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Hara, K.

Paper Title Page
TUPCH128 New Cutting Scheme of Magnetic Alloy Cores for J-PARC Synchrotrons 1313
 
  • C. Ohmori, S. Anami, E. Ezura, Y. Funahashi, K. Hara, K. Hasegawa, A. Takagi, M. Toda, K. Ueno, M. Yoshii
    KEK, Ibaraki
  • Y. Morita, T. Yoshioka
    ICEPP, Tokyo
  • M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  
  A new cutting method using a grindstone was developed to manufacture the magnetic alloy cores. The problem of local temperature rise around the cut surfaces was solved. Long-term high-power tests have been performed for both J-PARC RCS and MR RF systems. Mechanism of local heating, new cutting scheme, and manufacturing method are presented.  
TUPCH130 Development of the Feed-forward System for Beam Loading Compensation in the J-PARC RCS 1319
 
  • F. Tamura, M. Nomura, A. Schnase, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Yoshii
    KEK, Ibaraki
  
  In the J-PARC Rapid Cycling Synchrotron (RCS), the heavy beam loading effects due to the high intensity proton beam must be compensated for stable acceleration. The beam feedforward technique is used to compensate the beam loading in the RCS. We present the development of the feedforward system. We designed and built the full-digital system with modern FPGAs to realize high accuracy, stability and predictability of the compensation. Because of the low Q value of each accelerating cavity, the wake voltage consists of not only the accelerating harmonic component but also higher harmonics. Thus, the system is designed to compensate the beam loading at several harmonics. The system has two parts. In the first part, vector components of the selected harmonic are detected from the beam signal picked up by a wall current monitor. The compensation RF signal is generated from the vector components with proper gain and phase in the latter part. The gain and phase are set individually for each harmonic and each cavity of the twelve cavities. We also present the preliminary test results of the newly developed modules.  
TUPCH131 High Power Test of MA Cavity for J-PARC RCS 1322
 
  • M. Yamamoto, M. Nomura, A. Schnase, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
    KEK, Ibaraki
  • K. Hasegawa
    JAEA, Ibaraki-ken
  
  We have been constructing the RF system for the J-PARC RCS. Almost all of the power supplies and the tube amplifiers have been constructed, and the cavities are under construction. All of them are tested at the experimental hall before installing into the J-PARC RCS building. We test the hybrid cavity scheme to realize the optimum cavity Q-value. The results of the test are described.  
TUPCH193 Low Level RF Control System Modules for J-PARC RCS 1465
 
  • A. Schnase, M. Nomura, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Yoshii
    KEK, Ibaraki
  
  After completing the design phase, the VME modules for the Low Level RF Control (LLRF) of the Rapid Cycling Synchrotron of J-PARC are now in the production and debugging phase. First all modules are tested for basic functionality, for example dual harmonic signal generation. Then sets of modules are connected together to check higher-level functions and feedback. Finally, the LLRF modules are interfaced to high voltage components like amplifiers and cavities. We present the results of these tests, the test methods and test functions on several levels. This way we simulate beam operation working conditions and gain experience in controlling all parameters.  
TUPLS108 Realization of Thick Hybrid Type Carbon Stripper Foils with High Durability at 1800K for RCS of J-PARC 1753
 
  • I. Sugai, K. Hara, H. Kawakami, M. Oyaizu, A. Takagi, Y. Takeda
    KEK, Ibaraki
  • T. Hattori, K.K. Kawasaki
    RLNR, Tokyo
  • Y. Irie, J. Kamiya, M. Kinsho
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  
  The J-PARC requires thick carbon stripper foils (250-500 ug/cm2) to strip electrons from the H-beam supplied by the linac before injection into a 3 GeV Rapid Cycling Synchrotron. The 200 MeV H- beam from the linac has a pulse length of 0.5 ms with a repetition rate of 25 Hz and an average beam current of 335 uA. By much energy deposition of these high-intensity H- and circulating bunched beams, commercially available best stripper foils (CM) will break in a very short time and even a diamond foil will rupture at around 1800K by MW class accelerators. We have realized for first time the hybrid boron doped carbon stripper foils with long life time for J-PARC. The foils of 250-500 ug/cm2 were made by a controlled DC arc-discharge method. The lifetime was tested by using 3.2 MeV Ne+ DC beam of 2.5 uA and 750 keV H- DC beam of 500 uA, in which a significant amount of energy was deposited in the foils. The maximum lifetime was extremely long, 120- and 480-times than those of diamond and CM foils. The foils were also free from any shrinkage, and showed low thickness reduction rate even at high temperature of 1800K during long time irradiation of 90h.