High power acceleration of an HSC type injector for cancer therapy

A hybrid single cavity（HSC） linac, which is formed by combining a radio frequency quadrupole（RFQ）and a drift tube（DT） structure into one interdigital-H（IH） cavity, is fabricated and assembled as a proof of principle injector for cancer therapy synchrotron, based on the culmination of several years of research. The HSC linac adopts a direct plasma injection scheme（DPIS）, which can inject a high intensity heavy ion beam produced by a laser ion source（LIS）. The input beam current of the HSC is designed to be 20 m A C6+ ions. According to numerical simulations, the HSC linac can accelerate a 6-m AC6+ beam, which meets the requirement of the needed particle number for cancer therapy（108-9ions/pulse）. The HSC injector with the DPIS method makes the existing multiturn injection system and stripping system unnecessary, and can also bring down the size of the beam pipe in existing synchrotron magnets, which could reduce the whole cost of synchrotron. The radio frequency（rf） measurements show excellent rf properties for the resonator, with a measured Q equal to 91% of the simulated value. AC6+ ion beam extracted from the LIS was used for the HSC commissioning. In beam testing, we found the measured beam parameters agreed with simulations. More details of the measurements and the results of the high power test are reported in this paper.