Structural and thermoluminescence properties of lithium borate glass matrices under UV and beta radiation.

In the present work, glass samples in the (100 - x)B2O3-xLi2O binary system, with x varying from 30 to 50 mol%, were prepared using the conventional melting and moulding method, with the main objective of evaluating the thermoluminescence response when exposing these materials to ultraviolet (UV) radiation. Complementary analysis based on density, optical absorption on the UV-visible region (UV-vis absorbance), Fourier transform infrared spectroscopy on the medium region, X-ray diffraction, and differential thermal analysis measurements were performed. Thermoluminescence measurements of vitreous samples showed glow curves with at least one peak with a maximum temperature of ~170°C after exposure to UV radiation in the temperature range 50-250°C. Samples were also exposed to beta radiation in the temperature range 25-275°C, also showing single peaks with a maximum temperature of ~150°C.

Thermoluminescent composites of sintered synthetic-topaz/in situ corundum for dosimetry by a novel reversible process.

Topaz (Al2F1·44(OH)0·56SiO4)/corundum (Al2O3) composites were prepared by a facile and novel reversible process from the sintering of synthetic topaz and AlF3 powders, with corundum formed in situ into the topaz matrix. The corundum formation reaction occurs in the temperature range 875-975 °C, from 40 min sintering time, obtaining the topaz- Al2F1·44(OH)0·56SiO4/corundum- Al2O3 composites. Although sintering temperature and time increment lead to higher corundum formation in the topaz matrix (78.4 wt % Al2O3 at 975 °C for 60 min), longer residence times give place to corundum percentage decrease due to topaz reconversion. The composites' microstructure is characterized by a rectangular bar with stacked pyramidal ends and polycrystals of hexagonal plates for topaz and corundum, respectively. For the topaz/corundum composites, the maximum density was 3.05 g/cm3 (17 % porosity) for specimens sintered at 925 °C for 20 min. The glow curves of the topaz/in situ corundum composite sintered at 975 °C and 0 min dwell time show thermoluminescent peaks between 180 and 250 °C, useful for dosimetric applications. The most helpful peak (at 221 °C) in the topaz/corundum composite's glow curves determined by computational deconvolution is sharp and exhibits the highest thermoluminescent response. Dose-response analysis of the composite (sintered at 975 °C for 0 min) with the best thermoluminescent response revealed two ranges of linear behavior, the first from 2 to 200 mGy, with an adjustment of 99.9 % and the second in the range 5-300 Gy (99.8 % fitting). The thermoluminescent response improvement of the topaz/corundum composites is attributed to the corundum formed in situ during sintering. Fading rate studies of the composite with the best sintering treatment revealed a signal decrease of 4 % after 15 days, which remained constant for up to 30 days, and 8 % after 60 days. The kinetic parameters, kinetics order (b), activation energy (E), and frequency factor (s) determined using the glow peak shape method showed second-order kinetics. The topaz/corundum composite with the best TL response (975 °C, 0 min) presents an effective atomic number (Zeff) of 11.74. The detection of lower doses (mGy) and the linear response at higher doses (Gy) of beta 90Sr, together with the other thermoluminescent properties, suggest that the topaz/corundum composites sintered at 975° for 0 min dwell time may find application in radiotherapy, geological dating, and environmental dosimetry.

Synthesis, photo- and thermo-luminescent properties of Mg2P2O7:Tm3+ phosphors.

In this work, both undoped and Thulium (Tm3+) doped (0.3-10 mol%) magnesium pyrophosphate (Mg2P2O7) powders were synthesized by the solvent evaporation method to study their photo-and thermoluminescent properties. Two crystalline phases were observed in the powders by X-Ray diffraction (XRD), the main phase being Mg2P2O7 and the second one thulium phosphate (TmPO4). The superficial morphology was analyzed by scanning electron microscopy (SEM), which revealed that the powders are agglomerates with an undefined form and grains with non-uniform size distribution. The photoluminescence (PL) emission spectra of Tm3+ doped powders show the 1D2 → 3F4 transition, associated with Tm3+ ions, at 452 and 458 nm. The thermoluminescence (TL) properties were analyzed in the undoped and Tm3+ doped powders exposed to 90Sr beta source. The TL glow curve of Tm3+ doped powders exhibits three maxima at about ⁓64-66 °C, ⁓198-202 °C, and ⁓301 °C. The TL dose-response is sub-linear from 0.11 to 0.54 Gy, linear between 0.79 and 24.95 Gy, and supra-linear from 34.99 to 599.95 Gy. Acceptable repeatability with a coefficient of variation of ∼1% was obtained after ten cycles of irradiation and readout. At 63 d of storage, the powders show fading of 30%, and at 1.6 years (585 d), the integrated TL intensity decays by 47%. The kinetic parameters of activation energy and frequency factor were evaluated using the Initial Rise, Booth, Bohun, and Porfianovitch (BBP) and Hoogenstraaten methods and Glow Curve Deconvolution with a general order kinetic model.

Effect of Re-sintering on the morphological and thermoluminescence properties of the ALOX-520 detector.

Significant research is being conducted on new materials suitable for dosimetry in recent decades with particular focus on their luminescent properties. For instance, a new ceramic detector, aluminum oxide 520 (ALOX-520), was developed at CDTN in 2011 using the sol-gel method. The detectors were doped with C, Fe, Mg, Ca, Cr, Ni, and Mo impurities that generated the necessary dosimetric trap levels to enhance the luminescence effects. Consequently, the resultant material was appropriate for the quantification of ionizing radiation fields by both thermally and optically stimulated luminescence techniques. Originally, ALOX 520 was sintered at 2023 K under a highly reducing atmosphere. At the end of this process, it exhibited important dosimetric properties, as already described in existing literature. The objective of this study is to conduct tests at higher temperatures in vacuum to investigate the effect of thermal treatments under these conditions on the structural and dosimetric properties of the material. Accordingly, ALOX-520 was re-sintered at high temperatures and the changes in its physical, morphological, and dosimetric properties were analyzed. ALOX 520T exhibited better dosimetric properties in terms of homogeneity, reproducibility, linearity, and signal fading. Physically, an increase in the detection threshold value of ALOX-520T could be linked to a decrease in the sensitivity of this detector. The energy dependence, the thermal quenching correction, and kinetic studies for ALOX-520T conducted as part of this work are original. However, the obtained results are consistent with those reported in the literature for α-Al2O3 ceramic detectors. XRD and XRF analyses demonstrated that the thermal treatment did not change the crystalline structure or composition of the material. All the results indicate that an appropriate thermal treatment could improve the dosimetric properties of the ALOX-520 detector without causing significant changes in its crystalline structure.

Thermoluminescence properties and identification of irradiated cocoa beans during long-term storage.

This work reports on the thermoluminescence (TL) properties and detection of contaminating minerals isolated from Mexican cocoa beans irradiated with gamma radiation and stored for 4 years. Contaminating minerals isolated from cocoa beans consisting of quartz, diopside, plagioclase, albite, and iron oxide with irregular and rectangular grains and average length of 135 µm. Cocoa beans are detected as irradiated even after 4 years of storage using the shape and maximum temperature of the TL glow curve of contaminating minerals. The TL properties of dose-response, and fading of minerals were also analysed. The TL dose-response is linear from 5 to 100 Gy, supra-linear between 250 and 1000 Gy, and sub-linear above 1500 Gy. Based on the TL1/TL2 ratio the minerals are identified as irradiated from 250 Gy to 4500 Gy in the dose-response test and after different storage times in the darkness at room temperature. A continuum trap distribution can be associated with the TL glow curve of minerals using the Tm-Tstop method. First order kinetic peaks were used in the Glow Curve Deconvolution of natural and irradiated (1 and 10 kGy) TL curves.

Beta radiation excited thermoluminescence of solid-state synthesized SrZrO3 phosphors.

In this work, we report on the solid-state reaction synthesis of SrZrO3 phosphors, and their beta particle irradiation excited thermoluminescence (TL) characterization. X-ray diffraction data confirmed the obtention of the orthorhombic phase of SrZrO3. Through computational glow curve deconvolution, the whole glow curve was resolved into six individual first order kinetics peaks. This is the first report concerning the usefulness of SrZrO3 as TL dosimeter. The synthesized phosphors exhibit TL emission from below 100 °C up to above 300 °C, being the most intense TL between 200 and 300 °C, as well as a remarkable reproducibility of the TL response in repeated irradiation-TL readout cycles.

Synthesis, optical and thermoluminescence properties of thulium-doped KMgF3 fluoroperovskite.

KMgF3 fluoroperovskite doped with thulium at different concentrations were synthesized by the solid-state reaction method. The phase composition and the thermal stability up to 600 °C of the polycrystals were analyzed by X-ray diffraction and thermogravimetric analysis, respectively. The KMgF3 at 1.0 mol% of Tm polycrystals showed the best thermal stability and did not present another phase. The gamma radiation (0.1-10 kGy) effect in thulium-doped KMgF3 produced the F color centers, and their aggregates such as F2, and F3 centers. The F centers, and the potassium vacancies (VK-) in the fluoroperosvkites were analyzed by the optical absorption and emission measurements. Optical absorption at 275 nm and 443 nm were assigned to F and F2, respectively, in undoped KMgF3. Tm-doped fluoroperovskite shows the optical absorption bands at 277, 393, 432, and 577 nm, which were ascribed to the F, F3, F2 and VK- centers, respectively. When the F band for undoped polycrystals was excited at 275 nm, a clear emission associated with F2 and F3 centers was observed. In the case of Tm-doped, an enhancement of the blue emission at 457 nm occurred and a UV band (354 nm) was observed upon exciting the F band. The blue emission of thulium was overlapped with the F3 color center band. The emission bands at 457 and 354 nm were ascribed to 1D2 - 3F4 and 1D2 - 3H6 transitions of Tm in KMgF3. The optical absorption and glow curves were investigated too. The glow curves were assisted by the color centers, vacancies, and thulium impurity. Thermal bleaching shows that the F center was the main participant to give rise to the TL intensity of the glow curves. Thulium acts as a deep electron trap in the bandgap of the KMgF3 fluoroperovskites forming TL peak at the higher temperature, from 430 to 408 °C. The absorption, emission, and thermoluminescence glow peaks of the undoped and Tm-doped KMgF3 were compared.

Beta radiation excited thermoluminescence of SrB4O7 phosphors synthesized through solid state reaction.

In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited thermoluminescence (TL) are reported. The glow curves show maxima around 200 and 300 -considered suitable for TL dosimetry-, and a remarkable reproducibility in successive irradiation - TL readout cycles. The integrated TL exhibits a linear dependence upon the irradiation dose in the tested dose range (from 1.0 up to 8.0 Gy). The lower detection limit and the sensitivity relative to the TLD-100 dosimeter are 88 mGy and 0.49, respectively. From the results here presented, we conclude that SrB4O7 synthesized through solid state reaction can be considered a phosphor material interesting to develop TL dosimeters.

Beta particle excited thermoluminescence of CaZrO3 phosphors synthesized by solid state reaction.

In this work, the synthesis through solid state reaction and the thermoluminescence (TL) characterization of pellet shaped CaZrO3 samples is reported. X-ray diffraction confirms that orthorhombic CaZrO3 was obtained. The glow curve has two maxima located at 149 and 216 °C as well as a less intense maximum around 350 °C when a 5.0 °C/s heating rate is used after 64 Gy of beta particle exposure. A remarkably reproducibility of the TL response is observed in repeated irradiation - TL readouts cycles. The TL as a function of the dose displays linear dependence in the dose range from 0.5 to 256 Gy. The intensity of the maximum located around 216 °C remains 61% 14 days after irradiation, and then remains closely constant for longer times. The synthesized CaZrO3 exhibits TL properties potentially of interest for use in radiation detection and dosimetry.

Comportamiento termoluminiscente de matrices de alúmina bajo diferentes condiciones de sinterización y dopaje con cerio / Termoluminiscent behavior of alumina matrices under different conditions of sinterization and doping with cerio / Comportamento termoluminiscente de matrizes de alumina sob diferentes condições de sinterização e doping com cerio

Resumen Introducción: en la búsqueda de nuevos materiales útiles como dosímetros termoluminiscentes (TL) la alúmina (α-Al2O3) ha adquirido gran atención. La α-Al2O3 posee una sensibilidad TL que es perceptible a las concentraciones de impurezas y a las condiciones térmicas del crecimiento de sus cristales, por lo que encontrar nuevas variaciones del material permitirá aumentar su respuesta TL. Objetivo: analizar las curvas de brillo de matrices de alúmina pura sinterizadas bajo diferentes condiciones de calcinación y dopadas con cerio a concentración 0.1 % p/p (Al2O3:Ce), usando la función asimétrica logística, para calcular sus parámetros cinéticos termoluminiscentes y explicar el comportamiento del material. Materiales y métodos: polvo de alúmina bohemita fue utilizado para preparar muestras puras sintetizadas de bajo diferentes condiciones de calcinación (NALO y ALO). El cerio se introdujo mediante impregnación húmeda utilizando nitrato de cerio hexa-hidratado. El análisis estructural de las matrices se realizó mediante Difracción de Rayos X. La lectura TL se realizó en un TLD 4500. Resultados: la deconvolución obtenida en las curvas de brillo para los grupos ALO y NALO evidencia la presencia de tres y cuatro señales TL respectivamente, y de seis señales TL en la muestra Al2O3:Ce. Conclusión: los tratamientos térmicos aplicados introdujeron un cambio sustancial en la curva de brillo del material y en su cinética TL, en términos del número de trampas y de la cantidad inicial de portadores de carga atrapados. La introducción de impurezas de cerio produjo una modificación fundamental en la curva de brillo de las matrices de alúmina.

Abstract Introduction: in the search for new materials useful as thermoluminescent dosimeters (TL) alumina (α-Al2O3) has acquired great attention. The α-Al2O3 has a sensitivity TL that is perceptível to the concentrations of impurities and to the thermal conditions of the growth of its crystals, so finding new variations of the material will allow to increase its TL response. Objective: analyze the brightness curves of pure alumina matrices sintered under different calcination conditions and doped with cerium at a concentration of 0.1 % p/p (Al2O3:Ce), using the asymmetric logistic function, to calculate its thermoluminescent kinetic parameters and explain the behavior of the material. Materials and methods: boehmite alumina powder was used to prepare pure sintered samples of under different calcination conditions (NALO and ALO). The cerium was introduced by wet impregnation using cerium hexahydrate nitrate. The structural analysis of the matrices was carried out by X-ray diffraction. The TL reading was performed in a TLD 4500. Results: the deconvolution obtained in the brightness curves for the ALO and NALO groups evidences the presence of three and four TL signals respectively, and of six TL signals in the sample Al2O3:Ce. Conclusion: the applied heat treatments introduced a substantial change in the brightness curve of the material and its TL kinetics, in terms of the number of traps and the initial amount of charge carriers trapped. The introduction of cerium impurities produced a fundamental modification in the brightness curve of the alumina matrices.

Resumo Introdução: na busca por novos materiais úteis como dosímetros termoluminescentes (TL), a alumina (α-Al2O3) tem adquirido grande atenção. O α-Al2O3 possui uma sensibilidade TL que é perceptível às concentrações de impurezas e às condições térmicas do crescimento de seus cristais, portanto, encontrar novas variações do material permitirá aumentar sua resposta TL. Objetivo: analisar as curvas de brilho de matrizes de alumina pura sinterizadas sob diferentes condições de calcinação e dopadas com cério na concentração de 0,1 % p/p (Al2O3:Ce), utilizando a função logística assimétrica, para calcular seus parâmetros cinéticos termoluminescentes e explicar a comportamento do material. Materiais e métodos: o pó de alumina boehmite foi usado para preparar amostras de puro sinterizado sob diferentes condições de calcinação (NALO e ALO). O cério foi introduzido por impregnação a úmido com nitrato de cério hexaidratado. A análise estrutural das matrizes foi realizada por difração de raios X. A leitura TL foi realizada em um TLD 4500. Resultados: a deconvolução obtida nas curvas de brilho para os grupos ALO e NALO mostra a presença de três e quatro sinais TL respectivamente, e de seis sinais TL na amostra Al2O3: Ce. Conclusão: os tratamentos térmicos aplicados introduziram uma mudança substancial na curva de brilho do material e sua cinética de TL, em termos do número de armadilhas e da quantidade inicial de portadores de carga aprisionados. A introdução de impurezas de cério produziu uma modificação fundamental na curva de brilho das matrizes de alumina.

Silver Nanoparticles Enhance Thermoluminescence and Photoluminescence Response in Li2B4O7 Glass Doped with Dy3+ and Yb3.

Lithium borate glass matrices doped with Dy3+ and Yb3+, containing silver nanoparticles in different concentrations are synthesized and characterized in this work. The Scanning Transmission Electron Microscopy confirms formation of silver nanoparticles in the samples. Absorption spectra of the samples show the presence of a broadband spectrum associated due to the surface plasmon effect of the silver nanoparticles. A strong surface plasmon band bellow 400 nm appears after the annealing process, due to the formation of silver nanoparticles with radius of 5-15 nm. The transition peaks of Dy3+ are also observed at 386, 446, 798, 917, 1088, 1265 and 1669 nm. Additionally, a large peak at 976 nm belonging to the absorption band corresponding to the Yb3+ is observed. Emission spectra under 406 nm pumping show two prominent bands at 506 and 590 nm belonging to the Dy3+ transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2, respectively. The fluorescence in the 480 nm and 525 nm spectral ranges enhanced with the silver nanoparticles contained in the samples. Is the first time, the luminescence studies of the lithium borate matrix doped with Dy3+ and Yb3+ containing silver nanoparticles is done. The basic parameters defining the lasing-amplifying potential of the glass matrices as a function of silver nanoparticles concentration are calculated. The Thermoluminescence response to UV irradiation also exhibits significant enhancement with the increment of silver nanoparticles in the samples.

Thermoluminescence emission on lead oxychloroborate glasses under UV exposure.

Glassy materials were prepared using two different systems: 50B2 O3 - (50 - x)PbO - xPbCl2, with x = 0, 2 and 5 in mol % (System BPCl-I) and 50BO1.5 - (50 - x)PbO - xPbCl2 with x = 0, 2, 5 and 7 in cationic % (System BPCl-II). Structural and optical characterization showed that PbCl when substituted for PbO changed the structure of the glass network by replacing nonbridging oxygens for chlorine ions. This substitution also caused a change in the number of defects responsible for thermoluminescence (TL) emission (electrons and hole trap centres). Thermoluminescence emissions were observed for the first time in lead oxychloroborate glasses after exposure to UV radiation. Sample BPCl-I-2 (x = 2 from System I) demonstrated better TL emission compared with other glass samples. One intense peak in the glow curve, centred at ~122°C followed by a shoulder at ~180°C, was highly sensitive to UV radiation. There were also good linear responses at dose range ~0.4 to ~2 J/cm2 for the first peak (low temperature) and ~0.4 to ~4 J/cm2 for the second peak (high temperature).

Mass energy absorption coefficients and energy responses of magnesium tetraborate dosimeters for 0.02 MeV to 20 MeV photons using Monte Carlo simulations.

Thermoluminescence dosimeters containing boron, such as magnesium tetraborate (MgB4O7), are of interest because of their very high sensitivity, near tissue-equivalent absorption coefficients, low cost, easy handling, and very large linearity range for absorbed dose. Another important parameter that should be considered when working with thermoluminescent dosimeter (TLD) is the mass energy absorption coefficient (µen/ρ), which is a close approximation to the energy available for production of chemical, biological and other effects associated with exposure to ionizing radiation, therefore important in estimating dose in medical and health physics. In this study the mass energy absorption coefficients and energy responses of undoped and some doped magnesium tetraborates were calculated by Monte Carlo N-particle transport code for a range of photon energies between 20 keV and 20 MeV. The calculated parameters for MgB4O7, MgB4O7:Dy and MgB4O7:Dy,Li were evaluated in comparison with standard TLDs as Al2O3:C and TLD-100 (LiF: Mg, Ti) and ICRU tissue data. The influence of the dopant concentration in the MgB4O7 matrix on the energy dependence of TLD was also investigated. The analyses indicated a good agreement between the simulations and theoretical calculations. The µen/ρ and energy dependence of the materials are higher in the low energy range (E < 100 keV), which is related to the high probability of interaction between radiation and matter due to photoelectric absorption. With regard to the influence of dysprosium concentration in the MgB4O7 matrix an increase in the energy dependence of MgB4O7 for higher concentrations of dopants was observed in the low energy range.

Synthesis and thermoluminescence characterization of self-agglomerating CaSO4 exposed to beta radiation.

The synthesis and thermoluminescence (TL) characterization of self-agglomerating pellet-shaped CaSO4 phosphors, through a low cost and environmentally friendly method is reported. In order to investigate their TL features, some samples were exposed to beta particle irradiation in the dose range from 0.07 to 10 Gy. Characteristic TL glow curve consists of a single main maximum located at 216 °C, which is considered stable, hence, suitable for dosimetry applications. The dose-response was remarkable linear. Moreover, the lower detection limit was determined to be 6.0 µGy, and the relative TL sensitivity twice the one from the commercial TLD-100 dosimeter.

Dosimetric properties of KMgF3:Tb + PTFE.

This work presents the results obtained from the dosimetric properties of the new radiation detectors of KMgF3:Tb + PTFE. The thermoluminescent material was obtained by microwave technique. The polycrystalline powder obtained was mixed with polytetrafluoroethylene resin powder in the ratio 2:3 to make dosimeters in pellet form. The thermoluminescent response of these new detectors presented a linear behavior, in the dose range between 1 and 1000 Gy 60Co gamma radiation, the repeatability test in the measurements, during ten cycles of heat treatment, irradiation and readouts, showed ±â€¯3.7% DS, the stability test of thermoluminescent signal, during two months showed that the fading is practically null. For the results obtained, this new detector could be very useful for radiation dosimetry, in clinical applications.

Synthesis and luminescence studies of Tb-doped MgO-MgAl2O4-Mg2SiO4 ceramic for use in radiation dosimetry.

In the present work, MgO ceramic samples with different terbium concentrations were produced and the Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties analyzed and discussed, aiming the use in radiation dosimetry. The samples were produced using MgO, Mg(NO3)2·6H2O, Al2O3, SiO2 and Tb(NO3)3·6H2O precursors in stoichiometric concentrations with five different terbium concentrations between 0.1 and 0.5 mol% and after, heat-treated at high temperature ~1500 °C. X-ray diffraction measurements on samples showed the formation of MgO as principal phase, and others in low concentration due to MgAl2O4, Mg2SiO4 and Tb4O7 phases. The TL glow curve of samples showed an intense and well-defined peak having the maximum at ~210 °C and other less intense at ~350 °C. The sample with 0.1 mol% of terbium concentration presented highest luminescence peak when compared to the other samples. The relationship between 210 °C TL peak intensity and dose was linear to doses between 1 and 20 Gy and the minimum detectable dose obtained by interpolation taking into account three times the standard deviation of the zero dose reading, was ~40 µGy. A fading of ~20% during the first 5 hours after irradiation of 210 °C peak was observed. TL emission spectra showed strong emission lines due to Tb3+ ion. The OSL signal presented a linear behavior to doses between 1 and 10 Gy using 532 nm wavelength stimulation.

Thermoluminescence of metallic oxides. Development and applications in Mexico: An overview.

Interest in the study of the thermoluminescence of metallic oxides doped with various elements has been steadily increasing due to the characteristics of these materials and their possible applications in the dosimetry of ionizing radiation. Metal oxides such as zirconium oxide (ZrO2), aluminum oxide Al2O3, titanium oxide (TiO2), hafnium oxide (HfO2) and beryllium oxide (BeO) are very interesting semiconductor materials having a wide band gap with different important applications. Since 1998, in our country we have developed these materials un-doped and doped with various elements, using different preparation methods. These materials have been obtained in powder form, thin films or in pellets made by mixing the TL powder with PTFE. Thermoluminescent and dosimetric characteristics of these materials have been studied and have been used successfully in various applications. It is presented an overview of the development of these materials in Mexico for the past 20 years.

Synthesis and thermoluminescence of LaAlO3:Pr3+ to UVC radiation dosimetry.

Thermoluminescent (TL) response of trivalent praseodymium ion doped lanthanum aluminate (LaAlO3:Pr3+) obtained by Pechini method and Spray Dryer was studied. TL response of LaAlO3:Pr3+ powders submitted at 1600°C exhibited one peak centered at 157°C. Sensitivity of LaAlO3:Pr3+ was improved in around 90 times compared with undoped LaAlO3. TL response as a function of wavelength showed a maximum in 230nm. Dosimetric characteristics of LaAlO3:Pr3+ under UVR radiation effects were analyzed. Evaluation of activation energy was obtained by Glow Fit v.1.3 software. Experimental results about thermoluminescent characteristics of LaAlO3:Pr3+ suggest as good candidate to be employed as a complementary thermoluminescent device with other TL phosphors as aluminum oxide.

Thermoluminescence, OSL and defect centers in Tb doped magnesium orthosilicate phosphor.

Mg2SiO4:Tb phosphor exhibits four thermoluminescence (TL) peaks at 124, 244, 300 and 370°C for a heating rate of 2°C/s, 244°C peak being the main dosimetry peak. The irradiated phosphor exhibits CW-OSL response on stimulation with blue (470nm) light. Thermal decay of OSL shows that all the TL traps contribute to CW-OSL signal. Its TL and OSL sensitivities are 0.21 and 0.038, respectively, than that of Al2O3:C (Landauer Inc.). Its CW-OSL response increases linearly up to 30Gy, thereafter increase was supralinear up to the studied dose of 1000Gy. Electron Spin Resonance (ESR) studies were carried out to study the defect centers induced in the phosphor by gamma irradiation and also to identify the centers responsible for the TL process. Room temperature ESR spectrum of irradiated phosphor appears to be a superposition of at least three distinct centers. One of the centers (center I) with an isotropic g-factor 2.0122 is attributable to an intrinsic O(-) radical and this correlates with the main TL peak at 244°C. Center II with an isotropic g-factor 2.0012 is assigned to an F(+)-center (singly ionized oxygen vacancy) and is the likely recombination center for all the TL peaks. Both the centers grow with radiation dose at least up to 1 kGy. Center III with an axial symmetric g-tensor with principal g-values g||=2.0049 and g⊥=2.0029 is identified as an F(+)-center and is not related to the observed TL peaks in the phosphor.

OSL and TL response characterization of LiF:MG,Ti microdosimeters to be applied to VMAT quality assurance.

This paper aims to evaluate the feasibility of applying LiF:Mg,Ti microdosimeters as a new method of dosimetry to volumetric-modulated arc therapy (VMAT) RapidArc. The response of microdosimeters presented a maximum variation of ±3.18% and ±0.510% using optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques, respectively. Although studies were conducted on LiF:Mg,Ti microdosimeters previously, the microdosimeters in this study showed precision and high potential of application in VMAT dosimetry and in the verification of treatment planning using the VMAT technique.