Testing the radiation hardness of lead tungstate scintilating crystals

Large Hadron Collider operation will produce high radiation background, lea d tungstatecrystal is selected as scintillator of the CMS electromagnetic c alorimeter To reach the pricision requirement of the energy measurement, st rict requirement of the radiation hardness to PWO is needed. In this paper, we present a method for evaluating the radiation hardness and measuremen. results for several full size (23 cm length) lead tungstate crystals under Co-60 gamma-ray side irradiating, investgating the light yield loss and its longitudinal uniformity.