Comparison of radiation damage in different PbWO4 scintillating crystals

From a comparison of the radiation damage of 16 different PbWO4 samples (most of them being undoped, the others being doped with Nb, Mo and Cl), we found and/or confirmed the following: (1) the purity of the raw material is important concerning the radiation hardness, (2) repeated crystallization at least three times improves the radiation hardness, and (3) there were no significant effects of Nb- and Mo-dopings on the radiation hardness.