Realizing a high-intensity low-emittance beam in the J-PARC 3-GeV RCS

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

For this past year, RCS beam tuning was focused on realizing a high-intensity low-emittance beam required from the downstream facility. The extraction beam emittance including its tail part was successfully decreased by optimizing transverse injection painting, and tune and chromaticity manipulations, where bipolar sextupole field patterns were newly introduced to simultaneously achieve emittance growth mitigation at the early stage of acceleration and beam instability suppression after the middle stage of acceleration. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.