UV radiation resistance and solar blindness of CsI and KBr photocathodes

Abstract

A detailed study of the stability of CsI and ,KBr photocathodes under UV irradiation is presented. UV quantum efficiency degradation was found to be more pronounced' :at lower illumination intensity for the same accumulated doseand illumination wavelength. For an equal number of extracted photoelectrons in-band UV exposure led to a larger sensitivity decay as compared to out-of-band illumination. The angle of radiation incidence was not important for the UV sensitivity degradation, while changes of visible light ' rejection (i.e. degradation of solar blindness) did depend on the incidence angle: the photocathodes illuminated at normal incidence were activated much faster than the films irradiated at grazing angle. We found that the increase of visible sensitivity can be characterized by the total accumulated dose and is independent of irradiation flux during UV activation. We also observed that heat annealing substantially improves the visible light rejection of CsI photocathodes.I.

Recent Progress in Research on CsI Thin Film Photocathodes

“…由于 CsI 薄膜光阴极在正常工作环境中老化过 程比较缓慢, 对辐照老化的研究一般采用了加大剂 量、加速老化的方法。对于特定剂量的辐射, 某些 情况下加大辐射强度而 QE 值反而下降较慢, 这使 得对辐照老化的研究变得更为复杂, 并与实际老化 过程有一定差异 [7,58] 。 人们对辐照老化机理有几种解释。 Breskin 等 [24] 将 CsI 薄膜光阴极在辐照中效率下降归因于 CsI 的 光解和表面 I 的挥发, 表示为:…”