<title>Stability of GaAs photocathode</title>

Present work focuses on the mechanism of the stability of GaAs NEA photocathode. A series of measurements was made in various operation conditions in the Ultra-high-Vacuum (UHV) System, experimental curves of the quantum efficiency of GaAs NEA photocathode decay vs. time with different residual gas in the Ultra-high-Vacuum (UHV) System were offered. In addition, a model was presented to describe the stability of GaAs NEA photocathode after activated by Cs,O in vacuum chamber. Furthermore, theoretical research has been carried out using Monte Carlo method to simulate the quantum efficiency decay of GaAs NEA photocathode, the calculated lifetimes showed good agreement with the experimental results. The mechanism of stability of GaAs NEA photocathode was also discussed. Some methods that were used to improve the lifetime of GaAs NEA photocathode was suggested.