Final concept and performance of the electromagnetic calorimeters of the PANDA detector at FAIR

The PANDA collaboration at FAIR, Germany, will focus on undiscovered charm-meson states and glue balls in antiproton annihilations to study QCD phenomena in the non-perturbative regime. For fixed target experiments at the storage ring HESR a 4π-detector for tracking, particle ID and calorimetry is under development and construction to operate at high annihilation rates up to 20 MHz. The electromagnetic calorimeters are composed of a Target Spectrometer (EMC) based on PbWO₄ crystals and a shashlyk-type sampling calorimeter at the most forward region. The EMC, comprising more than 15,000 crystals, is operated at a temperature of -25·C and read-out via large-area avalanche photo-diodes or vacuum photo-triodes/tetrodes. The photo sensor signals are continuously digitized by sampling ADCs. More than 50% of the high quality PWO-II crystals are delivered and tested. The excellent performance with respect to energy, time and position information was determined over a shower energy range from 10 MeV up to 15 GeV by operating several prototype detectors. In addition, the concept of stimulated recovery has been investigated to recover radiation damage on- and off-line during the calorimeter operation. Besides the overall concept of the Target Spectrometer the response function of the shashlyk spectrometer down to photon energies even below 100 MeV is presented.