PATRICIA DE LARA ANTONIO

PATRICIA DE LARA ANTONIO

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Investigation of dosimetric properties of CaSO4:Mn phosphor prepared using slow evaporation route
2023 - SILVA, ANDERSON M.B.; RODRIGUES, DANIEL S.; ANTONIO, PATRICIA L.; JUNOT, DANILO O.; CALDAS, LINDA V.E.; SOUZA, DIVANIZIA N.
The objective of this work was to investigate the luminescent properties of CaSO4:Mn synthesized by slow evaporation route. The crystalline structure, morphology, thermal and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), photoluminescence (PL) and thermogravimetric analysis (TGA). Moreover, using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques, the dosimetric properties of the phosphors, such as emission spectra, glow curve reproducibility, dose-response linearity, fading of the luminescent signal, variation of the TL intensity with the heating rate, OSL decay curves, correlation between TL and OSL emissions and minimum detectable dose (MDD) were comprehensively investigated. For dosimetric analyses, the samples were irradiated with doses from 169 mGy to 10 Gy. The emission band fits with the characteristic line of the Mn2+ emission features, ascribed to 6 A1→4 T1 transition. CaSO4:Mn pellets present a TL glow curve with a single typical peak centered around 494 nm, an OSL decay curve with predominance of a fast decay component, and a MDD on the order of mGy. The luminescent signals showed to be linear and reproducible in the studied dose range. The trapping centers located between 0.83 eV and 1.07 eV were revealed for different heating rates in the TL study. The high TL sensitivity of CaSO4:Mn was proven when comparing with commercially available dosimeters. The luminescent signals exhibit a smaller fading than described in the literature for CaSO4:Mn produced by other methods.
Investigation of dosimetric properties of CaSO4:Mn phosphor prepared using slow evaporation route
2022 - SILVA, ANDERSON M.B.; RODRIGUES, DANIEL S.; ANTONIO, PATRICIA L.; JUNOT, DANILO O.; CALDAS, LINDA V.E.; SOUZA, DIVANIZIA N.
The objective of this work was to investigate the luminescent properties of CaSO4:Mn synthesized by slow evaporation route. The crystalline structure, morphology, thermal and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), photoluminescence (PL) and thermogravimetric analysis (TGA). Moreover, using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques, the dosimetric properties of the phosphors, such as emission spectra, glow curve reproducibility, dose-response linearity, fading of the luminescent signal, variation of the TL intensity with the heating rate, OSL decay curves, correlation between TL and OSL emissions and minimum detectable dose (MDD) were comprehensively investigated. For dosimetric analyses, the samples were irradiated with doses from 169 mGy to 10 Gy. The emission band fits with the characteristic line of the Mn2+ emission features, ascribed to 6A1→4T1 transition. CaSO4:Mn pellets present a TL glow curve with a single typical peak centered around 494 nm, an OSL decay curve with predominance of a fast decay component, and a MDD on the order of hundreds of mGy. The luminescent signals showed to be linear and reproducible in the studied dose range. The trapping centers located between 0.83 eV and 1.07 eV were revealed for different heating rates in the TL study. The high TL sensitivity of CaSO4:Mn was proven when comparing with commercially available dosimeters. The luminescent signals exhibit a smaller fading than described in the literature for CaSO4:Mn produced by other methods.
Plastic bottle caps as radiation detectors for high gamma radiation doses
2021 - OLIVEIRA, L.N.; NASCIMENTO, E.O.; ANTONIO, P.L.; CALDAS, L.V.E.
Introduction: Plastic detectors represent an important role in radiation dosimetry [1]. They have been used in a variety of applications, such as portal monitors, and for solar, cosmic, UV, thermal and gamma radiations. Dosimetric evaluation is indicated for material characterization seeking to identify possible applications; proper preprocessing techniques are critical features of this process. This work aimed to determine the linearity response of plastic samples exposed to gamma radiation, using the Fourier Transform Infrared (FTIR) measurements technique. Material and method: Plastic bottle caps were used as sample detectors. They were composed of a hollow cylindrical shape with a 14 mm radius, 0.05 mm thickness, 28 mm height and 3.1 g mass, and they were made of polyethylene (F217). These samples were irradiated in triplicates, with absorbed doses of 0.01 kGy, 0.05 kGy, 0.10 kGy, 0.25 kGy, 0.50 kGy, 1.0 kGy, 5.0 kGy and 10.0 kGy using a 60Co Gamma Cell-220 system (dose rate of 1.089 kGy/h at the Radiation Technology Center of IPEN). Afterwards, each sample absorbance spectrum was acquired on a Fourier Transform Infrared (FTIR) Spectrometer (Frontier/Perkin Elmer) from 400 cm-1 to 4000 cm-1, with 1 cm-1 spectral resolution. The preprocessing was performed in the raw data composed by the broadband source interferogram with a +/- 0.04 cm-1 (2σ) precision for each absorbed dose profile. Subsequently, applying the Fast Fourier Transform (FFT), FTIR was generated. Then, the derivates in the frequency (wavenumber) space were calculated seeking to assess high-order effects. The complex FFT coefficients were explicitly obtained for peak regions, which provided localized information regarding the spectrum approximate shape from the FTIR evaluations to obtain linearity estimatives. The resulting FTIR spectra for each peak was to numerical differentiation at the 1st, 2nd and 3 rd orders (D1, D2 and D3, respectively). The derivates obtained were useful in achieving the spectra shapes and the linearity of response. Results: Figure 1 presents the results after the application of the PCR method: Predicted absorbed dose versus absorbed dose, for: I, II and III regions (from spectrum). The results of the PCR method are the maximum values for linearity, 1.000 for all regions. This result demonstrates that the PCR method is more robust than the linear method, and the preprocessing via PCA provides the information pertinent to the evaluated plastic detector. Conclusion: The results on linearity of response show that plastic bottle caps represent potential radiation detectors for high gamma radiation doses.
Evaluation of high-linearity bone radiation detectors exposed to gamma-rays via FTIR measurements
2021 - OLIVEIRA, LUCAS N. de; NASCIMENTO, ERIBERTO O. do; MORAIS JUNIOR, PEDRO de A.; ANTONIO, PATRICIA de L.; CALDAS, LINDA V.E.
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.
Evaluation of the thermally and optically stimulated response of an Italian Obsidian irradiated in 60Co beams
2019 - ANTONIO, PATRICIA L.; OLIVEIRA, RAQUEL A.P.; KHOURY, HELEN J.; CALDAS, LINDA V.E.
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.
Characterization of lithium diborate, sodium diborate and commercial sodalime glass exposed to gamma radiation via linearity analyses
2019 - OLIVEIRA, LUCAS N. de; NASCIMENTO, ERIBERTO O. do; ANDREETA, MARCELLO R.B.; ANTONIO, PATRICIA L.; CALDAS, LINDA V.E.
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.
Applying the TSEE technique to Spectrolite and Opal pellets irradiated with high doses of gamma radiation
2017 - ANTONIO, PATRICIA L.; CALDAS, LINDA V.E.
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 Co-60 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 dosimettic chatacteristics verified in previous works after exposure to high doses of a Co-60 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.
Characterization of lithium diborate, sodium diborate and commercial glass exposed to gamma radiation via linearity analyses
2017 - OLIVEIRA, LUCAS N. de; NASCIMENTO, ERIBERTO O. do; ANTONIO, PATRICIA L.; ANDREETA, MARCELLO R.B.; CALDAS, LINDA V.E.
The linearity characteristic in radiation dosimetry presents a growing interest in medical physics. In this work, the 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 then they were evaluated with the UV-Vis technique. The linearity analyses were applied through four methodologies, which the objetive to find linear regions in their response. The results show that all four analyses indicate linear regions for the studied radiation detectors. The samples with higher linearity range, in descending order, were lithium diborate, sodium diborate and commercial glass. In conclusion, the materials may be promising in dosimetry for intermediate and high doses of radiation.
Evaluation of the thermally and optically stimulated response of as Italian Silicate irradiated in 60Co beams
2017 - ANTONIO, PATRICIA L.; OLIVEIRA, RAQUEL A.P.; KHOURY, HELEN J.; CALDAS, LINDA V.E.
In this work, pellets were manufactured in a proportion of 2:1 of powdered samples of Obsidian black:Teflon (dimensions of 6.0 mm in diameter and 0.8 mm in thickness). The pellets were irradiated using a Gamma-Cell 220 System, model 200, Atomic Energy of Canada LTD (60Co). The TL and OSL responses were analyzed using the reader system composed by the TL/OSL meter Risø, model TL/OSL-DA-20, and the TSEE response was obtained using a homemade reader system developed at the Calibration Laboratory, at IPEN. After the TL, OSL and TSEE measurements, the pellets were thermally treated at 400 °C during 1 h, for reutilization. The physical and chemical characterization of powdered Obsidian was also investigated using the X-ray diffraction, XRD (using a diffractometer Equinox 1000, Inel), scanning electron microscope, SEM, and energy dispersive X-ray spectroscopy, EDX (the last two using a scanning electron microscope with an energy dispersive X-ray microanalyser Vega 3 SEM, Tescon) techniques. The results proved, basically, that Obsidian is a natural glass and composed mainly of silica (82.4%). The TL glow curve revealed a dosimetric peak at the temperature of 220 °C, and the TSEE emission curve showed a peak at about 300 °C. The results obtained in the reproducibility of response test were: 2.9% (TL), 3.0% (TSEE) and 3.1% (OSL). The lower detection limits were: 48.1 Gy (TL), 18.1 Gy (TSEE) and 79.3 Gy (OSL). The dose-response curves showed, in the case of TL, a supralinearity behavior between only 500 Gy and 2 kGy with a following saturation of the response. For the TSEE response, a sublinearity was seen with a following saturation of the response. For the OSL technique, linearity could be observed in the interval from 500 Gy to 2 kGy and then a tendency to saturation.
Applying the TSEE technique to Spectrolite and Opal pellets irradiated with high doses of gamma radiation
2016 - ANTONIO, PATRICIA; CALDAS, LINDA