CALCIUM-FLUORIDE, CAF2-TM (TLD-300) AS A THERMOLUMINESCENCE ONE HIT DETECTOR

The Microdosimetric One-Hit Detector Model was applied to analyse the thermoluminescence response of peak 3 in Harshaw-produced TLD-300 CaF2 :Tm ribbons (0.9 x 3.2 x 3.2 mm) after doses of X-rays, gamma-rays, al pha-particles and protons. The model was able to fit the relative TL e fficiency for X-rays, alpha-particles and protons and dose response cu rves for gamma-rays. The model uses two parameters: the diameter of th e spherical, sensitive volume (target) d and the saturation coefficien t alpha which determines the probability of TL effects occurring follo wing the energy deposition event. A fit to the set of experimental val ues of relative TL efficiency of CaF2:Tm, published by Lakshmanan (198 1), Shachar and Horowitz (1988), Pradhan and Rassow (1987), Hoffman an d Prediger (1984), and Loncol et al. (1996) yielded d = 14 nm in 3.54 g cm(-3) CaF2 and alpha = 3.47 x 10(-3) Gy. The estimated tar get dime nsions are of the same order of magnitude as the 24 nm target site, fo und for LiF:Mg,Cu,P TL detectors. The hypothetical target could perhap s be related to large defect complexes in CaF2:Tm, comprising recombin ation centres and charge traps. The fairly good agreement of the model prediction with experimental data supports the hypothesis that for pe ak 3 in TLD-300 the initial spatial distribution of energy deposited i n the detector is stored in the detector and serves as the pattern for further TL phenomena during the heating stage. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.