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space-charge

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TUBX01 Impedance and radiation generated by a ceramic chamber with RF shields and TiN coating impedance, electromagnetic-fields, synchrotron, extraction 125
 
  • Y. H. Chin, S. Lee, K. Takata, T. Toyama
    KEK, Ibaraki
  • Y. Shobuda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Tsutsui
    SHI, Tokyo
  In the RCS (Rapid Cycle Synchrotron) ring of J-PARC, we use ceramic chambers with the interior TiN coating and exterior Cu RF shields in the magnet sections. A new theory has been developed for calculation of impedance in this unusual configuration. When it was applied to a prototype RCS ceramic chamber, the calculation results got good agreement with the measurement results. We also considered the dipole radiation from gaps between Cu shields of the ceramic chamber in the bending magnets. The effects turn out to be rather small thanks to the special configuration of the ceramic chambers. We measured the radiation from a ceramic break with and without RF shields and capacitors in the KEK, PS and found that the RF shields with capacitors considerably suppress the radiation from the ceramic break. We summarize all these studies in this paper.  
 
TUBX02 Collective Transverse Instabilities in the GSI Synchrotrons damping, simulation, octupole, impedance 131
 
  • V. Kornilov, O. Boine-Frankenheim, I. Hofmann
    GSI, Darmstadt
  One of the primary challenges for the design of the FAIR synchrotrons at GSI Darmstadt is the high current operation close to the stability limits, with small tolerable beam losses. Collective instabilities are a potential limiting factor for the performance of the rings. We discuss results of experimental and numerical investigations of transverse collective beam behavior in the SIS 18 synchrotron. Also damping mechanisms in the presence of space charge, including the linear Landau damping and decoherence due to nonlinearities are discussed. These are the essential factors to define impedances budgets for the GSI synchrotrons. As a computational tool accounting the beam nonlinear dynamics with impedances and self-consistent space charge, the particle tracking code PATRIC is used.  
 
WEAX01 Resonance trapping due to space charge and synchrotron motion, in theory, simulations, and experiments beam-losses, resonance, emittance, synchrotron 167
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  With the development of high intensity accelerator, the role of space charge effect in a nonlinear lattice gained special attention, as in the FAIR project at GSI, where long term storage of high intensity beams is required. The simultaneous presence of space charge and a nonlinear lattice creates an unprecedented challenge for ring designers as well as a new area of studies in beam physics. We present our understanding of the effect of space charge and chromaticity on the nonlinear beam dynamics of a bunched beam.  
 
WEAX02 Space charge simulation of J-PARC main ring injection, resonance, sextupole, emittance 177
 
  • A. Y. Molodozhentsev, M. Tomizawa
    KEK, Ibaraki
  The space charge effect in combination with the intrinsic field nonlinearity like the sextupole nonlinearity, used for the chromaticity correction, could lead to significant particle losses in a high beam intensity proton machine. For J-PARC Main Ring (MR) the total particle losses at the ring’s collimator should be less than 1% from the expected maximum beam power of 45kW at the injection energy of 3GeV. To keep the particle losses during the injection process within the required limit it is necessary to optimize the beam parameters from the injector (J-PARC RCS), the collimator aperture of the beam-line from RCS to MR and the collimator aperture of MR. Influence of the structure and non-structure high-order resonances for different working points is discussed. The budget of the beam losses for different MR commissioning scenario is presented.  
 
WEAX03 Space charge neutralization and its dynamic effects electron, linac, simulation, proton 187
 
  • R. Duperrier, N. Pichoff, D. Uriot
    CEA, Gif-sur-Yvette
  • A. BenIsmail
    LLR, Palaiseau
  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 controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), 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 beam dynamics study. This contribution aims to modelize the beam behavior in such a regime and to give order of magnitude to the linac designer for the neutralization rise time and the induced emittance growth.  
 
WEAX04 High Intensity Cyclotron Simulations: Towards Quantitative Predictions simulation, cyclotron, injection, proton 202
 
  • A. Adelmann, S. R.A. Adam, M. Humbel, P. A. Schmelzbach
    PSI, Villigen
  PSI operates the most powerful cyclotron worldwide to the benefit of a multi-user, cross-disciplinary research facility. The accelerator complex consists of a Cockcroft-Walton pre-injector, a 72-MeV separated sector injector cyclotron and a 590-MeV separated sector Ring Cyclotron. A beam current of 1.9 mA is routinely extracted from the Ring Cyclotron overall absolute losses are below 1·10-3. The facility has a considerable potential for further improvements, an ongoing upgrade project aims at a beam current of 3 mA. The purpose of our multi-scale three-dimensional parallel code and methods development is to make the step from qualitative to quantitative predictions. Their simulation requires the accurate three-dimensional modeling of large and complicated accelerator structures including space charge, beam lines, collimation, and in the future secondary effects. We will show methods, both numerically and computational, that we use presently and give an overview on future directions. Measurements from the cyclotrons and beamlines will be compared with simulations carried out in the frame of the high intensity upgrade program.  
 
WEAX05 Space-Charge Beam Physics Research at the University of Maryland Electron Ring (UMER)* quadrupole, dipole, injection, lattice 218
 
  • S. Bernal, B. L. Beaudoin, D. W. Feldman, R. Feldman, R. B. Fiorito, T. F. Godlove, I. Haber, R. A. Kishek, P. G. O'Shea, C. Papadopoulos, B. Quinn, D. Stratakis, K. Tian, C. Tobin, M. Walter
    IREAP, College Park, Maryland
  • M. Reiser
    University Maryland, College Park, Maryland
  • D. F. Sutter
    HENP, SW Washington
  The University of Maryland electron ring (UMER) is a low-energy, high current recirculator for beam physics research with relevance to any applications that rely on intense beams of high quality. We review the space-charge physics issues, experimental and computational investigations, which are currently being conducted at the UMER facility. The physics issues cover a broad range, but we focus on transverse beam dynamics: halo formation, strongly asymmetric beams, Montague resonances, equipartitioning, etc. Furthermore, we report on recent developments in experiments, simulations, and improved diagnostics for space-charge dominated beams.  
 
WEAX06 Measurements and Synergia simulations of emittance dilution at the Fermilab Booster. simulation, resonance, injection, booster 236
 
  • P. Spentzouris
    Fermilab, Batavia, Illinois
  We present a study of the beam evolution in the Fermilab Booster operating both under nominal conditions and in the vicinity of the sum resonance for different beam currents. We simultaneously recorded the horizontal and vertical beam profiles using the Ion Profile Monitor and beam current. Our analysis extracted 2-D emittances and beam shape information from the IPM data. We compare the results with Synergia simulations including 3-D space charge and higher-order optics to analyze and interpret the experimental results.  
 
WEBX02 Observation of Emittance Growth at the injection in the KEK PS Main Ring injection, emittance, proton, simulation 250
 
  • S. Igarashi, T. Miura, E. Nakamura, Y. Shimosaki, M. J. Shirakata, K. Takayama, T. Toyama
    KEK, Ibaraki
  We have been studying the emittance growth and beam loss mechanism during the injection period of the 12 GeV main ring of the KEK proton synchrotron to achieve higher intensity. The typical beam loss is about 30 % during the injection period of 500 milliseconds for the high intensity operation. Measurement of the transverse beam profiles using flying wires has revealed a characteristic temporal change of the beam profile within a few milliseconds after the injection. Horizontal emittance growth was observed when the horizontal tune was close to the integer. The effect was more enhanced for higher beam intensity and could not be explained with the injection mismatch. A resonance created by the space charge field was the cause of the emittance growth. A multiparticle tracking simulation program, ACCSIM, taking account of space charge effects has successfully reproduced the beam profiles.  
 
WEBX05 Scaling laws for space charge resonances emittance, resonance, focusing, simulation 268
 
  • I. Hofmann, G. Franchetti
    GSI, Darmstadt
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  Space charge can be the driving term of nonlinear resonances, like the resonant emittance exchange 2Qx-2Qy=0 ("Montague resonance", in linacs and high-intensity rings), or the fourth-order structure resonance 4Qx=n (high-intensity rings, FFAG's). In this study we present scaling laws to describe the dependence of the expected emittance growth effect on the initial emittances, the tune shift and/or the crossing rate through the resonance.  
 
WEBX06 Analysis of emittance growth in the Fermilab Booster emittance, quadrupole, injection, resonance 271
 
  • K. Y. Ng
    Fermilab, Batavia, Illinois
  • X. Huang
    SLAC, Menlo Park, California
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  Multi-particle similations are performed to study emittance growth in the Fermilab Booster. Analysis shows that the sourcce of the vertical emittance growth comes mostly from random errors in skew quadrupoles as well as the transverse space-charge force. Random errors in the dipole fields and the Montague resonance do contribute but to a much lesser extent. The effect of random errors in the quadrupoles is small because the betatron envelope tunes are resonably far away from the half-integer stopband.  
 
THAW03 RF Barrier Cavity Option for the SNS Ring Beam Power Upgrade electron, proton, injection, target 298
 
  • J. A. Holmes, S. M. Cousineau, V. V. Danilov, A. P. Shishlo
    ORNL, Oak Ridge, Tennessee
  RF barrier cavities present an attractive option for facilitating the path to higher beam intensity in the SNS power upgrade. Barrier cavities lead to flat longitudinal current densities, thus minimizing bunch factor effects. In addition to allowing more beam to be injected in this fashion, flat current profiles may lead to increased e-p instability thresholds due to reduced multipacting during the trailing stage of the bunch. Finally, it is possible to inject self-consistent beam distributions into barrier buckets, thus providing the additional advantages of uniform transverse beam density (good for meeting target constraints) and little or no halo (good for low losses). Simulations addressing all these issues will be presented and discussed.  
 
THBW01 Code benchmarking on induce space charge particle trapping emittance, resonance, synchrotron, sextupole 344
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  • S. Machida
    CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
  Trapping of particles in a high intensity bunch has been studied by using the MICROMAP. The numerical studies were used to interpret the CERN-PS experiments and explore the underlying beam loss/emittance growth mechanisms. We present in this contributed talk the first attempt of code benchmarking in modeling the long term storage of a high intensity bunch. The code benchmarking is initiated between MICROMAP and SIMPSONS.  
 
FRAP02 Summary of Working Gropu B simulation, resonance, beam-losses, linac 363
 
  • S. M. Cousineau
    ORNL, Oak Ridge, Tennessee