On the Temperature Lag Effect in TLD Crystals - I

In one of our recent publications we dealt with the issue of linearity of the high temperature peaks in LiF:Mg,Ti (TLD-100). LiF:Mg,Ti is known to have peaks also at temperatures higher than the main dosimetry peaks (peaks 4-5), which have different LET sensitivity. The different LET response of these peaks (mainly peaks 6 and 7) can be used in principle for discrimination between neutron and gamma components of a mixed radiation field, which may be a convenient method for neutron dosimetry. Works in the past reported a supra-linear response of peak 7 to gamma-rays, making the applicability of the peak ratio method to neutron-gamma discrimination questionable. As most of the results in the past were obtained for high irradiation doses, we performed experiments with much lower doses, common to personal dosimetry (up to about 50 mSv). We could prove that for this dose range, when using the (Region of Interest method, the sum of peaks 6+7, as well as the sum of peaks 4+5, is linear with dose for both gamma and neutrons radiations. However, our publication was criticized by a note sent to the Journal. It was claimed that we have made a basic mistake in our interpretation of the results, and that we actually have not measured the response of peaks 6 and 7, but some kind of isothermal decay. This controversy brings up an important aspect in Thermoluminescence dosimetry, which should be clarified