Heat enhancement of radiation resistivity of evaporated CsI, KI and KBr photocathodes

The photoemissive stability of as-deposited and heat-treated CsI, KI and KBr evaporated thin "lms under UV radiation is examined in this paper. After the deposition, some photocathodes were annealed for several hours at 903C in vacuum and their performance was then compared to the performance of non-heated samples. We observed that the post-evaporation thermal treatment not only increases the photoyield of CsI and KI photocathodes in the spectral range of 115}190 nm, but also reduces CsI, KI and KBr photocurrent degradation that occurs after UV irradiation. KBr evaporated layers appeared to be more radiation-resistant than CsI and KI layers. Post-deposition heat treatment did not result in any signi"cant variation of KBr UV sensitivity. ( 2000 Elsevier Science B.V. All rights reserved.