Neutron area monitor with passive detector

Abstract

Using Monte Carlo methods the responses of a passive neutron monitor area has been calculated. To detect thermal neutrons the monitor has a gold foil that is located at the center of a polyethylene cylinder. Impinging neutrons are moderated by polyethylene nuclei reaching the gold foil with the energy to induce activation through the reaction $^{197}$Au(n, $\gamma)\;\;^{198}$Au. The $^{198}$Au decays emitting 0.411 MeV gamma rays with a half life of 2.7 days. The induced activity is intended to be measured with a gamma-ray spectrometer with a 3'' ${\O} \times$ 3'' NaI(Tl) scintillator and the saturation activity is correlated to the ambient dose equivalent. The response was calculated for 47 monoenergetic neutron sources ranging from 1$\times10^{-9}$ to 20 MeV. Calculated fluence response was compared with the response of neutron monitor area LB 6411.