GUILHERME SOARES ZAHN

GUILHERME SOARES ZAHN

(Fonte: Lattes)

Resumo

Has a bachelor's degree in Physics from Universidade de São Paulo (1991), master's at Nuclear Engineering from Universidade de São Paulo (1994) and doctorate at Nuclear Engineering from Universidade de São Paulo (2006). Has experience in nuclear ans applied physics, focusing on nuclear structure, acting on the following subjects: beta decay, neutron activation, gamma spectroscopy, nuclear structure, neutron flux determination and detection, and also on the development od instrumentation and sotware aimed at nuclear applications. (Text obtained from the Currículo Lattes on October 14th 2021)

Possui graduação em Física pela Universidade de São Paulo (1991), mestrado em Tecnologia Nuclear pela Universidade de São Paulo (1994) e doutorado em Tecnologia Nuclear pela Universidade de São Paulo (2006). Atualmente é pesquisador da Comissão Nacional de Energia Nuclear, lotado no Centro do Reator de Pesquisas do Instituto de Pesquisas Energéticas e Nucleares. Tem experiência na área de Física Nuclear, com ênfase em Estrutura Nuclear, atuando principalmente nos seguintes temas: decaimento beta, detecção de nêutrons, irradiadores de nêutrons, ativação neutrônica, fluxo de nêutrons, desenvolvimento de instrumentação e de software para aplicações nucleares. (Texto extraído do Currículo Lattes em 14 out. 2021)

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Examination of Natural Radioactivity Concentration and Radiological Exposure of Soil Within Mining Site in Umuahia South Abia State Nigeria, Using High Purity Germanium (HPGe) Gamma Ray Spectrometry
2023 - ONUDIBIA, MOSES E.; SILVA, PAULO S.C. da; ESSIETT, ANIESUA A.; ZAHN, GUILHERME S.; GENEZINI, FREDERICO A.; IMEH, EDET E.; NNAMANI, NGENE C.; OGODO, ALLOYSIUS C.; MFOM, CELESTIAL B.; OKOH, FRANCA O.
Mining activity is one of the major sources of exposure to radiation. The main goal of this study was to determine the natural radioactivity level and its radiological exposure risk in mining site Umuahia South Abia State, Nigeria, using High Purity Germanium (HPGe) gamma ray spectrometry. The activity concentration of 40K, 226Ra and 232Th in the soil ranges from 31±2 to 367±27 Bq kg-1, with mean value of 142±11 Bq kg-1; from 26±2 to 65±5 Bq kg-1, with mean value of 49±4; and from 53±9 to 109±17 Bq kg-1, with mean value of 77±16 Bq kg-1, respectively. The activity concentrations of 226Ra and 232Th are above the global values of 32 and 45 Bq kg-1 while 40K is depleted in relation to the global mean of 412 Bq kg-1. Radiological parameters are generally in agreement with the values observed for other Nigerian and other countries soil reported in literature. The main responsible for the values observed for the radiological parameters is 232Th followed by 226Ra. The use of this soil for dwelling construction is unlikely to pose any radiological harm for the residents.
Radioactivity concentration and radiological effect of soil from Umuahia Abia State, Nigeria
2022 - ONUDIBIA, M.E.; SILVA, P.S.C.; ESSIETT, A.A.; ZAHN, G.S.; GENEZINI, F.A.
Preliminary results of Monte Carlo study of an experiment to calculate thermal neutron cross section using neutron beam from the IEA-R1 reactor
2021 - LONGHINI, EDUARDO P.; GENEZINI, FREDERICO A.; ZAHN, GUILHERME S.; MORALLES, MAURICIO
Determination of scale factor for Ni-59 and Ag-108m in ion exchange resin from Angra 1
2021 - RIBEIRO JUNIOR, I.S.; GENEZINI, F.A.; SILVA, P.S.C. da; ANGELINI, M.; JUNQUEIRA, L.S.; ZAHN, G.S.
The IEA-R1 62 years of operation
2020 - GENEZINI, F.A.; FERNANDES, A.J.; ZAHN, G.S.
Early in 1956, the Atomic Energy Institute (IEA, from the acronym in portuguese) was founded with the aim of installing the nuclear research reactor purchased from the American company Babcock & Wilcox in the framework of the “Atoms for Peace” program. The start-up was on September 16, 1957, where the first criticality in the Southern hemisphere was achieved. The IEA-R1 is a pool type, light water cooled and moderated, beryllium and graphite reflected research reactor. Although designed to operate continuously at up to 5 MW, it operated at 2 MW for 40 years and only rather recently started operating at 5 MW. This year IEA-R1 completed 62 years of operation. The reactor is the core of the Nuclear and Energy Research Institute – IPEN (former IEA) – with its laboratories working for radiopharmaceutical applications, in the areas of radiological protection, nuclear fuel cycle, nuclear engineering, and radiation applications among others. Throughout this period it underwent several reforms, renovations and changes of management. In 2000 an Integrated Management System (IMS) has been structured, based on ISO-9001, in order to keep the operation safe, which implied certain procedures together with a continuous modernization program, and to comply with the regulatory requirements at the date as well. The first certification dates to 2002 and since then the reactor has been successfully renewing its ISO certification. The history, experiences and lessons learned during the 62 years of the IEA-R1 operation are described and shared in this paper.
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.
A compact electronic system for a photodiode neutron detector
2019 - COSTA, PRISCILA; RAELE, MARCUS P.; DOMIENIKAN, CLAUDIO; COSTA, FABIO E.; MADI FILHO, TUFIC; ZAHN, GUILHERME S.; GENEZINI, FREDERICO A.
The demand for portable neutron detectors is on the rise, and for that purpose, low cost boron-10 has been frequently used instead of helium-3, which is usually employed in large and expensive detectors. Portable detectors are of interest in some applications, such as neutron dosimeters or inspection systems targeted in the detection of fissile material and drugs in airports. In this work a portable thermal neutron detection system was developed which is based on a commercial silicon photodiode coupled to a boron converter; this prototype is then plugged into a portable electronic system. The boron layer was produced by pulsed laser deposition, either on a thin glass slide or on the photodiode itself. The boron deposition in the photodiode was made directly in the active area of the detector, so before and after the deposition process a characterization of the device regarding both the dark current and the operation voltage was performed using an americium source. Finally, both configurations were tested. The neutron detection process occurs by detecting the alpha and lithium particles produced by the interaction of the incoming neutron with the boron-10 nuclides. These heavy ions then interact with the active area of the reverse-biased photodiode, producing an electric signal that has to be preamplified and then properly amplified by the portable electronic system, which in turn produces an output that can either be sent to a multichannel analyzer or to a digital counter. The integrated circuit of the low noise preamplifier transforms the detector’s current pulse into a voltage pulse with amplitude proportional to the charge carried by the current pulse. The shaper-driver consists of a differentiator and an integrator and is responsible for filtering and further amplifying the preamplifier signal, generating a NIM-compatible energy output pulse. The performance of the photodiode-amplifier set for alpha particles was successively tested using a 243Am radioactive source. Initial tests were made using the boron-deposited glass, and the electronic signal was properly read. However, when the same system was tested using the boron deposited directly in the photodiode, the output signal couldn’t be read, due to the fact that during the deposition process there was an increase in the dark current and a decrease in the operation bias. In this way, a new portable electronic system was developed using a hybrid integrated amplifier circuit. This new electronic setup allowed the use of both configurations, and was tested both with alpha-emitting Americium and neutron-emitting AmBe sources. In conclusion, both portable electronic systems have proven suitable for the thermal neutron detector developed.
Evaluation of the maximum emitting layer of Rn-222 in cementitious building materials
2019 - CORREA, J.N.; PASCHUK, S.A.; BARRETO, R.C.; DENYAK, V.; SCHELIN, H.R.; NARLOCH, D.C.; DEL CLARO, F.; HASHIMOTO, Y.; MATIN, A.C.; SILVA, A.C.M.; ZAHN, G.S.; SILVA, P.S.C.
Introduction – Radionuclides present in construction materials are of interest in the view of environmental radioactivity. The limitations established have focused on the concentration of Ra-226 and the consequent exhalation of Rn-222. A physical/mathematical model developed at the Laboratory of Applied Nuclear Physics (LFNA/UTFPR) correlates the exhaled Rn-222 with the Ra-226 inherent to the material. The model considers the exhalation of Rn-222 by a plane surface that simulates exhalation in fl oors, walls and ceilings. Determination of the maximum emitting layer of Rn-222 that effectively exhales is important to support the model. The objective of this research is to determine the maximum emissive layer of Rn-222 that provides internal diffusion and exhalation of radon-222 in cementitious materials. Methods - Cylindrical samples were made of common cement paste and cement paste with sand of high Ra-226 concentration. The samples (thicknesses 1 to 5 cm) were sealed in order to ensure the exhalation of Rn-222 through one surface. Samples and diffusion chambers containing CR-39 solid-state detectors were inserted into a glass vessel. The samples/detectors were stored for 30 days. Subsequently, the detectors were chemically etched and the nuclear tracks in the CR-39 detectors were counted. Results – For each type of sample a curve was fi tted whose threshold indicated the maximum emitting layer. The results obtained on the samples of common cement paste indicated a maximum emitting layer of 2cm. For samples of cement paste with sand with high Ra-226 concentration, no threshold was observed, indicating that the maximum emitting layer is greater than 5cm. Conclusions - The maximum emitting layer thickness of Rn-222 of common materials determined by curve fi tting was 2cm. For materials with high concentration of Ra-226 there is an indication that the emitter layer is larger than 5cm. The obtained results subsidize the physical/mathematical model developed in the LFNA/UTFPR.
AnalisaCAEN, a simple software suite to reduce and analyze coincidence data collected using CAEN v1724 digitizer
2019 - ZAHN, G.S.; GENEZINI, F.A.; RIBEIRO JUNIOR, I.
In this work a small software suite for the reduction and analysis of coincidence data collected using CAEN’s proprietary software was developed. These software check the output files for coincidences, generate a single list mode file with the coincident events, build histograms for each input, plus a time difference histogram and a 2-detector data matrix, perform time gates and allows for the subtraction of accidental coincidences, and perform energy gating on the final data matrices, generating histograms with the gated spectra. Moreover, the suite has an integrator that guides the user through all the required steps.
A proposal to study long-lived isotopes produced by thermal neutron irradiation of digital devices
2019 - ZAHN, G.S.; GENEZINI, F.A.; MORALLES, M.; SIQUEIRA, P.T.D.; MEDINA, N.H.; AGUIAR, V.A.P.; MACCHIONE, E.L.A.; ADDED, N.; SILVEIRA, M.A.G. da
In this work, we present a facility to study errors in digital devices exposed to thermal neutrons from a beam hole in the IEA-R1 nuclear reactor, as well as the long-lived isotopes produced in the irradiation of digital electronic devices under a slow neutron field. Preliminary results obtained with the analysis of a 28nm SRAM-based Xilinx Zynq-7000 FPGA are presented.