A study on radiation hardness of PWO-II crystals

We report in this paper an investigation on radiation hardness of 20 cm long PWO-II crystals produced at BTCP for the proposed PANDA experiment at GSI. The optical and scintillation properties of PWO-II crystals, such as transmittance, light output and light response uniformity, were measured before and after γ-ray irradiations at different dose rates. PWO-II crystals are compared to crystals used in the CMS experiment. Progresses are observed in the radiation hardness for PWO-II crystals. Its use for crystal calorimeters in future high energy physics experiments is discussed. To maintain crystal precision, a precision light monitoring system is mandatory to trace variations of crystal transparency in situ for a PWO crystal calorimeter in a radiation environment.