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Thermoluminescence (TL) and extended dosimetric characteristics of naturally occurring sodium chloride (NaCl) salt were studied. Pellets were prepared from mined crystalline salt obtained from Khewra Salt Mines, Pakistan and irradiated from 1 mGy to 10,000 mGy using cobalt‐60 gamma source. The TL response showed two dominant peaks around 125°C and 230°C, respectively, at low doses, with an additional peak in between at doses beyond 300 mGy. A linear and supra‐linear TL response was observed between 1 mGy–100 mGy and 100 mGy–10 Gy dose ranges, respectively. During the first 24 h post‐irradiation, the TL intensity dropped by 20%. A maximum angular dependence of up to 50% was observed between 0° to 360°. For photon energies between 33 keV and 1.25 MeV significant energy dependence was observed for photons < 100 keV only. Sample sensitivity increased with dose a qualitatively similar behaviour to TLD‐200. Effective atomic number (Zeff) of the sample (14.6) was comparable to TLD‐200 (16.3). No significant dose rate effects (deviation for a cobalt‐60 source within 3.5%) on the TL sensitivity of the sample were found. The lowest detectable dose limit (LDDL) for salt sample was found to be 0.8 mGy whereas the sample reproducibility test showed a maximum of ±11% deviation from the first value. [ABSTRACT FROM AUTHOR]

In this study an open-source tool GCD Analyzer, based on Microsoft® Excel, for Computerized Glow Curve Deconvolution analysis (CGCD) of thermoluminescence (TL) glow peak has been developed using a more accurate rational approximation. It is capable of deconvolution of glow curves having discrete or continuous trap distribution and can be used for routine as well as emergency radiation dosimetric analysis. This tool has a unique feature of TL glow curve analysis by combining discrete and continuous energy distributions for crystalline, amorphous, and mixed materials. To obtain best values of trap parameters like activation energy (E), frequency factor (s), order of kinetics (b), GCD Analyzer has the capability of analyzing glow curve using selectable individual peak of various physical kinetic models i.e. FOK, SOK, GOK, MOK, and Continuous Traps Distribution (CTD) with subtraction of optional background signal. The residual graph gives a clear visual understanding of the Figure of Merit (F.O.M). A comparison of asymptotic and rational approximation to the built-in second order exponential integral function E 2 (E/KT) for E/KT < 600 is also presented. The results are verified by deconvolution of test synthetic glow curves with F.O.M up to 0.0005%, experimental glow curve for CTD with F.O.M of 0.9781%, and in the case of GLOWCANIN project glow curves, the F.O.M is comparable to the least values achieved by inter-comparison participants. • Development of easy to use CGCD tool based on Microsoft Excel®. • Deconvolution of TL glow curves using individual or combination of various models. • An inter-comparison of asymptotic and rational approximations in TL expressions. • Accuracy of fitted results depends upon the selection of approximation. • Use of GLOWCANIN project and synthetic glow curves for validation and analysis. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL) response of naturally occurring Eocene rock salt (Gray halite) is assessed for its potential use as a cost-effective phosphor for dosimetric applications. Natural deposits of the Eocene salt lie on the Himalayan foothills in Pakistan. The grayish color of the halite is due to the intermixing of black bitumen/shale. EDS and ICP-OES techniques are used for the analytical study of the sample. It confirms the presence of Ca, K, Mg, Sr, Zn SO 4 , Mn, Al, Si and Fe along with the main matrix-NaCl. The Eocene salt is sulfur (S) rich, and potassium (K) poor mineral as compared to the other regional halite. The XRD analysis shows that lattice structure of the halite is composed of two interpenetrating FCC-sublattices of Na and Cl. Cold pressed pellets weighing 40 mg are produced for dosimetric study of the material. Standard gamma source is used for pellet irradiaition. Three different samples of Eocene salt (i.e. rock salt, naturally precipitated salt and refined salt) are prepared. It is observed that, if the material is used as such in its natural form, the dosimetric peak of the glow curve occurs at higher temperature >260 °C. The raw form of rock salt is therefore pre-processed (refined) whereby the major glow peak has shifted onto the dosimetrically significant position at 230 °C. Because of the optimal shape of the glow curve, the refined salt sample is investigated in detail: TL glow curves are acquired from 50 °C to 300 °C, the phosphor reveals a composite glow curve where four peaks are observed at approximate positions of 110 °C (P1), 145 °C (P2), 180 °C (P3) & 230 °C (P4). TL response is studied in the range of 5 mGy to 2 Gy; where a linear/superalinear dose-response behavior is observed for the current material. The Minimum Detectable Dose Limit (MDDL) is measured from the linear region and found to be 0.37 mGy. The first readout results in very low residues <0.005 % and is sufficient to afresh the dosimeter for the next reading. A repeatability test is performed up to 20 identical cycles: the resultant COV, obtained for refined salt sample, is 2.3 % (and 1.5 % in 10 cycles). The irradiated pellets show about 20 % loss of the initial signal for one month fading study. T m -T stop method and CGCD techniques are used for kinetic analysis. Kinetic parameters (b, E and s) are estimated from multiple glow curves and found similarities in the results. The results of the preliminary investigations suggest that the pellet prepared from Eocene salt has a potential for use in TL dosimetry. • Dosimetric characteristics of Eocene salt using thermoluminescence. • Revealing of linear/superalinear dose-response behaviour via individual peak study. • No oven/reader annealing is required to reset the newly developed TLD pellets. • Type of radiation (gamma/beta) modifies the relative sensitivity of individual glow peak. • Kinetic analysis of gamma and beta induced TL glow curves using CGCD technique. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL), kinetic parameters and dosimetric features of Pakistani limestone (CaCO 3) is reported in this study. Both compositional and structural analyses reveal that the material has a crystalline nature with rhombohedral structure and non-uniform crystallite size having major content of CaCO 3. A powdered limestone sample of 30 mg is found to be the optimized weight for TL and other dosimetric studies. After irradiating the samples with a test dose of 100 Gy using a β source three composite glow peaks termed as P1, P2 and P3 are visible at 100, 230 and 330 °C respectively using a linear heating rate of 1 °C/s during the TL readout. The Coefficient of Variation (COV) is found to be about 4%. Kinetic parameters (i.e., frequency factor (f), activation energy (E), and the kinetic order (b)) are estimated using both first and second Order of kinetics using an in-house Computerized Glow Curve Deconvolution (GCD) software. The figure-of-merit (FOM) is found to be 2.12%. The distribution of continuum traps with activation energy in the range of 0.77–2.59 eV is observed in the kinetic parameter analysis of the glow peaks of the sample. The TL response in the dose range of 1–5 Gy (not reported previously) and linearity in the dose response in the dose range of 1–10 Gy is observed in samples of Pakistani limestone. The Minimum Detectable Dose (MDD) is 1.01 Gy clearly resembling the experimentally linear fitted results. After a fading study for a period of thirty days, only the first peak i.e., P1 majorly fades while no major change is observed in the amplitude of peaks P2 and P3. In addition, P1 is the main contributor fading by 92% within the first 24 h of irradiation while P2 fades by 30 %. However, P3 shows stability with a very minor fading of 0.05% within 24 h of irradiation. This study concludes that Pakistani limestone can be further assessed as a potential radiation dosimeter for various applications. • Material characterization, TL, kinetic parametric analysis and other dosimetric features of Pakistani limestone were investigated. • Sample weight optimization study was performed for powdered Pakistani limestone. • Three glow peaks P1, P2 and P3 were observed with a test dose of 100 Gy with beta source while fourth peaks was identified using deconvolution by CGCD method. • TL response observed between 1–5 Gy with Minimum Detectable Dose (MDD) of 1 Gy and 3.4 % Coefficient of Variation (COV). [ABSTRACT FROM AUTHOR]

The Material characterization and kinetic parameters based Thermoluminescence (TL) study of virgin and heat treated Pakistani Onyx marble is reported. Pellets of mineral under various heat treatments named as virgin (S1), pre-heated (S2), annealed (S3), heat-treated-slowly-cooled (S4), are prepared. Material characterization is performed using TGA, XRD, SEM-EDX, and ICP-OES techniques. ICP & EDXs shows C, O, Ca as major elements and Al, Mn, Mg, Fe, Si as impurity content. Crystalline nature under heat treatment remains unaffected up to 773 K as indicated by the XRD analysis. TGA shows sample is CaCO 3 with no mass loss from 303 to 893 K. XRD and TGA analysis concludes that TL analysis is possible within 303–673 K. After 03 Gy of β-irradiaton dose, the TL responses are investigated. All samples show a thermally stable peak around 552 ± 3 K. The kinetic features responsible for TL response are studied using Initial rise (IR) method, Chen Peak Shapes (CPS) analysis and P.N. Keating technique. Kinetic order values vary within 1.75–1.05. The activation energy ranges from 0.88 to 1.33 eV, frequency factor appears within 106-1010 s−1. Calculated parameters are validated by comparing MATLAB generated synthetic curves with experimental results. CPS and IR based synthetic curves are in good agreement with the experimental curves. Heat treated Sample S4 shows enhanced TL response as compared to other samples. [Display omitted] • Material characterization and TL kinetic parameters analysis of Pakistani Onyx. • Various heat treatments are used to observe Thermoluminesce response. • Thermally stable TL peak appears around at 552 ± 3 K for all sample groups. • IR, Chen peak shapes and P.N. Keating methods used to evaluate TL glow curves. • Curves are generated using GOK equation in Matlab to verify kinetic parameters. [ABSTRACT FROM AUTHOR]