Investigation of Dose-Rate Effects in the Thermoluminescence of LiF:Mg,Ti (HARSHAW)

Abstract: The literature describing the experimental investigations of possible dose-rate effects in the thermoluminescence (TL) of LiF:Mg,Ti (Harshaw) has been recently reviewed [1]. The total lack of glow curve analysis, coupled with inclusion of all or part of the high temperature TL and lack of parallel measurements of possible dose-rate effects in the irradiation stage monitored by optical absorption severely limit the scientific and technical level of the experiments. In addition, the description of the details of the experimental procedures and adopted protocols are far from sufficient to warrant any decision concerning the presence or absence of dose-rate effects in the TL of LiF:Mg,Ti. This is contrary to the common 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 (OA) of LiF are reviewed and are found contradictory. No dose-rate studies have been carried out on OA in LiF:Mg,Ti. Theoretical considerations suggest the possibility, of dose-rate effects are mainly due to competition between excitation and recombination in the irradiation stage [2] as well as other possible mechanisms involving multiple charge carrier trapping. Preliminary experiments at the Soreq Nuclear Research Center in which TLD-100 samples are irradiated to 1 Gy using different source-sample distances do not seem to follow the r-2 law, thereby implying the possible presence of dose-rate effects. Other possibilities/hidden variables also require further investigation.

References:

Horowitz, Y.S., Oster, l. and Eliyahu, I., Review of dose rate effects in the thermoluminescence of LiF:Mg, Ti (Harshaw), doi:10.1093/rep/ncx248
Chen R. and Leung, P.L., A model for dose-rate dependence of thermoluminescence intensity, J. Phys. D: Appl. Phys., 33, 846-850 (2000).