Beam loss caused by odd harmonics of beam loading in J-PARC RCS

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

A harmonic number of J-PARC RCS is two, and when all RF buckets are filled with bunches, the major parts of the beam Fourier components are the even harmonics. However, the particle tracking simulation suggests that the odd harmonics promote asymmetry on each bunch shape and they rapidly increase under some conditions. When the asymmetry becomes larger and larger monotonously, it causes severe beam loss. Furthermore, although the odd harmonics remain small amplitude, an amplitude modulation of them makes a beam halo and causes small beam loss. We describe the particle tracking simulation results to investigate the odd harmonics.