Fabrication and auto-activation of GaAs photocathode

The computer-automated system has been successfully developed to intelligently activate the GaAs photocathode by the standardized activation technique and to evaluate in-situ the spectral response. The time evolutions of the photocurrent during both the manual activation and auto-activation with the system were compared. The comparisons show that the auto-activation outperforms the manual activation. In the manual-activation, the photocurrent increases more slowly, the peak photocurrent decreases faster, and the (Cs, O) alternation number is fewer as compared with the auto-activation, possibly because of some mis-operation. For instance, in manual activation of the GaAs photocathode, we observed the (Cs, O) alternation number of 6, a peak photocurrent of 43 μA and an integrated sensitivity of 796 μA/lm; whereas in auto-activation, the (Cs, O) alternation number of 9, a peak photocurrent of 65 μA and an integrated sensitivity of 1100 μA/lm.