RF design of a C-band compact spherical RF pulse compressor for SXFEL

A new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed for the Soft X-ray Free Electron Laser facility (SXFEL) at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS). Using only one high Q0 spherical RF resonant cavity which works on two TE113 modes and a dual-mode polarized coupler, this pulse compressor could achieve an average power gain of 3.8. Associated with the C-band accelerator, an energy gain of 1.85 with the coupling coefficient of 4.9 could be achieved. Particularly it could make the output power stable. This paper presents the scheme of the C-band spherical pulse compressor, as well as the RF design and details of the frequency sensitivities and machining considerations.