Study of thermoluminescence, photoluminescence and dosimetry for the YAGG:Ce (Y2.96Al3.4Ga1.6O12:0.04Ce) phosphor

The comprehensive effect of ionizing radiation should be considered in the use and or analysis of certain electronic equipment. Fluorescent powders are widely used in electronic equipment, so they are attempted to be used as thermoluminescence (TL) dosimeter directly. Green YAGG:Ce phosphors were prepared by a high-temperature solid-state reaction method. The TL glow curves, TL dose response, TL three-dimensional (3D) spectra (80 K-800 K) and photoluminescence spectra for the phosphors were measured. The measurement results show that the luminescence peak temperature for the sample occurs at approximately 458 K and the luminescence peak temperatures in the TL 3D spectra are located at 130 K, 240 K and 458 K; there are four kinds of activation energies of traps in the material; the TL response of each component for the YAGG:Ce phosphor shows good linearity and the detection sensitivity of the phosphor is estimated to be less than 2 mGy. TL 3D spectra and PL spectra show that the luminescence from the phosphors arises from the ²D_3/2 → ²F_5/2,7/2 transition of Ce ions, and the TL 3D spectra at 130 K, 240 K and 458 K are almost the same, which proves that the temperature can hardly change the relative probability of the ²D_3/2 → ²F_5/2,7/2 transitions. The results show that YAGG:Ce could be used as dosimeter material.

Thermoluminescence properties and kinetic parameters of β-irradiated Turkish slate stone

The current study includes a detailed investigation of the thermoluminescence (TL) characteristics and kinetic analysis of beta-irradiated slate stone from Muğla, Turkey. The heating treatment above 400 °C enhanced the visible TL intensity of the maxima, but the trap system is significantly modified with thermal annealing at temperatures higher than 700 °C. The structural, morphological, and chemical analyses of the samples were verified by X-ray diffraction, scanning electron microscope equipped with energy dispersive X-ray spectroscopy, and atomic absorption spectroscopy techniques, respectively. The TL dosimetric parameters of annealed slate stone including TL glow curves, reusability, fading characteristics, dose response, and heating rate behavior have been studied in detail. There are four apparent TL maxima in the glow curves for both non-annealed and annealed powdered samples, while the natural emission has shown a presence of 395 °C TL maximum as a form of spurious signal that was observed within a few hours during the storage time analysis as well. The material has proven to have very good reusability within the confidence interval (less than ± 5%). A linear response in the dose range of 0.1-10³ Gy was achieved when the peak maximum at 258 °C is examined. The kinetic analysis was achieved using T_M-T_stop, initial rise, and computing glow curve deconvolution methods. The TL glow curve of the beta-irradiated slate stone annealed at 700 °C consisted of twelve overlapping TL peaks by following first- and general order kinetics.

Computerized glow curve deconvolution (CGCD): A comparison using asymptotic vs rational approximation in thermoluminescence kinetic models

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 E₂(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.

Thermally and optically stimulated luminescence properties of BeO dosimeter with double TL peak in the main dosimetric region

Beryllium oxide (BeO), which has a widely known single main TL peak over the main dosimetric region, is an important luminescent material widely used in personal, medical, and environmental dosimetry fields. The thermal and optically stimulated luminescence properties (TL and OSL) of the BeO dosimeter, supplied by a private company in Turkey (BeO_R) that yields a double peak in the main dosimetric region (100-300 °C; heating rate = 2 °C/s) were studied. The corresponding properties were compared to the commercially prevalent Thermalox 995 BeO (BeO_T). Multiple characterization techniques including x-ray diffraction analysis (XRD), energy dispersive x-ray spectroscopy (EDX), scanning electron microscope (SEM) image and electron spin resonance (ESR) were used to detect possible differences in TL and OSL signals. It was hypothesized that the calcination and or sintering process applied during the manufacturing process might lead to a double peak in the main dosimetric region of BeO_R TL signals. Moreover, dosimetric properties of this dosimeter such as reproducibility, dose-response, minimum detectable dose (MDD), thermal quenching, bleaching, and thermal stability in combination with annealing properties were comprehensively investigated. An analysis of the results shows that BeO_R has lower detection limits in TL than BeO_T. In contrast, BeO_T exhibited lower detection limits in the OSL signal than BeO_R. Although both dosimeters have dissimilarities in several aspects, both are appropriate for dosimetric research on health physics applications. Therefore, selecting the appropriate BeO dosimeter could be an important factor to consider when assessing accurate doses in studies. With this outline in mind and by investigating using different characterization methods, the available luminescence knowledge base of BeO dosimeters was expanded.

Determination of thermoluminescence properties of ZnB2O4:Tm3+,Li+ for dosimetric purposes

This study aims to investigate the comparison of the thermoluminescence (TL) emission of Li⁺ and Tm³⁺ co-doped and un-doped zinc borate (ZnB₂O₄) phosphors prepared by wet chemical synthesis method. The crystal structure of the samples has been determined by means of X-ray powder diffraction and matched with the standard pattern of ZnB₂O₄ (PDF Card No. 039-1126). TL glow curves of 5 Gy beta irradiated Li⁺ (at different concentrations of 0.2, 0.5, 0.8 and 1.0%) and Tm³⁺ (1.0%) co-doped ZnB₂O₄ have been recorded using various band pass filters to determine both the optimum concentration and the suitable filter. The TL green emission (565 nm) of Li⁺ (1.0%), Tm³⁺ (1.0%) co-doped ZnB₂O₄ phosphor displays a complex structure where one can distinguish, at least, three groups of components peaked at 69, 166 and 291 °C where the more suitable dosimetric maxima appears at higher temperature. It could be observed how the 166 and 291 °C TL glow maxima of this material exhibits (i) good linearity in the range of 0.11-15 Gy, (ii) a minimum detectable dose value of 1.11 mGy, (iii) does not modify significantly the TL emission in shape and intensity after reusability (10 cycles) and (iv) a negligible fading effect for 5 Gy irradiated aliquots stored in darkness and room temperature up to 169 h. Additionally, it could be found that (v) kinetic parameters estimated by using variable heating rate method of Hoogenstraaten and initial rise method give similar results.

Thermoluminescence and infrared light stimulated luminescence of limestone (CaCO3) and its dosimetric features

Thermoluminescence (TL) and infrared light stimulated luminescence (IRSL) of limestone (CaCO₃) collected from the Mawsmai Cave, India is reported. Structural and compositional analyses show that the sample has a rhombohedral crystal structure and contains 33.45% of CaO. TL measured at 1 °C/s from a sample irradiated to 600 Gy produces three composite glow peaks P1, P2 and P3 at 92, 165 and 239 °C respectively. The nature of the glow peaks is suggestive of the presence of a continuum trap distribution with activation energy between 0.40 eV and 1.12 eV. As regards to dose response, the TL intensity of P1 increases at a uniform rate with dose between 10 and 1000 Gy. Interestingly, the intensity of P3 increases with dose through two uniform regions, one within 10-100 Gy and the other between 100 and 1000 Gy. The IRSL measurement produces ill-shaped decay curves. The IRSL intensity also increases with dose at two different uniform rates within 10-100 Gy and 100-1000 Gy. Residual TL recorded after each IRSL measurement shows similar dose response as that under the conventional TL. Regarding fading, P1 fades by 88% and P3 by 14% within 12 h of irradiation.

Spectrally resolved thermoluminescence of pure potassium chloride crystals

Alkali halides are wide band gap dielectric materials, which are very important for luminescence dosimetry. Nevertheless, only some of them were studied comprehensively. Potassium chloride (KCl) is alkali halide material, which shows pronounced thermoluminescence (TL) and optically stimulated luminescence (OSL). The material occurs also in natural mineral form as sylvite (or sylvine). This paper presents results of spectrally resolved thermoluminescence (SR-TL) measurements of pure KCl crystals in temperature range 300-550K for various doses of beta irradiation. Four emission bands were found relating to different recombination centers in this material. TL curves relating to these centers have different shape. It indicates that recombination centers are not filled concurrently.

An investigation of the dosimetric and kinetic properties of sand using ESR and TL techniques

In this research, the general dosimetric and kinetic properties of sand from a beach in southern Turkey were investigated using electron spin resonance (ESR) and thermoluminescence (TL) techniques. The ESR dose response curve presents linear behaviour in the dose range of 250-1000 Gy followed by sublinear behaviour in the dose range of 2-8 kGy. Kinetic behaviors and activation energy of the free radical were also calculated using the data obtained from annealing studies performed at four different temperatures (220, 240, 260 and 280°C). The activation energy value was calculated as 1.47 eV. The long-term fading of the ESR signal at room temperature turned out to be best described by a second-order kinetic decay function. The presence of measurable ESR signal intensity even after a storage period of 90 days was considered as providing an opportunity in the dose estimation of irradiated sand sample. Although the TL glow curve of the natural (unirradiated) sand sample only has a single broad peak at 317°C, the glow curve of the irradiated sample has four glow peaks located at ~115°C, ~156°C, ~231°C and ~308°C and their intensity tends to be increased with absorbed dose.Tmax-Tstop and glow curve fitting results showed that presence of at least five peaks located at ∼116°C, 149°C, 228°C, 306°C and 360°C. This result suggests that the apparently single glow peak D may consist of two or more overlapping glow peaks. According to the thermal fading of the sand sample at room temperature, the TL signal intensities (23°C and 308°C) were found to be quite large after 30 days of storage this allows a more accurate measurement of the glow peak intensity. The additive dose method, variable heating rate method (VHRM), Tmax-Tstop and glow curve fitting method were used to number of peaks, dosimetric properties and kinetic parameters. This study shows that ESR and TL techniques could be successfully used to investigate the kinetics and dosimetric properties of sand sample. Furthermore, the results in this study plus the previous work done by the authors suggest that sand could, by using the ESR and TL techniques, be a suitable material for alternative dose measurement.