1 MW beam tuning for beam loss mitigation in the J-PARC 3 GeV RCS

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

After the RF power supply upgrade, the J-PARC 3-GeV RCS restarted a 1-MW beam test in October 2015. In the beam test in October, we successfully removed longitudinal beam loss by beam loading compensation as well as minimized space-charge induced beam loss by injection painting. In addition, in this beam test, beam instability was also well suppressed by controlling the tune and the chromaticity. Furthermore, in the following beam test, the transverse painting area was successfully expanded by introducing both quadrupole correctors and anti-correlated painting scheme, by which a foil scattering part of beam loss during charge-exchange injection was further reduced. By these recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents recent progresses of 1-MW beam tuning with particular emphasis on our approaches to beam loss issues.