Kinetic simulation of charge transfer following 5.08 eV (F band) optical excitation of irradiated LiF:Mg,Ti (TLD-100): Participation of holes released via V3-VK transformation

KINETIC SIMULATIONS OF THE THERMOLUMINESCENCE CHARACTERISTICS OF LIF:MG, TI INCORPORATING LOCALISED AND DELOCALISED RECOMBINATION

Kinetic simulations of the thermoluminescence characteristics of LiF:Mg, Ti are reviewed in the framework of conduction band/valence band models. Delocalised recombination models have been mainly applied to the simulation of glow peak shapes, although comparison with experimental data has proven difficult if not impossible due to the scarcity of materials with demonstrably proven 'single-peak' glow curves. The delocalised models are incapable of the simulation of TL dose response linear/supralinear behaviour and the dependence of the supralinearity on particle energy. These characteristics require the incorporation of localised, nanodosimetric, recombination processes in the TL mechanisms. These investigations have simulated many of the TL characteristics of LiF:Mg, Ti in kinetic models based on a mixture of both delocalised and localised recombination.

REVIEW OF DOSE-RATE EFFECTS IN THE THERMOLUMINESCENCE OF Lif:mg,ti (HARSHAW)

The literature describing the experimental investigations of possible dose-rate effects in the thermoluminescence (TL) of LiF:Mg,Ti (Harshaw) is reviewed. The total lack of glow curve analysis, coupled with inclusion of all or part of the high temperature TL and absence of parallel measurements of possible dose-rate effects in the irradiation stage severely limit the scientific and technical level of the experiments. In addition, the experimental procedures are far from sufficient to warrant any conclusion concerning the presence or absence of dose-rate effects in the TL of LiF:Mg,Ti. This decision is contrary to the widely held belief that there are no dose-rate effects in the TL of LiF:Mg,Ti. In addition, the literature on dose-rate effects in the optical absorption (irradiation stage) of LiF is reviewed and is found contradictory. No dose-rate studies have been carried out on optical absorption in LiF:Mg,Ti. Kinetic simulations demonstrating the possibility, even likelihood, of dose-rate effects are also reviewed. Dose-rate effects are shown to be likely due to competition between excitation and recombination in the irradiation stage. Some other possible mechanisms involving multiple charge carrier trapping are suggested. Further definitive experiments are sorely needed, but the interested researcher should beware, it is not an easy task.