RF FEEDFORWARD SYSTEM FOR BEAM LOADING COMPENSATION IN THE J-PARC MR

For acceleration of high intensity proton beams in the JPARC MR, beam loading compensation is important. In the MA-loaded rf cavity in the MR, which has a Q-value in the order of 20, the wake voltage consists of the accelerating harmonic (h =9 ) and the neighbor harmonics (h =8 , 10). We employ the rf feedforward method for the beam loading compensation, like in the J-PARC RCS, in which the impedance seen by the beam is greatly reduced by the feedforward. The full-digital feedforward system developed for the MR has a similar architecture to that of the RCS. The system compensates the beam loading of the important three harmonics (h =8 , 9, 10). We present the structure of the rf feedforward system. Also, we report the preliminary results of the beam tests.