The data,such as photocurrents,currents of Cs source and O source in the activation process of gradient-doping GaN photocathode,were measured in the preparation and evaluation system designed by us.The effects of vacuum,surface cleaning,the first flux of Cs,Cs/O ratio,and Cs/O flux on/off were analyzed based on the curves of spectral response and quantum yield obtained by testing the gradient-doping GaN photocathode after being fully activated.The optimized activation technique of gradient-dopin...