Low dose-rate irradiation set-up for scintillating crystals

With a 1 Ci60Co-source we measured the radiation damage and its recovery in PbWO4 crystals. The method consists in measuring the anode current produced in the silicon diode of a Hybrid PhotoMultiplier Tube (HPMT) during the irradiation of the crystal. At regular time intervals, we took photon counting spectra with the same HPMT. By checking the resulting channel positions of the photoelectron peaks, we controlled the stability of our experimental set-up. Temperature control and monitoring were achieved by forced thermostatized water circulation inside the irradiation box and by using a PT100 and two AD590 temperature probes. First results on irradiations of a few PbWO4 crystals are presented and future plans are communicated.