Development of a C-band prebuncher

We have developed a C-band prebuncher used for electron linear accelerator cooled to cryogenic temperatures for generating coherent X-rays. This is operated by RF power of about 1 [kW] and frequency of 5712 [MHz]. Since the resonant cavity of the prebuncher is small, it is difficult to apply the usual loop coupling. In order to avoid this problem, an iris coupling structure with waveguide was adopted. By accurate 3D-RF simulation and careful manufacture, the prebuncher which satisfies the specifications was completed. A Q value of 94 [%] of the design value and a coupling(β) of 5.27 were obtained by low power RF measurements. This paper explains its design and manufacture. (author)