Claudio Antonio Federico

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.

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).

Determinação da Radiação Espalhada no Laboratório de Calibração com Nêutrons do IPEN

Com o aumento do uso de tecnicas que utilizam radiacao de neutrons, houve um crescimento consideravel no numero de detectores para esse tipo de radiacao. Foi projetado um laboratorio de calibracao de detectores com neutrons ( 241 AmBe). Nas situacoes praticas neste tipo de laboratorio, um dos problemas principais esta relacionado ao conhecimento da radiacao espalhada. Com o intuito de avaliar esta radiacao espalhada, foram realizadas simulacoes sem a presenca dos elementos estruturais e com a sala completa. Foram avaliados quatorze pontos de medicoes em direcoes diferentes a varias distâncias.

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.