Design, fabrication and cold-test results of a 3.6 cell C-band photocathode RF gun for SXFEL

The increasing demands for electron beams with short bunch length and high brightness for Soft X-ray Free Electron Laser (SXFEL) have stimulated active efforts to develop suitable photoinjectors for these accelerators. One promising direction in this regard is increasing the gradient of rf gun. The rf design, beam dynamics and cold-test results of a novel 3.6 cell C-band 150 MV/m rf photocathode gun are presented in this paper. The rf gun and its beam dynamics modeling have been done using a combination of codes including POSSION, CST, and ASTRA. The impact of first half-cell length, cell number, and solenoid on beam dynamic are analyzed and described. The gun has state-of-the-art rf features including: elliptical irises profile; a non-brazed cathode plate; and a rectangular mode launcher. The fabrication and cold-test of the rf gun prototype are successfully implemented, and the measured solenoid field agrees well with simulations.