Radiation damage of CsI(Tl) crystals in a long term exposure at PETRA

Abstract

We have tested the radiation resistance of two 10 cm long CsI(Tl) crystals in the radiation environment of the PETRA e +e − storage ring. The crystals were exposed for 38 d to an average dose of 50 and 20 rad, respectively. The exposure leads to a continuous decrease of pulse height with a final reduction of 13 ± 1% (crystal 1 with photodiode readout at 50 rad) and 19.5 ± 2% (crystal 2 with photomultiplier readout at 20 rad). Most of the damage occurred in the first days of exposure. After the end of the exposure we observed a partial recovery of a few percent.