High intensity single bunch operation with heavy periodic transient beam loading in wide band RF cavities

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

The RCS in the J-PARC was originally designed to accelerate two high intensity bunches, while some of neutron experiments in the MLF and a muon experiment using MR beams require a single bunch operation mode. The beam intensity in the single bunch operation has been limited by longitudinal beam losses due to the rf bucket distortions by the wake voltage of the odd harmonics in the wide band MA cavities. We installed an additional rf feedforward system to compensate the wake voltages of the odd harmonics (h=1,3,5). The longitudinal beam losses during the single bunch acceleration disappeared with feedforward for the odd harmonics. We also confirmed that the beam quality in the single bunch acceleration are similar to that of the normal operation with two bunches. Thus, high intensity single bunch acceleration at the intensity of 2.310 protons per bunch has been achieved in the J-PARC RCS.