Glow Curve Analysis Research Articles

Synthesis and TL glow analysis by Ce, Cu, Eu Dy and Mn doped LiMgBO3 and LiSrBO3Phosphor

The present paper reports the combustion synthesis of LiMgBO3 and LiSrBO3 phosphor by various dopants Ce Cu, Eu, Dy and Mn and study their TL glow curve for TL dosimetry. During the combustion synthesis we have synthesized LiMgBO3 and LiSrBO3 phosphor by using various activators Ce, Cu, Eu, Dy and Mn so as to explore the possible compound for TL glow curve analysis and their application for TL dosimetry. The combustion synthesis method is very simple and time saving method. This work deals with detail procedure for synthesis LiMgBO3 and LiSrBO3 phosphor by various dopants Ce Cu, Eu, Dy and Mn and study of their TL glow curve analysis and luminescent characteristics for TL dosimetry.

Role of Lithium Codoping in Enhancing the Scintillation Yield of Aluminate Garnets

The aim of this work is to clarify the scintillation-yield enhancement in $\mathrm{Lu}\mathrm{YAG}:\mathrm{Pr}$ scintillators obtained by $\mathrm{Li}$ codoping via integrated study of the valence state of activators, the preferential site occupancy of $\mathrm{Li}$ codopants, and defect structures from experimental and theoretical insights. With $\mathrm{Li}$ codoping, the light yield and energy resolution of $10\ifmmode\times\else\texttimes\fi{}10\ifmmode\times\else\texttimes\fi{}10\phantom{\rule{0.1em}{0ex}}{\mathrm{mm}}^{3}$ $\mathrm{Lu}\mathrm{YAG}:\mathrm{Pr}$ samples are improved from 15 600 to 24 800 photons/MeV, and 5.3 to 4.3% at 662 keV, respectively. The optical absorption spectra indicate that $\mathrm{Li}$ codoping does not induce conversion of stable ${\mathrm{Pr}}^{3+}$ to ${\mathrm{Pr}}^{4+}$ in $\mathrm{Lu}\mathrm{YAG}:\mathrm{Pr}$ single crystals. Based on the formation energies of substitutional and interstitial $\mathrm{Li}$ sites using density-functional-theory (DFT) calculations and the ${}^{7}\mathrm{Li}$ nuclear magnetic resonance results, it is shown that the $\mathrm{Li}$ ions prefer to dominantly occupy the fourfold coordinated interstitial sites and fourfold coordinated $\mathrm{Al}$ sites. The systematic analysis of thermoluminescence glow curves, positron annihilation lifetime spectroscopies, and defect formation energies derived from DFT calculations reveals that the concentration of isolated $\mathrm{Lu}$ and $\mathrm{Al}$ vacancies as dominant acceptor defects is reduced by $\mathrm{Li}$ codoping, whilst the shallow ${\mathrm{Li}}_{i}$ interstitial defects and the deep ${V}_{O}$ oxygen vacancies are introduced simultaneously. We propose that the lowering of hole trapping at defects resulting from $\mathrm{Li}$ codoping contributes to the scintillation-yield enhancement.

Structural and optical properties of beta irradiated YAlO3 single crystals

We report on the growth, structural and optical properties of YAlO3 single crystals grown by optical floating zone technique. Powder X-ray diffraction and Raman spectroscopic studies confirm the phase purity of the crystals. Raman analysis reveals that the intensity and line-width of Raman bands increase significantly with beta irradiation indicating the formation of structural defects in YAlO3 lattice. The optical properties are studied through UV–visible absorption, and photoluminescence emission and excitation spectroscopies under pre- and post- beta irradiation. The optical studies indicate the presence of Sm and Cr impurities by exhibiting characteristic emission lines in the orange red region. Further, a systematic study on the thermoluminescence (TL) characteristics of the crystal is also carried out at different doses of beta irradiation. The crystals exhibit a prominent TL glow peak at 239 °C for less than 5 Gy doses while a weak second glow peak evolves at higher doses. Also, the crystals show a nearly linear dose response in the studied range from 0.1 to 10 Gy. The glow curve analysis reveals that the TL emission obeys the first order kinetics model. Based on the optical studies, the plausible mechanism for the TL glow curve is discussed in terms of the intrinsic defects and impurities that are present in the crystal.

Advanced glow curve analysis of fabricated fibres for various sources of ionizing radiation

Determination is made of glow curves attributes of Ge-doped silica fibres fabricated from Ge-doped preforms. In particular interest is in Ge-doped cylindrical (Ge-CF) and Ge-doped flat (Ge-FF). The fabrications are irradiated using various ionizing radiation sources types, protons (150 MeV, 210 MeV), 6 and 10 MV photons, 6 MeV electrons, and 60Co gammas (mean energy 1.25 MeV), all at a constant dose of 5 Gy. The fibres have been fabricated using the MCVD technique, notably with a Ge-CF having a larger core compared to the commercial cylindrical fibres (CF). Using WinGCF software the glow curves have been deconvolved, revealing five contributory glow peaks, evaluation being made of three kinetic parameters: maximum temperature (Tmax), activation energy (Ea) and peak integral (PI). Ge-CF Ea and PI values are found to be greater than those for Ge-FF. Moreover, for Ge-CF, the activation energy for electromagnetic irradiation (gamma photons) achieves a maximum reading at peak number 3 while its PI is found to be the least. The PI for photon irradiation is shown to be greater than that for electron and proton irradiation. For Ge-FF, Ea again achieves its greatest value at peak 3, the PI being maximum at peak 2 and least at peak 3. Particle irradiations are more greatly associated with deeper trapping levels. Additionally, the overall conclusion is that Ge-CF offers superior TL yield to that of Ge-FF. One-way analysis of variance (ANOVA) for the individual peaks shows there to be significant differences in terms of PI and Ea, p < 0.05 for all types of radiation, but weakly significant in terms of Tmax for both types of fibres (p < 0.05), mostly for proton and photon irradiation.

Quantum tunneling processes in feldspars: Using thermoluminescence signals in thermochronometry

During the past decade, our understanding of the nature of quantum tunneling processes in luminescence materials has been advanced significantly, by both experimental work and modeling insights into the underlying luminescence mechanism. This paper provides examples of analysis of thermoluminescence (TL) signals in feldspars, based on recent modeling work which showed that the shape of the TL glow curves remains practically unchanged after thermal and/or optical treatment of the samples. Analysis of the experimental TL glow curves in thermally or optically pretreated feldspars shows that these signals can be described as the sum of several Gaussian curves. While the positions and height of these Gaussians depend on the thermal and optical history of the sample, the width of the Gaussians apparently remains the same across the TL glow curve. TL glow curves are analyzed for 10 different samples, and the width of the Gaussian curves is found to be a common property characterizing all samples, at least within experimental error. Specifically it is found that the Gaussian width stays practically unchanged when the irradiated samples undergo thermal treatments for different times and temperatures, or alternatively when they undergo optical bleaching treatments with blue LEDs. The common overall shape of the TL glow curves has important implications for the use of these signals in thermochronometry.

Thermoluminescence glow curve analysis of gamma irradiated Sr2SiO4:Dy3+ nanophosphor

Undoped and Dy3+ doped nanocrystalline Sr2SiO4 phosphor was synthesised by solution combustion technique. The phosphors were characterised by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermoluminescence (TL) of pure and Dy3+ doped Sr2SiO4 nanophosphors irradiated with gamma rays were measured at room temperature. The effect of dopant and heating rate on TL glow curves were investigated. The dose response curve exhibit sub-linear nature, in the dose range 0.3 kGy–4 kGy. The optimised sample with 1 mol% Dy3+ ions exposed to gamma dose of 8 kGy was de-convoluted to obtain different TL kinetic parameters using general order kinetics by computerised glow curve de-convolution (CGCD) technique. The obtained values of activation energies (E) and frequency factor (s) were in the range 1.05–1.30 eV and 1010−1012 s−1. The kinetic parameters calculated were further compared with Chen, Grossweiner and Lushchik peak shape methods. TL emission (TLE) exhibited the characteristic Dy3+ transitions. Thus, the results reveal that the phosphors may be a suitable candidate for white light emission and further can also be used for dosimetry in the irradiation of food products.

Thermoluminescence study and evaluation of trapping parameter of rare earth activated Ca3Al2O6: RE (RE = Eu2+,Ce3+) phosphors

In the present work, we have successfully synthesized rare-earth doped Ca3Al2O6 phosphors for dosimetric application. In this work, Eu2+ and Ce3+doped Ca3Al2O6 phosphors were successfully synthesized by high-temperature solid-state reaction method. The crystallinity was determined by using X-ray Diffraction (XRD) pattern. The vibrational features of synthesized phosphors were observed by using Fourier Transform Infrared Spectroscopy (FT-IR). The Thermoluminescence (TL) properties of synthesized phosphors were also investigated. The TL glow curves of the phosphors exposed to γ-rays from 60Co were recorded. The Eu2+ and Ce3+ doped Ca3Al2O6 phosphors shows simple TL glow curve structures with a single prominent peak at around the temperature 172 °C and 196 °C, respectively. The TL glow curves show linearity with increasing exposure. Theoretical analysis of glow curves of samples irradiated by γ-rays was done by computerized glow curve deconvolution (GCD) method and trapping parameter of synthesized phosphors such as activation energy, frequency factor and order of kinetics were calculated. This trapping parameter was determined by different methods such as Chen’s peak method, Initial rise method,and Ilich method. Every one of these outcomes demonstrated that synthesized Eu2+, Ce3+ doped Ca3Al2O6 phosphors have outstanding thermoluminescence properties. The synthesize phosphors are found to be a good candidate for dosimetric applications.

Dosimetric features and kinetic parameters of a glass system dosimeter.

Lithium borate (LB) glasses doped with dysprosium oxide (Dy2 O3 ) have been prepared by utilizing the conventional melt-quench technique. The prepared glass samples were exposed to 60 Co to check their dosimetric features and kinetic parameters. These features involve glow curves, annealing, fading, reproducibility, minimum detectable dose (MDD), and effective atomic number (Zeff ). Kinetic parameters including the frequency factors and activation energy were also determined using three methods (glow curve analysis, initial rise, and peak shape method) and were thoroughly interpreted. In addition, the incorporation of Dy impurities into LB enhanced the thermoluminescence sensitivity ~170 times. The glow from LB:Dy appeared as a single prominent peak at 190°C. The best annealing proceeding was obtained at 300°C for 30 min. Signal stability was reported for a period of 1 and 3 months with a reduction of 26% and 31%, respectively. The proposed glass samples showed promising dosimeter properties that can be recommended for personal radiation monitoring.

Thermoluminescence glow curve analysis and trap parameters calculation of UV-induced La2Zr2O7 phosphor doped with gadolinium

Thermoluminescence (TL) glow curve analysis and calculation of trap parameters are reported for gadolinium (Gd3+)-doped La2Zr2O7 (LZO) phosphor. Phosphors were prepared by modified solid-state reaction method with varying concentration of Gd3+ (0.1–2.5 mol%) including proper calcination and sintering temperature. Structural analysis of prepared phosphor for optimized TL concentration was recorded by X-ray diffraction analysis technique. Morphology was analyzed by scanning electron microscopic technique. The UV ray induced to the phosphor and effect of dose response recorded for variable dose rates of UV and TL glow curve were observed. The experimental and theoretical comparison was done by computerized glow curve deconvolution technique which determines the trap parameters such as trap depth, order of kinetics, and frequency factor for optimized concentration of dopant. The trap parameters and trap model are discussed in detail.

Effect of lithium codopant concentration on the luminescence properties of (Lu0.75Y0.25)3Al5O12: Pr3+ single crystals: Before and after air annealing

In this paper, we present the photoluminescence and scintillation performance of Pr3+ doped (Lu0.75Y0.25)3Al5O12 single crystals as a function of Li+ concentration. Lithium concentration had no effect on the optical properties of LuYAG: Pr single crystal scintillators regardless of concentration. On the other hand, scintillation light yield increased by as much as 94% with the incorporation of lithium as a codopant, and the energy resolution at 662 keV was improved to 4.1%, which is an outstanding energy resolution for an oxide single crystal scintillator. Lithium codoping slightly lengthened the fast component of the scintillation decay time, and slightly decreased the contribution from the slow component. Additionally, the samples were annealed in air and scintillation properties were compared before and after this annealing treatment. The change in scintillation properties is explained through the analysis of thermoluminescence glow curves.

New designed software to deconvolute the thermoluminescence glow-curves

Within the framework of the one trap-one recombination (OTOR) level model, a new software was designed to deconvolute the thermoluminescence glow-curves. The computer code was written considering deconvolution equations obtained, without any approximations, from the (OTOR) model with free parameters TM, IM, and e. The code can also use the original equations of the OTOR model with free parameters s, e, no, and β. The new software was applied to deconvolute glow curves measured from irradiated in-house prepared Al2O3 doped with Cr2O3 dosimeters. The consequences of the deconvolution analyses of the reference glow curves agree with those reported in the literature.

Thermoluminescence response of X-ray irradiated commercial chalk

Present research concerns the TL signal stored in chalk of the variety commercially available for writing on blackboards. Samples of this have been subjected to x-ray irradiation, the key dosimetric parameters investigated including dose and energy response, sensitivity, fading and glow curve analysis. Three types of chalk have been investigated, each in five different colours. The samples were annealed at 323 K prior to irradiation. For all three chalk types and all five colours, the dose response has been found linear over the investigated dose range, 0–9 Gy. Regardless of type or colour, photoelectric energy dependency is apparent at the low energy end down to the lowest investigated accelerating potential of 30 kV. Crayola (Yellow) has shown the greatest TL sensitivity, thus selection has been made to limit further analysis to this medium alone, specifically in respect of glow curve and fading study. In addition, elemental compositional and structural change characterizations were made for the same medium, utilizing Energy Dispersive X-Ray (EDX) and Raman spectroscopy, respectively.

Color tunability and energy transfer studies of Dy3+/ Eu3+ co-doped calcium aluminozincate phosphor for lighting applications

Dy3+ doped and Dy3+/Eu3+ co-doped calcium aluminozincate (CAZ) phosphor synthesized by Pechini sol-gel method. Structural and morphological analysis were carried out by using X-ray diffractometer (XRD) and field emission scanning electron microscope (FE-SEM). The photoluminescent (PL) spectra were recorded and energy transfer mechanism between Dy3+ and Eu3+ ions were studied using Dexter and Reisfeld’s approximation. The colorimetric properties were studied by evaluating CIE coordinates and correlated color temperature (CCT). The energy transfer mechanism was analysed by applying Inokuti-Hirayama (I-H) model on decay curves as well. The thermoluminescence (TL) glow curve analysis reveals two trap centres in the present host. The obtained results indicate that the CCT can be tuned from warm to cool region and color tunability can also be achieved in Dy3+/Eu3+ co-activated CAZ phosphor by varying the excitation wavelength or activator concentration in the host lattice and hence can be effectively utilized in white light emitting diodes (wLEDs).

Analysis of the BeO thermoluminescent glow curve by the deconvolution method

Results of studying the behavior of the thermoluminescent glow curve of beryllium oxide (BeO) obtained in a wide range of absorbed doses are presented. The kinetic parameters and the TL response as a function of dose were determined using two deconvolution methods: Glow-Fit (Puchalska and Bilski 2006) and “tgcd” in “R” (Peng et al., 2016). Both methods showed that the glow curve of BeO obtained at a heating rate of 5 Ks−1 can be resolved in two peaks at temperatures of approximately 477 and 586 K respectively, with an activation energy of 1.1 eV for both peaks. The Glow-Fit method assumes first-order kinetics; while the “tgcd” in “R” method allows to determine the order of kinetics, finding that both peaks follow a kinetic of first order. Regarding the TL response as a function of dose, it was found that the first peak exhibits a quadratic dependence while the second peak exhibits a linear behavior with respect to the dose throughout the dose range studied, thus showing great advantages for its application as a TL dosimeter.

Thermo-luminescence Glow Curve Analysis and Characterization of BaZrO3 Phosphor Doped with Eu3+, Tb3+

Thermo-luminescence Glow Curve Analysis and Characterization of BaZrO3 Phosphor Doped with Eu3+, Tb3+

A machine learning approach to glow curve analysis

We present a first study of using artificial neural networks to estimate the fading time and irradiation dose using glow curve data from LiF thermoluminescent (TL) dosemeters. The resulting uncertainties in the inference process are compared to those obtained in previous studies without machine learning algorithms. The current study is based on measurement and simulated data using an effective model of the kinetic parameters. We show that the resulting uncertainties of the estimated quantities can be significantly reduced with the machine learning algorithm applied: fading times of up to 30 days can be predicted with an uncertainty of up to 10%, irradiation doses larger than 1 mSv can be estimated with an uncertainty of up to 10% for batch-calibrated dosemeters.

Spectroscopic studies of strong red emitting Sr2SiO4:Eu3+ nanophosphors with high color purity for application in WLED using Judd-Ofelt theory and TL glow curve analysis

Un-doped and Eu3+ doped Sr2SiO4 nanophosphors were synthesized by self-propagating solution combustion synthesis and are characterised with different material and optical characterisations. X-ray diffraction (XRD) confirmed orthorhombic phase, transmission electron microscopy (TEM) revealed the nanophosphors with irregular shape but crystalline in nature. The photoluminescence (PL) excitation, emission spectra and lifetime are thoroughly discussed. The emission spectra due to the excitation under 393 nm showed better asymmetric ratios than the 260 nm excitation ensuring better color purity of 97%. The comparative investigations using commission international del’Eclirage (CIE) diagram also established that the color purity of 393 nm excitation is superior with CIE co-ordinates (0.66, 0.34) and is close to NTSC standards. The Judd Ofelt (JO) intensity parameters (Ω2andΩ4) were obtained from PL emission spectrum and the JO parameters followed the trend Ω2>Ω4 for all Eu3+ concentration. Asymmetric ratios and JO analysis both indicated that the crystal field is non-centrosymmetric in nature. The radiative properties such as branching ratios, emission cross section, optical gain and gain bandwidth of optimised concentration are calculated. Photoluminescence lifetimes exhibited bi-exponential nature and showed higher lifetime for 393 nm excitation. Furthermore, the quenching due to non radiative energy transfer mechanism is dominated by multipole-multipole interaction. All these optical characterisations supported the fact that the nanophosphors excited at 393 nm have better pertinence towards display, laser and lighting application. Thermoluminescence (TL) studies of the nanophosphors were carried out. The kinetic parameters are calculated using general order kinetics and are verified by computerised glow curve de-convolution (CGCD). TL emission spectra and contour plots were analysed that further confirmed that the emission resembled the same as PL emission spectra.

UV effect on the cathodo- and thermoluminescence properties of a gem-quality Cr-rich diaspore (α-AlOOH)

This work reports on the cathodoluminescence (CL) and thermoluminescence (TL) properties of gem-quality diaspore samples from Milas/Muğla (Turkey) after 100 h of ultraviolet-C (UVC) exposure. The UVC exposure induces significant changes in the intensity of the CL emission in the range of 400–800 nm that would be mainly associated with photo-oxidation processes of the impurities (Cr3+, Ti3+, Fe2+) that substitute for Al3+ in the diaspore (α-AlOOH) lattice. The UVC effect on the 400 nm-TL behavior of beta irradiated samples in the range of 0.1–8 Gy modifies the TL glow curves probably due to both photo-transfer process where electrons release from deeper to shallower traps and redox reactions involving, also, breakages-linkages of chemical bonds. Meanwhile, the ‘as received’ samples consist of three maxima centered at about 120, 180, and 234 °C, the 100 h UVC-irradiated samples display three maxima at 122, 220 and 270 °C. The physical trapping parameters (intensity and peak position, trap depth and pre-exponential factor) for each TL curve were estimated by using a computerized glow curve analysis program.

Glow curve analysis of glassy system dosimeter subjected to photon and electron irradiations

Abstract The current paper illustrates glow curve analysis of newly developed Borate glass dosimeters. A series of dosimetric properties including dose response for photons and electrons, energy response, optical fading, and precision were determined. Glow curve deconvolution based on the general order kinetics equation was applied to extract the trapping parameters. Excellent fitting was obtained with the superposition of three-second order glow peaks. The quality of fitting was monitored through the r2 value which is always in excess of 0.9998. Thermoluminescence (TL) measurements showed that the material exhibits good linear dose–response over the delivered range of absorbed dose from 0.5 to 4 Gy for photons and electrons irradiation with low energy dependence. The material exhibits large signal loss when exposed to direct sunlight and moderate signal loss when exposed to fluorescent light. Therefore, it is recommended to use the current dosimeters indoor and to avoid prolonged direct exposure to fluorescent light. This combination of properties makes the material suitable for radiation dosimetry.

Automatic detection of anomalous thermoluminescent dosimeter glow curves using machine learning

Computerized Glow Curve Analysis (CGCA) has been, and still is, an intensively-investigated subject for the past two decades. CGCA has applied different methods for various applications, from glow curve deconvolution into isolated peaks, through semi-automatic software tools for detecting outliers, to software that discovers exceptional curves by using predefined rules. The method presented herein addresses the subject using a new approach in which a completely automatic algorithm is used for the accurate detection of anomalies in thermoluminescent dosimeter (TLD) glow curves. A Support Vector Machines (SVM) technique, which is a machine learning classification algorithm, is used for the first time for radiation dosimetry applications. The algorithm classifies glow curves into two categories: an acceptable i.e. 'regular' curve, or a curve that exhibits any kind of anomaly i.e. an 'anomalous' curve. The classification method treats the glow curves raw data as a large ensemble of statistical data, and tries to identify exceptional glow curve shapes by statistical means. This classification method is performed in three steps. First, a library of glow curves is manually classified by a human user of the system into the above two classes. Then an iterative training algorithm is applied to these glow curves. The final stage applies a method of comparison between an unidentified glow curve and these two pre-classified sets, and assesses a classification probability to each of the two classes. The results show between 96.2% and 97.7% accuracy of the correct classification to either one of the classes, depending on the admissible false negatives rate.