Drive laser shaping and transport system for photocathode RF gun

To meet the requirements of Hefei Advanced Light Facility (HALF) for high quality injection beam, a photocathode RF gun is developed as the electron source of the injector in the R&D project. To obtaining an electron beam with high qualities, it is necessary to carry out experimental research on drive laser shaping and transport system. For suppressing the beam emittance growth caused by space charge force, the temporal pulse shape is modified by using birefringent crystals, while an aperture is used for spatial pulse shaping. An optical image transport system is designed to achieve high stability of the laser beam position on the photocathode. Detailed design of the optical system is presented in this paper. The experimental result shows that a quasi uniform distribution in the three-dimensional space of laser pulse is obtained, and the laser beam position jitter on the photocathode is less than 4 µm. The performance of the laser pulse meets the experiment requirements.