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Paper Title Other Keywords Page
MOPPH005 Improvements of the Tracking Code Astra for the Simulation of Dark Current Losses in the FLASH Linac simulation, linac, space-charge, vacuum 22
 
  • S. M. Meykopff, L. Fröhlich
    DESY, Hamburg
  At the Free Electron Laser in Hamburg FLASH, the activation of components due to dark current emitted by the gun has become a serious problem. To improve the understanding of dark current transport in the linac, simulations with the Astra tracking code have been conducted. These studies require a big amount of computing time due to the high number of simulated macroparticles. Therefore, the parallelized version of Astra had to be enhanced by features like dynamic load balancing and an improved aperture model. The paper will provide an overview of the new features and discuss possible remedies of the dark current problem based on the simulation results.  
 
MOPPH055 Measurements of the Projected Normalized Transverse Emittance at PITZ emittance, booster, cathode, laser 138
 
  • G. Asova, K. Boyanov, I. Tsakov
    INRNE, Sofia
  • J. W. Baehr, C. H. Boulware, H.-J. Grabosch, L. H. Hakobyan, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Lederer, A. Oppelt, B. Petrosyan, S. Riemann, S. Rimjaem, J. Roensch, A. Shapovalov, F. Stephan, L. Staykov
    DESY Zeuthen, Zeuthen
  • K. Floettmann
    DESY, Hamburg
  • R. Richter
    BESSY GmbH, Berlin
  The main objective of the Photo Injector Test facility at DESY in Zeuthen (PITZ) is the production of electron beams with minumum transverse emittance at 1 nC bunch charge. PITZ consists of a photo cathode RF gun, solenoids for the compensation of space charge induced emittance growth and a booster cavity. In order to study the emittance evolution along the beam line three Emittance Measurement SYstems (EMSY's) were installed downstream of the booster cavity. In a first operation periode in October 2006 the emittance was measured for moderate gun gradients of about 40 MV/m. A new gun cavity is presently installed at PITZ and conditioning up to a gradient of 60 MV/m is ongoing. In this work we present recent results from measurements of the normalized projected transverse emittance of the electron beam. The emittance is measured using the so called single slit technique. Data are presented for different gun and booster gradients, solenoid strengths and initial beam size at the cathode.  
 
MOPPH060 The Drive Laser System for CFEL laser, feedback, electron, radio-frequency 146
 
  • Y. C. Chen, W. Li
    CAEP/IAE, Mianyang, Sichuan
  A reliable and compact drive system is one of the key components for the stable operation of FEL. We have developed a solid-state drive laser system to meet the requirements of the CFEL(CAEP FEL) research. The system consisted of a passive mode-locked oscillator with a timing stabilizer,a regenerative amplifier and a frequency conversion part. After the 4-th harmonics,the duration of 15 picoseconds Gaussian pulses with wavelength 266nm at a repetition rate 54.17MHz were obtained. These micropulses were contained within a macropulses envelope as long as 1 to 6μmicroseconds,which was emitted from the drive laser at a repetition rate at 3Hz,6Hz or 12Hz,one single micropulse energy as large as 4μmicroJoules was achieved. The design specifications, configuration and diode-pumped amplifier of the drive laser system are also described.  
 
TUBAU02 Status of SCSS & X-ray FEL Project in Japan emittance, electron, undulator, cathode 216
 
  • T. Shintake
    RIKEN Spring-8 Harima, Hyogo
  Staus of SCSS project after the first lasing last year will be reported. The X-ray FEL, which uses 8 GeV C-band, is under construction, whose status will be reported.  
slides icon Slides  
 
TUPPH002 High Order Mode Analyses for the Rossendorf SRF Gun emittance, resonance, coupling, focusing 228
 
  • D. Janssen
    FZD, Dresden
  • V. Volkov
    BINP SB RAS, Novosibirsk
  High Order Modes (HOM) excited by the beam in a superconducting RF gun (SRF gun) could destroy the quality of the electron beam. This problem is studied on the base of frequency domain description by considering of the equivalent RLC circuit contour for each HOM, periodical excited by a pulsed current source. Expression for the voltage, the field amplitude and the phase of the excited HOM has been obtained. The equations for the coupling impedances of monopole TM-HOM and TE-HOM in the RF gun cavity has been derived. In this calculation the change of the particle velocity due to acceleration is taken into account. Resonance frequencies, coupling impedances, unloaded and external quality factors, excitation voltages and field distributions for each HOM including trapped HOM are calculated for Rossendorf SRF gun up to the frequency of 7.5 GHz, using the complex field solver CLANS. The dependence of the calculated parameters from a cavity deformation has been studied. The influence of the seven most dangerous HOM on the beam quality has been estimated by particle tracking using the ASTRA code.  
 
TUPPH006 FEL Potential of the High Current ERLs at BNL electron, emittance, linac, simulation 232
 
  • I. Ben-Zvi, V. Litvinenko, E. Pozdeyev, D. Kayran
    BNL, Upton, Long Island, New York
  An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL)* for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL prototype will be used as a test bed to study issues relevant for very high current ERLs. High average current and high performance of electron beam with some additional components make this ERL an excellent driver for high power far infrared Free Electron Laser (FEL). A possibility for future up-grade to a two-pass ERL is considered. We present the status and our plans for construction and commissioning of the ERL. We discus a FEL potential based on electron beam provided by BNL ERL.

* Litvinenko, V. N. et al. High current energy recovery linac at BNL. Proc. 26th International Free Electron Laser Conference and 11th FEL Users Workshop (FEL 2004).

 
 
TUPPH019 Simulations for the LCLS Injector emittance, simulation, laser, cathode 260
 
  • Y. T. Ding, D. Dowell, P. Emma, J. C. Frisch, A. Gilevich, G. R. Hays, P. Hering, Z. Huang, R. H. Iverson, P. Krejcik, H. Loos, A. Miahnahri, J. F. Schmerge, J. L. Turner, W. E. White, J. Wu, C. Limborg-Deprey
    SLAC, Menlo Park, California
  The commissioning of the LCLS Injector has started this year. The electron beam quality for producing high power SASE X-rays is very challenging to reach. In this paper, we will describe comparisons between simulations made with multi-particle tracking code and electron beam measurements performed on the LCLS injector.  
 
WEAAU01 Commissioning Results of the SLAC LCLS Gun laser, cathode, emittance, radiation 276
 
  • R. Akre, J. Castro, P. Emma, J. C. Frisch, A. Gilevich, G. R. Hays, P. Hering, R. H. Iverson, P. Krejcik, C. Limborg-Deprey, H. Loos, A. Miahnahri, J. F. Schmerge, J. L. Turner, J. J. Welch, W. E. White, J. Wu, D. Dowell
    SLAC, Menlo Park, California
  The beam quality and operational requirements for the Linac Coherent Light Source (LCLS) currently being constructed at SLAC are exceptional, requiring the design of a new s-band RF photocathode gun for the electron source. Two guns (Gun1 and Gun2) have been fabricated and tested at high RF power. Gun1 was installed March 17, 2007 and began providing beams for the LCLS injector commissioning on April 5, 2007. Gun2 is reserved as a backup gun. The results and analysis of the gun’s performance in the LCLS injector will be presented.  
slides icon Slides  
 
WEAAU02 Direct Measurement of Phase Space Evolution in the SPARC High Brightness Photoinjector emittance, simulation, laser, brightness 284
 
  • D. Alesini, M. Bellaveglia, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, M. Incurvati, C. Ligi, L. Pellegrino, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, F. Tazzioli, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario, E. Chiadroni
    INFN/LNF, Frascati (Roma)
  • A. Bacci
    INFN/LASA, Segrate (MI)
  • L. Catani, A. Cianchi
    INFN-Roma II, Roma
  • S. Cialdi, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • L. Giannessi, M. Quattromini, C. Ronsivalle
    ENEA C. R. Frascati, Frascati (Roma)
  • M. Migliorati, A. Mostacci, L. Palumbo
    Rome University La Sapienza, Roma
  • P. Musumeci, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Petrarca
    INFN-Roma, Roma
  The characterization of the transverse phase space for high charge density relativistic electron beams is a fundamental requirement in many particle accelerator facilities, in particular those devoted to fourth-generation synchrotron radiation sources, such as SASE FEL. The main purpose of the SPARC initial phase was the commissioning of the RF photoinjector. At this regard, the evolution of the phase space has been fully characterized by means of the emittance meter diagnostics tool, placed in the drift after the gun exit. The large amount of collected data has shown not only that we can achieve the SPARC nominal parameters, but has also allowed for the first time a detailed reconstruction of the transverse phase space evolution along the drift, giving evidences of the emittance compensation process to occur as predicted by theory and simulations. In particular the peculiar behavior of a flat top longitudinal electron distribution compared to a gaussian distribution has been studied giving important insights for the correct matching with the following linac based on the double emittance minimum effect.  
slides icon Slides  
 
WEAAU04 Superconducting Photoinjector for High-Power Free Electron Lasers electron, cathode, emittance, linac 290
 
  • A. Burrill, R. Calaga, X. Chang, R. Grover, R. C. Gupta, H. Hahn, L. Hammons, D. Kayran, J. Kewisch, R. F. Lambiase, V. Litvinenko, G. T. McIntyre, D. Naik, D. Pate, D. Phillips, E. Pozdeyev, T. Rao, J. Smedley, R. J. Todd, D. Weiss, Q. Wu, A. Zaltsman, I. Ben-Zvi
    BNL, Upton, Long Island, New York
  • M. D. Cole, M. Falletta, D. Holmes, J. Rathke, T. Schultheiss, A. M.M. Todd, R. Wong
    AES, Medford, NY
  One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders.  
slides icon Slides  
 
WEPPH009 Recent Measurements of the Longitudinal Phase Space at PITZ booster, simulation, electron, emittance 342
 
  • G. Asova, J. W. Baehr, C. H. Boulware, H.-J. Grabosch, L. H. Hakobyan, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Lederer, B. Petrosyan, S. Riemann, S. Rimjaem, T. A. Scholz, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • R. Richter
    BESSY GmbH, Berlin
  • K. Rosbach
    Humboldt University Berlin, Institut für Physik, Berlin
  • J. Rossbach, J. Roensch
    Uni HH, Hamburg
  The Photo Injector Test facility at DESY in Zeuthen (PITZ) was built to test and optimize electron guns for short wavelength Free-Electron Lasers (FELs) like FLASH and XFEL at DESY in Hamburg. For a detailed analysis of the behaviour of the electron bunch, the longitudinal phase space and it projections can be measured behind the gun cavity. The electric field at the photo cathode was increased from 40 MV/m to 60 MV/m, to optimize the transverse emittance. The momentum distributions for different gradients and gun phases will be presented. The determination of the field balance from the momentum distribution will be discussed. In order to study emittance conservation, a booster cavity and additional diagnostics were installed. The evolution of the longitudinal phase space in the booster cavity will be investigated. Measurements of the momentum distribution and longitudinal distribution behind the booster cavity will be discussed.  
 
WEPPH013 Status and Perspectives of the PITZ Facility Upgrade emittance, cathode, diagnostics, booster 354
 
  • G. Asova, J. W. Baehr, C. H. Boulware, H.-J. Grabosch, L. H. Hakobyan, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Lederer, A. Oppelt, B. Petrosyan, S. Riemann, T. A. Scholz, L. Staykov, F. Stephan, S. Rimjaem
    DESY Zeuthen, Zeuthen
  • K. Boyanov
    INRNE, Sofia
  • K. Floettmann
    DESY, Hamburg
  • R. Richter
    BESSY GmbH, Berlin
  • J. Roensch
    Uni HH, Hamburg
  • K. Rosbach
    Humboldt University Berlin, Institut für Physik, Berlin
  • A. Shapovalov
    MEPhI, Moscow
  The Photo Injector Test facility at DESY in Zeuthen (PITZ) has been established to develop and optimize electron sources that cover requirements of FEL facilities such as FLASH and the European XFEL. A major upgrade of the facility is ongoing in steps, in parallel to the commissioning of the extended setup and first experiments. The new setup towards the final design mainly includes a photo cathode RF gun, a post acceleration booster cavity and several diagnostic systems. In order to fulfil the high brightness electron source characterization, the diagnostic systems will consist of three emittance measurement systems, two high-energy dispersive arms, an RF deflecting cavity and a longitudinal phase space tomography module as well as bunch length diagnostics. In this paper, results of the commissioning of the new RF gun, which has been installed and conditioned at PITZ in spring and summer of 2007, the current PITZ status and details of the future facility upgrade will be presented.  
 
WEPPH017 UV Performances of Pulsed Laser Deposition Grown Mg Photocathodes laser, cathode, vacuum, electron 366
 
  • G. Gatti, F. Tazzioli, L. Cultrera
    INFN/LNF, Frascati (Roma)
  • P. Miglietta, A. Perrone
    INFN-Lecce, Lecce
  • C. Ristoscu
    INFLPR, Bucharest - Magurele
  We report a detailed description of the laser cleaning procedure and emission performance measurement on a Pulsed Laser Deposited Mg film. During the tests performed after the end of each cleaning operation we have evidenced an increase of Quantum Efficiency (QE) in time. Then the QE apparently stabilizes at a remarkably higher value. The study of this phenomenon is important because it determines both the working QE value and the lifetime of the cathode. Moreover, the stability of the QE has been revealed for a time scale of several days after each laser cleaning process, in our vacuum conditions.  
 
WEPPH018 A High Brightness X-band Split Photoinjector Concept and Related Technological Challenges emittance, brightness, electron, klystron 370
 
  • D. Alesini, M. Migliorati, L. Palumbo, B. Spataro, M. Ferrario
    INFN/LNF, Frascati (Roma)
  • J. B. Rosenzweig
    UCLA, Los Angeles, California
  • L. Serafini
    INFN-Milano, Milano
  Future light sources based on high gain free electron lasers, require the production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake fields effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, hence the photo-injector design and its operation is the leading edge for high quality beam production. The state of the art photoinjector beam brightness can be in principle brought above the 1015 A/m2 threshold with an X-band gun and a proper emittance compensation scheme. We discuss in this paper an optimized design of a split X-band photoinjector, a convenient matching scheme with the downstream linac, based on the SPARC project experience, and the further technological developments required to reach such an appealing goal.  
 
WEPPH022 Feasibility Test of Shottoky Effect-Gated Photocathode RF Gun laser, cathode, polarization, focusing 382
 
  • M. Kobayashi
    Nanophoton corporation, Osaka
  • H. T. Tomizawa
    JASRI/SPring-8, Hyogo-ken
  We proposed Shottoky effect-gated photocathode RF gun using z-polarization of laser source. Radically polarized laser propagation modes exist theoretically and were recently generated practically. Focusing a radically polarized beam on the photocathode, the z-polarization of laser is generated at the focusing point. The generated Z-polarization can exceed an electrical field of 1GV/m easily with fundamental wavelength from compact femtosecond laser systems. According to our calculations, the z-field of 1GV/m needs 100MW at peak power for fundamental wavelength (790nm) and 25MW for SHG. In the field of 1GV/m, the work function of copper cathode reduces ~2 eV. The quantum efficiency will be ~10-4 at SHG by the Shottoky effect associated with the 1GV/m. This Shottky effect can be used as a gate of photo-emission process. In our design of Shottoky effect-gated Photocathode, the fundamental is used as gate pulse and SHG as laser source for photo-emission process. The same single laser pulse can also gate its emission by itself. To keep normal incidence on the cathode, we developed modified-Cessegrain-type incident optics combining with axicon lens pair. In the first test run, we are preparing z-polarizer for SHG to generate radial and azimuth polarizations. Comparing photo-emission process with these polarizations, we make clear the feasibility of this new concept of photocathode.  
 
WEPPH023 Beam Properties from S-band Energy Compensated Thermionic RF Gun and Linac for KU-FEL electron, emittance, free-electron-laser, klystron 386
 
  • K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama, H. Zen, T. Kii
    Kyoto IAE, Kyoto
  Energy degradation arising from back-bombardment effect was quite serious problem for using a thermionic RF gun as injector of FEL device. Thus we have developed energy compensation technique, which keeps cavity voltage as constant by controlling input RF power to the RF gun. We have successfully extracted electron beam with constant energy from the thermionic RF gun with the energy compensation technique*. However, PFN tuning of the Klystron modulator and time-varying beamloading would affect macro-pulse properties; energy spread, emittance, phase mismatch between RF gun and accelerator, etc. Thus we have estimated effects to the beam properties by using the 1D thermal conduction model** and PARMERA, and also evaluated these properties experimentally. The estimated and measured results were not so serious for KU-FEL system. We will discuss the comparison between the experimental results and the calculation results in this conference.

* N. Okawachi, et al., Proc. of the FEL 2006, pp.664-667 (2006)** T. Kii, et al., Nucl. Instr. and Meth. A 483 310-314 (2002)

 
 
WEPPH024 Numerical Evaluation of Oscillator FEL with Multi-Bunch Photo-Cathode RF-gun in Kyoto University electron, undulator, laser, emittance 390
 
  • Y. Kamiya, M. Washio
    RISE, Tokyo
  • T. Kii, K. Masuda, S. Sasaki, T. Shiiyama, H. Zen, H. Ohgaki
    Kyoto IAE, Kyoto
  • M. Kuriki, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
  An infrared FEL (4-13 micro-m) facility to develop new energy materials is constructed in Institute of Advanced Energy, Kyoto University. The electron beam of 40 MeV has been successfully accelerated by a linac system which consists of a 4.5-cell thermionic RF gun*. However, due to severe back-bombardment effect, there still needs several efforts to extend the macro-pulse duration to obtain a stable FEL. Upgrade from the present thermionic RF gun to a photocathode RF gun has been planned in KU-FEL**, because a photocathode RF gun is free from the back-bombardment and can generate a high brightness electron beam. A multi-bunch photo-cathode RF gun system has been developed*** and will be installed into the KU-FEL linac. Thus a design work on the new linac system from the gun to the FEL has been performed by using PARMELA and GENESIS. The evaluated peak current is about 4 times and the expected FEL gain is about 10 times as high as those with the present system. The required laser system will be discussed in this conference, as well.

* H. Ohgaki, et al., NIM A, vol.528, pp.366-370 (2004).** H. Ohgaki, et al., Proc. of the FEL 2004, pp.454-457 (2004).*** K. Hirano, et al., NIM A, vol. 560, pp.233-239 (2006).

 
 
WEPPH025 Progress in the FEL Lasing in Kyoto University electron, cathode, undulator, alignment 394
 
  • T. Kii, K. Masuda, H. Ohgaki, T. Shiiyama, H. Zen, S. Sasaki
    Kyoto IAE, Kyoto
  We have constructed an infrared (4～13μm) FEL facility for advanced energy researches in Kyoto University. The numerical studies on the expected FEL gain, which was based on the experimental measurements both of the undulator and of the electron beam parameters, were carried out*. However, g-parameter of the mirror cavity was located close to the unstable region. In order to obtain a stable FEL, we calculated the FEL gain taking into account the duct shape, the tilt angle, and the offset of the mirror, then for the first lasing the mirror parameter was optimized. At the present stage, we have installed the undulator and the mirror cavity. A spectrum of the spontaneous emission was measured, which was consistent with the result of spectrum calculation obtained with measured magnetic field of the undulator. In this conference, we will present the result of the mirror optimization, and measurement of the spontaneous emission. The status of the experiment on FEL lasing will also be addressed.

* M. Nakano, et al., Proceedings of the 2006 FEL conference, (2006)

 
 
WEPPH026 Design Study of the Triode-Type Thermionic RF Gun cathode, coupling, electron, emittance 398
 
  • K. Kanno, E. Tanabe
    AET Japan, Inc., Kawasaki-City
  • T. Kii, K. Masuda, H. Ohgaki, S. Sasaki, H. Zen, T. Shiiyama
    Kyoto IAE, Kyoto
  We use a 4.5-cell RF gun with a thermionic cathode as the injector for our KU-FEL facility, having taken its advantageous features compared with photocathode guns, such as high averaged current, low cost and easy operation, while we suffer from the limited macro-pulse duration and peak current by the back-bombardment effect. To mitigate these adverse effects, we proposed the triode-type thermionic RF gun with an additional small cavity providing the accelerating phase nearby the cathode independent of the main cavity phase*. Results from PIC simulations show that the back-bombardment power can be reduced drastically by more than 80%, and in addition the peak current of the output electron beam will be improved greatly by supplying a moderate RF power of tens kW to the RF triode structure. The RF system of up to 100 kW capabilities has been prepared and tested. Also the prototype design of the triode-type thermionic RF gun was completed. The cavity parameters, namely the quality factor, shunt impedance, and the coupling coefficient with the RF feed coaxial cable were designed taking into account both the available maximum field on the cathode and the phase and amplitude stability against the expected variations of the beam loading and cavity temperature. We will also present PIC simulation prediction on the output beam characteristics promising the first FEL lasing.

* K. Masuda, et al., Proceedings of the 2006 FEL conference, (2006)

 
 
WEPPH027 Beam Diagnostics for the First Lasing of the KU-FEL electron, emittance, simulation, undulator 402
 
  • T. Kii, K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama, H. Zen
    Kyoto IAE, Kyoto
  Mid-IR FEL (4-13μm) device for energy science has been constructed in Institute of Advanced Energy, Kyoto University and the electron beam of 40MeV has been successfully accelerated*. The transverse phase space distribution and the corresponding emittance of the electron beam were measured by using a tomographic method**. As the result, normalized emittance was around 3 pi mm mrad. An FEL gain calculation*** shows that the peak current of 10A is the minimum value for the FEL amplification, and that of 40A is required to achieve the FEL saturation. Therefore the bunch compression experiment has been carried out to shorten the micro-bunch length by 2 ps in KU-FEL. The 180 deg. arc section was used for the bunch compression. We will report the result of the emittance measurement and of the bunch compression experiment in the conference.

* H. Ohgaki, et al., NIM A, vol.528, pp.366-370 (2004).** H. Zen, et al., Proc. of the FEL 2006, pp.592-595(2006)*** M. Nakano, et al., Proc. of the FEL 2006, pp.660-664 (2006).

 
 
WEPPH030 Development of a Precise Timing System for the ISIR L-Band Linac at Osaka University linac, laser, electron, single-bunch 413
 
  • T. Igo, G. Isoyama, R. Kato, M. Morio, S. Suemine, S. Kashiwagi
    ISIR, Osaka
  We are developing a free electron laser (FEL) in the infrared region and also conducting SASE experiment in the same wavelength region using the L-band linear accelerator at the Institute of Scientific and Industrial Research (ISIR), Osaka University. In order to conduct such studies, stable operation of the linac is critical, so that we have developed a highly precise and flexible timing system for stable generation of the high intensity electron beam with the energy region of 10-30 MeV. In the timing system, a rubidium atomic clock producing 10 MHz rf signal is used as a time base for a synthesizer which is used as the master oscillator for generating the acceleration frequency of 1.3 GHz. The 1.3 GHz signal from the master oscillator is directly counted down to produce the clock signal of the timing system at 27 MHz and the four rf signals for the linac and laser used in the beam line. The start signal for the linac is precisely synchronized with the 27 MHz clock signal. To make an arbitrary delayed timing signal, a standard digital delay generator is used to make a gate signal for a GaAs rf switch, which slices out one of the 27 MHz clock pulses to generate the delayed timing signal. Any timing signal can be made at an interval of 37 ns and the timing jitter of the delayed signal is less than 2 ps (rms). We will report the new timing system and its performance in detail.  
 
WEPPH031 Development of A Low Emittance DC Gun for Smith-Purcell BWO FEL emittance, cathode, simulation, electron 417
 
  • K. Akiyama, H. Hama, F. Hinode, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda, K. Kasamsook
    Tohoku University, School of Scinece, Sendai
  An electron DC gun capable for producing very low emittance beam is under developed at Laboratory of Nuclear Science, Tohoku University. The DC gun employs a high voltage of 50 kV to extract electrons, which is suitable to drive Smith-Purcell backward wave oscillator free electron laser (BWO FEL). A result of numerical simulation using a 3-D finite deference time domain (FDTD) method shows the BWO FEL oscillation at the terahertz wavelength region maybe achieved by using the electron beam with an emittance around 0.1 mmmrad. Average power is expected to be more than 100 W per square mm. In addition to which a very small cathode of LaB6 single crystal is employed for the gun, the geometrical structure is optimized to produce the lower emittance beam. A numerical calculation of the elctro-static model for the DC gun to solve equilibrated beam envelope predicts a normalized beam emittance of 0.2 mmmrad will be realized at the beam current of a couple of hundreds mA. Particularly by applying special bias voltage between the cathode and the wehnelt, the transverse distribution of electrons is possibly becoming to be an ideal Kapchinskij-Vladimirskij (K-V) beam, so that the space charge effect will be minimized. The paper will present the status of the development of the low emittance DC gun and various simulation result of the terahertz BWO FEL oscillation.  
 
WEPPH037 Coherence of Space Charge Vibrarion and Parameters of Electron Guns emittance, electron, space-charge, cathode 432
 
  • S. V. Miginsky
    BINP SB RAS, Novosibirsk
  Space charge effect always determines the motion of particles in electron guns. Coherence of space charge vibration leads to oscillation of the emittance along a gun or a charge affected beamline. This phenomenon is closely related to a technique known as emittance compensation. These phenomena together with others (non-coherent) have been considered in the paper. The optimal parameters of guns and the expected emittance of the beam from the optimal ones have been estimated and scaled.  
 
WEPPH046 A Superconducting RF Photo-Injector for Operation at the ELBE Linear Accelerator laser, cathode, vacuum, electron 449
 
  • A. Arnold, H. Buettig, D. Janssen, M. Justus, U. Lehnert, P. Michel, K. Moeller, P. Murcek, Ch. Schneider, R. Schurig, F. Staufenbiel, R. Xiang, J. Teichert
    FZD, Dresden
  • T. Kamps
    BESSY GmbH, Berlin
  • G. Klemz, I. Will
    MBI, Berlin
  • W.-D. Lehmann
    IfE, Dresden
  • A. Matheisen, B. van der Horst
    DESY, Hamburg
  • J. Stephan
    IKST, Drsden
  • V. Volkov
    BINP SB RAS, Novosibirsk
  • P. vom Stein
    ACCEL, Bergisch Gladbach
  For the ELBE superconducting linear accelerator at Forschungszentrum Dresden-Rossendorf (FZD) a radiofrequency photoelectron injector with a superconducting cavity (SRF gun) is under development. The SRF gun combines the excellent beam quality which can be delivered by RF photoinjectors with the possibility of continuous wave operation. The superconducting niobium cavity of the injector consists of 3½ cells and contains a Cs2Te photocathode which is normal-conducting and cooled by liquid nitrogen. The RF frequency of the cavity is 1.3 GHz. The final electron energy will be about 9.5 MeV and the average electron current will be 1 mA. In the past years the SRF photo injector has been designed and fabricated. Several critical subsystems have been tested. For the cavity, the results of the RF measurements will be shown. An UV driver laser system has been developed which fulfils the different requirements (77 pC at 13 MHz, 1 nC at 500 kHz) for the future operation at ELBE. A photo cathode preparation system was developed and installed. The equipment is now in operation and the first series of Cs2Te photo cathodes have been produced.  
 
WEPPH054 Coherent THz Light Source Using Very Short Electron Bunches from a Thermionic RF Gun electron, undulator, radiation, simulation 476
 
  • K. Akiyama, H. Hama, F. Hinode, K. Kasamsook, M. Kawai, K. Nanbu, T. Tanaka, M. Yasuda, T. Muto
    Tohoku University, School of Scinece, Sendai
  To develop a narrowband coherent Terahertz (THz) light source, a project for producing very short electron bunch has been progressed at Laboratory of Nuclear Science, Tohoku University. Coherent synchrotron radiation is another promising source for generation of high-power THz light. Passing through a conventional undulator with a field period length of ~ 10 cm, the very short electron bunch at the energy around 15 MeV can produce coherent THz radiation. The electron beams of which the bunch length is less than 100 femto-second will be generated by a combined injector system of a thermionic RF gun and a bunch compressor. We have developed an independently-tunable-cells (ITC) RF gun consisted with two uncoupled cavities in order to manipulate the longitudinal phase space. It was found out that the ITC-RF gun is possibly quite suitable to produce such a very short bunch employing a magnetic bunch compressor. In theoretical investigation at the moment, a bunch length of less than 50 fs has been achieved in the numerical tracking simulation. Employing Lienard-Weichert potential, we have performed a 3-D simulation of the coherent THz radiation. The paper will describes the latest status of development of the ITC RF gun and tracking simulations for the bunch compressor as well. Characteristics of the coherent THz radiation resulted from the simulation will be also reported  
 
FRAAU02 Status of the FEL Test Facility at MAX-lab laser, electron, linac, emittance 513
 
  • M. Abo-Bakr, J. Bahrdt, K. Goldammer
    BESSY GmbH, Berlin
  • M. Brandin, F. Lindau, D. Pugachov, S. Thorin, S. Werin
    MAX-lab, Lund
  • A. L'Huillier
    Lund University, Division of Atomic Physics, Lund
  An FEL test facility is built on the existing MAX-lab linac system in collaboration between MAX-lab and BESSY. The goal is to study and analyse seeding, harmonic generation, beam compression and diagnostic techniques with the focus of gaining knowledge and experience for the MAX IV FEL and the BESSY FEL projects. The test facility will in the first stage be using the 400 MeV linac beam to generate the third harmonic at 90 nm from a 266 nm Ti:SA seed laser. The optical klystron is installed and magnetic system, gun and seed laser systems are currently being finalised. Start-to-end simulations have been performed and operation modes for bunch compression defined. The linac and beam transport system is already in operation. We report the status and layout of the project, the issues to be addressed, the solutions for bunch compression and operation. We also report on the prospects of extending the seeding to HHG laser systems.  
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