The kinetic parameters of peak 5 in LiF:Mg,Ti (TLD-100) were studied as a function of the duration of post-irradiation annealing at 165 degrees C. A post-irradiation anneal at 165 degrees C for 20 min reduces the intensity of the lower-temperature satellite, peak 4, to negligible levels. The shape of isolated peak 5 changes as a function of the duration of the post-irradiation annealing. All three kinetic parameters show important changes as the duration of the anneal increases. Computerized peak shape analysis shows that the order of kinetics of peak 5 increases from 1.2+or-0.05 (1 SD) following a 5 min anneal to 1.72+or-0.07 (1 SD) following a 30 min anneal. The activation energy increases from 1.75 eV after annealing for 5 min to 2 eV after annealing for 15 min and then remains constant for longer annealing times. However, the position of isolated peak 5 (Tmax) does not vary with dose, illustrating the weakness of this criterion for determining the order of kinetics or alternately the breakdown of the GO model applied to peak 5. Our results indicate important structural modifications in the trapping structure of peak 5 as a function of annealing time and/or the presence of underlying defect reactions leading to these changes in the shape of peak 5.

The significance of the use of different analytical glow peak shapes in the application of computerized glow curve deconvolution to LiF-TLD is discussed. The contention by Gartia et al. that the use of the Podgorsak-Moran-Cameron approximation to the Randall-Wilkins model can lead to significant errors in dosimetric applications is rebutted.

Thermoluminescence (TL) - fluence response characteristics for peaks 5, 7, 8 and 9 in LiF:Mg,Ti (TLD-100; Harshaw/Bicron) were measured for 5 MeV alpha particles, in both `non-parallel' and `near-parallel' geometries,and for 1 MeV alpha particles in `near-parallel' geometry. The onset of supralinearity in the non-parallel configuration is always at a significantly lower fluence (by approximately a factor of five) than in the nearly parallel configuration. This dependence of the onset of supralinearity on the vector properties of the alpha particle radiation field is interpreted as `proof positive' of the dominant importance of track interaction effects in the linear/supralinear behaviour of the glow peaks of TLD-100. A mathematical expression for the linear/supralinear behaviour for heavy charged particles in near-parallel geometry has been developed and fitted to the TL - fluence response curves. The model incorporates both possibilities of electron and hole diffusion in the glow curve heating stage as well as the contribution to the supralinearity of all the participating nearest-neighbour track interactions. The model is capable of yielding excellent fits to the experimental data; the inclusion of hole diffusion and retrapping is preferred to predict the very abrupt transition from linear to supralinear behaviour for the high-temperature peaks.

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