Development of the feedforward system for beam loading compensation in the J-PARC RCS

Tamura, Fumihiko   ; Schnase, A.; Nomura, Masahiro  ; Yamamoto, Masanobu   ; Yoshii, Masahito*; Anami, Shozo*; Ezura, Eiji*; Hara, Keigo*; Omori, Chihiro*; Takagi, Akira*

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. 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 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.