Odair Lélis Gonçalez

Determination of the cosmic-ray-induced neutron flux and ambient dose equivalent at flight altitude

There is interest in modeling the atmosphere in the South Atlantic Magnetic Anomaly in order to obtain information about the cosmic-ray induced neutron spectrum and angular distribution as functions of altitude. In this work we use the Monte Carlo codes MCNPX and Geant4 to determine the cosmic-ray-induced neutron flux in the atmosphere produced by the cosmic ray protons incident on the top of the atmosphere and to estimate the ambient dose equivalent rate as function of altitude. The results present a reasonable conformity to other codes (QARM and EXPACS) based on other parameterizations.

Alternate Biasing Modular Redundancy: An alternative tolerance technique to cope with TID effects

In this work a novel radiation tolerance technique based on modular redundancy, associated to an alternated biasing scheme, is presented. The goal of this technique is to extend electronic systems lifetime in radiation environments for circuits that are susceptible to TID effects. In order to validate this technique, a board level prototype was built, considering an FPAA (Field Programmable Analog Array) as Device Under Test (DUT), to which the concept was applied. The prototype was exposed to Co60 gamma radiation with a dose rate of 1 krad(Si)/h. Results show that devices that are alternated biased are able to tolerate higher accumulated doses than the one that is permanently biased.

DETERMINATION OF THE RESPONSE TO THE ATMOSPHERIC COSMIC RADIATION OF A NEUTRON DOSIMETER ASSISTED BY MONTE CARLO SIMULATION

A TLD-based dosimeter of polyethylene-lead-polyethylene, was developed and characterized with Monte Carlo simulations, using the MCNPX code. This passive system for the determination of the ambient dose equivalent (H*(10)) for neutrons over a wide energy range can be used for the dosimetry of neutrons from atmospheric cosmic radiation, on the ground, and onboard aircraft. A method assisted by Monte Carlo simulations that improves the calibration of fast neutron dosimeters based on moderation and thermalization of the incident fast flux and the measurement of the thermal flux by a sensor, which respond mainly to thermal neutrons, is presented in this work. The H*(10) energy response of this dosimeter was obtained from simulations for monoenergetic neutrons from 10-10 to 104 MeV. The validation of the modeling was done with irradiations for ISO standard neutron fields of 241Am-Be, 252Cf and 252Cf(D2O) at Instituto de Radioproteção e Dosimetria (IRD, Brazil) and at CERN-EU high-energy reference field (CERF).

Evaluation of a mixed-signal design diversity system under radiation effects

In this work a data acquisition system, based on a design diversity redundant scheme, is tested under total ionizing dose effects. The data acquisition system is composed by three ADCs and two voters, implementing different levels of diversity (architectural and temporal). This system is implemented on a 130nm commercial mixed-signal programmable SoC (PSoC 5), from Cypress Semiconductor. The system was tested under 60Co gamma radiation with a dose rate of 1 krad(Si)/h reaching a total dose of 242 krad(Si). One of the system copies presented a significant degradation on its linearity during the irradiation, while the others kept the functionality with less severe degradation, evidencing the advantage of using diversity to improve resilience in mixed-signal redundant systems.

Measurements of radiation effects on a 4 Mb PSRAM memory

The results of a static test of total ionizing dose (TID) effects on an ISSI 4Mb PSRAM memory are reported in this work. The irradiation was performed at the IEAv’s Laboratory of Ionizing Radiation with 1.17 and 1.32 MeV gamma-rays from a 60Co source at a dose rate of 2.5 krad/h up to an accumulated dose of 215.7 krad. The TID threshold for bit flip found in this experiment was 52.5 krad. From a sampling of 4096 memory addresses it was estimated a bit flip rate of approximately 50% at an accumulated dose of 215.7 krad.

Influence of clouds on the cosmic radiation dose rate on aircraft

Flight missions were made in Brazilian territory in 2009 and 2011 with the aim of measuring the cosmic radiation dose rate incident on aircraft in the South Atlantic Magnetic Anomaly and to compare it with Monte Carlo simulations. During one of these flights, small fluctuations were observed in the vicinity of the aircraft with formation of Cumulonimbus clouds. Motivated by these observations, in this work, the authors investigated the relationship between the presence of clouds and the neutron flux and dose rate incident on aircraft using computational simulation. The Monte Carlo simulations were made using the MCNPX and Geant4 codes, considering the incident proton flux at the top of the atmosphere and its propagation and neutron production through several vertically arranged slabs, which were modelled according to the ISO specifications.

The prototype of a detector for monitoring the cosmic radiation neutron flux on ground

This work presents a comparison between the results of experimental tests and Monte Carlo simulations of the efficiency of a detector prototype for on-ground monitoring the cosmic radiation neutron flux. The experimental tests were made using one conventional 241Am-Be neutron source in several incidence angles and the results were compared to that ones obtained with a Monte Carlo simulation made with MCNPX Code.

OPEN INNOVATION AS AN ALTERNATIVE FOR STRATEGIC DEVELOPMENT IN THE AEROSPACE INDUSTRY IN BRAZIL DOI 10.5028/jatm.2010.02038910

We present in this paper a case of technological competence development in the aerospace sector in Brazil, by addressing the complete cycle of integrated circuits for satellite applications, an area of high technology which is strategic to the country. The development of technological and business competences is linked to an understanding of the existing relations between different participating institutions, both public and private. There is an effort to establish a network for the development of radiation-hard integrated circuits in Brazil, comprising universities, research centers, private companies, design houses, funding and governmental agencies. These institutions have been working to define their roles, through participation in federally funded projects to develop robust component technology for the aerospace industry in Brazil. As a means to maintain and improve this network, it is suggested that long term planning tools such as technology roadmaps be adopted, as well as measures to increase awareness of and help clarify intellectual property issues, which is considered a significant bottleneck to advance technology development in this area. In this sense, open innovation may be considered an alternative for competitively enhancing the outcomes of the sector.