Simulation of the direct geometry spectrometer for neutron time of flight based on the Monte Carlo method to calculate the energy spectrum of the neutron source

Abstract

Abstract In the present study, simulation of a direct geometry spectrometer for neutron Time-of-Flight (nTOF) is performed based on the Monte Carlo method to calculate the energy spectrum of the neutron source. To this end, the ability to simulate the simultaneous emission (such as the simultaneous emission of the neutron and gamma particles from the 241Am-9Be neutron source) and the neutron Pulse Height Distribution (nPHD) were added to the MCNPX computer code. In addition, a post-processing software was developed to analyze the massive amounts of the data in the output of the PTRAC card. The application of the nTOF as a direct method to calculate the neutron spectrum eliminates the error induced by the unfolding approach. Therefore, the direct methods for neutron spectroscopy such as nTOF give the results with high energy resolution and efficiency. The simulation of the nTOF measurement gives the opportunity to investigate the effect of the parameters such as the distance, angle, and detector type on the results. Therefore, it leads to select the best arrangement of the equipments to measure the neutron energy spectrum using the nTOF method. The results of the simulation in the present paper have an acceptable agreement with the standard ISO-8592 spectrum of the 241Am-9Be neutron source.