Re-Investigation of the Kinetic Trapping Parameters of Peak 5 in TLD-100 via 'Prompt' and 'Residual' Isothermal Decay

The mean-life of peak 5 in LiF:Mg, Ti (TLD-100, Harshaw) has been measured as a function of temperature via both 'prompt' and 'residual' isothermal decay in 10°C intervals from 120°C to 210°C. Measurements were carried out at two dose levels (2 mGy and 0.1 Gy) and on both 0.8 mm thick chips and thin 25 mg.cm-2 powdered samples. Computerised glow curve deconvolution (CGCD) was used, also peak cleaning techniques, and careful selection of annealing times to avoid the interference of satellite peaks. In order to minimise clustering and precipitation effects as much as possible, the mean-lives are measured over as short a time interval as possible, but still consistent with the required accuracy of measurement. Under these conditions the mean-lives seem to follow an exponential behaviour with temperature. Analysis of all the combined data yields E = 1.25±0.03 eV and 4 × 1010 s-1 < s < 3 × 1011 s-1. These results, very different from E and s values deduced from peak shape techniques, strengthen the premise that the trapping structure(s), and/or the extent of clustering/precipitation, and perhaps even the mechanism for charge carrier release responsible for peak 5, are different in isothermal decay than in linear heating for glow curve readout.