A Prototype system of multiharmonic vector voltage control for the J-PARC rapid cycling synchrotron

Tamura, Fumihiko   ; Sugiyama, Yasuyuki*; Yoshii, Masahito*

Beam loading compensation for the magnetic alloy (MA) cavities is a key for acceleration of high intensity proton beams in the J-PARC RCS. A multiharmonic rf feedforward system is implemented in the existing LLRF control system for the RCS and it served fairly well for the beam tests up to the design beam power, 1 MW. During high intensity beam tests, we found some practical disadvantages of the feedforward method due to its open loop configuration. Therefore, We are considering to employ the vector voltage control in the next generation LLRF control systems as well as feedforward for beam loading compensation. We developed a prototype system of multiharmonic vector voltage control in JFY 2016. It handles six harmonics and has features to adapt to frequency sweeps following to the velocity change of the beam during acceleration. We present the system configuration, its commissioning, and the beam test results with a very high intensity beams at the beam power of 900 kW.