Effects of a High Energy Particle Environment on the Quantum Efficiency of Spectrally Selective Photocathodes for the Middle and Vacuum Ultraviolet

The quantum efficiences of spectrally selective photocathodes for the middle and vacuum uv (semitransparent depositions of CsI, CuI, and CsTe on Al(2)O(3) windows, a solid tungsten photocathode behind a MgF(2) window) were measured before their use as detectors in a rocket experiment, one year later, and after irradiation by high energy electrons. Only the CsI photodiode showed any change in quantum efficiency, a notable increase after irradiation. Two additional CsI diodes were then irradiated, one with high energy electrons, the other with gamma rays. However, these diodes showed no change in quantum efficiency. The quantum efficiencies of all the photodiodes appear stable with time. The CuI and CsTe diodes also remain stable under irradiation, while the CsI diode may exhibit an increase in quantum efficiency after irradiation.