RF systems of J-PARC proton synchrotrons for high-intensity longitudinal beam optimization and handling

Tamura, Fumihiko   ; Yamamoto, Masanobu   ; Yoshii, Masahito*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Okita, Hidefumi  ; Seiya, Kiyomi*; Nomura, Masahiro  ; Shimada, Taihei ; Hasegawa, Katsushi*; Hara, Keigo*; Miyakoshi, Ryosuke*

The application of MA cores to the accelerating rf cavities in high intensity proton synchrotrons was pioneered for the J-PARC synchrotrons. The MA cavities can generate high accelerating voltages. The wideband frequency response of the MA cavity enables the frequency sweep without the tuning loop. The dual harmonic operation is indispensable for the longitudinal bunch shaping to alleviate the space charge effects in the RCS. These advantages of the MA cavity are also disadvantages when looking at them from a different perspective. Since the wake voltage consists of several harmonics, the beam loading compensation must be multiharmonic. The operation of tubes in the final stage amplifier is not trivial when accelerating very high intensity beams; the output current is high and the anode voltage is also multiharmonic. We summarize our effort against these issues in the operation of the RCS and MR for more than 10 years.