Recent progress of GaAs high-voltage DC photo-injector

The GaAs photocathode high-voltage DC injector has been demonstrated as one of the most important electron sources for future high-repetition short-wave free electron lasers (FELs) and energy recovery linacs (ERLs). In this paper, recent progress of the GaAs high-voltage (HV) photo-injector for the FEL-THz facility is presented, and the chance of which for driving a future high-repetition short-wave FEL is discussed. All the factors that affect the GaAs photocathode operation life-time are considered and a qualitative physical model is proposed. Under the guidance of this model and with some optimization strategies, a 5 mA/32 min CW output is reached in the HV DC injector. Some electron beam parameters are measured, including normalized emittance under 4.8 mA output that is about 6.0 mmmrad, thermal emittance about 0.6mmmrad, intrinsic transverse energy about 92 meV, and root-mean-squared length with 250 keV kinetic energy that is 11.5 ps at 90.6 cm after the cathode. The state of the injector now meets the needs of FEL-THz electron source requirements preliminarily.