Investigation of CsI photocathodes in a multiwire proportional chamber

A multiwire proportional chamber with CsI photocathode as a detector of Cherenkov photons has been studied. Cherenkov radiation has been produced in an NaF radiator by cosmic rays and by electrons from /sup 90/Sr. Results on the variation of the CsI quantum efficiency over a period of 500 days are presented. Some preliminary data concerning the production of CsI photocathodes and the regeneration of the quantum efficiency by heating are given.<<ETX>>