Author: Igarashi, S.
Paper Title Page
MOPAB229 Compensations of Third-Order Resonances in J-PARC MR 744
 
  • T.Y. Yasui, S. Igarashi, T. Koseki, Y. Kurimoto, Y. Morita, K. Ohmi, Y. Sato, T. Shimogawa
    KEK, Tokai, Ibaraki, Japan
 
  The main ring synchrotron (MR) of the Japan Proton Accelerator Research Complex (J-PARC) provides high-power proton beams for the neutrino and hadron experiments. In the fast extraction (FX) operation, the beams are injected with the energy of 3 GeV and the intensity of 3.3 × 1013 protons per bunch, and accelerated to 30 GeV. Most of the beam losses are observed in the low-energy period, because the space charge tune spread is large, and crosses various kinds of resonances. In this study, the compensations of the third-order resonances are performed. The present operation tune is (νx, νy) = (21.35, 21.43) in FX operation. The nearest third-order structure resonance is νx-2νy=-21. It was clearly compensated by optimizing the phase advances in the arc sections. The compensation was confirmed by the aperture survey simulations and demonstrated by the three different experiments. The third-order nonstructure resonances near the operation tune are 3νx=64 and νx+2νy=64. They are simultaneously compensated by introducing four trim coils of the sextupole magnets. The beam loss was successfully reduced by adopting the compensations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB229  
About • paper received ※ 20 May 2021       paper accepted ※ 02 June 2021       issue date ※ 29 August 2021  
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THPAB245 A Simulation Study of Beam Pipe Eddy Current Effects on Beam Optics 4288
 
  • T. Asami, T. Koseki
    The University of Tokyo, Graduate School of Science, Tokyo, Japan
  • S. Igarashi, T. Koseki, Y. Kurimoto, Y. Sato
    KEK, Ibaraki, Japan
 
  In synchrotrons, fast changes of magnetic field induce eddy currents at the wall of beam pipes. The eddy currents cause a phase delay between excitation currents of the magnets and the magnetic field. The undesired magnetic field affected by eddy currents might be a serious obstacle in controlling beam optics precisely. In fact, in the operation of a high-intensity proton synchrotron J-PARC MR, the largest beam loss is observed at the beginning of acceleration when the magnetic field starts to vary in time. Therefore, it is important to estimate and understand the effects of eddy currents on beam optics. In this study, we have calculated the effect of eddy currents on magnetic field for some magnets in J-PARC MR, using electromagnetic simulation software. In this paper, we would like to report the details and results of the simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB245  
About • paper received ※ 19 May 2021       paper accepted ※ 26 July 2021       issue date ※ 17 August 2021  
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