The study of the thermoluminescent detector characteristics used in environmental dosimetry

In this study the thermoluminescent detectors of CaSO4:Dy have been used. These detectors, tablets in shape, were obtained in our laboratory by pressing a homogeneous mixture of CaSO4:Dy and Teflon powder, with a weight ratio of 1:1. The tablets have the diameter of 10 mm and the thickness of 0.8 mm. The colour is bright-white to pink. The characteristic thermoluminescent glow curve presents three peaks: the main peak situated from 210 deg. C to 220 deg. C corresponds to a wavelength of the emitted signal of 571 nm and the secondary peaks situated at 90 deg. C and 100 deg. C, correspond to 360 nm and 470 nm, respectively. The following dosimetric parameters were studied by using a set of 50 detectors: - the homogeneity of the detector lot: ± 25 %; - the energy range: 30 keV - 3 MeV; - the linearity has been studied in the range: (10-5 - 10-1) Gy; - the measuring error is less than 30 % for all range; - the reproducibility has been determined by irradiating the same detectors ten times with dose values of 5.10-5 Gy and 2.10-4 Gy. Values less than 0.0062 were obtained. The detectors were tested in extreme environmental conditions (the temperature between -25 deg. C and +55 deg. C; the humidity between 55 % and 85 %), the obtained values being satisfactory (the temperature between -25 deg. C and +55 deg. C; the humidity between 55 % and 85 %). The main characteristics are in good agreement with the requirements of the international standards. These detectors can be used for the environmental dosimetry. (authors)