Sensitivity and stability of LiF thermoluminescence dosimeters

Three different batches of LiF TLD-100 rods were subjected to investigation of their radiation sensitivity and the stability of the sensitivity after subsequent cycles of irradiation readouts. An old batch (circular rods from 1985), R85, showed an initial sensitivity of approximately 720 (nC/Gy). A new batch of circular rods (R0059) had an initial sensitivity more than a factor of 2.5 higher than the old batch. A batch of square rods (S3720) had an even higher sensitivity; a factor of almost 4 higher than batch R85. Both batches of circular rods showed a statistically significant change in sensitivity with increasing cycles of irradiations and readouts. No significant change was observed for the batch S3720. Batch R85 showed an increasing sensitivity with increasing number of cycles, and a small reduction in the width of the sensitivity distribution within the batch. However, the newer batch (R0059), showed a marked decrease in sensitivity and a doubling of the broadening of the sensitivity distribution after 10 cycles. No significant change in the sensitivity distribution within the S3720 batch was observed after 10 cycles.