Longitudinal painting studies in the J-PARC RCS

Tamura, Fumihiko   ; Yamamoto, Masanobu   ; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro  ; Schnase, A.; Toda, Makoto*; Suzuki, Hiromitsu; Shimada, Taihei ; Hara, Keigo*; Hasegawa, Katsushi*

In the J-PARC RCS, we employ the longitudinal painting methods, the momentum offset injection method and applying the second harmonic RF voltages, to increase the bunching factor so that the space-charge tune shift is reduced. By the dual-harmonic operation with wide-band MA loaded cavities, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals, we can generate a large amplitude second harmonic RF voltage without extra cavities for the second harmonic RF. We present the results of the beam tests for the longitudinal painting in the J-PARC RCS. Also, we present the beam behavior at very high beam power.