Radiation hardness and recovery processes of cooled PWO-II crystals for PANDA

Detailed studies of the radiation hardness of cooled high-quality PWO-II crystals for the electromagnetic calorimeter of the target spectrometer of PANDA at the future FAIR facility have been performed. Operating at low temperatures, such as T=−25°C, slows down significantly any recovery process in competition with the radiation damage. The investigations show, that one can overcome this problem by extremely radiation hard crystals selected at room temperature. In spite of light losses, the effective gain of the light yield at T=−25°C still remains at a factor close to three.