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cathode

     
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MOP29 RHIC Electron Cooler electron, gun, emittance, linac 102
 
  • J. Kewisch, I. Ben-Zvi, R. Calaga, X.Y. Chang, A. Jain, V. Litvinenko, C. Montag, V. Yakimenko
    BNL, Upton, Long Island, New York
  Electron cooling has been applied in many accelerators with low energies where cooling times are short. Electron cooling is now considered for RHIC, where gold ions are stored at 100 GeV/u. For a cooling time of one hour an electron beam with 55 MeV and 10 nC/bunch is necessary. The transverse normalized emittance must be 50 mm·mrad, the energy spread 10-4. Only a Photo-cathode Energy Recovery LINAC (PERL) promises such quality. For a minimum electron temperature inside the 1 Tesla cooling solenoid it is necessary to have a "magnetized beam", i.e. a beam from a cathode immersed in a longitudinal magnetic field. The emittance compensation scheme used in RF guns was adapted so that the magnetization does not lead to strong emittance growth. A super-conducting cavity was developed for the RHIC electron cooler, optimized for high current operation. Simulations with the TBBU computer code show a multi-bunch beam breakup threshold of 3 Amperes. After acceleration the bunches are lengthened and the energy spread is reduced by rotation in the longitudinal phase space. The original bunch length must be restored by a second rotation before deceleration and energy recovery.  
 
MOP76 Ultra-High-Vacuum Problem for 200 keV Polarized Electron Gun with NEA-GaAs Photocathode gun, emittance, electron, ion 201
 
  • T. Nakanishi, F. Furuta, M. Kuwahara, K. Naniwa, S. Okumi, M. Yamamoto, N. Yamamoto, K. Yasui
    DOP Nagoya, Nagoya
  • H. Kobayakawa, Y. Takashima
    DOE Nagoya, Nagoya-City
  • M. Kuriki, H. Matsumoto, M. Yoshioka
    KEK, Ibaraki
  For a polarized electron source based on photoemission from GaAs, a NEA (Negative Electron Affinity) surface makes an indispensable role to extract polarized electrons in conduction band into vacuum. The NEA surface is also considered as a best surface to provide a beam with a minimum initial beam-emittance. However, the NEA surface state is realized by a mono-layer of electric dipole moment (that is Ga(-)-Cs(+)) formed at the surface and thus it is easily degraded by
  1. desorption of harmful residual gas,
  2. desorption of harmful gas created by field emission from HV-cathodes and
  3. ion back-bombardment.
In order to reduce the effects of (a) and (c), extremely good UHV is required. Presently total pressure of 4·10-12 torr and respective partial pressures of 3·10-13 torr and 4·10-13 torr for H2O and CO2 were achieved at our gun chamber. Field emission dark current must be extremely suppressed to reduce the effect of (c). The maximum field gradient of 7.8 MV/m is applied for electrode envelope (3.0 MV/m for cathode surface) at 200 kV DC bias-voltage, but total dark current was suppressed below 1 nA for our electrodes. The NEA lifetime under these conditions will be reported at the conference. 		 
 
MOP80 Development of Adaptive Feedback Control System of Both Spatial and Temporal Beam Shaping for UV-Laser Light Source for RF Gun laser, electron, gun, emittance 207
 
  • H. Tomizawa, T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T.  Taniuchi, K. Yanagida
    JASRI-SPring-8, Hyogo
  • F. Matsui
    FKLAB, Fukui City
  The ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from a photo-cathode rf gun. We have been developing highly qualified UV-laser pulse as a light source of the rf gun for an injector candidate of future light sources. The gun cavity is a single-cell pillbox, and the copper inner wall is used as a photo cathode. The electron beam was accelerated up to 4.1 MeV at the maximum electric field on the cathode surface of 175 MV/m. For emittance compensation, two solenoid coils were used. As the first test run, with a microlens array as a simple spatial shaper, we obtained a minimum emittance value of 2 π·mm·mrad with a beam energy of 3.1 MeV, holding its charge to 0.1 nC/bunch. In the next test run, we prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. We applied the both adaptive optics to automatically shape the both spatial and temporal UV-laser profiles with a feedback routine at the same time. We report herein the principle and developing process of our laser beam quality control system.  
 
TU202 Low Emittance 500 kV Thermionic Electron Gun emittance, gun, electron, space-charge 261
 
  • K. Togawa, H. Baba, T. Inagaki, K. Onoe, T. Shintake, T. Tanaka
    RIKEN Spring-8 Harima, Hyogo
  • H. Matsumoto
    KEK, Ibaraki
  A 500 kV pulsed electron gun has been constructed for the injector system of the SASE-FEL project at SPring-8 (SCSS project). A CeB6 single crystal was chosen as a thermionic cathode, because of its excellent emission properties. We have succeeded in generating a 500 keV beam with 1 A peak current and 3 μs FWHM. The beam was very stable with low jitter. The beam emittance has been measured by means of double-slits method, and the normalized rms emittance of 1.1 π·mm·mrad has been obtained. We report on the experimental result on the emittance measurement of the CeB6 electron gun.  
Transparencies
 
TUP47 The Photo Injector Test Facility at DESY Zeuthen: Results of the First Phase emittance, laser, gun, electron 375
 
  • A. Oppelt, K. Abrahamyan, I. Bohnet, J. Bähr, U. Gensch, H.-J. Grabosch, J.H. Han, M. Krasilnikov, D. Lipka, V. Miltchev, B. Petrosyan, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • W. Ackermann, W.F.O. Müller, S. Setzer, T. Weiland
    TU Darmstadt, Darmstadt
  • J.-P. Carneiro, K. Flöttmann, S. Schreiber
    DESY, Hamburg
  • E. Jaeschke, D. Krämer, D. Richter, M. von Hartrott
    BESSY GmbH, Berlin
  • P. Michelato, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
  • J. Rossbach
    Uni HH, Hamburg
  • W. Sandner, I. Will
    MBI, Berlin
  • I. Tsakov
    INRNE, Sofia
  The photo injector test facility at DESY Zeuthen successfully concluded it's first phase of operation in November 2003 (PITZ1). After a complete characterization of the injector, the gun has been delivered to Hamburg and has already been taken into operation on the VUV-FEL. The measurement program for the year 2003 included RF commissioning, emittance studies, momentum and bunch length measurements, and studies of the influence of the drive laser parameters. We provide an overview on the latest achievements in all of these topics.  
Transparencies
 
TUP48 Progress Report on the Flat Beam Experiment at the Fermilab/Nicadd Photoinjector Laboratory laser, emittance, simulation, quadrupole 378
 
  • Y.-E. Sun, K.-J. Kim
    Chicago University, Chicago, Illinois
  • N. Barov
    Northern Illinois University, DeKalb, Illinois
  • K. Desler
    DESY, Hamburg
  • H. Edwards, P. Piot, J. Santucci, J. Wennerberg
    FNAL, Batavia, Illinois
  • M. Huening
    Fermilab, Batavia, Illinois
  • S. Lidia
    LBNL/AFR, Berkeley, California
  • R. Tikhoplav
    Rochester University, Rochester, New York
  We report on our present progress toward the investigation on the generation of flat beam from an incoming angular-momentum-dominated beam, along with the associated diagnostics development. We focus on the evolution of the four-dimensional beam matrix upstream and downstream of the round-to-flat beam transformer. Finally we compare our latest experimental results with numerical and analytical models.  
 
TUP80 A Long-Pulse Modulator for the TESLA Test Facility (TTF) klystron, linac, coupling, linear-collider 459
 
  • W. Kaesler
    PPT, Dortmund
  The long-pulse (1.6 ms) klystron modulator for TTF is a hardtube pulser using a Bouncer-circuit for droop compensation. It is built up with new advanced components representing industrial standards. The on-/off switch is a rugged 12 kV IGCT-stack with a fast 4kA turn-off capability. The 100 kJ storage capacitor bank contains only three capacitors with self-healing, segmented PP-foil technology. A new 100 kA solid-state switch based on light triggered thyristors (LTT) replaced the standard ignitrons as crowbar switches. The 300 kW high voltage power supply is based on modern switched mode technology.  
 
TUP98 The Finite State Machine for Klystron Operation for VUV-FEL and European X-FEL Linear Accelerator klystron, power-supply, vacuum, bunching 510
 
  • W. Cichalewski, B. Koseda, A. Napieralski
    TUL, Lodz
  • F.-R. Kaiser, S. Simrock
    DESY, Hamburg
  In order to provide a pulsed RF power signal that fulfills all designers and users demands the work on power supplies, pulse transformers, waveguides and klystrons has to be well coordinated. Because operators not engineers will operate mention user facility therefore software has to be implemented in order to automate the enormous quantity of hardware operation accompanying regular operation of linear accelerator collider. A finite state machine is adequate formal description of reactive systems that has become starting point for designing our control software. To present the complexity of the task that establishing FSM for Klystron system would be, one has to become acquainted with complexity of the system itself. Therefore this article describes the construction and principles of the klystron and modulator as well as ideas concerning the implementation of a FSM for such a system.  
 
THP23 An Electrode With Molybdenum-Cathode and Titanium-Anode to Minimize Field Emission Dark Currents electron, ion, vacuum, feedback 645
 
  • T. Nakanishi, F. Furuta, T. Gotou, M. Kuwahara, K. Naniwa, S. Okumi, M. Yamamoto, N. Yamamoto, K. Yasui
    DOP Nagoya, Nagoya
  • H. Matsumoto, M. Yoshioka
    KEK, Ibaraki
  • K. Togawa
    RIKEN Spring-8 Harima, Hyogo
  A systematic study to minimize field emission dark currents from high voltage DC electrode has been continued. It is clearly demonstrated that much lower field emissions observed for Molybdenum (Mo) and Titanium (Ti) in comparison to Stainless-steel and Copper. Furthermore, by analyzing gap-length dependence data of the dark current from Mo and Ti, we can find a method to separate the primary field emission currents (FEC) from secondary induced currents (SIC). The latter currents will be created by possible bombardments of metal surface of anode or cathode by electrons or positive ions, respectively. From this data analysis, it is suggested that Mo is suitable for cathode due to its smallest FEC, and Ti is adequate for anode due to relatively small SIC. This prediction was confirmed by our experiment using a pair of Mo and Ti electrode, which showed the total dark current is suppressed below 1 nA at 105 MV/m applied for an area of 7 mm2 with a gap-length of 1.0 mm. Therefore this Mo-Ti electrode seems useful for a high field gradient DC gun, especially for a GaAs-photocathode gun using an NEA (Negative Electron Affinity) surface.  
 
THP24 Highly Polarized Electrons from GaAs-GaAsP and InGaAs-AlGaAs Strained Layer Superlattice Photocathodes electron, photon, laser, polarization 648
 
  • T. Nakanishi, F. Furuta, M. Kuwahara, K. Naniwa, T. Nishitani, S. Okumi, N. Yamamoto, K. Yasui
    DOP Nagoya, Nagoya
  • H. Horinaka, T. Matsuyama
    OPU, Osaka
  • H. Kobayakawa, Y. Takashima, Y. Takeda, O. Watanabe
    DOE Nagoya, Nagoya-City
  GaAs-GaAsP strained layer superlattice photocathode has been developed for highly polarized electron beams. This cathode achieved a maximum polarization of 92% with a quantum efficiency of 0.5%. Criteria for achieving the highest polarization together with high quantum efficiency using superlattice photocathodes are discussed based on experimental spin-resolved quantum efficiency spectra of GaAs-AlGaAs, InGaAs-AlGaAs and GaAs-GaAsP superlattice structures.  
 
THP25 Development of Field-Emission Electron Gun from Carbon Nanotubes electron, acceleration, vacuum, gun 651
 
  • Y. Hozumi
    GUAS/AS, Ibaraki
  • M. Ikeda, S. Ohsawa, T. Sugimura
    KEK, Ibaraki
  Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2] was achieved with 8 kV acceleration voltage by applying short grid pulses between cathode-grid electrodes. In order to proof utility, 100 kV gun system had been designed and structured since last year. Then the value of 300 mA was obtained based on 10-5…10-6 [Pa] back ground pressures. With some improvements anode currents of Ampere order is expected.  
 
THP26 Comparison of 2 Cathode Geometries for High Current (2 kA) Diodes simulation, electron, emittance, focusing 654
 
  • N. Pichoff
    CEA/DAM, Bruyères-le-Châtel
  • F. Bombardier, M. Caron, E. Merle, C. Noël, O. Pierret, R. Rosol, C. Vermare
    CEA, Pontfaverger-Moronvilliers
  • D.C. Moir
    LANL, Los Alamos, New Mexico
  • A. Piquemal
    CEA/PTN, Bruyères-le-Châtel
  AIRIX (FRANCE) and DARHT axis-1 (USA) are two high current accelerators designed for flash X-ray radiography. The electron beam produced (2 kA, 3.5 to 3.8 MV, 60 ns) is extracted from a velvet cold cathode. Specific calculations have demonstrated the influence of the cathode geometry on the emitted beam profile [1]. To check this assumption we have made two different experiments (DARHT March 2003 – AIRIX March 2004). We have compared the beam characteristics with two different geometries both theoretically and experimentally. The beam simulations have been done with 3 codes: a home-made code (M2V) and 2 commercial codes (PBGUNS and MAGIC). The extracted beam current and transverse profiles, for the first experiment, have been measured and compared to simulations results. In the second one, we have compared the beam’s extracted current and the energy spread.

[1] E. Merle et al., "Efforts to Improve Intense Linear Induction Accelerator (LIA) Sources for Flash Radiography",Proceedings of the LINAC2002 conference. August 19-23, 2002 Gyeongju, Korea.

 
 
THP27 Ultra Low Emittance Electron Gun Project for FEL Application emittance, gun, electron, simulation 657
 
  • R. Ganter, M. Dehler, J. Gobrecht, C. Gough, G. Ingold, S. Leemann, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, V. Schlott, A. Streun, A. Wrulich
    PSI, Villigen
  • A. Candel, K. Li
    ETH, Zürich
  Most of the current 1Å Free-Electron Laser (FEL) projects are based on thermionic or photocathode guns aiming at an electron beam emittance of 0.5 to 1 mm·mrad. The design of a gun capable of producing a beam with an emittance one or two order of magnitude lower than the state of the art would reduce considerably the cost and size of such a FEL. Due to the recent advances in nanotechnologies and vacuum microelectronics, a field-emitter based gun is a promising alternative scheme. We present first measurements on commercial field emitter arrays as well as 3-D numerical simulations of the electron beam dynamics for typical bunch distributions generated from field emitters in realistic gun geometries. The design and some experimental results on a 500kV pulser is also presented.  
Transparencies
 
THP39 Operation of a 1.3 GHz, 10 MW Multiple Beam Klystron klystron, electron 693
 
  • H.P. Bohlen, A. Balkcum, M. Cattelino, L. Cox, M. Cusick, S. Forrest, F. Friedlander, A. Staprans, E. Wright, L. Zitelli
    CPI, Palo Alto, California
  • K. Eppley
    SAIC, Boston
  Results will be reported for a 1.3 GHz, 10 MW multiple beam klystron that is being developed for the TESLA linear accelerator facility. The design parameters for the device are 10 MW peak RF output power with 150 kW average power, 1.5 ms pulse length, 65% efficiency, 50 dB gain, and 2.0 A/cm2 maximum cathode loading. Initial testing of the device has validated the basic design approach. Six 120 kV electron beams of measurably identical currents of 22.9 A each have been successfully propagated through the klystron circuit with 99.5% DC beam transmission at full operating video duty and with 98.5% saturated RF transmission. A peak power of 10 MW at 1.3 GHz with 60% efficiency and 49 dB of gain has been measured.  
 
THP45 The Toshiba E3736 Multi Beam Klystron klystron, electron, gun, simulation 706
 
  • A. Yano, S. Miyake
    TETD, Saitama
  • Y.H. Chin
    KEK, Ibaraki
  • S.Y. Kazakov
    IHEP Protvino, Protvino, Moscow Region
  • A.V. Larionov, V.E. Teryaev
    BINP SB RAS, Protvino, Moscow Region
  A 10 MW, L-band multi beam klystron (MBK) for TESLA linear collider and TESLA XFEL has been under development at Toshiba Electron Tubes & Devices Co., Ltd. (TETD) in collaboration with KEK. The TESLA requires pulsed klystrons capable of 10 MW output power at 1300 MHz with 1.5 ms pulse length and a repetition rate of 10 pps. The MBK with 6 low-perveance beams in parallel in the klystron enables us to operate at lower cathode voltage with higher efficiency. The design work has been accomplished and the fabrication is under way. We are going to start conditioning and testing of prototype #0 in the beginning of June 2004. The design overview and the initial test results at the factory will be presented.  
 
THP47 The RF-System for A High Current RFQ at IHEP klystron, power-supply, rfq, monitoring 712
 
  • Z. Zhang, J. Li, J. Qiao, X. Xu
    IHEP Beijing, Beijing
  The R&D of a high current proton RFQ is one of the most important research tasks of the Accelerator Driven Sub-critical system (ADS) basic research project. In preliminary research phase, the 352.2 MHz RF system will be operated in pulse mode. CERN kindly provided IHEP with some RF equipment. Because the given RF system was used for CW operation at CERN before, to apply them to our pulse mode operation, some modifications and improvements are necessary. We made some indispensable assemblies, and also did some tests and commissioning of every sub-system. At present, the initial high power conditioning of the klystron is finished, and output power can reach nominal value. A description of RF power system is given, in particularly, the performance of HV power supply, thyratron crowbar and capacitors, hard tube modulator and its control electronics, and klystron power conditioning are presented.  
Transparencies
 
THP50 The CEBAF RF Separator System Upgrade power-supply, resonance, controls, ion 721
 
  • C. Hovater, M. Augustine, A. Guerra, R. Nelson, R.A. Terrel, M. Wissmann
    TJNAF, Newport News, Virginia
  The CEBAF accelerator uses RF deflecting cavities operating at the third sub-harmonic (499 MHz) of the accelerating frequency (1497 MHz) to “kick” the electron beam to the experimental halls. The cavities operate in a TEM dipole mode incorporating mode enhancing rods to increase the cavity’s transverse shunt impedance. As the accelerators energy has increased from 4 GeV to 6 GeV the RF system, specifically the 1 kW solid state amplifiers, have become problematic, operating in saturation because of the increased beam energy demands. Two years ago we began a study to look into replacement for the RF amplifiers and decided to use a commercial broadcast Inductive Output Tube (IOT) capable of 30 kW. The new RF system uses one IOT amplifier on multiple cavities as opposed to one amplifier per cavity originally. In addition the new RF system supports the proposed 12 GeV energy upgrade to CEBAF. Currently we are halfway through the upgrade with two IOTs in operation and two more to be installed. This paper reports on the new RF system and the IOT performance.  
 
THP95 Electro Polishing of Niobium Cavities at DESY acceleration, synchrotron, electron 824
 
  • A. Matheisen, L. Lilje, H. Morales, B. Petersen, M. Schmoekel, N. Steinhau-Kühl
    DESY, Hamburg
  At DESY a facility for electro polishing (EP) of the super conducting (s.c.) TESLA/TTF cavities have been built and is operational since summer 2003. The EP infrastructure is capable to handle single-cell structures and the standard TESLA/ TTF nine-cell cavities. Several electro polishing processes have been made since and acceleration voltage up to 40 MV/m have been reached in nine cell structures. We report on measurements and experiences gained since 2003 as well as on handling procedures developed for the preparation of electro polished resonators. Specific data like heat production, variation of current density and bath aging will be presented. Another important point for reproducible results is the quality control of the electro polishing process. First quality control steps to be implanted in the EP procedure for large-scale production will be described.  
 
FR104 Overview on High-Brightness Electron Guns electron, emittance, brightness, gun 842
 
  • J.W. Lewellen
    ANL, Argonne, Illinois
  In an electron storage ring, the quality of the electron beam is generally a function of the ring lattice parameters and has little to do with the source of the electrons. In most electron linear accelerators, the beam brightness is set by the beam source. It is very difficult to improve the overall beam brightness after it has been produced; on the other hand, providing a brighter beam source can provide an “instant upgrade” to the performance of a brightness-limited electron linac-based facility. The development and routine operation of high-brightness guns, therefore, is critical to the success of next-generation linac-based light sources. This includes sources already under construction, such as LCLS, as well as proposed and as-yet completely theoretical machines. In this talk I present a general overview of the state-of-the-art in high-brightness electron beam source development, discuss the concept of “situational brightness”, and highlight some interesting paths towards future devices. I conclude with thoughts on some possible alternate applications for high-brightness beams.  
Transparencies