CsBr and CsI UV photocathodes: new results on quantum efficiency and aging

We report on the photoemission properties of 300 إ thick transmissive- and 5000 إ thick reflective UV-sensitive CsBr photocathodes. Following post-evaporation heat treatment at 70°C the absolute quantum efficiency is 35% at 150 nm, with a red boundary cut-off at about 195 nm. Extensive aging studies of CsBr and CsI photocathodes, under high photon flux and under ion bombardment in gas avalanche multiplication mode, were carried out for the first time without exposure to air. The results are compared with the previously published data on CsI aging and the methodology of the aging tests is discussed in details.