Dual-harmonic phase control in the J-PARC RCS

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

The wide-band RF cavities in the J-PARC RCS are operated in the dual-harmonic operation, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals. By the dual-harmonic operation large amplitude second harmonic signals for the bunch shape manipulation are generated without extra cavities. The phase control of the second harmonic RF is a key for the bunch shape manipulation. The fundamental RF signal is controlled by the phase feedback loop to damp the dipole oscillation. The second harmonic is locked to the phase of the vector-sum phase of the fundamental RF signals. We present the system detail and the performance in the beam operation of the RCS.