Quality of the PbWO4 crystals for the PANDA-EMC

More than 7,300 PbWO₄ crystals of PWO-II quality have been delivered by BTCP (Bogoroditsk Technical Chemical Plant, Russia) and tested, which corresponds to almost 50% of the electromagnetic calorimeter of the future PANDA detector at FAIR. The existing crystals comprise both end caps completely and a small part out of the 2×11 crystal geometries forming the barrel. Beside the verification of the geometrical shape and surface quality the very stringent controlling process focuses on the longitudinal and transversal optical transmittance, radiation hardness and the relevant scintillation parameters such as light output and decay kinetics. All crystals are exposed at room temperature to an integral dose of 30 Gy (⁶⁰Co) to determine the radiation hardness, which is a crucial parameter due to the operation of the calorimeter at T= -25°C, when recovery mechanisms are slowed down. Significantly less than 10% had to be rejected. The overall performance will be compared to crystal samples of identical geometry provided by SICCAS (Shanghai, China).