LLRF control system of the J-PARC linac

Fang, Z.*; Anami, Shozo*; Michizono, Shinichiro*; Yamaguchi, Seiya*; Kobayashi, Tetsuya; Suzuki, Hiroyuki

In the J-PARC proton linac, each klystron drives two RF cavities. The RF amplitude and phase of the cavities are controlled by an FPGA-based digital feedback control system. The test results show that the variations in the cavity amplitude and phase are less than 0.1% and 0.1 without beam loading, or 0.3% and 0.2 with beam loading. The tuning of each cavity is also controlled by a DSP of this control system. The cavity auto-tuning is successfully controlled to keep the detuned phase within 1 degree. In our RF system, the tuning information including detuned frequency and phase, and Q-value of each cavity are measured in real-time and displayed in the PLC touch panel of the control system.