Various usages of wall current monitors for commissioning of RF systems in J-PARC synchrotrons

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

Wall current monitors (WCM) for RF system commissioning are installed in the J-PARC synchrotrons, the RCS and the MR. The WCM signals are used for diagnosis to adjust the RF system parameters. For the diagnosis, the WCM signals are taken by an oscilloscope with the revolution clock signal generated by the LLRF control system, and slices of the WCM waveform with lengths of the revolution periods are generated. By stacking the slices, one can get a mountain plot, which shows motions of bunches and variations of the bunch shapes. Also, time variations of the bunching factor, which are important for acceleration of high intensity proton beams, are obtained. The harmonic analysis is performed on the WCM signal and the cavity voltage monitor signal. By using complex amplitudes of them, one can calculate the impedance seen by the beam. The RF parameters for high intensity beams have been successfully adjusted by using these analyses.