RF feedforward system for beam loading compensation in the J-PARC MR

Tamura, Fumihiko   ; Yamamoto, Masanobu   ; Schnase, A.; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro  ; Toda, Makoto*; Shimada, Taihei ; Hara, Keigo*; Hasegawa, Katsushi*

For acceleration of high intensity proton beams in the J-PARC MR, beam loading compensation is important. In the MA-loaded RF cavity in the MR, which has a -value in the order of 20, the wake voltage consists of the accelerating harmonic ( = 9) and the neighbor harmonics ( = 8, 10). We employ the RF feedforward method for the beam loading compensation, like in the J-PARC RCS, in which the impedance seen by the beam is greatly reduced by the feedforward. The full-digital feedforward system developed for the MR has a similar architecture to that of the RCS. The system compensates the beam loading of the important three harmonics ( = 8, 9, 10). We present the structure of the RF feedforward system. Also, we report the preliminary results of the beam tests.