THERMOLUMINESCENCE OF LIF - DEPENDENCE OF THERMAL HISTORY

The influence of the thermal history on the yield of thermoluminescence has been investigated. Dosimeters (mostly LiF-Teflon) have been stored at various temperatures for various times (pre-annealing) prior to irradiation and readout. Temperatures as high as 300 degrees C may give the LiF-crystal a state of thermal equilibrium in seconds, while the same equilibrium will not be reached for months at 80 degrees C. For precision dosimetry, pre-annealing at a high temperature should last only long enough to give thermal equilibrium and to empty all filled traps. Especially important is reproducibility of the cooling rate. With an appropriate heating circuit, the demands of both pre-annealing and cooling rate can be satisfied with the readout heating.