High-energy proton induced damage study of scintillation light output from PbWO 4 calorimeter crystals

Eight PbWO4 crystals produced for the electromagnetic calorimeter of t he CMS experiment at LHC have been irradiated in a 20 GeV/c proton beam up to fluences of 5.4 × 10 13 p/cm 2 . The damage recovery in these crystals, stored in the dark at room temperature, has been followed for over a year. Comparative irradiations with 60 Co photons have been performed on seven other crystals using a dose rate of 1 kGy/h. The issue whether hadrons cause a specific dam age to the scintillation mechanism has been studied through light output measurements on the irradiated crystals using cosmic rays. The correlation between light output changes and light transmission changes is measured to be the same for proton-irradiated crystals and for -irradiated crystals. Thus, within the precision of the mea surements and for the explored range of proton fluences, no additional, hadron-specific damage to the scintillation mechanism is observed.