We report here the results of lead tungstate single crystal irradiation with a fast neutron fluence of about 1019 cm2. Definitely, such fluence is extreme and will be never achieved at high energy physics experiments. However we were motivated, firstly, to study with this heavy irradiation a new approach that we call “nuclear doping” to obtain impurity-activated centers in the crystal. The transmutation of tungsten to rhenium by neutron irradiation was supposed to be a way to introduce rhenium in the tungstate lattice. Re ions are well known luminescence centers and may change scintillation properties of the PbWO4 crystal. Secondly we aimed to study the degradation of the material and possible loss of the scintillation properties due to an eventual amorphisation of the material by fast neutrons, and to investigate recovery of the damage under heat treatment.
We present in this paper the study of the optical and scintillation properties of the irradiated sample compared to a control sample. Initially very degraded, the irradiated sample recovers partially after annealing at 600 °C. Even after a 900 °C annealing, the recovery is not complete. For the irradiated sample, the X-ray luminescence spectrum intensity is approxi¬mately 35 % of these of the control sample. The optical transmission is not totally recovered as well, inducing a shift toward the red in the photoluminescence emission spectrum. No trace of Re or other center emission is detected. If PbWO4 survives quite well to such an extreme fluence of neutrons, this method does not seem to be practical to induce Re-activated lumines¬cence centers and to enhance its luminescence yield.
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