Dosimetry properties of Tm-doped single CaF2 crystals

The dosimetry properties of thermoluminescence CaF2:Tm detectors with thuli um concentrations of 0.1%, 0.3%, 0.5%, 0.6% and 0.7%, developed from single crystals grown by the Stockbarger method at the Institute of Geochemistry, Irkutsk, Russia, were investigated. The relative TL efficiency, eta, after 5.3 MeV Am-241 alpha -particle irradiation and the Cs-137 gamma -ray dose response after doses up to 10 Gy, of interest for radiation therapy, were e valuated. Linearity and reproducibility of the dose response, the shape of the glow-curve (ratio of area under peaks 3 and 5 for alpha- and gamma -rad iation) were studied and referred to the properties of standard Harshaw TLD -300 detectors. The relative TL a-particle efficiency, eta, for the high te mperature peak 5 was found to grow with increasing Tm concentration, from 0 .13 for 0.1% Tm, 0.17 for 0.3% Tm to 0.92 for 0.5% Tm where the correspondi ng values of ty for peak 3 were 0.073, 0.059 and 0.211. Detectors with 0.6 wt% Tm appear to reproduce the properties of TLD-300 quite well, showing a similar shape of the glow curve and a similar ratio of peak areas under pea ks 5 and 3. The highest ranges of linear dose-response for Cs-137 gamma -ra ys for peaks 3 and 5, were obtained for detectors with 0.5% Tm. These detec tors, due to their high efficiency after high-LET irradiation and extended linearity range are most suitable for dosimetry of high-LET radiotherapy be ams. (C) 2001 Elsevier Science Ltd. All rights reserved.