Commissioning of beam loading compensation system in the J-PARC MR

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

Beam loading compensation is indispensable to accelerate high intensity proton beams in the J-PARC MR. The MA-loaded rf cavities in the MR are driven by the single harmonic (h = 9) rf signals, while the cavity frequency response covers also the neighbor harmonics (h = 8, 10). The wake voltage induced by the beam consists of the three harmonics (h = 8, 9, 10). We employ the rf feedforward method to compensate the beam loading of these harmonics. The full-digital feedforward system was developed for the MR. We have successfully commissioned the feedforward patterns for all of eight cavities by using high intensity beams with 1.010 ppp. We present the commissioning results. The impedance seen by the beam is reduced and the longitudinal oscillations due to the beam loading are reduced. By the beam loading compensation, high power beam operation at the beam power of 200 kW has been achieved.