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Several doped materials are being studied for dosimetric application, but when some dopant is used with the aim to increase the sensibility, some of these can increases the hygroscopic properties of the sample, which is not suitable for dosimetry. If the material absorbs water during the storage period, it may change their luminescent properties, reducing or completely erasing the signal produced by ionizing radiation. Unlike thermoluminescence, OSL measurements do not need high temperature to read the signal, however, sometimes some assisted temperature or preheating is required. In this work is presented a new low-cost option for performing OSL measurements, even with preheating up to 160 oC. It was tested a transparent enamel for sticking the luminescent powdered samples on aluminum disc and also covering the samples with the enamel avoiding in this way the absorption of humidity from the environment, even the signal decreases, the reproducibility and fading do not depend of their hygroscopic properties.

The main objective of this work was to study a new technique for the sintering of marine sodium chloride (NaCl) crystals obtained from seawater. In order to obtain an efficient luminescence, a better control in the amount of sample to be used, a better distribution of crystals in every aliquot and verify its applicability as a dosimeter, with dosimetric requirements testing. The common salt is a material that have been already studied in the area of ​​dosimetry, because it has a high sensitivity when exposed to ionizing radiation, therefore can thus be used in luminescent dosimetry. With the purpose of synthesizing the marine crystals with low cost and easy fabrication, we pulverized a concentrated sea salt solution, on 1 cm recycled aluminum discs placed on an oven at 70aºC, with this process we obtained homogeneous aliquots. The salt has a hygroscopic property, we waterproof it using a commercial enamel, in order to inhibit this property. For analyzing the crystalline structure formed with this new technique, we used X-ray diffraction (XRD). For OSL measurements, we use the RISØ TL/OSL reader by blue light stimulation (470 nm) coupled with a beta source, at first, the heat treatment was carried out on the aliquots at 400 ºC, at different times to observe the effect on the OSL signal, irradiated with a dose of 162 mGy, with preheating at 160 °C for 1 s, afterwards we perform a measurement with an assisted temperature of 110 °C for 40 s with blue light. Lastly analyze the dosimetric requirement tests.

In this work, synthetic polycrystals of calcium silicate (CaSiO3) are prepared. The objective is to expand the current knowledge of low cost and easy production thermoluminescent detectors for doses of gamma radiation, thermal neutrons and accelerated ions beam, as well as, the possible applications in nuclear medicine or monitoring actual radiotherapy treatment. For that reason, calcium silicate doped with Boron, Cadmium, Dysprosium, and Europium were produced keeping in mind gamma and neutron detection. For the production of synthetic calcium silicate polycrystals, the devitrification method was used. In this process, two polytypes of undoped CaSiO3 were identified, alpha- and beta- polytypes. alpha-CaSiO3 is a very sensitive gamma radiation detector with main prominent thermoluminescence (TL) peak occurring at about 250-270 ºC and a low-temperature peak at 120 ºC, using 4 ºC/s heating rate. The TL response of alpha-CaSiO3 is linear for dose < 10 Gy and then has a supralinear behavior up to about 7 kGy and saturating beyond. The TL behavior changes very little by doping with B, Cd, and Dy while Eu doping brings changes. Additionally, beta-CaSiO3 polycrystal exhibits three TL peaks at 124, 250, and 306 ºC. All peaks at 124, 250 and 306 ºC for beta-CaSiO3 have a linear behavior in the dose range from cGy to 1 Gy. After that, the TL responses are supralinear up to about 3 kGy and then they are saturated. Synthetic polycrystals of CaSiO3 (doped or not) were also irradiated with neutrons from a nuclear research reactor. This thermal neutron reacts with Ca, Si and O through (n, gamma) process, all or part of the gamma emitted in this reaction is absorbed by the sample and is responsible for the induction of TL. The total energy emitted by the (n, gamma) reaction on the sample of CaSiO3 was calculated analytically. Furthermore, Monte Carlo simulations using the MCNP5 radiation transport code was carried out at the Nuclear Engineering Center in IPEN to calculate the deposited dose on CaSiO3 by the neutron interaction finding doses ranging from 42 Gy to 21 kGy. CaSiO3 TL glow curves, after radiation exposure from the reactor, display the main prominent TL peak around 234 - 259 ºC. Electron paramagnetic resonance (EPR) spectroscopy was used to study the defect centers induced in the polycrystals of alpha- and beta-CaSiO3 by gamma irradiation and to identify the centers responsible for the TL process. For beta-CaSiO3, three defect centers contribute to the observed spectrum at room temperature. Center I with principal g-values = 2.0135, 2.0094 and 2.0038 is attributed to O- ion and the center appears to be the recombination center for 124, 147, and 306 ºC TL peaks. Center II exhibiting an isotropic g-value of 2.00025 is identified as an F+-center. F+-center is also observed to be a recombination center for several TL peaks. Center III is assigned to a Ti3+ center displaying an orthorhombic g-tensor with principal values g1 = 1.9830, g2 = 1.9741 and g3 = 1.9046. This center is associated with 124 ºC and 147 ºC TL peaks. TL emission spectrum of beta-CaSiO3 shows two emission bands at 370 and 520 nm. In addition, pellets of CaSiO3 were irradiated at 160 MeV proton beam and at 290 MeV/n carbon ion beam from an upper synchrotron of HIMAC (Heavy Ion Medical Accelerator in Chiba, Japan) at NIRS (National Institute of Radiological Sciences). These pellets of calcium silicate presented a prominent TL peak at 120 ºC and at 270 ºC when irradiated with proton and carbon ion beam. The dose read out in Harshaw TL reader presented a good agreement with doses found using ion chamber in the case of proton beams and slightly less in the case of carbon beam due to the linear energy transference (LET). Neste trabalho, policristais sintéticos de silicato de cálcio (CaSiO3) foram preparados. O objetivo é ampliar o conhecimento atual dos detectores termoluminescentes de baixo custo e fácil produção para doses de radiação gama, nêutrons térmicos e feixe de íons acelerados e suas possíveis aplicações em medicina nuclear e radioterapia. Por essa razão o silicato de cálcio dopado com boro, cádmio, disprósio e európio foram produzidos tendo em mente a detecção de radiação gama e de nêutrons. Para a produção de policristais de silicato de cálcio sintético, foi utilizado o método de devitrificação. Nesse processo, foram identificados dois polítipos de CaSiO3 não dopados, alpha- e beta- CaSiO3. O alpha-CaSiO3 é um detector de radiação gama muito sensível, com o pico principal de termoluminescência (TL) ocorrendo em 250-270 ºC e um pico de baixa temperatura a 120 ºC utilizando uma taxa de aquecimento de 4 ºC/s. A resposta TL do alpha-CaSiO3 é linear para a dose < 10 Gy e, em seguida, apresenta um comportamento supralinear até 7 kGy, depois disso entra em saturação. O comportamento de TL muda muito pouco dopando com B, Cd e Dy, enquanto o dopado com o Eu traz mudanças. Além disso, o polycrystal beta-CaSiO3 exibe três picos TL em 124, 250 e 306 ºC. Todos estes picos têm um comportamento linear no intervalo de doses de cGy a 1 Gy. Depois disso, as respostas de TL são supralineares até cerca de 3 kGy e depois são saturadas. Policristais sintéticos de CaSiO3 (aqueles dopados e não dopados) foram também irradiados com nêutrons de um reator de pesquisa nuclear. Os nêutrons térmicos reagem com o Ca, Si e O através do processo (n, gamma), toda ou parte da radiação gama emitida nessa reação é absorvida pela amostra e é responsável pela indução de TL. A energia total emitida pela reação (n, gamma) na amostra de CaSiO3 não dopado foi calculada analiticamente. Além disso, simulações de Monte Carlo usando o código de transporte de radiação MCNP5 foram realizadas no Centro de Engenharia Nuclear no IPEN para calcular a dose depositada na amostra de CaSiO3 pela interação com os nêutrons do reator, encontrando doses variando de 42 Gy até 21 kGy. As curvas de TL do CaSiO3, após a exposição à radiação do reator, exibem o principal pico proeminente de TL em torno de 234 - 259 ºC. A Ressonância Paramagnética Eletrônica (RPE) foi usada para estudar os centros de defeitos induzidos nos policristais de alpha- e beta-CaSiO3 por irradiação gama e para identificar os centros responsáveis pelo processo de TL. Para beta-CaSiO3, três centros de defeitos contribuem para o espectro observado à temperatura ambiente. O centro I com os principais valores g = 2.0135, 2.0094 e 2.0038 é atribuído ao íon O- e o centro parece ser o centro de recombinação para os picos de TL em 124, 147, e 306 ºC. O Centro II que exibe um valor g isotrópico de 2.00025 é identificado como um centro F+. Também é observado que o centro F+ é um centro de recombinação para vários picos de TL. O centro III é atribuído a um centro de Ti3+ exibindo um tensor g ortorrômbico com valores principais de g1 = 1.9830, g2 = 1.9741 e g3 = 1.9046. Este centro está associado aos picos de TL em 124 e 147 ºC. O espectro de emissão TL de beta-CaSiO3 mostra duas bandas de emissão em 370 e 520 nm. Além disso, pastilhas de CaSiO3 foram irradiadas com um feixe de prótons de 160 MeV e com um feixe de íons de carbono de 290 MeV/n no sincrotron HIMAC no Instituto Nacional de Ciências Radiológicas (NIRS) em Chiba, Japão. As pastilhas de silicato de cálcio apresentaram um pico de TL em 120 ºC e um pico proeminente em 270 ºC quando irradiados com próton e feixe de íons de carbono. A dose lida no leitor Harshaw TL apresentou boa concordância com as doses encontradas na câmara de ionização no caso de feixes de prótons e um pouco menos no caso de feixes de carbono devido à dependência da transferência linear de energia (LET).