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The motivation of this work was to produce TL dosimeters based on crystals of CaSO4 doped with thulium and silver, by means of a suitable new route. The crystals were produced by an adaptation of the slow evaporation route using calcium carbonate (CaCO3) as precursor, and incorporating the dopants (Tm2O3 and silver nanoparticles) in a solution of sulfuric acid, which is evaporated resulting in CaSO4:Tm or CaSO4:Tm,Ag crystal powders. X-ray diffraction analyses showed that the produced samples exhibit only a single phase corresponding to the crystal structure of anhydrite. Optical characterization was performed to determine the band gap of the materials. Samples did not show a reasonable OSL signal after stimulation with blue LEDs. TL characteristics such as glow curves, linearity and reproducibility of response, minimum detectable dose and fading were evaluated. The CaSO4:Tm samples showed TL emission glow curves with peaks in temperatures proper for dosimetry. The CaSO4:Tm,Ag samples presented a very intense peak displaced to high temperatures that could only be observed by applying heating rates below 4 °C/s. Samples doped with thulium oxide and silver nanoparticles showed the highest TL intensity and lowest fading.

The linearity characteristic in radiation dosimetry presents a growing interest. Glasses have been applied to high radiation doses. In this work, materials will be analyzed and compared in relation to their linearity ranges. Lithium diborate, sodium diborate and commercial glass were irradiated with doses from 10 Gy to 10 kGy using a 60Co Gamma-Cell system 220 and evaluated with the UV–vis technique. The sensitivity analyses were applied through four methodologies, searching for linear regions in their response. The results show that all four applied analyses indicate linear regions for the tested radiation detectors. The materials with higher linearity range, in descending order, were lithium diborate, sodium diborate and commercial soda-lime glass. The radiation detectors present potential use for radiation dosimetry in intermediate and high doses.

From Obsidian silicate, in its natural form, pellets were manufactured adding Teflon to the material in powder. These pellets were exposed to the gamma radiation beams of a 60Co source in a dose interval from 10 Gy to 10 kGy. The Obsidian in powder was investigated in relation to its physical and chemical characteristics, by means of the X-ray diffraction, scanning electronic microscopy and energy-dispersive X-ray spectroscopy techniques. After the irradiation procedure, the signal of the samples was evaluated by means of three techniques: thermoluminescence (TL), optically stimulated luminescence (OSL) and thermally stimulated exoelectron emission (TSEE). The objective of this work was to verify the TL, OSL and TSEE response of the Obsidian+Teflon pellets after exposure to high doses of gamma radiation. Different response characterization tests were performed, as TL and TSEE emission curves, OSL signal decay, reproducibility, dose-response curves, lower detection limits and fading. From these results, it can be observed that the Obsidian+Teflon pellets present good conditions to be used as high dose gamma radiation detectors; the results obtained with the OSL technique were the most adequate in terms of response in function of absorbed dose. The fading of the signals, varying from about 26% (TSEE) to 44% (OSL), in a time interval of 360 h post-irradiation, also showed favorable results for the use of this material as radiation detector, when the measurements are taken after a defined time interval.

Introducao Diferentes materiais apresentam propriedades luminescentes que sao aplicadas a dosimetria das radiacoes, e que sao avaliadas usando tecnicas como a termoluminescencia (TL) e a luminescencia opticamente estimulada (OSL). Entretanto, ha outros fenomenos que podem ser empregados em dosimetria, que aplicam o uso da radiacao ultravioleta (RUV) ao sinal TL e OSL das amostras; sao as tecnicas de TL fototransferida (PTTL) e OSL fototransferida (PTOSL), utilizadas como uma alternativa para se tentar obter um sinal mais adequado para o uso do material como um dosimetro, o que e interessante para a dosimetria das radiacoes, principalmente no caso onde e necessario trabalhar com doses absorvidas mais altas. O LiF:Mg,Ti e um material dosimetrico ja bem estudado com relacao a sua resposta TL e OSL, para diferentes aplicacoes [1,2]. O CaSO 4 e outro material que possui resultados de sinal TL e OSL na literatura para uso em dosimetria [2-4]. Este mesmo material ja foi estudado com relacao ao seu sinal PTTL, utilizando uma lâmpada de RUV [5]. Para se obter o sinal de fototransferencia, e necessario que as seguintes etapas sejam realizadas: 1) irradiacao do material, 2) tratamento termico pos-irradiacao, 3) iluminacao do material, e 4) avaliacao do sinal PTTL e PTOSL. O tratamento pos-irradiacao ao qual o material e submetido, deve ser adequado o suficiente para que seja possivel obter um sinal PTTL e PTOSL apos a iluminacao; se ele nao for adequado, pode ocorrer esvaziamento das armadilhas rasas e profundas da amostra, eliminando todos os eletrons que forneceriam o sinal e impossibilitando, assim, a obtencao de qualquer resposta TL/PTTL ou OSL/PTOSL. Assim, o objetivo deste trabalho e estudar o efeito que um determinado tratamento termico pos-irradiacao pode causar na obtencao do sinal PTTL e PTOSL de amostras de LiF:Mg,Ti e CaSO 4 :Dy e, com isso, observar se estes sinais possuem valores suficientes para dar prosseguimento ao estudo da resposta fototransferida para aplica-la em dosimetria de doses altas. Metodologia Foram utilizados dois dosimetros comerciais: CaSO 4 :Dy (produzido no Laboratorio de Materiais Dosimetricos do IPEN) e LiF:Mg,Ti (comercializados como TLD-100 pela Thermo Fischer Scientific ). Para a analise do sinal das amostras, foi utilizado o sistema leitor TL/OSL Riso, modelo TL/OSL-DA-20. No caso das amostras de CaSO 4 :Dy, foi utilizada temperatura final de leitura de 350°C, numa taxa de aquecimento de 10°C/s, para a avaliacao do sinal TL/PTTL; para a analise da resposta OSL/PTOSL, o estimulo para a emissao do sinal foi feito utilizando LEDs azuis, com potencia optica de 90% e durante 80 s. No caso das amostras de LiF:Mg,Ti, para a analise do sinal TL/PTTL, foi utilizada temperatura final de leitura de 400°C, com taxa de aquecimento de 10°C/s; para a avaliacao do sinal OSL/PTOSL, o estimulo para emissao de luz ocorreu durante 50 s e a potencia optica dos LEDs azuis utilizados foi de 90%. Apos as medicoes dos sinais, as amostras de CaSO 4 :Dy foram tratadas termicamente a 300°C/3 h, e as de LiF:Mg,Ti a 400˚C/1h, para sua reutilizacao. Apos o tratamento termico pos-irradiacao, numa das fases as amostras foram iluminadas com uma lâmpada de alta pressao de mercurio, para a leitura das respostas PTTL e PTOSL. As condicoes de iluminacao foram: distância entre amostra e lâmpada de 10 cm, comprimento de onda de 250 nm e tempo de iluminacao de 30 minutos. Resultados Na primeira etapa do trabalho, as amostras foram irradiadas com uma fonte de 60 Co e dose absorvida de 1 kGy (irradiador Gamma-Cell, modelo 220, Atomic Energy of Canada , LTD), e em seguida tiveram seus sinais TL e OSL avaliados. As amostras de CaSO 4 :Dy apresentaram o pico principal de emissao do sinal TL em torno de 250°C e na altura correspondente a 2,5x10 4 contagens, e inicio do decaimento do sinal OSL em 1,4x10 5 contagens; os dosimetros de LiF:Mg,Ti tiveram um pico principal TL em 1,3x10 5 contagens, e inicio do decaimento do sinal OSL em 1,5x10 3 contagens. O sinal TL foi mais intenso para o LiF:Mg,Ti, e o OSL foi maior para o CaSO 4 :Dy. Na segunda fase, as amostras foram irradiadas com a mesma dose, tratadas termicamente a 280°C/15 min e, entao, analisadas para tres respostas: TL, OSL, e TL apos a OSL. Para o CaSO 4 :Dy, o sinal TL foi zerado e assemelhou-se ao sinal de fundo do material, e o sinal OSL apresentou inicio de decaimento em 3,5x10 3 ; logo apos esta leitura OSL foi feita uma medicao TL na mesma amostra, e pode-se observar um leve aumento no sinal e formacao de um pico de baixa intensidade em torno de 200°C (altura deste pico em torno de 40 contagens). Para o LiF:Mg,Ti, o maior sinal TL ocorreu em 350°C (deslocado se comparado ao obtido na leitura TL apos irradiacao), na altura de 1,2x10 4 contagens, e apresentou sinal OSL nulo, correspondente ao sinal de fundo da amostra; a leitura TL apos a OSL, na mesma amostra, apresentou um pico que se manteve na regiao de 350°C, e com altura de 1,3x10 4 contagens. A terceira etapa foi de irradiacao das amostras, tratamento termico, e iluminacao com a luz UV. Para as amostras de CaSO 4 :Dy, o pico principal de emissao do sinal PTTL ocorreu em torno de 160°C e na altura correspondente a 1,4x10 3 contagens, e inicio do decaimento do sinal PTOSL em torno de 3,0x10 3 contagens; os dosimetros de LiF:Mg,Ti apresentaram o pico principal de PTTL em torno de 6,0x10 2 contagens e em 165°C, e inicio do decaimento do sinal PTOSL em 2,5x10 3 contagens. Analisando-se os resultados obtidos, e evidente que os sinais TL e OSL sao mais intensos quando sao tomados logo apos a irradiacao, ao inves dos medidos apos o tratamento. Entretanto, mesmo apos o tratamento termico pos-irradiacao e a iluminacao, foi possivel obter-se um sinal significativo de ordem de grandeza para permitir a continuidade dos estudos utilizando o tratamento de 280°C/15 min e a luz UV. Conclusoes Preliminarmente, os experimentos realizados para verificacao dos sinais TL e OSL (apos irradiacao e apos tratamento termico), e dos sinais PTTL e PTOSL (apos irradiacao, tratamento termico e iluminacao com luz UV), apresentaram dados satisfatorios e favoraveis, em termos de curva de emissao do sinal TL/PTTL e curva de decaimento do sinal OSL/PTOSL, para um prosseguimento de estudos dos sinais de TL e OSL fototransferida com possivel aplicacao em dosimetria de doses altas.

Spectrolite + Teflon and Opal + Teflon pellets were studied in this work in relation to their dosimetric properties, using the thermally stimulated exoelectron emission (TSEE) phenomenon. The purpose of this work was to study these materials to be used in high-dose dosimetry of 60Co irradiators, which are employed for several industrial applications. The basic physical principle of this technique is the emission of low energy electrons from the surface of different crystals. For this reason, it is very employed in work with specially radiation sources of low penetrating power, as alpha and beta radiation, but also with gamma sources. Both materials had already their dosimetric chatacteristics verified in previous works after exposure to high doses of a 60Co source and measurements by means of thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques. The TSEE response was investigated in terms of the following tests: TSEE emission curves, reproducibility, minimum detectable doses and dose-response curves.

Glass has been used in radiation dosimetry mainly for its linear response with absorbed dose, low cost and easy evaluation. The lithium diborate glasses were irradiated with doses from 200 Gy to 10 kGy using a 60 Co Gamma-Cell system 220 and evaluated with the UV-Vis and FTIR techniques. The results indicate that the samples present lithium diborate, linearity with the absorbed dose, usefulness as YES/NO radiation detectors (due to their color change), low fading for time periods up to 60 days and a good response reproducibility. In conclusion, the lithium diborate glass may be promising for dosimetry in high doses of radiation.

This paper aims to show how the variance reduction technique "Geometry splitting/Russian roulette" improves the statistical error and reduces uncertainties in the determination of the absorbed dose rate in tissue using an extrapolation chamber for beta radiation. The results show that the use of this technique can increase the number of events in the chamber cavity leading to a closer approximation of simulation result with the physical problem. There was a good agreement among the experimental measurements, the certificate of manufacture and the simulation results of the absorbed dose rate values and uncertainties. The absorbed dose rate variation coefficient using the variance reduction technique "Geometry splitting/Russian roulette" was 2.85%.

In radiation physics, the study of new alternative dosimeters is of interest to the growing branch of dosimetric characterization for radiotherapy applications. The goal of this work was to expose bone samples to high doses and evaluate their linearity response to gamma rays. The Fourier Transform Infrared (FTIR) spectrophotometry technique was employed as the evaluation technique, and based on the spectrophotometry absorbance profiles the linearity was assessed based on the following methods: Area Under the Curve (AUC), Wavenumber Method (WM), Partial Component Regression (PCR) and Partial Least-Square Regression (PLSR) methods. The bone samples were irradiated with absorbed doses of 10 Gy up to 500 Gy using a 60Co Gamma Cell-220 system. The results showed, for the calibration curves of the system, adequate linearity on all methods. In conclusion, the results indicate a good linear response and therefore an interesting potential radiation detector.

In this work, the response of the natural material Opal was studied in relation to its thermoluminescence (TL) and optically stimulated luminescence (OSL), after exposure to the gamma radiation of a 60 Co source. The structure of the powdered Opal was verified using the X-ray diffraction, scanning electronic microscopy and energy-dispersive X-ray spectroscopy techniques. The material, in its stone form, was turned into powder and mixed to Teflon (also in powder) in three different concentrations, and then pellets were manufactured. The aim of this work was to evaluate the response of these pellets in high-doses of gamma radiation beams, and to observe their possible application as dosimeters, using the TL and OSL techniques. The dosimetric properties of the samples were analyzed by means of different tests, as: TL emission curves and OSL signal decay curves, reproducibility of TL and OSL response, minimum detectable dose, TL and OSL dose–response curves (5 Gy–10 kGy), and fading. The results obtained in this work, for the TL and OSL phenomena, demonstrated that the pellets of Opal + Teflon present an adequate performance e possibility of use as dosimeters in beams of high-dose gamma radiation.

The Spectrolite, from the silicate family, a variety of Labradorite, was already studied in relation to its thermoluminescence (TL) and optically stimulated luminescence (OSL) responses, in high-dose gamma radiation fields; the results indicated their good application as gamma radiation detectors. In the present work, the analyses performed to investigate powdered Spectrolite are presented, by means of the XRD, SEM and EDX techniques. The luminescent behavior of Spectrolite + Teflon samples, in the concentration of 1:1, was studied in beta radiation beams (90Sr + 90Y), using the luminescent phenomena of TL and OSL. The results showed adequate TL and OSL reproducibility of the samples; the dose–response curves for both techniques presented a linear behavior in a range from 0.5 Gy to 1 kGy, and the fading showed that after 150 h there were 46.7% and 31.6% of the remaining signal of samples for TL and OSL responses, respectively. Therefore, the Spectrolite + Teflon pellets may be used in beta radiation dosimetry.

The thermoluminescence (TL) and infrared stimulated luminescence (IRSL) responses of in-house produced CaF2:Tm dosimeters are investigated in this work, envisaging their application in electron beam (EB) radiation processing. The irradiations were performed at an industrial EB accelerator (1.5 MeV) covering a dose rate range of 2–8 kGy/s and dose up to 10 kGy. In general, the TL glow curves display four peaks, termed as peaks 2, 3, 4, and 5, corresponding to temperatures at ~150, 200, 240, and 300 °C, respectively. The intensity of the low-temperature peaks (2 and 3) grows with the dose, while the others remain constant (saturated). Nevertheless, an evident dose effect on the glow curves manifests in decreased peak3/peak2 ratio with increasing doses. The CW-IRSL curves exhibit similar patterns with an initial signal increase, followed by an exponential decay. Instead of the normal monotonic decays, these peak-shaped curves might be due to the charge capture competition between empty shallow traps and recombination centers. Both TL and IRSL intensities increase linearly with doses up to 6 kGy, and for higher doses, they become sub-linear with a saturation trend around 10 kGy. Another common feature of TL/IRSL response is its dose rate dependence, being more sensitive at higher dose rates. Despite being dose-rate dependent, the CaF2:Tm dosimeters might be suitable for EB processing dosimetry. However, for their use as routine dosimeters, relevant dosimetric characteristics, such as fading and response reproducibility, have to be investigated. Work in this direction is underway.

The understanding of the electron trapping and recombination processes is the key to successful applications of materials in ionizing radiation dosimetry, which unfortunately are not well known yet. In this work, the influence of the photoionization cross-section ( σ ) was investigated on the optically stimulated luminescence (OSL) response of the lithium fluoride (LiF) compound. The σ has been predicted through the expression proposed by Lima–Batista–Couto. In addition, OSL measurements were performed using the continuous-wave stimulation mode (CW-OSL), with 60 s of light stimulation. The samples were submitted to 10 Gy and 15 Gy of absorbed dose. Phonon dispersion and density calculations are presented by using the Density Functional Perturbation Theory. The results, obtained by a combination of different methodologies, show that the low sensitivity of LiF to the light stimulus ( λ = 470 nm) is due to the very low magnitude of σ at the used excitation wavelength. A comparison with Al 2 O 3 :C was also carried out, showing that the intensity and the pattern of the OSL curve decay are modified by the σ . These results play an important role in understanding the luminescent properties of this material, and they open a new opportunity to improve the light sensitivity of this detector.

A natural material called spectrolite, from Finland, was studied in this work. The purpose was to test it in gamma radiation beams to verify its performance as a high-dose detector. From this material, pellets were manufactured with two different concentrations of Teflon and spectrolite, and their responses were verified using two luminescent techniques: thermoluminescence (TL) and optically stimulated luminescence (OSL). The TL and OSL signals were evaluated by means of characterization tests of the material response, after exposure to a nominal absorbed dose interval of 5 Gy to 10 kGy. The results obtained, for both concentrations, showed a good performance of this material in beams of high-dose gamma radiation. Both techniques were utilized in order to investigate the properties of the spectrolite+Teflon samples for different applications.

MgB4O7 doped with lanthanides such as Dy3+ and Tm3+ are phosphors with very well established use in routine personal dosimetry. Certain characteristics, for example linearity in a broad dose range, low energy dependence, Z(eff)=8.5, high sensitivity and a relatively simple thermoluminescent (TL) emission curve make MgB4O7 a good material for thermoluminescent dosimetry. With the aim of analyzing other doping possibilitis, this paper presents some preliminary results on the use of Nd3+ as a dopant in the MgB4O7 matrix. Furthermore, we evaluated the effect of using two different lanthanides, Nd and Dy, in the host matrix. In the present work, the phosphors were produced through solid state synthesis and X-ray diffraction confirmed the success of the technique. The TL behavior of MgB4O7:Nd was assessed when irradiated with gamma (Co-60) and beta radiation, to determine the effect of the dopant concentration and the dose-response over a broad dose range. We also evaluated the dose-response of MgB4O7:Nd,Dy when irradiated with Co-60. The TL responses of the phosphors were compared with that of MgB4O7:Dy. These preliminary studies show that for the absorbed dose range studied, the sensitivity of MgB4O7:Nd,Dy was 3.8 and 28 times higher than that of MgB4O7:Dy and MgB4O7:Nd. The materials also presented linearity from 5 to 40 Gy. Above this value, the dose response curve exhibited sublinear behavior. These preliminary results will assist in developing a new temperature sensor based on a MgB4O7 dosimeter. (C) 2014 Elsevier B.V. All rights reserved.

This study has the purpose of assessing the radiation absorbed dose in organs/tissues and estimating the effective dose using five different models of Cone Beam Computed Tomography equipment using protocols with similar purpose. For this purpose, 26 thermoluminescent dosimeters were inserted in the position of the organs/tissues of a female anthropomorphic phantom. From the measurements the contribution of wT×HT in the organs and tissues the effective dose were calculated. The measurements have shown the effective dose values within the range 9.3–111.5 µSv. The effective dose values by field of view (FOV) size are within the following ranges: 9.3–51.2 µSv, 17.6–52.0 µSv, and 43.1–111.5 µSv for small/located, medium and large FOV respectively. Protocols with same purpose, carried out with different models of equipment, presented significant differences in the values of the equivalent and effective doses. From the point of view of radiological protection, it is not enough to have knowledge about the dimensions of the FOV and the purpose of the examination. It is necessary to assess the dose using the different models of the equipment and protocols available. In this context, this study provides useful information for this assessment.

Objective The objective of this study was to assess and compare protocols with a single field of view and multiple stitched field of view with a similar clinical purpose by means of effective dose value. Materials and methods Measurements of absorbed dose were performed with thermoluminescent dosemeters inserted in the position of organs/tissues of a female anthropomorphic phantom and from these values the effective dose was calculated, utilizing weighting factor tissue-ICRP 103 (2007). Results The results obtained in this study for effective dose are within the range of 43.1 µSv and 111.5 µSv for equipment using protocols with single FOV and in the range of 44.5 µSv and 236.2 µSv for equipments that using protocols with stitched field of view. Conclusions In terms of the value of effective dose, stitched FOV protocols do not have any advantage over the single field of view protocols. This results suggest the necessity for knowledge of the exposure parameters and effective dose values associated with each image protocol.

Al2O3:C is the best material example that presents OSL response and adequate dosimetric behaviour for OSL dosimetry. It was the first commercial material manufactured for use in personal monitoring based on an OSL reader system from Landauer. The purpose of this paper was to report the results of optical fading experiments for the nanoDot commercial OSL detectors (Al2O3:C), provided by Landauer Inc. Five groups of different experimental conditions were formed with all detectors, exposing them to fluorescent and semiconductor light sources and to sun light. The loss of OSL signal when the detectors are kept open, was verified, which was already expected, but a loss in the OSL signal even when the detectors are exposed to light and covered with the manufacturer plastic protection are also revealed. The results show also that the use of Mylar filters can delay the OSL fading of the detectors.

This work evaluates the dosimetric properties of crystals of CaSO 4 doped with unusual elements, such as europium (Eu) and silver (Ag), including their nanoparticle forms, after the incorporation of glass or Teflon and compares them with well-known thermoluminescent dosimeters (TLD). X-ray diffraction analyses showed that samples of doped CaSO 4 exhibit only a single phase corresponding to the crystal structure of anhydrite. Optical spectroscopy confirmed the presence of Eu 3+ in the crystal matrix and a luminescent gain due the presence of silver nanoparticles. The composites showed thermoluminescent emission glow curves, with a single peak centered at approximately 200 °C for pellets with Teflon and at 230 °C for pellets with glass. The dosimeters based on calcium sulfate doped with europium and silver nanoparticles provided the most intense thermoluminescent (TL) emission of the composites studied. In comparison with commercial TLD, such as LiF:Mg,Ti and CaSO 4 :Dy, the CaSO 4 :Eu,Ag(NP)+glass produced in this work presented similar low detection limits and higher sensitivity. The new methods for the preparation of dosimeters and the incorporation of glass are shown to be viable because all of the samples presented a linear, reproducible and first order kinetic TL emission.

The Calibration Laboratory (LCI) at the Instituto de Pesquisas Energeticas e Nucleares (IPEN) is going to establish a Bohm extrapolation chamber as a primary standard system for the dosimetry and calibration of beta radiation sources and detectors. This chamber was already tested in beta radiation beams with an aluminized Mylar entrance window, and now, it was characterized with an original Hostaphan entrance window. A comparison between the results of the extrapolation chamber with the two entrance windows was performed. The results showed that this extrapolation chamber presents the same effectiveness in beta radiation fields as a primary standard system with both entrance windows, showing that any one of them may be utilized.

A commercial ionization chamber, Bohm extrapolation chamber, PTW, model 23392, recommended for measurements in low energy X-rays and beta radiation fields, was tested in three different 90 Sr+ 90 Y beams to verify its performance as a primary standard system for the calibration and dosimetry of beta radiation sources and detectors. Characterization tests were performed, as determination of the chamber null depth using two methods (the results presented a difference of only 0.9%), transmission factors in tissue, in comparison with those of the certificate (the maximum difference was 2.1%), and absorbed dose rates of the 90 Sr+ 90 Y sources, in comparison with the values provided by the calibration certificates (the maximum difference was 4.90%). The results obtained confirmed that this extrapolation chamber presents a very good behavior in beta radiation fields as a primary standard system.

MgB4O7 is a promising matrix host for use in radiation dosimetry due to its low effective atomic number (Zeff = 8.2). The present work aims to investigate dosimetric and luminescent properties of the MgB4O7:Ce0,5%,Li0.5%, produced through solid-state synthesis, using the optically stimulated luminescence (OSL) technique. The first part of this work discusses the luminescent aspects of this phosphor, such as thermoluminescent emission spectra, photoluminescence emission, lifetime of emission centers and the effect of different lithium concentrations as co-dopant. In the second part, the basic OSL properties were evaluated, including dose-response curve, minimum detectable dose (MDD), step annealing, and best bleaching set-up for reuse of MgB4O7:Ce0,5%Li0.5% composites. The photoluminescence and thermoluminescence emission spectra of the composites present an emission peak at UV-VIS range centered around 370 nm, which is the most suitable for OSL dosimetry; this emission is related to Ce3+ electronic transitions and has a luminescence center lifetime of 0.003 ms. From the step-annealing analyses, it can be seen that the OSL emission is related to different depth trap centers in the band gap. The OSL dose-response curve is linear from 0.1 Gy to 100 Gy, with a MDD around 1 mGy. These properties make this material a strong candidate for different applications in radiation dosimetry field.

Topaz is a natural hard silicate mineral that has the potential to be used as a thermoluminescent dosimeter (TLD). It is difficult to manufacture chips of topaz and problematic to use its powder as TLDs. Topaz-glass composite (in the form of pellets) can be made easily and applied for radiation dosimetry. To produce pellets of topaz-glass composite in 2:1 wt (%), topaz powder was combined with commercial glass. The pellets with 6 mm diameter and 1 mm thickness were sintered in a furnace at 900°C for 1 h. The composite pellets were irradiated with x-ray and gamma photons and alpha and beta particles. The pellets yielded two peaks in the glow curve; Peak 1 at temperature range 150-160°C and Peak 2 at 250-260°C. The intensity of Peak 2 rose linearly with the increase in absorbed dose. The intensity of Peak 2 was comparable with peaks for photons and beta irradiation but relatively low for alpha exposure. The reproducibility of the intensity of Peak 2 was within 5-8%. Two months after irradiation of the pellets, the fading of the intensity of Peak 2 was found to be about 7%. The topaz-glass composite can be used effectively and efficiently for dosimetry of alpha, beta, and gamma radiation.

The present work describes the optically stimulated luminescence (OSL) of a tissue equivalent crystal, the magnesium tetraborate, doped with dysprosium or cerium and co-doped with lithium due to the lack of materials with characteristics suitable for several dosimetric applications. In the present work, MgB 4 O 7 :Dy,Li and MgB 4 O 7 :Ce,Li were characterized through their OSL and radioluminescence emissions. Our results indicate that MgB 4 O 7 :Ce,Li has a strong emission peaked at 420 nm that is connected to the Ce 3+ electronic transitions, while the emission of MgB 4 O 7 :Dy,Li has several peaks connected to the Dy 3+ transitions. The OSL decay curves from both materials are composed by two components: a slow one and a fast one. MgB 4 O 7 :Ce,Li is 10 times more sensitive than MgB 4 O 7 :Dy,Li, especially due to the wavelengths of the emission peaks. The dose response for both materials were sublinear from 0.2 Gy to 100 Gy, for MgB 4 O 7 :Ce,Li, and from 0.2 Gy to 40 Gy, for the MgB 4 O 7 :Dy,Li. The OSL signal from MgB 4 O 7 :Ce,Li showed good stability over 40 days (with a fading 4 O 7 :Dy,Li presented a complete fading of the signal after 40 days. These results suggest a clear potential of MgB 4 O7:Ce,Li for radiation dosimetry purposes using OSL technique.

The OSL characteristics of three different borate glass matrices containing magnesia (LMB), quicklime (LCB) or potassium carbonate (LKB) were examined. Five different formulations for each composition were produced using a melt-quenching method and analyzed in terms of both dose-response curves and OSL shape decay. The samples were irradiated using a 90Sr/90Y beta source with doses up to 30 Gy. Dose-response curves were plotted using the initial OSL intensity as the chosen parameter. The OSL analysis showed that LKB glasses are the most sensitive to beta irradiation. For the most sensitive LKB composition, the irradiation process was also done using a 60Co gamma source in a dose range from 200 to 800 Gy. In all cases, no saturation was observed. A fitting process using a three-term exponential function was performed for the most sensitive formulations of each composition, which suggested a similar behavior in the OSL decay.

Beta radiation emitters have been intensively used in therapeutic protocols, causing the increase of the radiation exposure of the workers. The thermoluminescent (TL) technique is largely utilized for the monitoring of beta radiation doses of workers. However, recently, the optical stimulated luminescence (OSL) technique has been shown useful for individual dosimetry and for beta radiation. In this study, the results obtained using Al2O3:C (OSL) and CaSO4:Dy (TL) detectors to measure beta absorbed doses inside a glove box at a radiopharmacy laboratory were compared.

A complete dosimetric characterization of two Amershan 90 Sr– 90 Y dermatologic applicators is described in this present work. The dosimetric parameters analyzed are: percentage depth dose curve, radial dose distribution, non-uniformity and asymmetry. Both applicators are planar–circular having 22.57 and 9.0 mm diameters. In the range where the percentage depth dose goes from 100% down to 20%, the measured percentage depth dose and that obtained by the Monte Carlo simulation have shown maximum discrepancy of 5.3% for both applicators. The radial dose distribution has been measured at several depths using a GafChromic ® EBT QD+ films and it was also calculated by simulation. The discrepancies found did not exceed 5.9% up to the depth of 1.8 mm, where the percentage depth dose drops to 40% of the maximum. The maximum non-uniformity and asymmetry are 1.7% and 5.3% for the first applicator and 22.7% and 25.9% for the second applicator, respectively. Both applicators meet the specification for the maximum non-uniformity established by the adopted protocol, whose limit is 30%. As for the asymmetry the limit is 20% and the second applicator exceeded it in about 5.9%.

90 Sr+ 90 Y clinical applicators are used for brachytherapy in Brazilian clinics even though they are not manufactured anymore. Such sources must be calibrated periodically, and one of the calibration methods in use is ionometry with extrapolation ionization chambers. 90 Sr+ 90 Y clinical applicators were calibrated using an extrapolation minichamber developed at the Calibration Laboratory at IPEN. The obtained results agree satisfactorily with the data provided in calibration certificates of the sources.

Devido à inexistência de um laboratório de padronização primária na América Latina, para calibração e dosimetria de fontes de radiação beta, neste trabalho uma câmara de extrapolação Böhm foi caracterizada e estabelecida como um sistema padrão primário no Laboratório de Calibração de Instrumentos (LCI) do IPEN. Como objetivo principal deste trabalho, a câmara de extrapolação Böhm foi caracterizada com relação à sua resposta em feixes padrões secundários de radiação beta de fontes de 90Sr+90Y, com duas janelas de entrada diferentes: Mylar aluminizado e Hostaphan grafitado, e com dois métodos de determinação de taxa de dose absorvida, para verificação do seu desempenho com cada material. Embora se trate do instrumento mais adequado para a calibração de detectores e fontes de radiação beta, a câmara de extrapolação deve ser utilizada apenas em laboratórios de calibração e não em programas de controle de qualidade, pois ela tem 7 kg e é de alto custo. Assim, é importante ter sistemas considerados padrões de trabalho e métodos alternativos para substituir a câmara de extrapolação em medições realizadas em campo, como em hospitais ou clínicas. Por este motivo, foram caracterizadas três câmaras de ionização de placas paralelas, com o objetivo de se verificar a possibilidade de seu uso como sistemas padrões de trabalho em programas de controle de qualidade, e também foram estudados materiais dosimétricos diferentes, em campos de radiação beta de 90Sr+90Y, utilizando-se os fenômenos da termoluminescência (TL) e da luminescência opticamente estimulada (LOE), como métodos alternativos na calibração de fontes de radiação beta. Inclui-se aqui o desenvolvimento de um sistema postal dosimétrico para a calibração de aplicadores clínicos de 90Sr+90Y. Os resultados obtidos com a câmara de extrapolação Böhm permitiram o seu estabelecimento como sistema padrão primário na calibração de fontes de 90Sr+90Y, pois a câmara com as duas janelas de entrada diferentes permitiram a determinação de taxas de dose absorvida no ar e no tecido, à profundidade nula e a 0,07 mm. A caracterização das três câmaras de ionização de placas paralelas mostraram que elas podem ser usadas em programas de controle de qualidade de fontes de radiação beta, pois suas respostas se apresentaram adequadas para esta finalidade. Os materiais dosimétricos testados com relação às suas respostas TL e LOE também se mostraram adequados para uso em campos de radiação beta, pois suas respostas foram satisfatórias. O sistema dosimétrico, utilizando dosímetros TL, foi testado em hospitais e, posteriormente, foi enviado na forma postal a um laboratório, contendo detectores TL e LOE, e o resultado da calibração dos aplicadores clínicos foi adequado. Due to the lack of a primary standard laboratory at the Latin America, for the calibration and dosimetry of beta radiation sources, it was decided to establish the Böhm extrapolation chamber at the Calibration Laboratory (LCI) at IPEN as a primary standard. As a main objective of this work, the Böhm extrapolation chamber was characterized in relation to its response in beta radiation secondary standard beams of 90Sr+90Y sources, using two different entrance windows: aluminized Mylar and graphited Hostaphan, and using two methods of determination of absorbed dose rates, to verify its performance in each material. Although it is the most adequate instrument for the calibration of beta radiation detectors and sources, the extrapolation chamber should only be used at calibration laboratories, and not in quality control programs, because it weights 7 kg, and it is expensive. Thus, it is important to have systems considered work standards and alternative methods to replace the extrapolation chamber in measurements performed outside laboratories, such as in hospitals and clinics. For this reason, three parallel plate ionization chambers were characterized, with the objective to verify the possibility of their use as work standard systems, and different dosimetric materials were also studied, in beta radiation fields, using the thermoluminescence (TL) and optically stimulated luminescence (OSL) phenomena, as alternative methods for the calibration of beta radiation sources. The development of a dosimetric postal system for the calibration of 90Sr+90Y clinical applicators was included in this objective. The results obtained using the Böhm extrapolation chamber allowed its establishment as a primary standard system at the calibration of 90Sr+90Y sources, because it was possible to determine the absorbed dose rates in air and in the tissue, at null depth and 0.07 mm using the chamber with the two different entrance windows. The characterization of the three parallel plate ionization chambers showed that they can be used in quality control programs of beta radiation sources, because their responses were adequate to this purpose. The dosimetric materials were tested in relation to their TL and OSL response, and their use showed also to be adequate in beta radiation fields. The dosimetric postal system, using TL dosimeters, was tested in hospitals, and afterwards, it was sent to a laboratory, by conventional mail, with TL and OSL detectors, and the results of the calibration of the clinical applicators was adequate.

90Sr+90Y sources used in betatherapy procedures are still used in Brazilian radiotherapy clinics and hospitals, although these sources are not commercialized anymore. These sources have to be periodically calibrated; a dosimetric system with thin CaSO4:Dy pellets was developed for this purpose. The objective of this work was to apply the dosimetric system in some clinics and hospitals of Sao Paulo city, as training for the users to calibrate the sources and for a future application of the dosimetric system as a postal system. The results obtained were satisfactory, and they presented an acceptable difference between the results obtained in this work and the values provided in the calibration certificates of the beta sources, when compared with the results obtained in a previous work.

Clinical applicators are used in brachytherapy to treat superficial lesions of skin and eye. They should be periodically calibrated according to quality control programs and international recommendations. Thin CaSO4:Dy thermoluminescent dosimeters were used to calibrate various applicators with a dermatological applicator as a reference. The obtained absorbed dose rates were compared with those quoted in their calibration certificates. Depth-dose curves were constructed for all the applicators. A mail dosimetry system was developed for calibration of clinical applicators.

Two secondary standard systems of beta radiation were used to calibrate a PTW extrapolation chamber Model 23391. Three 90Sr+90Y sources of different activities were used in this calibration procedure. Medium-term stability of the response of the chamber was also studied. The calibration was performed with and without field-flattening filters. The relative standard deviation of the obtained calibration factors was 8.3% for the aluminum collecting electrode and 4.1% for the graphite collecting electrode.

The kinetics of DPKSH (di-2-pyridylketone salicyloylhydrazone) adsorption onto silica gel has been investigated at (25+/-1) degrees C and pH 1 and 4.7. The kinetics of adsorption of DPKSH is discussed using three kinetic models, the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. The adsorption of DPKSH, at pH 1 and 4.7, onto silica gel proceeds according to the pseudo-second-order model and the correlation coefficients were very close to 1. The intraparticle diffusion of DPKSH molecules within the silica gel particles was identified as the rate-limiting step. The parameters of the pseudo-second-order model are q(max,calc)=1.02 x 10(-4) and 1.5 x 10(-4) g DPKSH/g silica; k(2)=3.01 x 10(4) and 9.67 x 10(4) h(-1)g silica/g DPKSH, respectively, for pH 1 and 4.7.

The adsorption of DPKSH onto silica gel was investigated, at 25±1 °C and pH 1, 4.7 and 12. For the same DPKSH concentration interval, the minimum required time of contact for adsorption maximum at pH 4.7 was smaller than at pH 1 and the maximum amount of DPKSH adsorbed per gram of silica at pH 1 is smaller than at pH 4.7. At pH 12 the DPKSH adsorption onto silica gel was not significant. The adsorption data followed Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms. The maximum amount of solute adsorbed ( m ads max ) and the adsorption constant, K L , were derived from Langmuir isotherm. The Freundlich constants 1/ n and K F related, respectively, to the energetic heterogeneity of adsorption sites and an empirical constant were evaluated. The mean sorption free energy ( E ) of DPKSH adsorption onto silica gel was calculated from D–R isotherm indicating a physical adsorption mode. Finally, conductimetric titrations showed the silica particle basicity and acidity as 0.002 and 0.3 mmol g −1 , respectively.