Dosimetric and TL investigation of natural and heat-treated Pakistani Onyx at high beta doses

Abstract

Extensive Thermoluminescence (TL) glow curve analysis of natural (S1) and heat-treated (S4) Pakistani Onyx marble is reported exploring an alternative natural radiation dosimeter. TL curves for β-doses ranging from 0.5 Gy to 10 kGy are measured within the temperature range of 25–500 °C and analyzed to generate dose response curves (DRCs). Single saturation exponential function and DRCs are used to evaluate the characteristic dose value and the intensity saturation level. The glow peak repeatability test identifies unstable TL trapping sites in S1 at high temperatures (≥350 °C). Fading analysis of S4 shows that a major signal loss (40%) occurs within 24 h because of low temperature (<130 °C) peaks. After irradiation, time-temperature investigations are performed to optimize the pre-heat condition and remove fast fading peaks. The kinetic parameters are estimated using the TM-Tstop technique and the curve deconvolution method. The post-irradiation preheat at 100 °C for 10 s and TL data collection up to 400 °C with a heating rate of 5 °C/s is concluded as appropriate measurement condition to perform dosimetric studies of S4. The quantitative analysis of S4 dose response showed a linear behavior from 2 to 20 Gy, supra-linear from 20 to 5000 Gy, and sublinear response after 5–10 kGy. The minimum detectable dose (MDD) and percentage coefficient of variation (COV) of repeatability for S4 are 236 ± 8 mGy and 1.53% respectively. The study concludes that Pakistani Onyx marble, with thermal treatment of 500 °C for 1 h, can be a radiation dosimeter for high dose applications.