Achievement of very low jitter extraction of high power proton beams in the J-PARC RCS

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

The RCS of J-PARC delivers high intensity proton beams to the MLF and MR. The operation period of the J-PARC is 3.2 s. Four beam pulses are for the MR and the other pulses are led into the MLF. Since a bucket-to-bucket injection scheme is used for the MR, the beam from the RCS must be injected with a precise phase to rf bucket of the MR. In case of the MLF, the beam has to be synchronized to the Fermi chopper, which has a tolerance of only a few 100 ns. To realize the stable beam timing, we employ the timing system, not synchronized to the AC power line. Also the magnetic-alloy cavities and the digital low-level RF control system are the keys. For acceleration of a high power beam, the phase feedback loop is necessary. The phase loop is a cause of the jitter of the beam extraction timing. We apply a gain pattern of the phase loop to avoid the influence on the beam phase at the extraction. We have achieved a very low jitter extraction of a high power beam within 1.7 ns.