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Objective To explore the feasibility of quartz glass for radiotherapy dosimetry through the experimental study of the thermoluminescence characteristics of synthetic quartz glass. Methods The thermoluminescence glow curves of quartz glass under different annealing conditions were analyzed, the thermoluminescence characteristics of quartz glass were studied, and the measurement parameters were optimized. Using the Co-60 reference radiation field in the National Secondary Standard Dosimetry Laboratory, the quartz glass samples under different annealing conditions were irradiated following the dose levels of radiotherapy, i.e., 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 Gy, respectively. According to the relationship between the absorbed dose of quartz glass and the relative thermoluminescence signal intensity, the linearity and dispersion of the dose response of quartz glass were obtained, and the feasibility of quartz glass for radiotherapy dosimetry was analyzed. Results The linear correlation coefficient of dose response of quartz glass under annealing condition of 430℃ for 10 min was 0.9984, and the dose response dispersion was 0.97% at the absorbed dose of 2 Gy. The linear correlation coefficient of dose response of quartz glass under annealing condition of 600℃ for 1 h was 0.9911, and the dose response dispersion was 1.4% at the absorbed dose of 2 Gy. Conclusion Preliminary results suggest that quartz glass with annealing condition of 430℃ for 10 min has the potential to be used for radiotherapy dosimetry.
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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.
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Objective To improve the quality of personal dose equivalent measurement by exploring optimal annealing temperature conditions.Methods Totally 60 pieces of thermoluminescent detectors were randomly and equally divided into 6 groups.The 6 groups underwent 10-min annealing under 200,220,230,240,250 or 260 ℃ respectively,and then were cooled with the same conditions and went through measurement after irradiation by the calibrated radiation source.The above operation of annealing,cooling and measurement were repeated for 10 times,and the 6 groups were compared on dispersity,sensitivity and glow curve.Results Single test proved that under 240 ℃ the dispersity,sensitivity and glow curve gained optimal results comprehensively,while repeated tests showed that the dispersity had the optimal value under 250 ℃ and the sensitivity decreased significantly as the times of annealing rose.Conclusion Annealing conditions have to be selected according to the requirements of the thermoluminescent detector.
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Objective To improve the quality of personal dose equivalent measurement by exploring optimal annealing temperature conditions.Methods Totally 60 pieces of thermoluminescent detectors were randomly and equally divided into 6 groups.The 6 groups underwent 10-min annealing under 200,220,230,240,250 or 260 ℃ respectively,and then were cooled with the same conditions and went through measurement after irradiation by the calibrated radiation source.The above operation of annealing,cooling and measurement were repeated for 10 times,and the 6 groups were compared on dispersity,sensitivity and glow curve.Results Single test proved that under 240 ℃ the dispersity,sensitivity and glow curve gained optimal results comprehensively,while repeated tests showed that the dispersity had the optimal value under 250 ℃ and the sensitivity decreased significantly as the times of annealing rose.Conclusion Annealing conditions have to be selected according to the requirements of the thermoluminescent detector.
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To achieve the accurate evaluation of given absorbed dose from output dose of linear accelerator photon beam through investigate the characteristics of LiF:Mg,Cu,P TLD powder. This experimental TL phosphor is performed with a commercial LiF:Mg,Cu,P powder (Supplied by PTW) and TL reader (LTM, France). The TLD was exposed to 6 MV X rays of linear accelerator photon beam with range 15 to 800 cGy in blind dose at two hospitals. The dose evaluation of TLD was through the experimental algorithms which were dose dependency, dose rate dependency, fading and powder weight dependency. The glow curve has shown the three peaks which are 110, 183 and 232 degrees of heating temperature and the main dosimetric peak showed highest TL response at 232 high temperature. In this experiments, the LiF:Mg,Cu,P phosphor has shown the 2.5 eV of electron trap energy with a second order. This experiments guided the dose evaluation accuracy is within 1% +2.58% of discrepancy. The TLD powder of LiF:Mg,Cu,P was analyzed to dosimetric characterists of electron captured energy and order by glow shape, and dose-TL response curve guided the accuracy within 1.0+2.58% of output dose discrepancy.