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cathode

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MOPPH055 Measurements of the Projected Normalized Transverse Emittance at PITZ emittance, gun, booster, 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.  
 
MOPPH063 Potentialities of ELMI Device for Submillimeter Generation by Stimulated Intercavity Scattering in Planar FEM radiation, scattering, electron, simulation 156
 
  • N. S. Ginzburg, N. Yu. Peskov, A. Sergeev, V. Yu. Zaslavsky, I. V. Zotova
    IAP/RAS, Nizhny Novgorod
  • P. V. Kalinin, S. A. Kuznetsov, A. V. Arzhannikov
    BINP SB RAS, Novosibirsk
  Paper describes main features of a project on two-stage generation of submillimeter radiation at the ELMI device. This novel variant of a two-stage scheme based on stimulated intercavity scattering was proposed earlier in the paper*. In accordance with the scheme, at the first stage a sheet electron beam drives a 2D Bragg free electron maser (FEM) of planar geometry to generate 4-mm pump wave. At the second stage this wave undergoes stimulated scattering at the supplementary electron beam to produce submillimeter radiation. A key feature of a proposed scheme is to use two sheet beams with a few kiloampers currents that transported in parallel channels, which are connected by a special waveguide* for synchronization of beam radiation in different channels**. Production of two sheet beams by one accelerator diode with two cathodes is also similar to the process of operation of the multibeam diode described in Ref.**. Two-stage scheme allows us to use high power 4-mm radiation produced in the first channel by the sheet beam moving in an undulator quasi-static magnetic field, as an EM-undulator for the secondary stage FEL operating in Terahertz wave range. In the paper we describe results of theoretical and experimental investigations of various aspects of the two-stage scheme and some testing experiments on units for realization of this scheme at the ELMI device.

* A. V.Arzhannikov et al. Proc. Int. Workshop, N. Novgorod, Vol.1,p.228-232,2006.** A. V.Arzhannikov et al. Digest Tech. Papers, PPPS-2001, Las Vegas, Nevada, Vol.1, p.561-564,2001.

 
 
TUBAU02 Status of SCSS & X-ray FEL Project in Japan emittance, electron, gun, undulator 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.  
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TUBAU04 Towards a Low Emittance X-ray FEL at PSI emittance, electron, acceleration, simulation 224
 
  • A. Adelmann, A. Anghel, R. J. Bakker, M. Dehler, R. Ganter, C. Gough, S. Ivkovic, F. Jenni, C. Kraus, F. Le Pimpec, S. C. Leemann, K. B. Li, P. Ming, B. S.C. Oswald, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, T. Schietinger, V. Schlott, L. Schulz, A. Streun, F. Stulle, D. Vermeulen, F. Q. Wei, A. F. Wrulich, A. Oppelt
    PSI, Villigen
  The Paul Scherrer Institute (PSI) in Switzerland aims at building a compact and cost-effective X-ray FEL facility for the wavelength range 0.1 - 10 nm. Based on the generation of very low emittance beams, it consists of a low-emittance electron gun (LEG) followed by high-gradient acceleration, and advanced accelerator technology for preserving the initial low emittance during further acceleration and bunch compression. In order to demonstrate the feasibility of the concept and the emittance preservation, a 250 MeV test facility will be built. This machine has been designed to be used as injector for the X-ray FEL at a later date. The accelerator design of the 250 MeV linac will be presented in the paper together with the status of the LEG and high gradient acceleration.  
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TUPPH019 Simulations for the LCLS Injector emittance, simulation, laser, gun 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, gun, 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.  
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WEAAU04 Superconducting Photoinjector for High-Power Free Electron Lasers gun, electron, 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.  
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WEBAU01 Adaptive 3-D UV-laser Pulse Shaping System to Minimize Emittance for Photocathode RF Gun laser, emittance, electron, controls 298
 
  • T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, K. Yanagida, H. T. Tomizawa
    JASRI/SPring-8, Hyogo-ken
  • F. Matsui
    Industrial Technology Center of Fukui, Fukui City
  We developed an adaptive 3-D shaping (both temporal (1D) and spatial (2D)) short pulse (80 fs~40 ps) UV-laser system as an ideal light source for yearlong stable generation of a low emittance electron beam with a high charge (1~2 nC/pulse). In its current form, the laser’s pulse-energy stability has been improved to 0.2~0.3% (rms; 10 pps, 0.4 TW in femtosecond operation) at the fundamental wavelength and 0.7~1.4% at the third-harmonic generation. Such improvement reflects an ability to stabilize the laser system in a humidity-controlled clean room. The pulse-energy stability of a mode-locked femtosecond oscillator has been continuously held to 0.3% (p-p) for 10 months, 24 hours a day. In addition, the ideal spatial and temporal profiles of a shot-by-shot single UV-laser pulse are essential to suppress emittance growth in an RF gun. We apply a deformable mirror that automatically shapes the spatial UV-laser profile with a feedback routine, based on a genetic algorithm, and a pulse stacker for temporal shaping at the same time. The 3D shape of the laser pulse is spatially top-hat (flattop) and temporally a square stacked pulse. Using a 3D-shaped laser pulse with a diameter of 0.8 mm on the cathode and pulse duration of 10 ps (FWHM), we obtain a minimum normalized emittance of 1.4 π mm mrad with beam energy of 26 MeV.  
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WEPPH011 Photocathode Laser Pulse Diagnostics at PITZ laser, diagnostics, electron, emittance 346
 
  • J. W. Baehr, S. A. Korepanov, M. Krasilnikov, F. Stephan, M. Hänel
    DESY Zeuthen, Zeuthen
  • Ye. Ivanisenko
    KhNU, Kharkov
  The main objective of the Photo Injector Test facility at DESY in Zeuthen (PITZ) is the development of electron sources that meet the requirements for existing and future FELs such as FLASH or the European XFEL. The goal is the minimization of the transverse emittance of the produced electron bunches. In this respect one of the key issues is the cathode laser system, which should provide longitudinal and transversal flat-top pulses with an excellent long-term stability. In this work we present the full system of laser diagnostics that is currently used at PITZ to monitor the laser pulse parameters.  
 
WEPPH012 Investigations on the Thermal Emittance of Cs2Te Photocathodes at PITZ emittance, electron, laser, free-electron-laser 350
 
  • G. Asova, J. W. Baehr, C. H. Boulware, H.-J. Grabosch, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, B. Petrosyan, S. Rimjaem, J. Roensch, T. A. Scholz, L. Staykov, F. Stephan, S. Lederer
    DESY Zeuthen, Zeuthen
  • K. Boyanov
    INRNE, Sofia
  • L. H. Hakobyan
    YerPhI, Yerevan
  • R. Richter
    BESSY GmbH, Berlin
  • A. Shapovalov
    MEPhI, Moscow
  The main objective of the Photo Injector Test facility at DESY in Zeuthen (PITZ) is the production of electron beams with minimal transverse emittance. The lower limit of this property of electron beams produced with a photocathode in an RF-gun is determined by the thermal emittance. To understand this crucial parameter for high performance FEL’s, measurements under RF operation conditions for Cesium Telluride (Cs2Te) photocathodes are done. Results for various accelerating gradients and the dependence on the laser spot size in the cathode plane are presented and discussed in this work.  
 
WEPPH013 Status and Perspectives of the PITZ Facility Upgrade gun, emittance, 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.  
 
WEPPH014 Performance of the FERMI FEL Photoinjector Laser laser, beam-transport, controls, monitoring 358
 
  • A. A. Demidovich, R. Ivanov, P. Sigalotti, M. B. Danailov
    ELETTRA, Basovizza, Trieste
  The photoinjector laser system for the FERMI FEL has been installed at the ELETTRA laser laboratory. It is based on a completely CW diode pumping technology and features a two stage pulse shaping system, a time-plate type third harmonic generation scheme and aspheric shaper based beam shaping. The paper will present experimental results describing the overall performance of the amplifier system as well as of the main sub-system listed above. The data demonstrates that all the initially set parameters were met and some largely exceeded. Special attention is dedicated to the pulse shaping allowing both flat-top and increasing ramp UV temporal shapes. A scheme for extraction and shaping of the laser heater pulses using the same laser system is also presented.  
 
WEPPH017 UV Performances of Pulsed Laser Deposition Grown Mg Photocathodes laser, vacuum, gun, 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.  
 
WEPPH021 Wide Band Seeding and Wavelength Compression laser, electron, undulator, radiation 378
 
  • T. Shintake
    RIKEN Spring-8 Harima, Hyogo
  Seeding with optical laser and compressing wavelength in chicane bunch compressor has been studied theoretically. Overlapping laser beam with in comming electron beam in free space, with oblique crossing, we may apply energy modulation on relativisitic electron beam. When we use forth harmonic YAG-laser, 255 nm, and compressing 20 times, we have 13 nm density modulation period. Passing in undulator, which resonates to the compressed wavelength, the super-radiation mode beam will be generated. In contrast with SASE-FEL, this type of radiation source does not require high quality beam, ease to operate and coherent.  
 
WEPPH022 Feasibility Test of Shottoky Effect-Gated Photocathode RF Gun laser, polarization, gun, 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.  
 
WEPPH025 Progress in the FEL Lasing in Kyoto University electron, undulator, gun, 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 gun, 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)

 
 
WEPPH028 Development of a Compact Cherenkov Free-Electron Laser Operating Terahertz Wave Range electron, radiation, vacuum, free-electron-laser 406
 
  • M. R. Asakawa, N. M. Miyabe
    Kansai University, Osaka
  • A. Ikeda, M. Kusaba, Y. Tsunawaki
    OSU, Daito, Osaka
  We designed a compact Cherenkov Free-Electron Laser(CFEL) device capable of delivering mW-level output power at frequencies of up to THz from 10GHz to 1 THz. CFEL has the advantage of generating higher frequencies at lower electron beam energy. Due to lower electron beam CFEL device is compact. Our CFEL device consists of a waveguide partially filled with two lined parallel dielectric slabs through which a relativistic electron beam propagates. We call this structure "double-slab". In our device, the electron beam is generated using the Spindt cathode. We used a super conducting magnet to compress and guide the electron beam along the dielectric slabs. Assuming a dielectric slab thickness of 0.65mm,length of 11cm and electron beam energy 50keV ,the output power generated by the device was numerically calculated to be mW-level at 46GHz. Currently , we are conducting the POP experiment at millimeter wave range.  
 
WEPPH031 Development of A Low Emittance DC Gun for Smith-Purcell BWO FEL emittance, gun, 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.  
 
WEPPH034 Fourier and Non-Fourier Models for Photoemission laser, electron, vacuum, lattice 428
 
  • A. M. Mihalache, E. Mitru, M. Oane, C. Petit-Jean-Genaz
    INFLPR, Bucharest - Magurele
  This paper is a theoretical study on the photoemission properties of metallic photocathodes in the high intensity ultrashort laser pulse regime, using Fourier and non-Fourier models. First of all the Fourier-model was used. Next an analysis of the electron gas heating phenomenon and how this phenomenon leads to coupled heat equations (two temperature models). The authors also try to show that it is possible to use, in the second approximation, a non-Fourier model instead of two temperature models, using a single temperature hypothesis (the electron gas temperature equals with the lattice temperature). The distributions for thermal fields and photocurrents function of space, time, laser-intensity, incident angle and relaxation time are also represented.  
 
WEPPH037 Coherence of Space Charge Vibrarion and Parameters of Electron Guns gun, emittance, electron, space-charge 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 gun, laser, 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.  
 
WEPPH048 XPS Studies of Cs2Te Photocathodes electron, photon, laser, survey 457
 
  • H. A. Duerr, R. Ovsyannikov, M. Sperling, A. Vollmer
    BESSY GmbH, Berlin
  • J. H. Han, S. Schreiber, S. Lederer
    DESY, Hamburg
  • P. Michelato, L. Monaco, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
  • F. Stephan
    DESY Zeuthen, Zeuthen
  Cesium Telluride (Cs2Te) photocathodes are used as sources for electron beams because of their high quantum efficiency (QE) and their ability to release high peak current electron bunches in a high gradient RF-gun. Starting from a high QE level of about 10% the quantum efficiency of these cathodes decreases during operation in a photo-injector to below 0.5%. To understand this behaviour, XPS investigations on the chemical composition were performed at BESSY. In this contribution we compare two fresh cathodes from INFN with one used under normal operation at FLASH and one used at PITZ at a higher than usual RF-gradient of 60 MV/m.  
 
WEPPH049 Test of a Wiresanner in the Diagnostic Section of PITZ electron, diagnostics, undulator, background 461
 
  • G. Asova, J. W. Baehr, J. H. Han, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, V. Miltchev, A. Oppelt, B. Petrosyan, M. Sachwitz, L. Staykov, F. Stephan, H.-J. Grabosch
    DESY Zeuthen, Zeuthen
  The Photo Injector Test facility at Zeuthen (PITZ) has been established to optimize electron beams of high brilliance needed for short wavelength FELs. In a first step one wire scanner station, developed and used in the undulator section of FLASH at DESY, was tested in the diagnostic section of PITZ. Measurements of the beam-profile and the beam-position were performed to test the useability of such type of wire scanner at PITZ. The obtained results are presented and discussed. The test has shown that wire scanners of this type can be used successfully as complementary measurement device for beam-profile measurements at PITZ. In the final state of extension of PITZ , two wire scanners are foreseen as standard diagnostic tools.