Fast Neutron Detection with a Segmented Spectrometer

TL;DR

This paper presents a segmented plastic scintillator and He-3 proportional counter neutron spectrometer capable of detecting low fluxes in high gamma backgrounds, with detailed characterization and comparison to simulations.

Contribution

It introduces a novel detector design that operates without pulse-shape discrimination and demonstrates its effectiveness through experimental measurements and simulations.

Findings

Successfully measured neutron fluxes at different locations.

Validated detector response with Monte Carlo simulations.

Achieved detection of low neutron fluxes amidst gamma background.

Abstract

A fast neutron spectrometer consisting of segmented plastic scintillator and He-3 proportional counters was constructed for the measurement of neutrons in the energy range 1 MeV to 200 MeV. We discuss its design, principles of operation, and the method of analysis. The detector is capable of observing very low neutron fluxes in the presence of ambient gamma background and does not require scintillator pulseshape discrimination. The spectrometer was characterized for its energy response in fast neutron fields of 2.5 MeV and 14 MeV, and the results are compared with Monte Carlo simulations. Measurements of the fast neutron flux and energy response at 120 m above sea-level (39.130 deg. N, 77.218 deg. W) and at a depth of 560 m in a limestone mine are presented. Finally, the design of a spectrometer with improved sensitivity and energy resolution is discussed.