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space-charge

  
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MOP07 High Current Beam Transport to SIS18 emittance, injection, ion, simulation 45
 
  • S. Richter, W. Barth, L. Dahl, J. Glatz, L. Groening, S. Yaramishev
    GSI, Darmstadt
  The optimized transversal and longitudinal matching of space charged dominated ion beams to SIS18 is essential for a loss free injection. This paper focuses on the beam dynamics in the transfer line (TK) from the post-stripper accelerator to the SIS18. Transverse beam emittance measurements at different positions along the TK were done. Especially, the different foil stripping modes were investigated. A longitudinal emittance measurement set-up was commissioned at the entry to the TK. It is used extensively to tune all the rebunchers along the UNILAC. An addition, a test bench is in use for measurements of longitudinal bunch profiles, which enables to monitor for the final debunching to SIS18. Multi particle simulations by means of PARMILA allow a detailed analysis of experimental results for different ion currents.  
 
MOP08 Investigation of the Beam Matching to the GSI-Alvarez DTL under Space Charge Conditions ion, quadrupole, emittance, simulation 48
 
  • S. Yaramishev, W. Barth, L. Dahl, L. Groening, S. Richter
    GSI, Darmstadt
  The UNILAC consists of the 36 MHz high current RFQ/IH-injector, a gas stripper section at an energy of 1.4 MeV/u and a 108 MHz Alvarez poststripper, accelerating all ions up to of 11.4 MeV/u. The design beam current for U28+ is 12.6 emA at full energy. After the stripping process the electrical beam current is increased by a factor of 7 for uranium. This leads to a significant beam emittance growth during the transport through the charge state separator and the matching section to the Alvarez DTL. The paper reports results of beam experiments focused on the matching of the high intensity beams to the Alvarez for different ion species. Measured data are compared with the results of beam dynamics simulations. Possible improvements of the transverse focusing in the Alvarez linac are discussed and the total impact to the beam quality at the synchrotron injection is evaluated.  
Transparencies
 
TU202 Low Emittance 500 kV Thermionic Electron Gun cathode, emittance, gun, electron 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
 
TUP15 Space Charge Compensation in Low Energy Proton Beams electron, emittance, 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.  
 
TUP16 Investigation on Beam Dynamics Design of High-Intensity RFQs rfq, focusing, acceleration, emittance 327
 
  • C. Zhang, A. Schempp
    IAP, Frankfurt-am-Main
  • J. Chen, J. Fang, Z.Y. Guo
    PKU/IHIP, Beijing
  Recently various potential uses of high-intensity beams bring new opportunities as well as challenges to RFQ accelerator research because of the new problems arising from the strong space-charge effects. Unconventional concepts of beam dynamics design, which surround the choice of basic parameters and the optimization of main dynamics parameters’ variation along the machine, are illustrated by the designing Peking University (PKU) Deuteron RFQ. An efficient tool of LANL RFQ Design Codes for beam dynamics simulation and analysis, RFQBAT, is introduced. Some quality criterions are also presented for evaluating design results.  
 
TUP19 Characterization of Beam Parameter and Halo for a High Intensity RFQ Output under Different Current Regimes rfq, emittance, simulation, proton 333
 
  • E. Fagotti
    INFN Milano, Milano
  • M. Comunian, A. Palmieri, A. Pisent
    INFN/LNL, Legnaro, Padova
  The characterization of the beam distribution at the exit of a high intensity RFQ is a crucial point in view of a correct simulation of beam behavior in the following linac structure. At this scope we need to know the beam halo quantification as a function of the input beam and RFQ parameters. In this paper, the description of Beam halo based upon moments of the particle distribution at the exit of the TRASCO-RFQ is given.  
 
TUP58 Alternative Linac Layout for European XFEL Project linac, emittance, gun, simulation 399
 
  • Y. Kim, K. Flöttmann, T. Limberg
    DESY, Hamburg
  • Y. Kim, D. Son
    CHEP Korea, Daegu
  To satisfy required beam parameters and to increase the jitter tolerance, we have designed an alternative linac layout with two bunch compressor stages for the European XFEL project. In this paper, we describe start-to-end (S2E) simulation of the alternative linac layout for the European XFEL project, and compare its results with our current linac layout with one bunch compressor stage.  
 
TUP59 Extraction of High Charge Electron Bunch from the ELSA RF Injector - Comparison Between Simulation and Experiment simulation, gun, laser, electron 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.  
 
TUP82 Low Energy Beam Transport using Space Charge Lenses rfq, ion, emittance, focusing 465
 
  • O. Meusel, A. Bechtold, H. Klein, J. Pozimski, U. Ratzinger, A. Schempp
    IAP, Frankfurt-am-Main
  Gabor lenses provide strong cylinder symmetric electric focusing using a confined nonneutral plasma. The density distribution of the enclosed space charge is defined by the enclosure conditions in transverse and longitudinal direction. For a homogeneous charge density distribution the resulting electrostatic field and therefrom the focusing forces inside the space charge cloud are linear. Additionally in case of a positive ion beam the space charge of the confined electrons causes compensation of the ion beam space charge forces. To study the capabilities of a Gabor double lens system to match an ion beam into a RFQ a testinjector was installed at the IAP and put into operation successfully. First beam profiles and emittance measurements as well as measurements of the beam energy and energy spread have already been performed and show satisfactory results and no significant deviation from the theoretical predictions. To verify the beam focusing of bunched beams using this lens type at beam energies up to 500 keV a new high field Gabor lens was build and will be installed behind of the RFQ.  
 
THP93 A 3D Self-Consistent, Analytical Model for Longitudinal Plasma Oscillation in a Relativistic Electron Beam plasma, electron, 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