A thermoluminescence study of CaF2:Dy under different types of irradiation sources towards environmental dosimetric applications

Abstract

CaF2:Dy dosimeters are widely used in radiation dosimetry, especially in environmental dosimetry measurements, owing to their high sensitivity. In this study, TL dosimetric properties of CaF2:Dy dosimeters under different irradiation sources (90Sr/90Y,137Cs, and X-rays) were investigated within environmental dose limits. The TL glow curves obtained for each case were deconvolved according to the general order of kinetics (GOK) model. As a result of deconvolution, the TL glow curve shape and trap parameters (E,s, and b) did not change according to irradiation sources and dose value. The dose-response features were investigated for each thermoluminescence glow-peak towards three different irradiation sources. Furthermore, the f(D) supralinearity index was presented for each TL peaks, yielding linear behavior for the TL peaks 2nd - 5th and non-linear behavior for the 1st and 6th peaks. Thermal quenching was rigorously investigated for heating rates of 1–25 °C/s. Although the intensity of each TL peak differently behaved with increasing heating rates, it was not observed a significant change on the total intensity. As a result, thermal quenching was not observed when the entire TL glow intensity value was considered. Therefore, the heating process of dosimeters to ≤400 °C could be performed at any heating rate. Additionally, light-induced effect was investigated for fluorescent, daylight, and ultraviolet lamp (UV-254nm). The results of light-induced effect following irradiation showed that the TL intensity was affected the most in the case of UV-254 nm, showing a reduction of ∼70% after 120 min of exposure. The effect of daylight and fluorescent light was observed as the values of ∼54% and ∼7%, respectively. Therefore, the dosimeters should be kept in the dark to avoid loss of intensity after irradiation.