DETECTION OF FAST BAF(2) SCINTILLATIONS WITH A CSI PHOTOCATHODE COUPLED TO A MWPC

We have investigated the efficiency of a CsI photocathode in a MWPC fo r detection of the fast BaF2 scintillation component, the variation of this efficiency over a period of two months and it's behaviour under an elevated radiation level. We find an extrapolated initial yield of 13 photoelectrons per MeV of energy deposited in the scintillator. Thi s yield decreased exponentially with two decay constants. During the f irst three weeks the decay constant amounted to 5% daily and then it r educed to 1% per day. No noticeable change in the photoelectron yield or it's rate of decrease was observed after a 3 day irraditation amoun ting to a collected charge of 0.3 mC/cm2.