Long-term fading of peak 5 in TLD-100 using computerised glow curve deconvolution (CGCD) and thermal peak isolation techniques

The long-term fading of peak 5 has been studied using four different annealing regimes. Following 400°C for one hour annealing and 'natural cooling', peaks 4 and 5 (separated via CGCD) appear to have an exquisitely complex time-dependent response, possibly due to clustering of dipole trapping centres associated with peaks 2 and 3. Peak 4 grows over the first nine months of storage and only then begins to decay; peak 5, on the other hand, decays rapidly in the first six months and then stabilises or even begins to grow. Peaks (4+5) together, however, fade in a montonically decreasing manner at a rate of approximately 8% per annum. Using thermal cleaning procedures to isolate the behaviour of peak 5 from its low temperature satellites, it has been established that the 20°C mean-life of peak 5 is 5.5 ± 1 year (1 SD). This mean-life is many orders of magnitude smaller than predicted by any of the kinetic measurements of s and E and suggests that precipitation of Mg²⁺ may be the major contributor to the decay of peak 5 over long storage intervals.