NATALIA FIORINI DA SILVA

NATALIA FIORINI DA SILVA

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Garfield++ simulation of a TH-GEM based detector for standard mammography beam dosimetry
2019 - SILVA, N.F.; SILVA, T.F.; CASTRO, M.C.; LUZ, H.N. da; CALDAS, LINDA V.E.
The TH-GEM based detector is a robust, simple to manufacture, high-gain gaseous electron multiplier. Its operation is based on a standard printed circuit board (PCB) coated on both sides by metallic material, perforated in a millimeter pattern, and immersed in gas. In order to study the feasibility of using TH-GEM type detectors in dosimetric applications for standard mammography beams, a prototype with adequate dimensions and materials was produced. The present work encompasses the calculations of electric fields by the Gmsh and Elmer software packages and the avalanche simulation using Garfield++ library of a TH-GEM detector filled with Ar/CO2 (70:30) mixture at atmospheric pressure.
Dosimetric tests of an extrapolation chamber in standard computed tomography beams
2019 - CASTRO, MAYSA C. de; SILVA, NATALIA F. da; CALDAS, LINDA V. E.
Computed tomography (CT) diagnostic exams are responsible for the highest dose values to the patients. Therefore, the radiation doses in this procedure must be accurate. For the dosimetry of CT beams, the radiation detector is usually a pencil-type ionization chamber. This type of dosimeter presents a uniform response to the incident radiation beam from all angles, which makes it suitable for such equipment since the X-ray tube executes a circular movement around the table during irradiation. However, there is no primary standard system for this kind of radiation beam yet. In order to search for a CT primary standard, an extrapolation chamber built at the Calibration Laboratory (LCI) of the Instituto de Pesquisas Energéticas e Nucleares (IPEN) was tested. An extrapolation chamber is a parallel-plate ionization chamber that allows the variation of its sensitive air volume. This chamber was used previously for low-energy radiation beams and showed results within the international recommended limits. The aim of this work is to perform some characterization tests (saturation curve, polarity effect, ion collection efficiency and linearity of response) considering the chamber depth of 1.25 mm in the radiation qualities for computed tomography beams at the LCI. The results showed to be within the international recommended limits.
Electrical characterization of the amplification plate of a thick-GEM detector for low energy X radiation dosimetry
2019 - SILVA, NATALIA F. da; SILVA, TIAGO F.; S. FILHO, LUCAS A.; CASTRO, MAYSA C. de; LUZ, HUGO N. da; CALDAS, LINDA V. E.
To evaluate the possible use of Thick-GEM detectors as dosimeters in standard mammography radiation qualities, a prototype is under development for tests. This is a collaboration project between the IPEN Calibration Laboratory and the High Energy Physics and Instrumentation Center (HEPIC-IFUSP). The prototype design takes into consideration many parameters that were obtained in an exploratory work using the Monte Carlo simulation code MCNP5. Using simulations, parameters such as typical dimensions and materials were optimized to match the characteristics of the detector to the requirements of a dosimeter for this purpose. At the present status of the project, electrical tests were undertaken to evaluate the quality of the amplification plate produced in-house. The amplification plate is composed of fiberglass with a thickness of 0.5 mm and 0.03 mm of copper on each side. The average diameter of the orifices in the plate is 0.25 mm, and the distance between centers is 1.00 mm. During the electrical tests, the amplification plate was in a gas chamber filled with Argon at atmospheric pressure. The leakage current was measured as a function of the applied voltage between the copper cladding of both sides. The electrical resistance of 15.3GΩ was obtained. Additionally, the breakdown voltage was observed at approximately 1.0 kV, limiting the maximum amplification voltages to this value.
Some characterization tests for an extrapolation chamber in CT standard beams in a specific chamber depth
2019 - CASTRO, M.C.; SILVA, N.F.; CALDAS, L.V.E.
Simulation of a TH-GEM based detector for standard mammography-quality beam dosimetry using the MCNP5 code
2019 - SILVA, N.F.; SILVA, T.F.; CASTRO, M.C.; LUZ, H.N. da; CINTRA, F.B.; CALDAS, L.V.E.
Simulation of geometry and materials of the TH-GEM based detector for radiation dosimetry
2018 - SILVA, NATALIA F.; SILVA, TIAGO F.; CASTRO, MAYSA C.; LUZ, HUGO N. da; CINTRA, FELIPE B.; CALDAS, LINDA V.E.
Evaluation of an extrapolation chamber for dosimetry in computed tomography beams using Monte Carlo code (MCNP5)
2018 - CASTRO, MAYSA C.; SILVA, NATALIA F.; SANTOS, LUCAS R.; CINTRA, FELIPE B.; CALDAS, LINDA V.E.
Testing an extrapolation chamber in computed tomography standard beams
2018 - CASTRO, M.C.; SILVA, N.F.; CALDAS, L.V.E.
The computed tomography (CT) is responsible for the highest dose values to the patients. Therefore, the radiation doses in this procedure must be accurate. However, there is no primary standard system for this kind of radiation beam yet. In order to search for a CT primary standard, an extrapolation ionization chamber built at the Calibration Laboratory (LCI) of the Instituto de Pesquisas Energéticas e Nucleares (IPEN), was tested in this work. The results showed to be within the international recommended limits.
Construction of the TH-GEM detector components for metrology of low energy ionizing radiation
2018 - SILVA, N.F.; SILVA, T.F.; CASTRO, M.C.; LUZ, H.N. da; CALDAS, L.V.E.
The Gas Electron Multiplier (GEM) detector was originally proposed as a position sensitive detector to determine trajectories of particles prevenient from high-energy collisions. In order to study the potential of TH-GEM type detectors in dosimetric applications for low energy X-rays, specifically for the mammography standard qualities, it was proposed to construct a prototype with characteristics suitable for such use. In this work the general, structural and material parameters applicable to the necessary conditions were defined, establishing the process of construction of the components of a prototype.
Testing an extrapolation chamber in computed tomography standard beams
2017 - CASTRO, MAYSA C. de; SILVA, NATALIA F. da; CALDAS, LINDA V.E.