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Fang, Z.

Paper Title Page
THP006 Performance of a Digital LLRF Field Control System for the J-PARC Linac 574
 
  • S. Michizono, S. Anami, Z. Fang, S. Yamaguchi
    KEK, Ibaraki
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Suzuki
    JAEA, Ibaraki-ken
  
  Twenty high power klystrons are installed in the J-PARC linac. The requirements for the rf field stabilities are ±1% in amplitude and ±1 deg. in phase during a 500 us flat-top. In order to satisfy these requirements, we adopt the digital feedback and feed-forward system with FPGAs and a commercial DSP board. The FPGAs (Virtex-II 2000) enable a fast PI control for a vector sum of two cavity fields. The measured stability during rf pulse was ±0.15% in amplitude and ±0.15 deg in phase. The tuner control was successively operated by a way of the DSP board by measuring the phase difference between the cavity input wave and the cavity field. Beam loading effects were emulated using a beam-loading test box. By proper feed-forward, the rf stability was less than ±0.3% and ±.15 deg.