Beam loss reduction by injection painting in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki  ; Harada, Hiroyuki  ; Hayashi, Naoki  ; Kinsho, Michikazu  ; Saha, P. K.   ; Shobuda, Yoshihiro   ; Tamura, Fumihiko   ; Yamamoto, Kazami   ; Yamamoto, Masanobu   ; Yoshimoto, Masahiro  ; Irie, Yoshiro*

The J-PARC 3-GeV RCS was commissioned in October 2007. Via the initial beam tuning and a series of underlying beam studies with low-intensity beams, since December 2009, we have intermittently been performing beam tuning experiments with higher-intensity beams including the injection painting technique. By optimizing the injection painting parameters, we have successfully achieved a 420 kW-equivalent output intensity at a low-level intensity loss of less than 1%. In this paper, we present the experimental results obtained in the course of the RCS beam power ramp-up, especially on the beam loss reduction achieved by employing the injection painting.