Longitudinal painting by using large amplitude second harmonic RF

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

For stable acceleration of the high intensity proton beams, increasing the bunching factor by the longitudinal painting is essentially important to reduce the space-charge tune shift. The momentum offset injection method and applying the second harmonic RF are employed for the longitudinal painting in the J-PARC RCS. We employ wide band magnetic alloy (MA) cavities to realize the dual-harmonic operation, in which each cavity is driven by the superposition of the fundamental and the second harmonic RF signals. By the dual-harmonic operation we can generate the large amplitude second harmonic RF without extra cavities for the second harmonic. We report the beam test results of the longitudinal painting.