Low Dose Rate Radiation Behaviors of Y~（3+） Doping PbWO_4 Crystals

Although trivalent ions (such as La3+, Lu3+ and Y3+) doping can significantly improve the radiation hardness of lead tungstate crystals, some Y3+ doping PWO crystals show exceptional behaviors under low dose rate radiation, namely, the light yield increases even exposed to UV irradiation. In addition the radiation hardness is sensitive to annealing temperature. In this study some Y3+ doping crystal samples that have the phenomenon mentioned above were chosen and the relationship between transmission and light yield of the samples investigated. The experimental results show that the increase of light output not only exists in the topside of the crystals, but also in the seed side, and is accompanied with optical transmission change from 380nm to 500nm simultaneously. The as grown and annealing induced 430nm color centers are unstable and can be bleached by low dose rate irradiation. The results of series annealing experiments of the sample segments can interpret the phenomenon that radiation hardness is sensitive to annealing temperature.