Radio frequency conditioning of an S-band accelerating structure prototype for compact proton therapy facility

The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment. Extensive experiments and numerous studies are being conducted to develop compact linear accelerators for proton therapy. Optimization of the electromagnetic and mechanical design has been performed to simplify the manufacturing process and reduce costs. A novel high-gradient structure with a low relativistic proton velocity (β), v/c = 0.38, was designed, fabricated, and tested at high power. The first full-scale prototype was also successfully tested with high radio frequency (RF) power, a repetition rate of 50 Hz, and pulse length of 3 µs to reach a high-gradient of 46 MV/m using a 50 MW S-band klystron power supply obtained from the Shanghai Soft X-ray Free Electron Laser Facility. This is the first high-power test in China, which is in line with the expected experimental goal. This study presents preliminary high-power testing of S-band standing wave accelerating structures with 11 cells. This work aims to verify the feasibility of using a high-gradient RF accelerating structure in compact proton therapy facilities. The cold test of the prototype cavity was completed in advance. Details of the high-power RF test setup, the process of RF conditioning, and the high-power results are described.