JOSEMARY ANGELICA CORREA GONCALVES

JOSEMARY ANGELICA CORREA GONCALVES

(Fonte: Lattes)

Resumo

Possui graduação em Física pela Pontifícia Universidade Católica de São Paulo (1987), mestrado em Técnicas e Aplicações Nucleares pelo Instituto de Pesquisas Energéticas e Nucleares (1990), doutorado em Técnicas e Aplicações Nucleares pelo Instituto de Pesquisas Energéticas e Nucleares (1993) e Pós-Doutorado de Curta duração na Universidade de Coimbra com bolsa FAPESP (1997). Foi professora da Pontifícia Universidade Católica de São Paulo entre 1996-2020. Atualmente é pesquisadora titular do Instituto de Pesquisas Energéticas e Nucleares. Tem experiência na área de Engenharia Nuclear, com ênfase em Instrumentação para Medida e Controle de Radiação, atuando principalmente nos seguintes temas: detectores semicondutores de Si, espectrometria e dosimetria de partículas carregadas e radiação eletromagnética, detectores gasosos de catodo resistivo e parâmetros de transporte de elétrons em gases. (Texto extraído do Currículo Lattes em 12 nov. 2021)

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Dose rate mapping of an industrial 60Co irradiator using an online photodiode-based dosimetry system
2022 - GONCALVES, JOSEMARY A.C.; MANGIAROTTI, ALESSIO; BUENO, CARMEN C.
In this work, a housemade dosimetry system based on a thin photodiode is applied for online mapping of dose rates, between 2.6 and 37.7 Gy/h, delivered by a Panoramic 60Co industrial facility. The operational principle of the dosimeter relies on the real-time acquisition of the induced currents from the irradiated diode operating in the short-circuit mode without externally applied voltage. The radial mapping of the radiation field is performed by rotating the diode around the central axis of the panoramic irradiator, covering 360° at intervals of 18°. The results are benchmarked with alanine dosimeters, Monte Carlo simulations, and reference dose rates retrieved from the facility calibration. The overall consistency of the whole data complies with the maximum response variation (8%, k = 2) recommended by the International Standard Protocols for routine dosimeters in radiation processing dosimetry. It reveals that the photodiode-dosimetry system is a reliable alternative to map dose rate fields and the effectiveness of Monte Carlo simulations as a predictive tool for dose rate measurements in an irradiator.
Performance characterization of dosimeters based on radiation-hard silicon diodes in gamma radiation processing
2022 - BUENO, C.C.; CAMARGO, F.; GONCALVES, J.A.C.; PASCOALINO, K.; MANGIAROTTI, A.; TUOMINEN, E.; HARKONEN, J.
The dosimetric response of silicon diodes produced with distinct engineering technologies, Magnetic Czochralski (MCz), and standard Float Zone (Fz), has been investigated, aiming at their use for online dosimeters in gamma radiation processing applications. The p+-n-n+ junction diodes, 300 µm thick with an active area of 25 mm2, are operated as online radiation dosimeters in the short-circuit current mode. In this case, the key dosimetric quantity is the dose rate, which is correlated with the output current from the diode subjected to radiation. Thus, the dose is obtained offline by the integration of the corresponding current signal. The irradiations are performed with an industrial Gammacell 60Co facility at 2.3–2.44 kGy/h covering doses up to 275 kGy. Under continuous irradiation, both diodes delivered current signals whose intensities decreased with accumulated doses. Mitigation of this decay has been accomplished by pre-irradiating the devices to 700 kGy. Polynomial functions best represent the dose responses for either pristine or preirradiated diodes. The relevant dosimetric parameters as response stability, charge sensitivity, and repeatability of current signals (<5%) reveal the better performance of the MCz diode. It is important to note that the whole dataset fully complies with the international standard protocols for routine dosimeters in radiation processing dosimetry. Regarding radiation damage, which in unbiased diodes manifests primarily in the decay of current sensitivity, the results also showed greater tolerance of the MCz diode. Based on these studies, large availability, and better cost-effectiveness, it is possible to endorse the potential use of MCz devices as online routine dosimeters in radiation processing applications. However, the data reproducibility with the accumulated dose, the dose lifespan, and the effect of the irradiation conditions (e.g., temperature, relative humidity, and dose fractionating) remain to be investigated. Works in this direction are currently in progress.
Evaluation of TL and OSL responses of CaF2:Tm for electron beam processing dosimetry
2021 - ASFORA, VIVIANE K.; ANTONIO, PATRICIA L.; GONCALVES, JOSEMARY A.C.; BUENO, CARMEN C.; BARROS, VINICIUS S.M. de; OLIVEIRA, CHARLES N.P.; CALDAS, LINDA V.E.; KHOURY, HELEN J.
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.
A low-cost small-size commercial PIN photodiode
2021 - MANGIAROTTI, A.; PETRI, A.R.; MALAFRONTE, A.A.; GONCALVES, J.A.C.; BARROS, S.F.; BUENO, C.C.; FERNANDEZ-VAREA, J.M.; MAIDANA, N.L.; MARTINS, M.N.; VANIN, V.R.
Commercial PIN photodiodes, repurposed as particle detectors, have received a lot of attention along the past decades because they can offer a low-cost solution suitable for several applications. The BPX-65 photodiode has been chosen because of its interesting features for measuring electrons in a harsh radiation environment close to the beam of an accelerator. Its electrical characterisation and its application to photon spectrometry have been presented in the companion paper I. Here, its response function (RF) to electrons is investigated using the beam from an electron accelerator with a small energy spread. The empirical expressions for the RF available in the literature have been improved, simplified, and combined to obtain a final form with 7 free parameters: 4 non-linear and 3 linear. A special fitting procedure, which takes advantage of the presence of the linear parameters, is described. The behaviour of these parameters with beam energy and bias is investigated to uncover the physical origin of the three components included in the proposed RF. The interpretation of the features of the spectra is confirmed by Monte Carlo simulations carried out employing the general-purpose PENELOPE/penEasy package. To take into account the charge-collection properties of the device, a simple model has been implemented and is compared to data. It has then been possible to estimate the thickness of the partially dead layer from the experiment.
A low-cost small-size commercial PIN photodiode
2021 - MALAFRONTE, A.A.; PETRI, A.R.; GONCALVES, J.A.C.; BARROS, S.F.; BUENO, C.C.; MAIDANA, N.L.; MANGIAROTTI, A.; MARTINS, M.N.; QUIVY, A.A.; VANIN, V.R.
Silicon PIN (p-type-intrinsic-n-type) photodiodes are well suited as particle detectors. Here the interest is on a low-cost solution by repurposing a commercial device meant to be used as a light sensor. The intended application is to measure the energy spectra of electrons scattered by thin metallic foils covering small angles close to the beam of the accelerator. The main requirements for a suitable device are: 1) a low-cost solution to allow frequent replacements; 2) a small size to avoid as much as possible an unused area that contributes with unnecessary capacitance; 3) a good energy resolution; and 4) an easy repurposing as a charged-particle detector. The photodiode type BPX 65 manufactured by Osram® fulfils well these requirements. Four samples of these commercial devices have been electrically characterised with respect to reverse current and depleted-region capacitance. At the selected working point of 18 V, comfortably below the maximum rating of 20 V recommended by the manufacturer for continuous operation, the total thickness of the depleted and intrinsic regions is estimated to be (60 ± 3) μm. For the four samples considered, the measured reverse currents for a reverse bias of 18 V are around 0.1 nA, well below the typical value specified by the manufacturer (1 nA). To evaluate the performance of the device as a detector, energy spectra have been acquired for γ-rays with energies from 10 to 140 keV using 241Am, 133Ba, and 57Co radioactive sources. The resolution of the BPX 65 encountered with the γ-rays emitted by 241Am at 59.5-keV is 2.5 keV (FWHM - Full Width at Half Maximum), which is close to the value obtained with a pulser, showing that its main limitation is the electronic chain employed in the setup. The response function to monoenergetic electrons in the same energy range is studied in the companion paper.
Count rate effect on the response of a low-cost PIN diode for electron spectrometry
2019 - PETRI, ANNA R.; BARROS, SUELEN F.; GONCALVES, JOSEMARY A.C.; BUENO, CARMEN C.; MAIDANA, NORA; MARTINS, MARCOS N.; VANIN, VITO R.
The response of a low-cost Si photodiode model BPX 65 for low-energy electron spectrometry is investigated envisaging its use in measurements of electron multiple elastic scattering. The electron beam with energy between 10-100 keV is delivered by the gun of the Racetrack Microtron at Instituto de Física, Universidade de São Paulo, with an energy dispersion less than 0.5 keV. The energy resolution achieved was less than 3.5 keV, limited mainly by noise from the electronic acquisition chain. For count rates between 20 and 5500 counts/s, the variation on the centroid of electron peak was smaller than 0.4% throughout the energy range. Therefore, the BPX 65 is suitable for electron spectrometry.
Effect of the ohmic drop in a RPC-like chamber for measurements of electron transport parameters
2019 - PETRI, A.R.; MANGIAROTTI, A.; GONCALVES, J.A.C.; BUENO, C.C.
The main advantage of Resistive Plate Chambers (RPCs), applied, for instance, in High-Energy Experiments and Positron Emission Tomography (PET), is that it is spark-protected due to the presence of, at least, one high-resistive electrode. However, the ohmic drop across the latter can affect the charge multiplication significantly. In this work, we investigate this effect in a RPC-like chamber. The counter was filled with nitrogen at atmospheric pressure and the primary ionization was produced by the incidence of nitrogen pulsed laser beam on an aluminum cathode. The illumination area of the cathode was measured using a foil of millimetric paper overlaid on this electrode. In this way, the resistance of the glass anode could be estimated using the known resistivity of the glass (ρ=2×1012 Ω.cm). Therefore, the voltage drop across the dielectric was calculated by the product of the current across the gas gap and the anode resistance. In order to mitigate the effect of the resistive electrode, the laser beam intensity was limited by interposing metallic meshes between the laser and the chamber window. The dependence of the ohmic drop from the applied voltage was analyzed. The results obtained shown that, without the meshes, the ohmic drop corresponds up to 7% of the applied voltage, preventing the detection system to reach values of density-normalized electric fields in the gas gap (Eeff/N) higher than 166 Td. By minimizing the laser beam intensity and, consequently, the primary ionization, the ohmic drop represented only 0.2% of the applied voltage, extending the Eeff /N range up to 175 Td.
Effect of the ohmic drop in a RPC-like chamber for measurements of electron transport parameters
2017 - PETRI, ANNA R.; MANGIAROTTI, ALESSIO; GONÇALVES, JOSEMARY A.C.; BUENO, CARMEN C.
The main advantage of Resistive Plate Chambers (RPCs), applied, for instance, in High-Energy Experiments and Positron Emission Tomography (PET), is that it is spark-protected due to the presence of, at least, one highresistive electrode. However, the ohmic drop across the latter can affect the charge multiplication significantly. In this work, we investigate this effect in a RPC-like chamber. The counter was filled with nitrogen at atmospheric pressure and the primary ionization was produced by the incidence of nitrogen pulsed laser beam on an aluminum cathode. The illumination area of the cathode was measured using a foil of millimetric paper overlaid on this electrode. In this way, the resistance of the glass anode could be estimated using the known resistivity of the glass (ρ=2×1012 Ω.cm). Therefore, the voltage drop across the dielectric was calculated by the product of the current across the gas gap and the anode resistance. In order to mitigate the effect of the resistive electrode, the laser beam intensity was limited by interposing metallic meshes between the laser and the chamber window. The dependence of the ohmic drop from the applied voltage was analyzed. The results obtained shown that, without the meshes, the ohmic drop corresponds up to 7% of the applied voltage, preventing the detection system to reach values of density-normalized electric fields in the gas gap (Eeff/N) higher than 166 Td. By minimizing the laser beam intensity and, consequently, the primary ionization, the ohmic drop represented only 0.2% of the applied voltage, extending the Eeff /N range up to 175 Td.
Measurement of the first Townsend ionization coefficient in a methane-based tissue-equivalent gas
2017 - PETRI, A.R.; GONÇALVES, J.A.C.; MANGIAROTTI, A.; BOTELHO, S.; BUENO, C.C.
Tissue-equivalent gases (TEGs), often made of a hydrocarbon, nitrogen, and carbon dioxide, have been employed in microdosimetry for decades. However, data on the first Townsend ionization coefficient (α) in such mixtures are scarce, regardless of the chosen hydrocarbon. In this context, measurements of α in a methanebased tissue-equivalent gas (CH4 – 64.4%, CO2 – 32.4%, and N2 – 3.2%) were performed in a uniform field configuration for density-normalized electric fields (E/N) up to 290 Td. The setup adopted in our previous works was improved for operating at low pressures. The modifications introduced in the apparatus and the experimental technique were validated by comparing our results of the first Townsend ionization coefficient in nitrogen, carbon dioxide, and methane with those from the literature and Magboltz simulations. The behavior of α in the methane-based TEG was consistent with that observed for pure methane. All the experimental results are included in tabular form in the Supplementary material.
A dedicated setup for the measurement of the electron transport parameters in gases at large electric fields
2010 - FONTE, P.; MANGIAROTTI, A.; BOTELHO, S.; GONCALVES, J.A.C.; RIDENTI, M.A.; BUENO, C.C.