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bunching

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MOPC003 Estimation of Undulator Requirements for Coherent Harmonic Generation on FERMI@Elettra undulator, electron, simulation, laser 67
 
  • E. Allaria, G. De Ninno, B. Diviacco
    ELETTRA, Basovizza, Trieste
  The FERMI project is devoted to the realization of a FEL user facility based on the principle of coherent harmonic generation (CHG). The advantages of such a method (with respect, e.g., to self amplified spontaneous emission) is that the output properties of the light are strongly determined by the interaction of the seed laser with the electron beam within the modulator undulator. In CHG FELs therefore, in addition to the requirements for the radiator where FEL radiation is produced, it is important to understand and satisfy the requirements for the modulator. In this work, we present a study focused on the first stage (FEL-1) of the FERMI@Elettra setup. The study aims at providing an estimation of the undulator requirements in terms of magnetic field accuracy for both the modulator and the radiator. The work is based on numerical simulations of the FEL-1 using the numerical code GINGERH [1]. The required undulator tolerances have been obtained by means of a large number of simulation runs taking into account different sets of undulator parameters.

[1] W. Fawley, “A User Manual for GINGER-H and its Post-Processor XPLOTGINH” LCLS-TN-07-YY Technical note, Lawrence Berkeley National Laboratory (2007)

 
 
MOPC010 Injector System for X-ray FEL at SPring-8 emittance, gun, linac, electron 85
 
  • H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki
    JASRI/SPring-8, Hyogo-ken
  • T. Hara, A. Higashiya, T. Inagaki, N. Kumagai, H. Maesaka, Y. Otake, T. Shintake, H. Tanaka, K. Togawa
    RIKEN/SPring-8, Hyogo
  The SPring-8 X-FEL based on the SASE process has been developed to generate X-rays of 0.1 nm by the combination of an 8 GeV high gradient linac (400 m) and a mini-gap undulator of in-vacuum type (90 m). The design goals of the slice beam emittance and peak current at the end of the linac are 1 π mm mrad and 3 kA, respectively. The injector of the linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps step by step. The injector has been designed on the basis of the SCSS test accelerator. We adopted the following keys to toward the goals:
  1. A 500 kV thermionic gun (CeB6) without a control grid ejecting a beam holding the low rms emittance of 1.1 π mm mrad,
  2. a beam deflector downstream gating the beam to form a bunch of a 1 ns length,
  3. multi-stage RF structures (238, 476 and 1428 MHz) bunching and accelerating the beam gradually to maintain the initial emittance, and
  4. extra RF cavities of 1428 and 5712 MHz linearizing the energy chirp of the beam bunch to achieve the bunch compression resulting the required peak current.
 
 
MOPC019 Velocity Bunching at FLASH emittance, electron, simulation, gun 112
 
  • T. Limberg, B. Beutner, W. Decking, M. Huening, M. Krasilnikov, M. Vogt
    DESY, Hamburg
  • O. Grimm
    Uni HH, Hamburg
  The vacuum-ultra-violet free electron laser in Hamburg (FLASH) is a linac driven SASE-FEL. High peak currents are, in routine operation, produced using magnetic bunch compression chicanes. Longitudinal dispersion in these chicanes allow bunch length changes of relativistic electron beams. For low energy electron beams (~5 MeV), the velocity dependence on electron energy can be utilized for bunch compression. Since strong bunch compression at low beam energies gives rise to strong space charge interactions which has an impact on, for instance, beam emittance and is therefore not suitable for full compression to the kA peak currents needed for SASE operation. Moderate velocity bunching, however, might be used to optimize the total bunch compression system of FLASH or the European XFEL. Experiments on the velocity bunching process at FLASH are presented here. Results on bunch length and transverse emittance measurements are discussed and compared with numerical tracking calculations.  
 
MOPD035 20 MW Pulse Amplifier Klystron with Multiple Frequency Two-Gap Bunching Resonators for Linear Electron Accelerators klystron, electron, focusing, vacuum 529
 
  • K. G. Simonov, A. N. Korolev, A. V. Mamontov
    ISTOK, Moscow Region
  A klystron design with a two-gap bunching resonator which provides interaction with electron beam by fields of multiple frequencies of two-gap resonator fundamental oscillations for increasing the klystron efficiency is being considered. At that the two-gap resonator is tuned to antiphased oscillation at operating frequency and to in-phase oscillation at the second harmonic. Such choice of frequency oscillation types allows to make the resonator compact and provide optimal conditions for electron beam interaction with microwave fields of the two-gap resonator both in antiphased and in-phase oscillation types. The relations for choosing two-gap resonator interaction area size providing a stable klystron operation without self-excitation are given. The compactness of the realized two-gap resonator with multiple frequencies allowed to locate it into klystron drift tube between the main resonators without increasing the klystron overall dimensions. The results of experimental research of klystron with such a two-gap resonator showed a possibility to increase its efficiency significantly.  
 
MOPP088 The High Harmonics Cavity System for the New Experimental Storage Ring at FAIR coupling, electron, impedance, emittance 757
 
  • R. G. Heine, C. Dimopoulou, U. Laier
    GSI, Darmstadt
  The "Facility for Antiproton and Ion Research" (FAIR) will consist of several synchrotrons and storage rings dedicated to target experiments as well as in-situ experiments. One of the in-situ experiments is ELISe, a head-on collision of a heavy ion beam in the new experimental storage ring(NESR) with an electron beam prepared in the electron ring (ER). The vertex is placed in a bypass to the NESR where both rings have a common straight section. To prepare the heavy ion beam for collision with the bunched electron beam circulating at a fixed repetition rate a dedicated RF system called high harmonics cavity system (HHC) operating at a frequency of 44.7MHz is needed. The HHC will be realised as a disk loaded coaxial quarter wave resonator. This paper deals with the actual development status of this RF system, including analytically derived voltage demands, multipactor thresholds and considerations on input coupling and HOM damping.  
 
TUPC004 The Diagnostic Line of Elettra Booster 100MeV Pre-injector diagnostics, controls, booster, pick-up 1044
 
  • S. Bassanese, L. Badano, M. Bossi, A. Carniel, G. Ciani, S. Di Mitri, M. Ferianis, G. Mian, G. Penco, M. Veronese
    ELETTRA, Basovizza, Trieste
  In order to fully characterize the beam of the new 100MeV linac pre-injector for the Elettra Booster, a standard diagnostic set-up has been designed which includes strip line BPMs, scintillating screens and current transformers. During the initial tuning of the pre-injector, a thermo-ionic gun followed by a 500MHz pre bunching cavity, an S-band bunching structure and two LIL accelerating sections, some extra diagnostics have been used to get a deeper understanding of the pre-injector operating point. In particular some prototypes of the FERMI@elettra diagnostics, installed on the same booster pre-injector, have been used to better characterize the beam transverse and longitudinal beam axis. An improved resolution screen system, equipped with a YAG screen, has been used as well as a wideband longitudinal pick-up. The measurement results as well as the tuning procedure are here presented.  
 
TUPP006 Beam Test with a New Control System of Acceleration in HIMAC acceleration, controls, lattice, synchrotron 1538
 
  • M. Kanazawa
    NIRS, Chiba-shi
  • K. Maeda
    Toshiba Corporation, Tokyo
  • K. Watanabe
    Chiba University, Graduate School of Science and Technology, Chiba
  In the present acceleration system in HIMAC, acceleration frequency of a direct digital synthesizer is controlled with B-clock pulses of B+ and B- signals that correspond to 0.2 Gauss increment and decrement of dipole magnetic field. In the tested new control system, we will use only clock pulse whose clock rate is locked to the power line frequency. With this simple system, it is easy to build up the acceleration control system for multiple flat-top pattern. This pattern operation is expexted to use in the next irradiation system of spot-scanning in HIMAC. In this presentation, the used system and its beam tests will be presented.  
 
TUPP033 Alternative Scheme of Bunch Length Compression in Linacs for Free Electron Lasers damping, linac, simulation, laser 1610
 
  • S. Di Mitri, M. Cornacchia, S. V. Milton, S. Spampinati
    ELETTRA, Basovizza, Trieste
  The aim of this paper is to investigate the effect of an alternative scheme of bunch compression on the development of the microbunching instability. Two cases have been considered, one in the presence of a linear energy chirp at the compressor end and another without it. It is shown that after removing the linear energy chirp, a properly tuned R56 transport matrix element is able to dilute the initial energy modulation without affecting the bunch length and to damp the associated current spikes. A by-product of this study indicates that the global compression scheme can be further optimized in the direction of a double compression scheme in which the longitudinal Landau damping is enhanced by increasing the compression factor of the first compressor while reducing that of the second one. The limiting case of such a configuration is the single compression scheme at low energy. The study is based on analytical calculations and on the simulation code LiTrack.  
 
TUPP157 Commissioning of L-band Electron Accelerator for Industrial Applications electron, klystron, power-supply, gun 1875
 
  • S. H. Kim, M.-H. Cho, W. Namkung, H. R. Yang
    POSTECH, Pohang, Kyungbuk
  • J. Jang, S. D. Jang, S. J. Kwon, J.-S. Oh, S. J. Park, Y. G. Son
    PAL, Pohang, Kyungbuk
  An intense L-band electron linear accelerator is under construction at CESC (Cheorwon Electron-beam Service Center) for industrial applications. It is capable of producing 10-MeV electron beams with a 30-kW average beam power. For high-power capability, we adopted 1.3 GHz, and the RF source is a 25-MW pulsed klystron with a 60-kW average RF output power. A pre-buncher is used before the bunching section, which is built-in with the regular accelerating sections. The accelerating structure is a disk-loaded waveguide with a constant-impedance operated in the 2π/3-mode. It is to be operated under the fully beam-loaded condition for high average power with the 6-μs pulse length and the 350-Hz repetition rate. In this paper, we present details of the accelerator system and commissioning results.  
 
WEPC082 Technical Considerations of the TPS Linac linac, electron, controls, synchrotron 2186
 
  • A. P. Lee, H.-P. Chang, J. Chen, C.-S. Fann, K. T. Hsu, S. Y. Hsu, W. K. Lau, K.-K. Lin, K.-B. Liu, Y.-C. Liu, C. Y. Wu
    NSRRC, Hsinchu
  The technical considerations of the TPS (Taiwan Photon Source) linac will be presented in this report. A 150 MeV turn-key linac is chosen in this case in order to provide the ease of injection into the booster in which the electron energy will be raised up to 3 GeV. This linac will be similar to that equipping at recently commissioned synchrotron light sources. The major beam parameters are derived from the booster and storage ring injection requirements. The beam diagnostics arrangement for linac commissioning purpose will be briefly described.  
 
WEPC087 New Preinjector for the ESRF Linac gun, emittance, simulation, cathode 2195
 
  • T. P. Perron, B. Ogier, A. Panzarella, E. Plouviez, E. Rabeuf, V. Serriere
    ESRF, Grenoble
  A new preinjector of the 200 MeV Linac is under manufacture at the ESRF. Two operation modes are foreseen, a short pulse of 1ns-.4nC and a long pulse of 1000ns-10nC. The new triode type thermionic 100 Kev gun has been characterized experimentally. The transverse and longitudinal phase space measurements are compared with simulations. The design and the expected performance of the final set-up which includes vertical deflecting plates, pre-bunching and bunching sections will be presented.  
 
WEPC094 Thermo-Cathode RF Gun for BINP Race-Track Microtron-Recuperator emittance, cathode, gun, injection 2213
 
  • V. Volkov, E. Kendjebulatov, S. A. Krutikhin, G. Y. Kurkin, V. M. Petrov, I. K. Sedlyarov, N. Vinokurov
    BINP SB RAS, Novosibirsk
  In 2007 the thermo-cathode RF gun for the Budker INP energy recovery linac (ERL) was designed. The RF gun is capable to emit the electron bunches with the energy of 300 keV, average current of 100 mA, and repetition frequency of 90 MHz. The new injector is adapted to the existing RF system for beam bunching, accelerating and injecting to the linac of the microtron. Its advantage is the absence of high potential of 300 kV at the control circuits of the cathode; therefore the maintenance is simplified. Also due to the absence of the cathode back bombardment by residual gas ions in the RF cavity, the lifetime of the cathode is increased and the obtaining of the repetition frequency up to 90 MHz becomes feasible. In the paper the main characteristics of the injector, its design and results of beam dynamics calculations with optimised regimes are presented.  
 
WEPP098 Efficient Traveling-wave Accelerating Structure for Linear Accelerators electron, coupling, acceleration, linac 2746
 
  • V. M. Pirozhenko
    MRTI RAS, Moscow
  The shaped traveling-wave (STW) structure contains periodic structure of cavities with optimal shape and magnetic coupling operating in the forward traveling-wave mode. The structure combines the advantages of conventional standing-wave (SW) and traveling-wave (TW) structures. It ensures high efficiency of the use of radio-frequency (RF) power for the particle acceleration inherent in the SW structures. Also it gives a possibility to vary output energy of the particles by changing the beam loading and provides for good matching with RF generator without application of special matching devices that is inherent in the TW structures. The STW structure is well suited for compact variable-energy electron linear accelerators used for radiation technologies.  
 
THPC111 Simulation ofμBunching Instability Regimes in the FLASH Bunch Compressors simulation, space-charge, gun, linac 3236
 
  • M. Vogt, T. Limberg
    DESY, Hamburg
  • D. H. Kuk
    The University of Texas at Austin, Austin, Texas
  The bunch compression scheme for the European XFEL will operate in a regime in which, at least without additional energy spread introduced by a laser heater, theμbunching effect proposed in the literature may severely degrade the performance of the FEL. However, clear, unambiguous signals of theμbunching effect have not yet been seen neither in simulation nor experiment. The proposedμbunching effect amplifies initial current modulations by interleaved application of longitudinal collective energy kicks and transformations of energy modulation into current modulation in magnetic chicanes. In order to establish a parameter regime for experimental verification ofμbunching at the FLASH VUV-FEL at DESY, we have scanned the relevant part of the parameter space using a linear, quasi-analytic, noise-free gain-model and complemented this with particle tracking simulations. The tracking was performed using interleaved runs of ASTRA for acceleration modules and CSRTrack for the chicanes, automatically linked by the start-to-end simulation tool box Gluetrack.  
 
THPP036 The Superconducting Solution for the EURISOL DS Postaccelerator Injector rfq, emittance, ion, simulation 3446
 
  • P. A. Posocco
    Consorzio RFX, Euratom ENEA Association, Padova
  • G. Bisoffi, A. Palmieri, A. Pisent, P. A. Posocco
    INFN/LNL, Legnaro, Padova
  In the framework of EURISOL design study*, the superconducting solution for the Post-Accelerator injector foresees the use of two RFQs, one Super Conducting and one Normal Conducting, both operating CW at 88 MHz. After the multiple ionization in the ECR breeder on low voltage platform, the rare ions beam (3 ≤ A/q ≤ 7) is bunched at the main frequency by the NC RFQ without both losses and transverse emittance increase and accelerated afterwards through the SC RFQ up to 560 keV/u. A 8.8 MHz pulsed beam can be delivered to experiments placing a 3 harmonic buncher before the NC RFQ with overall beam losses lower than 25%. The beam dynamics results of the study of this solution as well as the main RF design and construction analysis of the main components are presented.

*http://www.eurisol.org

 
 
THPP048 Experimental Demonstration of Longitudinal Ion Beam Accumulation with Electron Cooling injection, electron, kicker, ion 3470
 
  • C. Dimopoulou, B. Franzke, T. Katayama, F. Nolden, G. Schreiber, M. Steck
    GSI, Darmstadt
  • D. Möhl
    CERN, Geneva
  Recently, two longitudinal beam compression schemes have been successfully tested in the Experimental Storage Ring (ESR) at GSI with a beam of bare Ar ions at 65 MeV/u injected from the ion synchrotron SIS18. The first employs Barrier Bucket pulses, the second makes use of multiple injections around the unstable fixed point of a sinusoidal RF bucket at h=1. In both cases continuous electron cooling maintains the stack and merges it with the freshly injected bunch *. Using the beam diagnostic devices in the ring both stacking processes were demonstrated under the same conditions. The dependence of the accumulation performance on the available rf potential, the electron cooling strength as well as on the synchronization conditions between injection kicker pulse and rf wave was investigated. These experimental results provide the proof of principle for the planned fast stacking of Rare Isotope Beams aiming at high luminosities in the New Experimental Storage Ring ** of the FAIR project ***.

* C. Dimopoulou et al., JACoW Proceedings of COOL07, Bad Kreuznach,2007.
** C. Dimopoulou et al., PRST-AB 10 (2007) 020101.
*** FAIR Baseline Technical Report,www.gsi.de/fair/.

 
 
THPP124 Commissioning of the 150 MeV SSRF Linac controls, linac, electron, gun 3649
 
  • M. H. Zhao, G. Q. Lin, W. H. Liu, B. L. Wang, J. Q. Zhang, S. P. Zhong, W. M. Zhou
    SINAP, Shanghai
  The 150 MeV SSRF linac has been integrated and commissioned from late 2006 to middle of 2007. This paper presents the design, installation, commissioning and status of this linac.