Author: Murasugi, S.
Paper Title Page
MOPPD051 Performance of Resonant Slow Extraction from J-PARC Main Ring 481
  • M. Tomizawa, Y. Arakaki, T. Kimura, S. Murasugi, R. Muto, H. Nakagawa, K. Okamura, H. Sato, Y. Shirakabe, T. Toyama, E. Yanaoka, M. Yoshii
    KEK, Ibaraki, Japan
  • D. Horikawa
    Sokendai, Ibaraki, Japan
  • K. Mochiki
    Tokyo City University, Tokyo, Japan
  • A. Schnase
    JAEA/J-PARC, Tokai-mura, Japan
  Proton beam accelerated by the J-PARC main ring (MR) with an imaginary transition lattice is slowly extracted by a third integer resonant extraction scheme and delivered to the hadron experimental hall. One of the critical issues in the slow extraction from a high intensity proton synchrotron is the inevitable beam loss caused by the extraction process at septum devices. A design with low beam loss (high extraction efficiency) is required to reduce machine damage and radiation exposure during hands-on maintenance. We have designed the slow extraction scheme to obtain high extraction efficiency for the MR lattice. The scheme has a large step size and a small angular spread enabling a hit rate of the beam on the developed thin septum device. Since the first 30 GeV proton beam was successfully delivered to the experimental hall in January 2009, an extremely high extraction efficiency of 99.5% has been achieved by an intensive beam tuning. In this paper, we report details of such performance. We will also describe some schemes to improve the serious spiky spill time structure due to large current ripples from the power supplies for the bending and quadrupole magnets.