Author: Kinsho, M.
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MOPOR003 Simulation Studies and Measurements of Beam Instabilities Caused by the Kicker Impedance at High Intensities in the 3-GeV RCS of J-PARC 589
  • P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, M. Kinsho, M. Nomura, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  The transverse impedance of the extraction kickers is a significant beam instability source in the 3-GeV Rapid Cycling Synchrotron of J-PARC. ORBIT code was developed for space charge and beam instability simulations by successfully introducing realistic time dependent machine parameters. The beam instability at high intensities, especially at the designed 1 MW beam power was found be very critical. As there was no practical measure yet to reduce the kicker impedance, a detail simulation studies were done in order to determine realistic machine parameters to suppress the beam instability. The simulation results were found to be very consistent with measurements to successfully accomplish 1 MW beam power. The simulation and beam study results in detail are presented in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR003  
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MOPOR004 Recent Progress of 1-MW Beam Tuning in the J-PARC 3-GeV RCS 592
  • H. Hotchi, H. Harada, S. Kato, M. Kinsho, K. Okabe, P.K. Saha, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, K. Yamamoto, M. Yoshimoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  The J-PARC 3-GeV RCS started 1 MW beam test from October 2014, and successfully achieved a 1 MW beam acceleration in January 2015. Since then, a large fraction of our effort has been focused on reducing and managing beam losses. This paper presents the recent progress of 1 MW beam tuning, especially focusing on our approaches to beam loss issues, such as space-charge induced beam loss and foil scattering beam loss during charge-exchange injection, etc.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR004  
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TUXA01 Status and Future Upgrade of J-PARC Accelerators 999
  • M. Kinsho
    JAEA/J-PARC, Tokai-mura, Japan
  The linac energy reached to 400 MeV as a design value and also a beam current was upgraded to 50 mA by replacing a new ion source. At the 3 GeV synchrotron, a high power beam of 8.41x1013 protons per pulse was demonstrated, which was equivalent to 1 MW when the repetition would be 25 Hz. At the main ring, beam loss was reduced by suppression of transverse instabilities and so on. The beam power for both the neutrino experiment and hadron experimental facility is increasing to reduce beam loss. J-PARC accelerators each have their own upgrade plan to increase beam power. The progress and future plan of J-PARC accelerators are reported in this paper.  
slides icon Slides TUXA01 [11.427 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUXA01  
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WEOBB03 A Non-destructive Profile Monitor Using a Gas Sheet 2102
  • N. Ogiwara, Y. Hikichi, J. Kamiya, M. Kinsho, Y. Namekawa
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Fukuda, K. Hatanaka, T. Shima
    RCNP, Osaka, Japan
  We are developing a dense gas-sheet target to realize a non-destructive and fast-response beam profile monitor for 3 GeV rapid cycling synchrotron (RCS) in the J-PARC. This time, to demonstrate the function of the gas sheet for measuring the 2 dimensional profiles of the accelerated beams, the following experiments were carried out: 1) The gas sheet with a thickness of 1.5 mm and the density of 2×10-4 Pa was generated by the combination of the deep slit and the thin slit. Here, the gas sheet was produced by the deep slit, and the shape of the sheet was improved by the thin slit. 2) For the electron beam of 30 keV with a diameter greater than 0.35 mm, the position and the two-dimensional profiles were well measured using the gas sheet. 3) Then the profiles of the 400 MeV proton beam with a current of 1×10-6 A was well measured, too.  
slides icon Slides WEOBB03 [4.718 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBB03  
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WEPMR046 Thermal Analysis of the Injection Beam Dump at J-PARC RCS 2380
  • J. Kamiya, M. Kinsho, P.K. Saha, K. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  In the J-PARC accelerator facility, 400 MeV H ions are injected from linac to rapid cycling synchrotron (RCS). A thin graphite foil with the thickness of about 300 ug/cm2 is located at the injection point to strip two electrons from H ion and convert it to proton. The charge stripping efficiency is usually more than 99.7 %. In other words, less than 0.3 % H ions are not accurately exchanged to protons. Most of those remaining H ions or H0 atoms (stripped only one electron from H ion) are eventually converted to protons by second and third graphite foils and transported to the beam dump. This beam dump consists of an iron block with the size of 0.3×0.3×0.4 m3 for beam stop and the iron block with the size of 3×3×2.5 m3 and concrete with the size of 6×6×6 m3 around the iron block for the radiation shielding. The radiation shielding was designed to endure the 4 kW proton beam to the beam dump. In this presentation, we show the thermal analysis of the beam dump and compare it to the real operation.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR046  
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