPC142

Burst Pulse Superimposed Electron Beam Acceleration in LEBRA FEL Linac

electron, FEL, acceleration, linac

3218

T. Tanaka, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, N. Sato
LEBRA, Funabashi, Japan
S. Aizawa, Y. Arisumi, K. Shinohara
Nihon Koshuha Co. Ltd, Yokohama, Japan
I. Sato
Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi, Japan

The electron beam for free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University had been extracted from a conventional DC triode electron gun system. In conjunction with the renewal of the gun high voltage terminal a Kentech high-speed grid pulser was installed in addition to the conventional grid pulser. The 89.25MHz sine wave frequency-divided from the 2856MHz accelerating RF has been applied to the high-speed grid pulser, generating 64 or 128 frequency-divided grid pulses synchronous with the round-trip time in the FEL optical resonator. The high-speed grid pulses have been applied to the EIMAC Y646B cathode simultaneously with the conventional macropulse through the pulse coupling strip-line circuit; the resultant beam has been the short pulse beam superimposed on the macropulse beam. By reducing the macropulse voltage, only the train of the burst beam with 0.6ns width has been extracted. The peak burst beam current roughly 6 times higher than the conventional macropulse beam has been obtained with the Farady cup at the end of the FEL beamline. The FEL lasing experiment with the burst beam is underway.

THPO008

Klystron and Modulator System for the PEFP 20 MeV Proton Linac

klystron, linac, rfq, proton

3352

D.I. Kim, Y.-S. Cho, H.S. Kim, H.-J. Kwon
KAERI, Daejon, Republic of Korea

Funding: This work is supported by the Ministry of Science and Technology of the Korean government.
A modulator developed for the 100 MeV proton linear accelerator is operating in the 20 MeV proton linac. The voltage and current of the modulator are -105 kV, 50 A with 1.5 ms pulse width, 60 Hz repetition rate. The modulator drives two klystrons simultaneously, one for the RFQ, the other for the DTL. The typical operation parameters of the modulator are 85 kV of the peak voltage, 34 A of the peak current, 1 ms of the pulse width, 4 Hz of the pulse repetition. The specifications of the klystron are 350 MHz of the frequency, 1.1 MW of the maximum average RF power, less than 95 kV of the beam voltage, triode type electron gun with mod-anode. The mod-anode voltage was supplied by the voltage dividing resistors which were located inside the klystron oil tank. In this paper, the operation performance of the klystron and modulator system for the PEFP 20 MeV proton linac is presented.

THPS026

Surface Plasma H⁻ Ion Source with Saddle RF Antenna Plasma Generator

plasma, ion, extraction, ion-source

3475

V.G. Dudnikov, R.P. Johnson
Muons, Inc, Batavia, USA
S.N. Murray, T.R. Pennisi, M. Santana, M.P. Stockli, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA

Funding: *Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0002690.
In this project is developed a prototype RF H⁻ surface plasma source (SPS) with saddle (SA) RF antenna which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with a small AlN test chamber and different antennas and magnetic field configurations were tested in the SNS ion source Test Stand. A prototype SA SPS was installed in the Test Stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency of 1.6 mA/kW. Control experiments with H⁻ beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma source (TPS) has been designed. A Saddle antenna SPS with water cooling is being fabricated for high duty factor testing.

THPS064

Application of X-band 3.95 MeV Linac X-ray Source for On-site Bridge Inspection

linac, site, target, electron

3571

H.F. Jin, K. Demachi, K. Dobashi, T. Fujiwara, M. Uesaka, H. Zhu
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan

We developed an X-ray non-destructive (NDT) system for on-site bridge inspection. A portable X-band (9.3-12 GHz) 3.95MeV linear accelerator (linac) has been developed for this system. The system consists of X-ray of 62kg without the target collimeter of 80kg, the RF power source of 62kg and other utility box of 116kg. For the onsite investigation, a flexible waveguide is used for this linac. And the linac is a point X-ray source. For X-ray detection, we chose 8-inch square size scintillation type flat panel detector. The spatial resolution of the detector is as high as 0.2mm, which is manufactured by Perkin Elmer Co. Cd2O2S:Tb is used for the scintillator crystal. The capable radiation energy range is 40keV to 15MeV. In order to realize quick inspection for a bridge, remote control robot which handles and compact X-ray source and detector are desired. Therefore, we developed 3D location system for this robot. The locating system is realized with image processing with its camera. For the operation, stereoscopic radiographic image is taken and analyzed, and computed tomography (CT) image analysis is taken for detailed inspection.
Non-destructive test (NDT) , X-ray Source, X-band, Linac, Detector, Computed Tomography (CT).

THPS090

Development of the Pulse Radiolysis System with a Supercontinuum Radiation using Photonic Crystal Fiber

laser, radiation, electron, optics

3645

K.B. Ogata, R. Betto, Y. Hosaka, Y. Kawauchi, K. Sakaue, T. Suzuki, M. Washio
RISE, Tokyo, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690
In usage of radiation, it is important to study the process of chemical effects of ionizing radiation in a material. Pulse radiolysis is a method to trace these rapid initial chemical reactions by ionizing radiation. As a pump beam, we are using 5MeV electron beam produced from the S-band photo cathode RF-Gun. In nanosecond timescale pulse radiolysis, it is required the stable probe light of a broad spectrum. And especially in picosecond timescale pulse radiolysis, probe light should have short pulse width to use stroboscopic method. Therefore, in order to develop a wide range of timescale experimental system, we have been developing a Supercontinuum (SC) light as a probe light, which is generated by nonlinear optical process of short pulse IR laser in photonic crystal fiber (PCF). As a result, the SC light spectrum is broad enough to use as a probe light. Then we tried to measure the absorption spectrum of hydrated electron by SC light, we successfully observed good signal-noise ratio data both nanosecond and picosecond experiment with unified pulse　radiolysis system. In this conference, we will report details of these results and future prospects.