Track interaction in gamma- and charged-particle-irradiated thermoluminescence dosimeters

The growth of thermoluminescence (TL) and optical absorption (OA) with absorbed dose was examined in LiF doped with Mg, as functions of both the linear energy transfer (LET) of the incident radiation and the impurity content of the samples. In addition, the TL growth curves were examined as a function of the heating rate during readout. The growth of TL as a function of dose is basically linear-supralinear-sublinear, but the precise character of the dose response function varies with the LET of irradiation, the Mg impurity content of the sample, and the heating rate during TL readout. the OA dose response is always linear-sublinear over the same dose ranges, even for those defect centers that are known to be involved in the TL process. The data indicate that the mechanisms responsible for the supralinear nature of the TL growth are operative during the TL readout phase rather than the absorption phase. A mathematical model is presented that qualitatively describes the results. The model is conceptually the same as the so-called track interaction model for high-LET irradiation, but the extension presented here makes it applicable to gamma-irradiated samples also