Long term performance and ageing of CsI photocathodes for the ALICE/HMPID detector

The performance of CsI photocathodes for the ALICE/HMPID detector with regard to long term stability and ageing effects has been investigated and monitored during the production phase and in dedicated ageing tests. During normal storage and test beam operations none of the monitored PCs has showed a decrease in quality within a time-frame of two years. In accelerated ageing tests with ion-bombardment in the detector caused by ionizing particles, pronounced ageing effects could be observed for charge doses ⩾1mC/cm2, whereas irradiations with ⩽0.2mC/cm2 showed no effect.