Commissioning of multiharmonic feedforward system for J-PARC MR

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

For acceleration of high intensity proton beam, it is important to compensate the beam loading due to the wake voltages in accelerating cavities. The Q-value of the magnetic-alloy cavity in the J-PARC MR is set to 22 to cover the frequency sweep of the accelerating harmonic (=9) without tuning bias loop. The cavity bandwidth also covers the neighbor harmonics (=8, 10). Thus, the wake voltage consists of the accelerating harmonic (=9) and the neighbor harmonics (=8, 10). We employ the RF feedforward method to compensate the multiharmonic beam loading. The full-digital feedforward system has been developed for the MR. We present the commissioning results of the system with high intensity (1.010 ppp) proton beams.