05 Beam Dynamics and EM Fields
D07 High Intensity Circular Machines Space Charge, Halos
Paper Title Page
TUXGBF4 ORBIT Simulation, Measurement and Mitigation of Transverse Beam Instability in the Presence of Strong Space Charge in the 3-GeV RCS of J-PARC 620
  • P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  The transverse impedance of eight extraction pulse kicker magnets (KM) is extremely strong source of transverse beam instability in the 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC. To realize the designed 1 MW beam power, collective beam dynamics with including the space charge effect for the coupled bunch instabilities excited by the KM impedance and associated measures were studied by incorporating all realistic time-dependent machine parameters in the ORBIT 3-D particle tracking code. The simulation results were all reproduced by measurements and, as a consequence, an acceleration of 1 MW beam power has been successfully demonstrated. In order to maintain variation of the RCS parameters required for multi-user operation, realistic measures for beam instability mitigation were proposed and also been successfully implemented in reality. To further increase the RCS beam power, beam stability issues and possible measures beyond 1 MW beam power are also considered.  
slides icon Slides TUXGBF4 [2.241 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF4  
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Space charge limitations for bunch compression in synchrotrons  
  • Y.S. Yuan
    TEMF, TU Darmstadt, Darmstadt, Germany
  Student poster award talk  
slides icon Slides TUYGBD7 [1.662 MB]  
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THPAF054 Characterization of Losses and Emittance Growth for Ion Beams on the SPS Injection Plateau 3091
  • Á. Saá Hernández, F. Antoniou, H. Bartosik, A. Huschauer
    CERN, Geneva, Switzerland
  Losses and transverse emittance growth in the Super Protron Synchrotron (SPS) impose presently the main performance limitation on the Large Hadron Collider (LHC) ion injector chain. In this paper we present the measurements performed in 2016 with Pb82+ ions and the analysis to characterize the observations of beam degradation during the long injection plateau. Residual gas scattering, intrabeam scattering (IBS) and resonance excitation have been studied.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF054  
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THPAF055 Space Charge Studies on LEIR 3095
  • Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, A. Huschauer, D. Moreno Garcia
    CERN, Geneva, Switzerland
  The performance of the CERN Low Energy Ion Ring with electron cooled ion beams is presently limited by losses occurring once the beam has been captured in the RF buckets. An intense machine study program was started by the end of 2015 to mitigate the losses and improve the performance of the accelerator. The measurements pointed to the interplay of direct space charge forces and excited betatron resonances as the most plausible driving mechanism of these losses. In this paper, we present the systematic space-charge measurements performed in 2017 and compare them to space-charge tracking simulations based on an adaptive frozen potential.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF055  
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THPAF069 Particle Tracking Simulation of Collective Modes - Parametric Landau Damping Off Coupling Resonance 3137
  • A. Macridin, J.F. Amundson, A.V. Burov, P. Spentzouris, E.G. Stern
    Fermilab, Batavia, Illinois, USA
  Employing Synergia simulations with the DMD method we investigate the Landau damping of space charge modes in bunched beams. The simulations reveal two instances of the parametric damping mechanism in bunched beams. The first example occurs in the proximity of coupling resonance and is due to the oscillation of particles' amplitudes in the transverse plane. This oscillation modulates the mode-particle coupling with particle dependent trapping frequency. The second example is due to the modulation of the mode-particle coupling in one transverse plane by the oscillatory motion in the other plane.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF069  
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THPAK035 Numerical Tools for Modeling Nonlinear Integrable Optics in IOTA with Intense Space Charge Using the Code IMPACT-Z 3290
  • C.E. Mitchell, J. Qiang
    LBNL, Berkeley, California, USA
  Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Several new numerical tools have been implemented in the code IMPACT-Z to allow for high-fidelity modeling of the IOTA ring during Phase II operation with intense proton beams. A primary goal is to ensure symplectic treatment of both single-particle and collective dynamics. We describe these tools and demonstrate their application to modeling nonlinear integrable dynamics with space charge in IOTA.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK035  
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THPAK056 Resonance Identification Studies at the CERN PS 3350
SUSPF081   use link to see paper's listing under its alternate paper code  
  • F. Asvesta
    NTUA, Athens, Greece
  • H. Bartosik, A. Huschauer, Y. Papaphilippou, G. Sterbini
    CERN, Geneva, Switzerland
  In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK056  
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THPAK067 Progress Toward a Self-Consistent Beam at the Spallation Neutron Source 3382
  • J.A. Holmes, S.M. Cousineau, T.V. Gorlov, M.A. Plum
    ORNL, Oak Ridge, Tennessee, USA
  • N.J. Evans
    ORNL RAD, Oak Ridge, Tennessee, USA
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the US DOE. This research was supported by the DOE Office of Science, Accelerator and Detector Research Program.
We have proposed to inject a self-consistent "rotating" beam into the Spallation Neutron Source (SNS). Self-consistent beam distributions are defined to be ellipsoidal, or elliptical in 2D, distributions that have uniform density and that retain these properties under all linear transformations. We have made much progress since the original proposal. We have demonstrated computationally the feasibility of injecting a rotating beam under realistic physics assumptions. We have optimized the injection scheme with respect to beam loss and to minimum necessary hardware changes. We have also determined how existing SNS beam diagnostic equipment can be used to verify the self-consistency of the injected beam. This paper will report the details of this work as well as the status of plans to carry out the self-consistency experiments.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK067  
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THPAK109 Improved Simulation for Centre Region of TRIUMF 500 MeV Cyclotron with Space Charge 3489
  • Y.-N. Rao, R.A. Baartman, T. Planche
    TRIUMF, Vancouver, Canada
  Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada
The TRIUMF 500 MeV cyclotron delivered routinely a total current up to 200 μA protons for 15 years till 2001. Since 2002, developments towards 300 μA total extraction became compelling because of the ISAC expansion. To meet future requirements (for addition of a new beam-line), a total extraction of 310 − 450 μA shall be envisioned. With such an increase of beam current, the space charge effect becomes a major concern in the centre region, as it limits the maximum amount of beam current achievable out of the machine. Therefore, numerical simulation on beam orbits with the space charge force has has been initiated, starting from the injection gap. This study is focused on the beam bunches which are very long compared with transverse size (because TRIUMF extraction is by stripping of H-minus and separated turns are not required). In order to achieve an improved understanding of the space charge effect, we worked to validate the simulations performed without and with the space charge force, using realistic centre region geometry. Our goal is to work out the space charge limits and their dependence upon the bunchers, rf voltage, and matching. In this paper we present our recent progress in this study.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK109  
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THPAK117 Space Charge Limitations for Bunch Compression in Synchrotrons 3518
SUSPF082   use link to see paper's listing under its alternate paper code  
  • Y.S. Yuan, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt, Germany
  Bunch compression achieved via a fast bunch rotation in longitudinal phase space is a well-accepted scheme to generate short, intense ion bunches for various applications. During bunch compression, coherent beam instabilities and incoherent single particle resonances can occur because of increasing space charge, resulting in an important limitation for the bunch intensity. We present an analysis of the relevant space charge driven beam instability and resonance phenomena during bunch compression. A coupled longitudinal-transverse envelope approach is compared with Particle-In-Cell (PIC) simulations. Two distinct cases of crossing are discussed and applied to the GSI SIS18 heavy-ion synchrotron. It is shown that during bunch compression, the 90° condition of phase advance is associated with a fourth order single particle resonance and the 120° condition with the recently discovered dispersion-induced instability. The agreement between the envelope and PIC results indicates that the stop band is defined by the 120° dispersion instability, which should be avoided during bunch compression.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK117  
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