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MO101 Advanced Analysis in Nanospace: Research with the XFEL laser, free-electron-laser, radiation 1
 
  • H. Dosch
    MPI, Stuttgart
  Little happens in industrialised countries without the use of high-tech materials which are the building blocks of all modern technologies ranging from information, communication, health, energy and environment to transport. In the last decades the development of novel materials has progressed at a breathtaking rate. This has become possible through our microscopic insight into the atomistic structure of condensed matter which finally enabled us to assemble new material systems atom-by-atom. These days, we are facing a revolution in the investigation of nanospace: Through new concepts in accelerator physics, electrons can be forced to emit short-pulsed x-ray laser radiation. Such a futuristic European x-ray free electron laser (XFEL) laboratory is currently being constructed and will allow mankind to finally get holographic snapshots of the motion of atoms and electrons in materials. Ultimate insights into matter, as the realtime-observation of the formation and the breaking of molecular bonds, sound like science fiction, but could become reality in less than a decade, if Europe embarks today into this bold adventure which will lead us into unexplored dimensions of nanospace.  
 
MO102 Accelerator Layout of the XFEL linac, site, photon, undulator 2
 
  • R. Brinkmann
    DESY, Hamburg
  The X-ray Free Electron Laser XFEL is a 4th generation synchrotron radiation facility based on the SASE FEL concept and the superconducting TESLA technology for the linear accelerator. In February 2003 the German government decided that the XFEL should be realized as a European project and located at DESY/Hamburg. The Ministry for Research and Eduation also announced that Germany is prepared to cover half of the investment and personnel costs of the project. This paper gives an overview of the overall layout and parameters of the facility, with emphasis on the accelerator design, technology and physics.  
Transparencies
 
MO202 High-Intensity, High Charge-State Heavy Ion Sources ion, laser, ion-source, plasma 8
 
  • J. Alessi
    BNL, Upton, Long Island, New York
  There are many accelerator applications for high intensity heavy ion sources, with recent needs including dc beams for RIA, and pulsed beams for injection into synchrotrons such as RHIC and LHC. The present status of sources producing high currents of high charge state heavy ions will be reviewed. These sources include ECR, EBIS, and Laser ion sources. The benefits and limitations for these type sources will be described, for both dc and pulsed applications. Possible future improvements in these type sources will also be discussed.  
Transparencies
 
MO203 Non-Interfering Beam Diagnostic Developments diagnostics, ion, linac, proton 13
 
  • A. Peters, P. Forck
    GSI, Darmstadt
  New high power proton and heavy ion linac projects are a big challenge for beam diagnostic developments. Due to the high inherent beam power mostly all destructive measurement techniques are not applicable. Thus a lot of beam diagnostic developments are under way from enhancements of well-known systems like beam position pick-ups or current transformers to new designs for profile or bunch length measurements using e.g. the interaction of the high power beams with the residual gas in the linacs. The latest progress in this field will be reviewed with descriptions of some remarkable solutions.  
Transparencies
 
MOP17 Design of the SPES-1 LEBT rfq, simulation, ion, proton 72
 
  • E. Fagotti
    INFN Milano, Milano
  • M. Comunian, A. Pisent
    INFN/LNL, Legnaro, Padova
  The low-energy-beam transport (LEBT) system for the SPES-1 accelerator transports the beam at 80 keV and 30 mA from the ion-source TRIPS to the TRASCO RFQ entrance. A second mode of operation corresponding to 10 mA current is also foreseen. The code PARMELA performed these simulations of the beam transport through the LEBT. This code is used to transport H+ and H2+ in the electrostatic fields of the ion-source extraction, in the magnetic fields of both the source and the solenoid lenses and under space charge and neutralization influence.  
 
MOP21 The Pre-Injector Linac for the Diamond Light Source linac, gun, diagnostics, booster 84
 
  • C. Christou, V. Kempson
    DIAMOND, Chilton, Didcot, Oxon
  • K. Dunkel, C. Piel
    ACCEL, Bergisch Gladbach
  The Diamond Light Source is a new medium-energy high brightness synchrotron light facility which is under construction on the Rutherford Appleton Laboratory site in the U.K. The accelerator facility can be divided into three major components; a 3 GeV 561 m circumference storage ring, a full-energy booster synchrotron and a 100 MeV pre-injector linac. This paper describes the linac design and plans for operation. The linac is supplied by ACCEL Instruments GmbH under a turn-key contract, with Diamond Light Source Ltd. providing linac beam diagnostics, control system hardware and standard vacuum components. Commissioning of the linac will take place in early 2005 and user operation of the facility will commence in 2007.  
 
MOP25 The LEBRA 125 MeV Electron Linac for FEL And PXR Generation linac, klystron, laser, undulator 90
 
  • K. Hayakawa, Y. Hayakawa, K. Ishiwata, K. Kanno, K. Nakao, T. Sakai, I. Sato, T. Tanaka
    LEBRA, Funabashi
  • K. Yokoyama
    KEK, Ibaraki
  A 125 MeV electron linac has been constructed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University for Free Electron Laser (FEL) and Parametric X-ray (PXR) generation. Two klystrons feed rf power of approximately 20 MW peak and 20 μsec pulse duration each to an injector and three 4 m accelerating structures. Phase of the rf fed to each component is controlled independently. Two accelerating structures connected with the second klystron and a ninety degrees bending system as a momentum analyzer constitute a magnetic bunching system. Electron bunches of 3 to 4 psec width formed at the injector are compressed to within 1 psec during passing through the magnetic bunching system. Peak current of the electron beam injected to the FEL system installed downstream of the momentum analyzer is expected to be about 50 A. FEL lasing has been achieved at the wavelength range from 1 to 6 mm. Estimated peak power of the extracted FEL light pulse is about 2 MW. Applied researches using the FEL started last autumn. Preliminary experiment for the PXR generation has been continued.  
 
MOP26 ERLP Gun Commissioning Beamline Design diagnostics, gun, emittance, laser 93
 
  • D.J. Holder, C.K.M. Gerth, F.E. Hannon
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • R.J. Smith
    CLRC, Daresbury, Warrington, Cheshire
  The 4GLS project is a novel next-generation solution for a UK national light source. It is based on an energy recovery linac (ERL) operating at high average beam currents up to 100 mA and with compression schemes producing pulses in the 10 - 100 fs range. This challenging accelerator technology, new to Europe, necessitates a significant R&D programme and a major part of this is a low-energy prototype, the ERLP, which is currently under construction at Daresbury Laboratory, in the north-west of England. The first components of ERLP to be built will be the DC photocathode gun and low-energy beam transport and diagnostics. The gun will initially be operated with a diagnostic beamline in order to measure the properties of the high-brightness beams generated as fully as possible. This will allow comparison of its performance with the results of multi-particle tracking codes, prior to its integration into the ERLP machine. The diagnostic beamline will include diagnostics for measuring the transverse and longitudinal properties of the electron beam. This paper will describe the design of this diagnostic beamline and demonstrate through simulation, the expected characteristics and performance achievable from this system.  
 
MOP27 Commissioning of a 6 MeV X-Band SW Accelerating Guide linac, vacuum, gun, injection 96
 
  • Q. Jin, Y. Lin, X. Sun, X. Tao, D. Tong
    TSINGHUA, Beijing
  • B. Chen, B. Sun, Y. Zou
    BIEVT, Beijing 100016
  A 6 MeV, X-band on-axis SW electron linear accelerating guide is being developed in Accelerator laboratory of Tsinghua University. It can be suitable for portable radiation therapy and radiography. The design, manufacture and high power test of the guide are given in this paper. The guide is 38 cm long and contains 25 accelerating cells with 24 coupling cells, operated in the π/2 mode. The RF power source is a pulsed magnetron at 9300 MHz with 1.5 MW peak power. The results of beam tests are following: the electron energy is more than 6 MeV at 50 mA and focal spot size is less than φ 1.5 mm without any focusing solenoid.  
 
MOP29 RHIC Electron Cooler cathode, 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.  
 
MOP30 Linear Accelerator LINAC-800 of the DELSY Project acceleration, linac, gun, radiation 105
 
  • V.V. Kobets, N. Balalykin, I.N. Meshkov, I.A. Seleznev, G. Shirkov
    JINR, Dubna, Moscow Region
  In the report the modernization of electron linear accelerator MEA (Medium Energy Accelerator) is discussed. The goal of the work is to create on the base of MEA a complex of free electron lasers overlaying a range of radiation waves from infrared to ultraviolet. Status of the work is reported.  
 
MOP31 Development of a C-band Accelerating Module for SUPERKEKB linac, positron, klystron, acceleration 108
 
  • S. Ohsawa, M. Ikeda, K. Kakihara, T. Kamitani, T. Oogoe, T. Sugimura, S. Yamaguchi, K. Yokoyama
    KEK, Ibaraki
  High power rf processing of 1 m C-band accelerating section for Super KEKB was successfully performed and power corresponding to 42 MV/m was achieved. Processing data were accumulated including acoustic sensor to find the arcing position. No structural damage was observed from the phase shift measurement performed after the processing. Processed accelerator was installed in the beam line of KEKB linac and being re-processed. The beam acceleration of 40 MV/m was successfully achieved in October 2003. Present status of C-band accelerator development is reported.  
 
MOP34 Injector Linac Upgrade for the BEPCII Project positron, linac, target, gun 111
 
  • S.H. Wang
    IHEP Beijing, Beijing
  BEPCII- an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e+e- collider. It requests its injector linac to have the higher beam energy (1.89 GeV) for on-energy injection and the higher beam current (40 mA e+ beam) for higher injection rate (≥50 mA/min). The low beam emittance (1.6 π·mm·mrad for e+ beam, and 0.2 π·mm·mrad for 300 mA e- beam) and low beam energy spread (±0.5%) are also requested to meet the storage ring acceptance. Hence the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and now being installed in their final positions, which are described in this paper. The beam commissioning is expected to start from the October of 2004.  
Transparencies
 
MOP35 The Research of a Novel SW Accelerating Structure with Small Beam Spot coupling, photon, focusing, target 114
 
  • X. Yang, H. Chen, Y. Chen, X. Jin, M. Li, H. Lu, Z. Xu
    CAEP/IAP, Mianyang, Sichuan
  A new kind of on-axis coupled biperiodic standing-wave (SW) accelerating structure has been built for a 9 MeV accelerator. The research progress was introduced in this paper, it includes the choice of the accelerating structure, the analysis of electron beam dynamics, the tuning of the cavity, the measurement of the accelerating tube and the powered test. The small beam spot is the most interesting feature of this accelerating structure, the diameter of the beam spot is 1.4 mm. This accelerator has been used for the x photons generation and the x-ray dose rate is about 3400 rad/min/m.  
 
MOP37 Optimization of Positron Capture in NLC positron, target, injection, emittance 120
 
  • Y.K. Batygin
    SLAC, Stanford
  In the Next Linear Collider design, the positron capture system includes a positron production target, a flux concentrator, and a linac to accelerate positrons up to 1.9 GeV, the injection energy of the positron pre-damping ring. Two schemes for positron production have been studied:
  1. a conventional approach with a 6.2 GeV electron beam interacting with a high-Z target and
  2. polarized positron production using polarized photons generated in a helical undulator by a 150 GeV electron beam which then interact with a positron production target.
The capture system has been optimized to insure high positron yield into the 6-dimensional acceptance of the pre-damping ring. Various parameters affecting the positron capture have been analyzed, including: positron deceleration after the flux concentrator, transverse and longitudinal electron beam sizes for positron generation, energy compression after acceleration, etc. As a result of these optimization studies, the positron yield in the conventional scheme has been increased from 1.0 to at least 1.5 and for the polarized positron scheme from 0.25 to 0.30 while maintaining 60% positron polarization.
 
Transparencies
 
MOP38 Background from Undulator in the Proposed Experiment with Polarized Positrons undulator, background, photon, positron 123
 
  • Y.K. Batygin
    SLAC, Stanford
  E-166 is a proposed experiment for verification of polarized positron production for linear collider. According to polarized positron source design, high energy electrons pass through helical undulator and produce circularly polarized photons, which interact with tungsten target and produce longitudinally polarized positrons. In the proposed E-166 experiment, 50 GeV beam propagates inside 1m long undulator followed by a drift space of 35 m before interaction with target. Polarized positrons are analyzed by Si-W calorimeter, which is placed along the axis. Polarized positrons are analyzed by CsI calorimeter after reconversion of positrons to photons at the second target. Background is an issue for a considered experiment. GEANT3 simulations were performed to model production of secondary particles from primary electrons hitting undulator. Energy density distribution of background particles at the target and effect of background collimation are discussed.  
 
MOP44 Electron-Cloud Effects in the Positron Linacs of Future Linear Colliders linac, positron, simulation, acceleration 141
 
  • D. Schulte, A. Grudiev, F. Zimmermann
    CERN, Geneva
  • K. Oide
    KEK, Ibaraki
  Inside the rf structures of positron linacs for future linear colliders, electron multipacting may occur under the combined influence of the beam field and the electromagnetic rf wave. The multipacting could lead to an electron-cloud build up along the bunch train. We present simulation results of this effect for various proposed designs, and discuss possible consequences and eventual countermeasures.  
Transparencies
 
MOP46 Experimental Investigation of the Longitudinal Beam Dynamics in a Photo-Injector using a Two-Macroparticle Bunch simulation, booster, laser, bunching 147
 
  • R. Tikhoplav, A.C. Melissinos
    Rochester University, Rochester, New York
  • N. Barov, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois
  • P. Piot
    FNAL, Batavia, Illinois
  We have developed a two-macroparticle bunch to explore the longitudinal beam dynamics through various component of the Fermilab/NICADD photoinjector laboratory. Such a two-macroparticle bunch is generated by splitting the photocathode drive laser impinging the photocathode. The presented method allows the exploration of rf-induced compression in the 1+1/2 cell rf-gun and in the 9-cell TESLA cavity. It also allows a direct measurement of the magnetic chicane bunch compressor parameters such as its momentum compaction. The measurements are compared with analytical and numerical models. Finally we present possible extension of the technique to investigate the transverse beam dynamics.  
 
MOP48 Gamma and X-rays Production for Experiments at ELSA Facility laser, emittance, target, linac 153
 
  • J. Lemaire
    CEA/DAM, Bruyères-le-Châtel
  The ELSA facility is a high brightness 18 MeV electron source dedicated to electron radiation, gamma-rays and picosecond hard and soft X-rays. It consists of a 144 MHz RF photoinjector producing short bunches which are further accelerated to a final energy varying from 2 to 18 MeV thanks to three 433 MHz RF cavities. Former beam compression design used a half turn magnet compressor system. It has been recently replaced by a double alpha magnet compressor. Electron beams are now delivered to a new experimental room. We present the new panel of interests offered by this facility in term of gamma-ray and X-ray production.  
 
MOP62 Energy Spread in BTW Accelerating Structures at ELETTRA linac, single-bunch, simulation, target 159
 
  • P. Craievich, R.J. Bakker, G. D'Auria, S.D. Di Mitri
    Sincrotrone Trieste S.C.p.A., Basovizza, Trieste
  The FEL project FERMI@ELETTRA will use the existing 1.0 GeV Linac, based on Backward Travelling Wave (BTW) structures, to produce VUV radiation between 100–10 nm. The project will be articulated in two different phases (100–40 nm/40–10 nm) and will require high quality beam with short bunches (500/160 fsec). Hence, wakefield effects have to be considered with respect to the electron beam quality. The single bunch energy spread induced by the short-range longitudinal wakefield is analyzed and results of start-to-end simulations are reported.  
 
MOP72 RF Breakdown in Accelerator Structures: From Plasma Spots to Surface Melting plasma, site, simulation, radio-frequency 189
 
  • P.B. Wilson
    SLAC, Menlo Park, California
  Plasma spots are known to form at field emission sites in regions of high dc or rf electric field. Several mechanisms for the formation of plasma spots in an rf field have been proposed, and one such mechanism which fits experimental data is presented in this paper. However, a plasma spot by itself does not produce breakdown. A single plasma spot, with a lifetime on the order of 30 ns, extracts only a negligible amount of energy from the rf field. The evidence for its existence is a small crater, on the order of 10 microns in diameter, left behind on the surface. In this paper we present a model in which plasma spots act as a trigger to produce surface melting on a macroscopic scale (~0.1 mm2). Once surface melting occurs, a plasma that is capable of emitting several kiloamperes of electrons can form over the molten region. A key observation that must be explained by any theory of breakdown is that the probability of breakdown is independent of time within the rf pulse–breakdown is just as likely to occur at the beginning of the pulse as toward the end. In the model presented here, the conditions for breakdown develop over many pulses until a critical threshold for breakdown is reached.  
Transparencies
 
MOP74 Recent Results of the 2.45 GHz ECR Source Producing H- Ions at CEA/Saclay plasma, ion, ion-source, extraction 195
 
  • R. Gobin, K. Benmeziane, O. Delferriere, R. Ferdinand, F. Harrault
    CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex
  • A. Girard
    CEA DSM Grenoble, Grenoble
  Low frequency ECR plasma sources have demonstrated their efficiency, reproducibility and long life time for the production of positive light ions. In 2003, the new 2.45 GHz ECR test stand based on a pure volume H- ion production, developed at CEA/Saclay, showed a dramatic increase of the H- extracted ion beam. In fact, a stainless steel grid now divides the plasma chamber in two different parts: the plasma generator zone and the negative ion production zone. By optimizing the grid position and its potential with respect to the plasma chamber, the negative ion current reached close to 1 mA. Ceramic plates, covering the plasma chamber walls help electron density and lead to an optimisation of the ion production. A 50 % improvement has been observed. A new 6 kW magnetron RF generator now replaces the 1.2 kW previous one and the current will be soon plotted versus the RF power. New Langmuir probe measurements are also expected on both sides of the grid. The last results will be reported and discussed.  
Transparencies
 
MOP75 Hminus Distribution in the HERA RF-Volume Source laser, plasma, acceleration, extraction 198
 
  • J. Peters
    DESY, Hamburg
  The HERA RF-Volume Source is the only source available that delivers routinely an Hminus current of 40 mA without Cs. The production mechanism for Hminus ions in this type of source is still under discussion. Laser photodetachment measurements have been started at DESY in order to measure the Hminus distribution in the source. The measurements have also been done under extraction conditions at high voltage. The results of the measurements with and without extraction are a basis for the development of a theory for the transition between plasma and vacuum (sheath), a cornerstone for beam transport programs. Knowledge of the H- distribution and where they are produced makes further source improvements possible.  
 
MOP76 Ultra-High-Vacuum Problem for 200 keV Polarized Electron Gun with NEA-GaAs Photocathode gun, emittance, ion, cathode 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, gun, emittance, cathode 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.  
 
MOP81 Analysis of the Qualification-Tests Performance of the Superconducting Cavities for the SNS Linac linac, simulation, radiation, ion 210
 
  • J. R. Delayen, J. Mammosser, O. Ozelis
    Jefferson Lab, Newport News, Virginia
  Thomas Jefferson National Accelerating Facility (Jefferson Lab) is producing superconducting radio frequency (SRF) cryomodules for the Spallation Neutron Source (SNS) cold linac. This consists of 11 medium-beta (β=0.61) cyomodules of 3 cavities each, and 12 high-beta (β=0.81) cryomodules of 4 cavities each. Before assembly into cavity strings the cavities undergo individual qualification tests in a vertical cryostat (VTA). In this paper we analyze the performance of the cavities during these qualification tests, and attempt to correlate this performance with cleaning, assembly, and testing procedures. We also compare VTA performance with performance in completed cryomodules.  
 
MOP82 SRF Cavity and Materials R&D at Fermilab superconductivity, superconducting-RF, vacuum, emittance 213
 
  • N. Khabiboulline, P. Bauer, L. Bellantoni, T. Berenc, C. Boffo, R. Carcagno, C. Chapman, H. Edwards, L. Elementi, M. Foley, E. Hahn, D. Hicks, D. Mitchell, A. Rowe, N. Solyak, I. Terechkine
    FNAL, Batavia, Illinois
  • A. Gurevich, M. Jewell, D. C. Larbalestier, P. Lee, A. Polyanskii, A. Squitieri
    UW-Madison/ASC, Madison, Wisconsin
  Two 3.9 GHz superconducting RF cavities are under development at FNAL for use in the upgraded Photoinjector Facility. A TM110 mode cavity will provide streak capability for bunch slice diagnostics, and a TM010 mode cavity will provide linearization of the accelerating gradient before compression for better emittance. The status of these two efforts and a review of the FNAL infrastructure development will be given.  
 
MOP85 Influence of Ta Content in High Purity Niobium on Cavity Performance: Preliminary Results* vacuum, superconductivity, coupling 219
 
  • P. Kneisel, G. Myneni
    Jefferson Lab, Newport News, Virginia
  • T. Carneiro
    RMC, Bridgeville
  • M. Imagumbai
    CBMM, Tokyo
  • Chr. Klinkenberg
    NPC, Düsseldorf
  • D. Proch, W. Singer, X. Singer
    DESY, Hamburg
  In a previous paper* a program designed to study the influence of the residual tantalum content on the superconducting properties of pure niobium metal for RF cavities was outlined. The main rationale for this program was based on a potential cost reduction for high purity niobium, if a less strict limit on the chemical specification for Ta content, which is not significantly affecting the RRR–value, could be tolerated for high performance cavities. Four ingots with different Ta contents have been melted and transformed into sheets. In each manufacturing step the quality of the material has been monitored by employing chemical analysis, neutron activation analysis, thermal conductivity measurements and evaluation of the mechanical properties. The niobium sheets have been scanned for defects by an eddy current device. From three of the four ingots—Ta contents 100, 600 and 1,200 wppm—two single cell cavities each of the CEBAF variety have been fabricated and a series of tests on each cavity with increasing amount of material removal have been performed. This contribution reports about the results from different tests and gives an analysis of the data.

*T. Carneiro et al; http://conference.kek.jp/SRF2001/

 
 
MOP87 Conceptual Layout of the European X-FEL Linear Accelerator Cryogenic Supply linac, vacuum, booster, superconducting-magnet 225
 
  • B. Petersen, H. Lierl, A. Zolotov
    DESY, Hamburg
  As a source for the European x-ray free electron laser (European X-FEL project) at DESY a superconducting linear accelerator will deliver a pulsed electron beam of about 20 GeV. A conceptual layout for the cryogenic supply of the linac is presented. The linac will consist of about 1000 superconducting niobium 1.3 GHz 9-cell cavities, which will be cooled in a liquid helium bath at a temperature of 2 K. Eight cavities and one superconducting magnet package will be assembled to a cryomodule of 12.2 m length. The cryomodules are equipped with two thermal shields at a 5 K and 80 K temperature level respectively. The linac of about 1.6 km length will be divided in 10 cryogenic sub units. Each sub unit will consist of 12 cryomodules. In addition to the main linac, two injector sections have to be supplied separately by means of helium refrigerators and a related helium distribution system.  
 
TU102 Survey of Advanced Acceleration Techniques laser, plasma, acceleration, undulator 242
 
  • C.J. Joshi
    UCLA, Los Angeles, California
  In this talk I will review the recent progress on the production, manipulation, transport, acceleration and focusing of relativistic electron beams using advanced techniques. In particular, I will report recent progress on cathode-less electron injectors, IFEL bunchers and accelerators, plasma accelerating and transport structures, and electron and positron beam focusing using plasmas. The plasma structures for acceleration can be excited either by laser beams or charged-particle beams. The acceleration gradients in either case can be enormous. For unmatched beams the betatron radiation loss, as the beam oscillates transversely in the high gradient accelerating structure, can generate a high brightness x-ray beam. These x-rays can, in turn, be used to generate positrons. Work done by different groups around the world will be reviewed.  
Transparencies
 
TU202 Low Emittance 500 kV Thermionic Electron Gun cathode, emittance, gun, 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
 
TU302 Future Developments in Electron Linac Diagnostics linac, emittance, instrumentation, laser 280
 
  • M.C. Ross
    SLAC/NLC, Menlo Park, California
  The next generation of electron linacs will fill two different roles:
  1. ultra-low emittance, very high power accelerators for linear colliders and
  2. ultra-short bunch, high stability accelerators for SASE X-ray production.
In either case, precision control based on non-invasive, reliable, beam instrumentation will be required. For the linear collider, low emittance transport is an important concern for both warm and superconducting linacs. Instrumentation will be used to control and diagnostics will be used to validate emittance preserving strategies, such as beam based alignment and dispersion - free steering. Tests at the KEK ATF and the SLAC FFTB have demonstrated the required performance for beam position and beam size monitors. Linacs intended for FEL's will require precision bunch length diagnostics because of expected non-linear micro-bunching processes. A wide variety of devices are now in development at FEL prototypes, including TTF2 at DESY and SPPS at SLAC. We present a review of the new diagnostic systems.
 
Transparencies
 
TUP15 Space Charge Compensation in Low Energy Proton Beams emittance, space-charge, proton, ion 324
 
  • A.B. Ismail, U.D. Uriot
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • R. Duperrier
    CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex
  • N. Pichoff
    CEA/DAM, Bruyères-le-Châtel
  High power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully managed. This nonlinear force can generate a high irreversible emittance growth of the beam. To reduce space charge effects, neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the dynamic study. Modelling the beam behaviour in such regime would be a significant contribution to the development of high intensity accelerators. Numerical and experimental study of SCC is in progress on the Saclay High Intensity Proton Injector. Experimental measurements and 2D/3D simulations of proton beam SCC will be presented.  
 
TUP41 Multi-Bunch Beam Dynamics Studies for the European XFEL emittance, linac, simulation, collider 357
 
  • N. Baboi
    DESY, Hamburg
  In the X-ray free electron laser planned to be built at DESY (TESLA XFEL) the acceleration of the electron bunches will be made with 9-cell superconducting cavities. These cavities have been initially developed within the TESLA linear collider study. The impact of the higher order modes (HOM) has been shown to be within the acceptable beam dynamics limits for the collider. For the XFEL the dynamics is relaxed from point of view of multi-bunch effects (e.g. shorter length, higher emittance). However the lower energy and different time structure of the beam make the study of the HOM effects in the XFEL linac necessary. Multi-bunch beam dynamics studies are ongoing. The results of the HOM measurements at the TESLA Test Facility are used. Several options for the beam structure, as necessary for various applications, are studied. The results will be discussed.  
Transparencies
 
TUP45 Extended Parametric Evaluation for 1 Å FEL - Emittance and Current Requirements emittance, undulator, radiation, gun 369
 
  • M. Pedrozzi, G. Ingold
    PSI, Villigen
  In the synchrotron radiation community there is a strong request for high brightness, coherent X-ray light pulses, especially in the 1 to 0.1 nm wave length range. A Free Electron Laser (FEL), driven by a linear single pass accelerator, is today the most promising mechanism able to produce such radiation. Since the electron beam brightness plays a major role in the laser saturation process and in the final energy of the driving linac, many laboratories are presently working on a new generation of low emittances sources. The present analysis will give an indication about the FEL behaviour and the undulator parameters versus the slice beam quality (emittance, current, energy spread).  
 
TUP46 A New Control System for the S-DALINAC alignment, target, diagnostics, beam-losses 372
 
  • M. Brunken, W. Ackermann, A. Araz, U. Bonnes, H.-D. Gräf, M. Hertling, A. Karnaukhov, W.F.O. Müller, O. Patalakha, M. Platz, A. Richter, B. Steiner, O. Titze, B. Truckses, T. Weiland
    TU Darmstadt, Darmstadt
  We will present recent results of the development of a new control system for the superconducting cw electron accelerator S-DALINAC. This system will be based on common industrial standards. Due to the large number of special devices existing to control the beamline, a simple and cheap communication interface is required to replace the current proprietary bus topology. The existing devices will be upgraded by a microcontroller based CAN bus interface as communication path to a control server. The servers themselves may be distributed over the location, giving required applications access to the device parameters through a TCP/IP connection. As application layer protocol for the Client Server communication a special binary protocol and a text protocol based on XML are considered.  
 
TUP47 The Photo Injector Test Facility at DESY Zeuthen: Results of the First Phase emittance, laser, gun, cathode 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
 
TUP49 Simulations of the Ion-Hose Instability for DARHT-II Long-Pulse Experiments simulation, induction, linac, resonance 381
 
  • K. C. D. Chan, C. Ekdahl
    LANL, Los Alamos, New Mexico
  • C. Genoni, P. Hughes
    MRC, Albuquerque, NM
  Ion-hose effect has been described extensively in literatures. Computer simulations of the effect typically use particle-in-cell (PIC) computer codes or codes using the spread-mass formulation [1]. PIC simulations, though offering more reliable results, will require extended running time in large computers To support commissioning experiments in the DARHT-II induction linac in Los Alamos National Laboratory, we have modified a spread-mass code so that we can survey quickly the parameter space for the experiment. It can also be used to provide quick answers during experiment. The code was originally written by Genoni from Mission Research Corporation (MRC) for constant linac parameters. We have modified it so that parameters can have dependence along the length of the linac. In this paper, we will describe simulation results using this code for the DARHT-II commissioning experiment and also our benchmarking results comparing to LSP, a PIC code from MRC.

[1] T. C. Genoni and T. P. Hughes, "Ion-hose instability in a long-pulselinear induction accelerator", PRST-AB, 6, 030401 (2003)

 
 
TUP52 Methods for Measuring and Controlling Beam Breakup in High Current ERLs feedback, damping, linac, pick-up 387
 
  • C. Tennant, K. Jordan, E. Pozdeyev, R.A. Rimmer, H. Wang
    Jefferson Lab, Newport News, Virginia
  • S. Simrock
    DESY, Hamburg
  It is well known that high current Energy Recovery Linacs (ERL) utilizing superconducting cavities are susceptible to a regenerative type of beam breakup (BBU). The BBU instability is caused by the transverse deflecting higher-order modes (HOMs) of the cavities which can have high impedance. We present MATLab simulation results for the BBU stability using the analysis tools of control theory. In this framework, methods of experimentally determining the threshold current and the means of suppressing the onset of the instability become more transparent. A scheme was developed to determine the threshold current due to a particular HOM by measuring the decay and rise times of the mode's field in response to an amplitude modulated beam as a function of the average electron beam current. To combat the harmful effects of a particularly dangerous mode, two methods of directly damping HOMs through the cavity HOM couplers were demonstrated. In an effort to suppress the BBU in the presence of multiple, dangerous HOMs, a conceptual design for a bunch-by-bunch transverse feedback system has been developed. By implementing beam feedback, the threshold for instability can be increased substantially.  
 
TUP56 Simulation of RF Breakdown Effects on NLC Beam simulation, linac, acceleration, ion 396
 
  • V.A. Dolgashev
    SLAC/ARDB, Menlo Park, California
  • T.O. Raubenheimer
    SLAC/NLC, Menlo Park, California
  The linacs of the Next Linear Collider (NLC) will contain several thousand traveling wave X-Band accelerator structures operating at input power of about 60 MW. At this input power prototypes of NLC structures have breakdown rates lower than one breakdown in ten hours. RF breakdowns disrupt flow of energy inside the structure and create arcs with electron and ion currents. Electromagnetic fields of these currents interact with the NLC beam. We simulated deflection of the NLC beam caused by breakdown currents using the particle-in-cell code MAGIC. In this paper we present modeling considerations and simulation results.  
 
TUP59 Extraction of High Charge Electron Bunch from the ELSA RF Injector - Comparison Between Simulation and Experiment simulation, space-charge, gun, laser 402
 
  • J. Lemaire, P. Balleyguier, A. Binet, J.M. Lagniel, V. Le Flanchec, N. Pichoff
    CEA/DAM, Bruyères-le-Châtel
  • R. Bailly-Salins, M. Millerioux, Chr. Quine
    CEA/DIF/DPTA/SP2A, Bruyeres-le-Chatel
  A new scheme based on a photoinjector and a RF linear accelerator operating at 352 MHz has been recently proposed as a versatile radiographic facility. Beam pulses of 60 ns duration contain 20 succesive electron bunches which will be extracted at 2.5 MeV from a photoinjector then accelerated through the next structure to the final energy of 51 MeV. Bunches carrying 100 nC are required for this purpose. As a first demonstrating step, 50 nC electron bunches have been produced and accelerated to 2.5 MeV with the 144 MHz ELSA photoinjector at Bruyères le Chatel. For this experiment, we compare the results and the numerical simulations made with PARMELA, MAGIC and MAFIA codes.  
 
TUP63 The First Results of Bunch Shape Measurements in SNS Linac emittance, target, linac, background 408
 
  • A. Feschenko, A. Gaidash, Yu. Kisselev, L.V. Kravchuk, A. Liyu, A. Menshov, A.N. Mirzojan
    RAS/INR, Moscow
  • S. Assadi, W. Blokland, S. Henderson, E.P. Tanke
    ORNL/SNS, Oak Ridge, Tennessee
  • D.-O. Jeon
    ORNL, Oak Ridge
  Three Bunch Shape Monitors with transverse scanning of low energy secondary electrons for the SNS Linac have been developed and fabricated. The peculiarity of the detectors is using of energy separation of the electrons. The separation enables to minimize influence of detached electrons originated from dissociation of H-minus ions in the detector wire target. The first detector was used at the exit of the first DTL tank during its commissioning. The results of Bunch Shape measurements are presented and discussed. These results were used to verify beam quality, to set parameters of the accelerating field, to estimate a longitudinal beam halo and to restore a longitudinal beam emittance.  
Transparencies
 
TUP64 Bunch Length Measurements at LEBRA linac, klystron, simulation, undulator 411
 
  • K. Yokoyama
    KEK, Ibaraki
  • K. Hayakawa, Y. Hayakawa, K. Nakao, I. Sato, T. Tanaka
    LEBRA, Funabashi
  The bunch length of the electron beam from the FEL linac at LEBRA (Laboratory for Electron Beam Research and Application) was estimated from the phase ellipse coefficient which is deduced from the dependence of the beam spread on the accelerating phase. The bunch length of FWHM was estimated approximately 0.33 mm from the results of the experiments. Besides, the pulse length of the FEL lights around the wavelength of 1.5 μm was measured by means of the autocorrelation. The pulse length was less than 0.06 mm according to the number of interfacial waves. These results indicate that the pulse length of the FEL lights isn’t equivalent to the electron bunch length.  
 
TUP68 The LANSCE Low Momentum Beam Monitor diagnostics, monitoring 423
 
  • R. Merl
    LANL, Los Alamos, New Mexico
  • F. R. Gallegos, C. Pillai, S. Schaller, F. E. Shelley, A. I. Steck
    LANL/LANSCE, Los Alamos, New Mexico
  • B. J. Sanchez
    ORNL/SNS, Oak Ridge, Tennessee
  A diagnostic has been developed at the Los Alamos Neutron Science Center (LANSCE) for the purpose of identifying low momentum beam tails in the linear accelerator. These tails must be eliminated in order to maintain the transverse and longitudinal beam size. Instead of the currently used phosphor camera system, this instrument consists of a Multi Wire Proportional Chamber (MWPC) front end coupled to an EPICS compliant VME-based electronics package. Low momentum tails are detected with a resolution of 5 mm in the MWPC at a high dispersion point near a bending magnet. While phosphor is typically not sensitive in the nano amp range, the MWPC is sensitive down to about a pico amp. The electronics package processes the signals from each of the MWPC wires to generate an array of beam currents at each of the lower energies. The electronics has an analog front end with a high-speed analog to digital converter for each wire. Data from multiple wires are processed with an embedded digital signal processor and results placed in a set of VME registers. An EPICS application assembles the data from these VME registers into a display of beam current vs. beam energy (momentum) in the LANSCE control room.  
 
TUP71 Highly Sensitive Measurements of the Dark Current of Superconducting Cavities for TESLA Using a SQUID Based Cryogenic Current Comparator pick-up, shielding, feedback, cryogenics 432
 
  • W. Vodel, R. Neubert, S. Nietzsche
    FSU, Jena
  • K. Knaack, M. Wendt, K. Wittenburg
    DESY, Hamburg
  • A. Peters
    GSI, Darmstadt
  This contribution presents a Cryogenic Current Comparator (CCC) as an excellent tool for detecting dark currents generated, e.g. by superconducting cavities for the upcoming TESLA project (X-FEL) at DESY. To achieve the maximum possible energy the gradient of the superconducting RF cavities should be pushed close to the physical limit of 50 MV/m. The undesired field emission of electrons (so-called dark current) of the superconducting RF cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. The main component of the CCC is a highly sensitive LTS-DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the dark current. For this reason the input coil of the SQUID is connected across a special designed toroidal niobium pick-up coil for the passing electron beam. A noise limited current resolution of nearly 2 pA/√(Hz) with a measurement bandwidth of up to 70 kHz was achieved in the laboratory. Design issues of the CCC and the application in the CHECHIA cavity test stand at DESY as well as experimental results will be discussed.  
 
TUP75 The High Accuracy RF Phase Detector Research for 200 MeV LINAC linac, synchrotron, radiation, synchrotron-radiation 444
 
  • S. Dong, G. Huang, D. Jia, G. Li, Y.G. Zhou
    USTC/NSRL, Hefei, Anhui
  The basic configuration of one experimental RF Phase detector and its research significance is introduced by characteristic of Hefei 200 MeV RF Linear accelerator and developments of RF Phase detector technology. The beam energy could be stabilized by implementing RF Phase detector into phase locked system for 5 cascaded accelerator tubes, which composed 200 MeV linac as the injector of Hefei Light Source (HLS). The tabletop experiments are given and the RF Phase detector is tuned in the off-line status. The microwave in 2856 MHz under CW mode is differentiated accurately by the developed RF phase detector. The measured results are better than prediction. The accuracy of the basic configuration of the RF Phase detector is verified, which establishes foundations for further in-line experiments.  
 
TUP79 A New RF System for the CEBAF Normal Conducting Cavities simulation, feedback, linac, extraction 456
 
  • C. Hovater, H. Dong, A. Hofler, G. Lahti, J. Musson, T. Plawski
    TJNAF, Newport News, Virginia
  The CEBAF Accelerator at Jefferson Lab is a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. CEBAF also has numerous normal conducting cavities for beam conditioning in the injector and for RF extraction to the experimental halls. The RF systems that presently control these cavities are becoming expensive to maintain, therefore a replacement RF control system is now being developed. For the new RF system, cavity field control is maintained digitally using an FPGA which contains the feedback algorithm. The system incorporates digital down conversion, using quadrature under-sampling at an IF frequency of 70 MHz. The VXI bus-crate was chosen as the operating platform because of its excellent RFI/EMI properties and its compatibility with the EPICS control system. The normal conducting cavities operate at both the 1497 MHz accelerating frequency and the sub-harmonic frequency of 499 MHz. To accommodate this, the new design will use different receiver-transmitter daughter cards for each frequency. This paper discuses the development of the new RF system and reports on initial results.  
 
TUP84 Spectrographic Approach to Study of RF Conditioning Process in Accelerating RF Structures RF-structure, plasma, vacuum, quadrupole 471
 
  • H. Tomizawa, H. Hanaki, T.  Taniuchi
    JASRI-SPring-8, Hyogo
  • A. Enomoto, Y. Igarashi, S. Yamaguchi
    KEK, Ibaraki
  The acceleration gradient of a linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited outgases emit light during rf breakdown, and the type of outgases depend on surface treatments and rinsing methods for their materials. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects when high-pressure ultrapure water rinsing (HPR) treatment was applied to these rf structures. We performed experiments to study the outgases under rf conditioning with quadruple mass spectroscopy and imaging spectrography. As a result, we could observe instantly increasing signals at mass numbers of 2 (H2), 28 (CO), and 44 (CO2), but not 18 (H2O) just after the rf breakdown. We also conducted spectral imaging for the light emissions from the atoms in a vacuum that are excited by rf breakdown. Without HPR, we observed the atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR, 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H I), and 740 nm (Cu II) were observed.  
 
TUP91 Compact Electron-Linac Design Concept for a Gamma Ray Source linac, klystron, linear-collider, collider 492
 
  • K. C. D. Chan, B.E. Carlsten, G. Dale, R. Garnett, C. Kirbie, F.L. Krawczyk, S.J. Russell, T.P. Wangler
    LANL, Los Alamos, New Mexico
  • E. Wright
    CPI, Palo Alto, California
  Gamma-ray sources, particularly sources that are easily transportable, are in high demand for different homeland security applications. We have carried out a review of commercially available electron-linac-based sources, and have investigated alternative compact electron-linac systems that use updated technologies compared with sources that are available commercially. As the results, we propose to develop a new source using an electron linac operating at 17 GHz. It uses a klystron, instead of a magnetron, and a IGBT-switched HV power supply. The source design takes advantages of the advances in X-band linac technology and solid-state HV technology. The higher frequency and upgraded technologies offer smaller size, lighter weight, better efficiency, easier operation, and higher reliability, compared with commercially-available linacs. In this paper, we will describe the source design and our choice of technologies.  
 
TUP94 Parallel Particle in Cell Computation of an Electron Gun with GdfidL gun, electromagnetic-fields, acceleration, scattering 498
 
  • W. Bruns
    TU Berlin TET, Berlin
  The paper describes an efficient algorithm to integrate the equations of a fast moving charge cloud of small size in a large electron gun. Particle in cell computations of a realistic electron gun is challenging due to the large discrepancy between the size of the cavity and the size of the cloud. A fine grid must be used to resolve the small volume of the charge, with a grid spacing in the order of 0.1 mm. The cavity has extensions of about 100 mm. Therefore one has to deal with about 1000 million gridcells. Such a large grid is handled best with parallel systems. Each node of the parallel system computes the electromagnetic field in its subvolume. As the extension of the charge keeps being small during the flight, at each timestep the charged particles will be located in only a few subvolumes of the nodes of the parallel system. This would lead to a strong load imbalance, if the particle related computations for each particle would be performed by the node where the particle is in. GdfidL instead spreads the data of all particle over all processors, which perform the particle related computations, and send back the results to the processors where the particles are in.  
 
TUP97 Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility vacuum, simulation, photon 507
 
  • V.V. Paramonov
    RAS/INR, Moscow
  The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.  
 
WE102 State of the Art SRF Cavity Performance damping, linac, higher-order-mode, coupling 518
 
  • L. Lilje
    DESY, Hamburg
  The paper will review superconducting RF cavity performance for β=1 cavities used in both linear and circular accelerators. These superconducting cavities are used in two kinds of applications: High current storage rings and efficient high duty cycle linacs. In recent years the performance of those cavities has been improving steadily. High accelerating gradients have been achieved using advanced surface preparation techniques like electropolishing and surface cleaning methods like high pressure water rinsing. High intensity beams can be handled with advanced higher-order-mode damping schemes.  
Transparencies
 
WE104 State of the Art Electron Bunch Compression radiation, synchrotron, emittance, bunching 528
 
  • P. Piot
    FNAL, Batavia, Illinois
  Many accelerator applications such as advanced accelerator R&D, free-electron laser drivers and linear colliders, require high peak current electron bunches. The bunch is generally shortened via magnetic compression. In the present paper we review various bunch compression schemes and discuss their limitations. We present experimental results, achieved at various facilities, along with on-going theoretical work on promising novel compression techniques.  
Transparencies
 
WE204 PAL Linac Upgrade for a 1-3 Å XFEL linac, undulator, emittance, radiation 544
 
  • J-O. Oh, W. Namkung
    POSTECH, Pohang
  • Y. Kim
    DESY, Hamburg
  With the successful SASE FEL saturation at 80 nm wavelength at TTF1, TTF2 will begin re-commissioning in the fall of 2004 as an FEL user facility to 6 nm with 1 GeV beams. The high gain harmonic generation is also confirmed by the DUV-FEL experiments at 266 nm with seeding wavelength at 800 nm. In order to realize a hard X-ray SASE FEL (SASE XFEL) with a lower energy beams, we need a long in-vacuum mini-gap undulator and a GeV-scale FEL driving linac that can supply an extremely low slice emittance, a high peak current, and an extremely low slice energy spread. PAL is operating a 2.5 GeV electron linac as a full-energy injector to the PLS storage ring. By adding an RF photo-cathode gun, two bunch compressors, and a 0.5 GeV S-band injector linac to the existing PLS linac, and by installing a 60 m long in-vacuum undulator, the PLS linac can be converted to a SASE XFEL facility (PAL XFEL) which supplies coherent X-ray down to 0.3 nm wavelength. The third harmonic enhancement technique can supply coherent hard X-ray beams to 0.1 nm. The technical parameters related to these goals are examined, and preliminary design details are reviewed for the PAL linac upgrade idea for a 1-3 Å PAL XFEL.  
Transparencies
 
TH103 Summary of the Argonne Workshop on High Gradient RF linac, ion, linear-collider, simulation 564
 
  • J. Norem
    ANL, Argonne, Illinois
  Workshop on High Gradient rf was held at Argonne from October 7 - 9, 2003. This workshop reviewed the problems encountered when a number of accelerator technologies approached the high gradient limits. The aim of the workshop was to involve materials scientists and try to look at trigger mechanisms and surface interactions, in addition to reviewing progress. Talks were presented on superconducting rf, progress with high and low frequency copper cavities, and dielectrics. The focus was on both experimental and theoretical aspects of the problem. The overall picture presented at the workshop will be summarized.  
Transparencies
 
TH104 Industrial RF Linac Experiences and Laboratory Interactions linac, vacuum, proton, site 569
 
  • M. Peiniger
    ACCEL, Bergisch Gladbach
  Since more than two decades ACCEL Instruments GmbH at Bergisch Gladbach (formerly Siemens/Interatom) is supplying the worldwide accelerator labs with key components like rf cavities and power couplers, s.c. magnets, insertion devices, vacuum chambers and x-ray beamline equipment. Starting with the design and production of turn key SRF accelerating modules in the late 80th, meanwhile ACCEL is engineering, manufacturing, on site commissioning and servicing complete accelerators with guaranteed beam performance. Today, with a staff of more than 100 physicists and engineers and about the same number of manufacturing specialists in our dedicated production facilities, ACCEL's know how and sales volume in this field has accumulated to more than 2000 man years and several hundred Mio €, respectively. Basis of our steady development is a cooperative partnership with the world leading research labs in the respective fields. As an example, for the supply of a turn key 100 MeV injector linac for the Swiss Light Source, and meanwhile also for the Diamond Light Source as well as for the Australian Synchrotron Project, we established a very fruitful partnership with DESY.  
Transparencies
 
TH201 IOT RF Power Sources for Pulsed and CW Linacs klystron, linac, gun, simulation 574
 
  • H.P. Bohlen
    CPI, Palo Alto, California
  • Y. Li, R.N. Tornoe
    CPI/EIMAC, San Carlos, California
  For many years, klystrons have been the preferred RF power amplifiers for both pulsed and CW linacs at UHF and higher frequencies. Their properties have earned them that position. But in recent years in UHF terrestrial television transmitters the earlier predominant klystron has been replaced the Inductive Output Tube (IOT) because the IOT provides higher efficiency and, due to its excellent linearity, can handle the simultaneous amplification of both the vision and the sound signal. Its robustness and life expectancy equals that of a klystron, and it more than compensates its lower gain by a lower price and a smaller size. For linac operation, derivates of UHF TV IOTs, capable of up to 80 kW CW output power, are already available and operating. In L-Band, they are presently joined by recently developed 15 to 30 kW CW IOTs. HOM-IOTs are expected to extend the CW range in UHF to 1 MW and beyond. Pulsed operation of an IOT can be achieved without a high-voltage modulator. Since the beam current is grid-controlled it is sufficient to pulse the drive power.  
Transparencies
 
THP04 Fabrication of Superconducting Cavities for SNS vacuum, linac 602
 
  • M. Pekeler, S. Bauer, J. Schwellenbach, M. Tradt, H. Vogel, P. vom Stein
    ACCEL, Bergisch Gladbach
  During the last three years ACCEL fabricated all 109 superconducting cavities for the Spallation Neutron Source (SNS) in Oakridge, Tennessee. Two series of 35 medium beta (β=0.61) and 74 high beta (β=0.81) cavities have been delivered. Besides cavity manufacturing ACCEL also performed rf tuning and chemical surface preparation. We give an outline on the current manufacturing experience and comment on future developments for industrial cavity production.  
Transparencies
 
THP07 Performance Improvement of the Multicell Cavity Prototype for Proton LINAC Projects proton, linac, shielding, target 611
 
  • B. Visentin, D. Braud, J.P. Charrier, B. Coadou, Y. Gasser, J.P. Poupeau, P. Sahuquet
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • S. Bousson, H. Gassot, H. Saugnac, P. Szott
    IPN, Orsay
  • G. Devanz
    CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex
  The CEA-Saclay/IPN-Orsay collaboration allowed to develop a multicell superconducting cavity prototype (704 MHz, β=0.65). Since the first experimental results[*], achieved in a vertical cryostat and the horizontal one "CryHoLab", the accelerating field Eacc has been recently improved up to 19 MV/m (Epeak = 43 MV/m, Bpeak = 83 mT, Q0 = 9.109). Eacc is now limited by quench. The previous one limitation, due to a non understood phenomenon, disappeared . The excellent performances of this 5-cell proton cavity validate the design, the technological choices, the manufacturing and the cavity preparation process. These results augur well for our future R&D program on multicell superconducting cavities within the European CARE/HIPPI framework.

[*] Proceedings of PAC2003, Portland, USA, TAB047, p.1303

 
 
THP21 Calculation of Electron Beam Dynamics of the LUE-200 Accelerator focusing, target, quadrupole, simulation 639
 
  • A.P. Sumbaev, V. Alexandrov, N.Y. Kazarinov, V.F. Shevtsov
    JINR, Dubna, Moscow Region
  The results of calculations of the focusing and transportation systems of the electron beam of LUE-200 accelerator – the driver of a pulse source of resonant neutrons IREN, JINR (Dubna), are presented. Simulations of the beam dynamics in the traveling wave accelerator were carried out by means of PARMELA code. The calculations have been fulfilled for various parameters of the focusing magnetic fields in the accelerator and the channel, various currents of the beam and various initial distributions of electrons.  
 
THP23 An Electrode With Molybdenum-Cathode and Titanium-Anode to Minimize Field Emission Dark Currents cathode, 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 cathode, 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 cathode, 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 cathode, simulation, 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, cathode, 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, cathode 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, cathode, 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.  
 
THP55 Electromagnetic Design of New RF Power Couplers for the S-DALINAC emittance, simulation, electromagnetic-fields, linac 736
 
  • M. Kunze, M. Brunken, H.-D. Gräf, W.F.O. Müller, A. Richter, T. Weiland
    TU Darmstadt, Darmstadt
  New rf power couplers for the Superconducting Darmstadt Linear Accelerator (S-DALINAC) injector have to be designed to transfer rf power of up to 2 kW to the electron beam. This allows injector operation at beam currents from 0.15 mA to 0.2 mA and electron energies up to 14 MeV. The new couplers should possibly provide a external Q of 5·106. The transverse kick should be as small as possible. The asymmetric field distribution of the couplers causes emittance growth of the electron beam and therefore the transverse kick has to be minimized. Electromagnetic simulations are applied to investigate different coupler designs and to localize possible problems at an early stage. Cavity external Q and transverse kick can be calculated from 3D electromagnetic eigenmode solutions. The present coaxial-coaxial input couplers at the S-DALINAC are limited to power operation below 500 W under full reflection. In order to reach power operation up to 2 kW a realizations of a low-kick waveguide coupler for the S-DALINAC injector is presented, namely a twin-waveguide coupler.  
Transparencies
 
THP58 Development of C-band High-Power Mix-Mode RF Window vacuum, resonance, klystron, acceleration 745
 
  • S. Michizono, S. Fukuda, T. Matsumoto, K. Nakao, T. Takenaka
    KEK, Ibaraki
  • K. Yoshida
    MELCO, Hyogo
  High power c-band (5712 MHz) rf system (40 MW, 2 μs, 50 Hz) is under consideration for the electron-linac upgrade aimed for the super KEKB project. An rf window, which isolates the vacuum and pass the rf power, is one of the most important components for the rf system. The window consists of a ceramic disk and a pill-box housing. The mix-mode rf window is designed so as to decrease the electric field on the periphery of the ceramic disk. A resonant ring is assembled in order to examine the high-power transmission test. The window was tested up to the transmission power of 160 MW. The rf losses are also measured during the rf operation.  
 
THP84 Design of a 300 GHz Broadband TWT Coupler and RF-Structure coupling, simulation, RF-structure, plasma 794
 
  • F.L. Krawczyk, F.E. Sigler
    LANL/LANSCE, Los Alamos, New Mexico
  • B.E. Carlsten, L.M. Earley
    LANL, Los Alamos, New Mexico
  • J.M. Potter
    JP Accelerator Works, Inc., 2245, Los Alamos, NM
  • M.E. Schulze
    GA, Los Alamos
  • E. Smirnova
    MIT/PSFC, Cambridge, Massachusetts
  Recent LANL activities in millimeter wave structures focus on 94 and 300 GHz structures. They aim at power generation from low power (100–2000 W) with a round electron beam (120 kV, 0.1–1.0 A) to high power (2–100 kW) with a sheet beam structure (120 kV, 20 A). Applications cover basic research, radar and secure communications and remote sensing of biological and chemical agents. In this presentation the design and cold-test measurements of a 300 GHz RF-structure with a broadband (>6% bandwidth) power coupler are presented. The design choice of two input/output waveguides, a special coupling region and the structure parameters themselves are presented. As a benchmark also a scaled up version at 10 GHz was designed and measured. These results will also be presented.  
 
THP93 A 3D Self-Consistent, Analytical Model for Longitudinal Plasma Oscillation in a Relativistic Electron Beam plasma, space-charge, simulation, linac 818
 
  • G. Geloni, E. Saldin, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg
  Longitudinal plasma oscillations are becoming a subject of great interest for XFEL physics in connection with LSC microbunching instability[1] and certain pump-probe synchronization schemes[2]. In the present paper we developed the first exact analytical treatment for longitudinal oscillations within an axis-symmetric, (relativistic) electron beam, which can be used as a primary standard for benchmarking space-charge simulation codes. Also, this result is per se of obvious theoretical relevance as it constitutes one of the few exact solutions for the evolution of charged particles under the action of self-interactions.

[1] E. Saldin et al., "Longitudinal Space Charge Driven Microbunching instability in TTF linac", TESLA-FEL-2003-02, May 2003, [2] J. Feldhaus et al., "Two-color FEL amplifier for femtosecond-resolution pump-probe experiments with GW-scale X-ray and optical pulses",DESY 03-091, July 2003

 
 
THP95 Electro Polishing of Niobium Cavities at DESY acceleration, cathode, synchrotron 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 emittance, brightness, gun, cathode 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