Development of the beam chopper timing system for multi-turn injection to the J-PARC RCS

Tamura, Fumihiko   ; Schnase, A.; Nomura, Masahiro  ; Yamamoto, Masanobu   ; Hasegawa, Katsushi; Yoshii, Masahito*; Anami, Shozo*; Ezura, Eiji*; Hara, Keigo*; Omori, Chihiro*; Takagi, Akira*; Toda, Makoto*

Multi-turn injection using charge exchange is employed for the J-PARC Rapid Cycling Synchrotron (RCS). To reduce space charge effects, the bunching factor of the beam in the ring should be increased. Therefore the momentum-offset injection scheme is used. In each turn, the bunch trains from the linac are injected into the RF buckets with a momentum offset. The bunch train is called the "intermediatepulse". The intermediate pulses are generated in the low energy section of the linac by the RF chopper and pre-chopper. Since the pulses must be synchronized to the RF voltage in the ring, the timing signals for the choppers are generated by the low-level RF (LLRF) system of the RCS. The chopper pulses are sent via optical cables. We developed the chopper timingmodule. We describe the details of the hardware.