Radiation Damage Of The Cerium Doped Lanthanum Bromide Crystal

Cerium activated Lanthanum bromide, LaBr3:Ce, discovered in2001byDelft University of Technology, has already aroused earthling attention due to itsexcellent performance. It has high light output, superb energy resolution and fastdecay time. Those properties are superior to NaI:Tl crystal which is one of the mostcommonly used scintillators. Due to its good time characteristic, it may be widelyused in nuclear physics, nuclear medical instrument and the nuclear industry. So it isnecessary to study radiation damage of LaBr3:Ce crystal in order to better use inreality.All the use of scintillation crystal is based on the measurement of irradiation, soradiation damage of crystal is inevitably, and radiation hardness of scintillationcrystal is very important. However, now study of radiation damage of LaBr3:Cecrystal is very few internationally.This thesis mainly studies radiation damage of LaBr3:Ce crystal by measuringthe optical property before and after irradiation, for example light output and energyresolution and so on. It also presents the radiation induced color centers and recoveryof LaBr3:Ce crystal after irradiation. Meanwhile, the change of light output andenergy resolution of LaBr3:Ce crystal was discussed before and after irradiation. Themain research results of the dissertation are as follows:(1) Radiation damage of crystal is not dose rate dependent. The recovery ofLaBr3:Ce crystal was studied by measuring light output within60days afterirradiation. Within60days after2000rad irradiation, the recovery of light output ofLaBr3:Ce crystal had almost no significant recovery at room temperature, indicatingthat radiation damage of LaBr3:Ce crystal is not dose rate dependent. Thespontaneous recovery of the radiation induced color center in the LaBr3:Ce crystalcan be neglected. Therefore we do not need to consider the effect of irradiation doserate. We only consider the irradiation dose in the investigation of the radiationinduced color center.(2) The radiation damage on light output and energy resolution were measuredbefore and after-rays irradiations with an integrated dose up to106rad. It was foundthat light out of crystal what had the most serious radiation damage decreased by49.7%, and energy resolution rised by15.9%.(3) The radiation induced color centers of LaBr3:Ce crystal also be studied bymeasuring transmittance after different dose irradiation. Transimittance was decreased as radiation dose was increasing, this result is different from foreign result.Then the multi-peak Gaussian fit was used to identify the position of the colorcenters. Three broad centers were found. They were the wavelength of448nm,510nm and590nm, and they were perhaps respectively corresponding to the Vkcenter, VFcenter and F center by color center physics.(4) The light output, energy resolution and transmittance were measured beforeand after irradiation. It was found that the light output and energy resolution all havedeterioration after irradiation with an integrated dose up to106rad. And with theincrease of irradiation dose, radiation damage was more and more serious.Meanwhile, the light output of LaBr3:Ce crystal had an obvious radiation damage at103rad irradiation, that was the first damage shock of crystal occurred in103radirradiation.