PAULO DE TARSO DALLEDONE SIQUEIRA

PAULO DE TARSO DALLEDONE SIQUEIRA

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Efficient computational modeling of electronic stopping power of organic polymers for proton therapy optimization
2024 - MATIAS, F.; SILVA, T.F.; KOVAL, N.E.; PEREIRA, J.J.N.; ANTUNES, P.C.G.; SIQUEIRA, P.T.D.; TABACNIKS, M.H.; YORIYAZ, H.; SHORTO, J.M.B.; GRANDE, P.L.
This comprehensive study delves into the intricate interplay between protons and organic polymers, offering insights into proton therapy in cancer treatment. Focusing on the influence of the spatial electron density distribution on stopping power estimates, we employed real-time time-dependent density functional theory coupled with the Penn method. Surprisingly, the assumption of electron density homogeneity in polymers is fundamentally flawed, resulting in an overestimation of stopping power values at energies below 2 MeV. Moreover, the Bragg rule application in specific compounds exhibited significant deviations from experimental data around the stopping maximum, challenging established norms.
Thermal neutron dose measurements using TLD-100 detectors in the IPEN/MB-01 reactor core
2024 - CAVALIERI, TASSIO A.; SIQUEIRA, PAULO de T.D.; SHORTO, JULIAN M.B.; YORIYAZ, HELIO
Considerable experimental effort has been aimed at uncovering a reliable way to perform a dosimetric assessment in mixed radiation fields. In fields composed by gammas and neutrons, TLD dosimeters are usually applied to execute such measurements, although there is no consensus on the most favorable strategy to employ them. In this context, TLD-100 measurements within two different core configurations of the IPEN/MB-01 research reactor and Monte Carlo simulations have been used to investigate the behavior of those detectors in multiple mixed radiation fields, deriving a methodology to evaluate the dose deposition in the dosimeter by different gamma and neutron energy spectra and intensities. A surprising outcome is the linear neutron dose response shown by TLD-100 even irradiated by so distinct irradiation fields.
Comparison of methodologies for creating spread-out Bragg peaks in proton therapy using TOPAS and MCNP codes
2023 - BRANCO, I.S.L.; BURIN, A.L.; PEREIRA, J.J.N.; SIQUEIRA, P.T.D.; SHORTO, J.M.B.; YORIYAZ, H.
In proton beam treatments, the superposition of several weighted Bragg curves with different incident energies is required to homogeneously irradiate a large tumor volume, creating a spread-out Bragg peak (SOBP). This paper confirms on the suitability of two different methods to create SOBPs – Bortfeld/Jette’s and MCMC (Monte Carlo calculations and Matrix Computations), using Monte Carlo simulations performed with TOPAS and MCNP6.1. To generate the SOBPs, algorithms were developed for implementation of the two methods, which enabled to find the weights for thirty variations of SOBPs, categorized according to their width and maximum depths. The MCMC method used weight optimization in designing SOBPs to avoid negative values. In contrast, the Bortfeld/ Jette’s method yielded the SOBPs according to the variation of a power-law parameter (p) introduced by the range-energy relationship. Optimal values of p, from MCNP and TOPAS, were selected in order to retrieve SOBPs with the best smoothness and then related to those obtained from the literature. In comparing both methods and codes, dose homogeneity parameters (HOM) were used to examine the SOBP flatness and gamma analyses were employed to assess the dose deposition along its full extension. The results showed that the SOBPs designed using the MCMC method had better HOM values and computational performance for both codes when compared to the Bortfeld/Jette’s method. The gamma analyses highlighted significant differences between the entrance doses comparing the two different methods, for SOBPs with intermediate and high depths and small width. This evaluation was not possible with the HOM values alone, which stresses the relevance of a broad analysis to avoid unintended doses in healthy tissues.
Simulação de um difratômetro de tensão residual no IEA-R1
2022 - SOUZA, ALEXANDRE P.S.; OLIVEIRA, LUIZ P. de; YOKAICHIYA, FABIANO; GENEZINI, FREDERICO A.; SIQUEIRA, PAULO de T.D.; FRANCO, MARGARETH K.K.D.
O reator nuclear IEA-R1, localizado no Instituto de Pesquisas Energéticas e Nucleares (IPEN), disponibiliza feixes de nêutrons para aplicação em técnicas de caracterização de materiais, atualmente contando com experimentos de difração de alta resolução e tomografia. Com o intuito de expandir os experimentos, aqui é apresentado um estudo prévio visando a implementação da técnica de tensão residual por difração de nêutrons. Tal escolha, deve-se à sua grande aplicabilidade às indústrias nuclear e aeronáutica, envolvendo estudos de fadiga e corrosão em ligas de Ni, Ti e aços submetidas à tensão. Além disso, as medições de tensão residual são também executadas em materiais cerâmicos, compostos intermetálicos e policristalinos. Este estudo prévio da viabilidade da implementação da técnica é baseado em simulações numéricas, em que são analisados os componentes necessários para a instalação de um difratômetro de tensão residual nas dependências do IEA-R1. Estudos sobre a geometria e componentes como filtros, monocromador, detector, fendas foram realizados por meio do método de Monte Carlo com o software McStas para estimar o posicionamento dos mesmos.
Neutron radiation effects on an electronic system on module
2020 - LO PRESTI, DOMENICO; MEDINA, NILBERTO H.; GUAZZELLI, MARCILEI A.; MORALLES, MAURICIO; AGUIAR, VITOR A.P.; OLIVEIRA, JOSE R.B.; ADDED, NEMITALA; MACCHIONE, EDUARDO L.A.; SIQUEIRA, PAULO de T.D.; ZAHN, GUILHERME; GENEZINI, FREDERICO; BONANNO, DANILO; GALLO, GIUSEPPE; RUSSO, SALVATORE; SGOUROS, ONOUFRIOS; MUOIO, ANNAMARIA; PANDOLA, LUCIANO; CAPPUZZELLO, FRANCESCO
The NUMEN (NUclear Matrix Elements for Neutrinoless double beta decay) project was recently proposed with the aim to investigate the nuclear response to Double Charge Exchange reactions for all the isotopes explored by present and future studies of 0νββ decay. The expected level of radiation in the NUMEN experiment imposes severe limitations on the average lifetime of the electronic devices. During the experiments, it is expected that the electronic devices will be exposed to about 105 neutrons/cm2/s according to FLUKA simulations. This paper investigates the reliability of a System On Module (SOM) under neutron radiation. The tests were performed using thermal, epithermal, and fast neutrons produced by the Instituto de Pesquisas Energéticas e Nucleares 4.5MWNuclear Research Reactor. The results show that the National Instruments SOM is robust to neutron radiation for the proposed applications in the NUMEN project.