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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Development of an environmental monitoring station for HPGe detectors
2021 - MELO, G.R.; ZAHN, G.S.; GENEZINI, F.A.; MOREIRA, E.G.
Neutron Activation Analysis (NAA) is a well-established nondestructive analytic technique where the gamma radiation emitted by an irradiated sample is analyzed using an HPGe detector. The Neutron Activation Laboratory (LAN) of IPEN-CNEN/SP has been performing NAA analyses for over 30 years, and has plans of implementing quality control protocols to their analyses. In this sense, the environmental monitoring of the laboratories where the detectors are used has been performed for many years, in a manual way with no more than 2 measurements per day. In this work, an automated monitoring station based on a microcontroller ArduinoUNO board has been developed which comprises four thermo hygrometer sensors for monitoring different parts of the environment, plus a thermocouple for monitoring the inside of the liquid nitrogen dewar. The results obtained allow for a discussion on the performance and adequacy of the sensors.
Efficiency stability of HPGe detectors under distinct count rates
2021 - ZAHN, G.S.; GENEZINI, F.A.
In this work the reproducibility of the efficiency of different HPGe detectors was analyzed under a series of different conditions. The detectors studied were plugged either to a regular analogical amplifier or to a digital signal processing (DSP) device, to evaluate the possible differences between either setup. Detectors were inspected by performing a long series of sequential measurements with standard calibration sources and comparing the standard deviation of the number of counts per second in each series to the uncertainty of the individual measurements. Detectors were also subjected to distinct count rates, to verify the possible experimental issues associated with this parameter. The results allow a discussion on the stability of the detectors’ efficiencies over a few days, the possible dependence with the count rate, and the estimation of the uncertainty related to the efficiency variation.
Pile-up correction for coincidence counting using a CAEN 1724 digitizer
2019 - ZAHN, GUILHERME S.; RIBEIRO JUNIOR, IBERE S.; GENEZINI, FREDERICO A.
In conventional gamma-ray spectrometry, the probability of pile-up effects is considered to be proportional to the dead-time, and is usually neglected for low dead-times (below 4-5%). In gamma-gamma coincidence spectrometry, though, while the dead time takes into account only events that are actually digitized, the pile-up effects are proportional to the actual gamma-ray detection rate in each detector, not only to the ones that trigger the coincidence gate. Thus, the pile-up corrections may not be so easy to assess as in single spectrometry systems. In this work, a system composed of two HPGe detectors coupled to a CAEN v1724 digitizer is studied. A 3kBq 60Co source was analyzed, both alone and in the presence of other radioactive sources (137Cs, 133Ba and 152Eu), and the resulting coincidence peak areas were compared to assess the effectiveness of two distinct corrections: a simple normalization by the live time of acquisition and the normalization by the count rate obtained using a pulse generator. The results obtained stress the need to use the pulse generator in this specific setup in order to get accurate results.