Multiharmonic Beam Loading Compensation in The J-PARC Synchrotrons

Abstract

Beam loading compensation is a key for acceleration of a high intensity proton beam in the synchrotrons, the RCS and MR, of the Japan Proton Accelerator Research Complex (J-PARC). Magnetic alloy loaded rf cavities are used to achieve high accelerating voltages without a tuning bias loop. The frequency response of the RCS cavity covers the fundamental accelerating harmonic (h = 2) and higher harmonics up to the third (h = 6) harmonic. In case of the MR, the accelerating harmonic (h = 9) and the neighbors (h = 8, 10) are covered. wake voltages in the MA cavities are multiharmonic, and multiharmonic beam loading compensation is necessary for both of the RCS and MR. We developed the multiharmonic feedforward systems for the J-PARC synchrotrons. A commissioning methodology of the feedforward patterns has been established. We describe the system architecture and the commissioning methodology of the feedforward patterns. The commissioning of the feedforward using high intensity proton beams was successfully performed in the RCS and MR. We report the commissioning results. The multiharmonic beam loading compensation is necessary for the high intensity user operation.