On the Causes of Changes in Sensitivity Due to Re-use of LiF Thermoluminescence Dosimeters

The causes of the changes in the sensitivity due to repeated use of thermoluminescence dosimeters were investigated. The phosphors used in this experiment were prepared by annealing at 600°C for 3000 min or over in argon gas and rapid cooling. When the phosphors irradiated with 106 R were annealed at 350°C for 30 min in argon gas, their pre-dose was ten times as great as the back ground noise of the electronic equipment, and their sensitivity was better than that of the original phosphors. However, in the case of thermal treatment at 600°C for 30 min, the color centers of the phosphors disappeared and their pre-dose was reduced to the same order as the back ground noise. Optimum procedures of annealing for the recovery of the sensitivity of the phosphor were discussed.