Achievement of a low-loss 1-MW beam operation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki  ; Harada, Hiroyuki  ; Hayashi, Naoki  ; Kato, Shinichi; Kinsho, Michikazu  ; Okabe, Kota  ; Saha, P. K.   ; Shobuda, Yoshihiro   ; Tamura, Fumihiko   ; Tani, Norio  ; Watanabe, Yasuhiro  ; Yamamoto, Kazami   ; Yamamoto, Masanobu   ; Yoshimoto, Masahiro  

The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is the world's highest class of high-power pulsed proton driver, aiming for an output beam power of 1 MW. The most important issues in realizing such a high-power beam operation are to control and minimize beam loss for maintaining machine activations within permissible levels. In RCS, numerical simulation was successfully utilized along with experimental approaches to isolate the mechanism of beam loss and find its solution. By iteratively performing actual beam experiments and numerical simulations, and also by several hardware improvements, we have recently established a 1-MW beam operation with very low fractional beam loss of a couple of 10. In this paper, our recent efforts toward realizing such a low-loss high-intensity beam acceleration are presented.