Influence of laser oblique incidence on beam quality and optimization

In allusion to Brookhaven National Laboratory(BNL) type photocathode RF gun, we simulated and optimized the influence of drive laser oblique incidence on beam quality. Different distributions of drive laser were considered. We optimized the transverse emittance by tuning the injection phase and magnetic field intensity of compensating coil. The “elliptical spot” caused serious increase of transverse emittance, which can not be optimized well. Whereas, the increase caused by “time slew” could be optimized well for Gaussian distribution pulse in temporal direction. We also presented an optical method to calibrate the “elliptical spot” and “time slew” problem on the photocathode and partial measurement results. The simulation results show that: for drive laser with uniform transverse