2020 年 17 巻 1 号 p. 4-11
Dielectric assist accelerating (DAA) structure, which has an extremely high-quality factor (Q0) and a shunt impedance (Zsh) at room temperature, has been proposed and demonstrated the expected cavity properties experimentally. The DAA structure consists of low-loss dielectric cylinders and disks with irises which are periodically arranged in a metallic cavity. The metal wall loss of a higher-order TM02n mode excited in this structure could be significantly reduced as compared with that of a TM01 mode excited in conventional normal-conducting linac structures, leading to high power efficiency. In the experiments, a C-band five cells DAA structure using high-purity magnesia ceramic showed that the Q0 of the accelerating mode was over 105 and the Zsh was 617 MΩ/m at room temperature, respectively.