Research of the influence to the stability factor of third generation experimental tube under illumination

By use of self-developing more-information measurement instrument, stability under illumination of transmission-mode GaAs photocathode sealed in the third generation intensifier was researched and analyzed. The spectral response curves under ebb-illumination 10 lx and strong-illumination 100 lx were obtained with illumination time. The results show that during initial several weak illuminations photocathode behaves no obvious decay and a maximum sensitivity was achieved, while under intense illumination the sensitivity of photocathode began to decrease largely at the first illumination. It was also found that under intense illumination the peak wavelength moved towards short-wave and peak response decreased, which show that the ability of long-wave response of photocathode is decreased. The performance parameters of GaAs photocathode were estimated by curve imitate. The result indicated that the variation of surface escape probability with illumination time is the direct cause of instability of photocathode under illumination, at the same time, it was found that the illumination increased the ion bombardment probability in GaAs tube, it was the reason for the decline of the cathode sensitive. The Cs quantity on cathode surface and the purge degree of cathode subassembly were the important factor to the cathode stability.