Lithium Fluoride Thermoluminescence Dosimetry

Abstract

Commercially available lithium fluoride thermoluminescent powder has been studied with a specially built readout device. Glow curves were recorded against temperature, and the area under them was integrated. A dispenser to deliver 30 mg batches of powder with a precision of 1% was built. Factors investigated were tribothermoluminescence; reprocessing by annealing; photomultiplier gain variation and ` fatigue ' effects; response vs. dose curves over the range 0·3 to 107 rad; dose-rate dependence over the range 5 × 102 to 2 × 108 rad/sec; accumulation of damage with increasing dose; comparative response of powders to X-rays and fast neutrons; and the effect of fusing microcrystalline powder into a single small block. It is concluded that for doses of 1 to 105 rad the LiF system provides a compact, convenient system possessing wide dose-rate independence. The change in sensitivity, after doses of 3 × 104 rad have been accumulated, requires that each batch of powder should be kept separate, and calibrated before use. The standard deviation for four to six 30 mg measurements from the same sample of powder varied from 1 to 6% but increased rapidly at doses below 3 rad. The use of an LiF dosemeter as a transfer dosimetry standard is attractive for quick, convenient intercomparison between two laboratories.