Developments and Preparations for the PANDA-EMC

Several major steps have been performed to prepare the final design of the electromagnetic calorimeter (EMC) of the target spectrometer of PANDA [1]. The main activities have focused on the quality control of the delivered PWO crystals, detailed studies on the recovery of radiation damage and the analysis of measurements of the response to high-energy photons using prototype detectors. The quality control as well as the detailed analysis of all 7355 PWO-II crystals, delivered by the manufacturer BTCP in Russia, was completed. Only 458 crystals had to be rejected corresponding to a fraction of 6.2% and confirms the excellent performance. The very selective limit on radiation hardness was the primary reason for rejection (85%). The final operation of the calorimeter at the low temperature of T=-25C requires extremely high radiation resistivity of the crystals since thermo-activated recovery processes are drastically slowed down. Therefore, the maximum loss of light output due to the deterioration of the optical transparency is primarily determined by the concentration of intrinsic defects created during the growing process.