Photoinjector beam quality improvement by shaping the wavefront of a drive laser with oblique incidence

To increase the quantum efficiency(QE) of a copper photocathode and reduce the thermal emittance of an electron beam,a drive laser with oblique incidence was adopted in a BNL type photocathode rfgun.The disadvantageous e?ects on the beam quality caused by oblique incidence were analyzed qualitatively.A simple way to solve the problems through wavefront shaping was introduced and the beam quality wasimproved.