Development and Characterization of a High Sensitivity Segmented Fast Neutron Spectrometer (FaNS-2)

• Published in: Journal of instrumentation Vol. 11; no. 1; p. P01006
• Main Authors: Langford, T J, Beise, E J, Breuer, H, Heimbach, C R, Ji, G, Nico, J S
• Format: Journal Article
• Language: English
• Published: England 01.01.2016
• Subjects: Fast neutrons; Fluxes; Neutron spectra; Proportional counters; Reconstruction; Sensitivity; Spectrometers; Well construction; Particle identification methods; Hybrid detectors; Spectrometers; Neutron detectors
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/11/01/P01006

We present the development of a segmented fast neutron spectrometer (FaNS-2) based upon plastic scintillator and He proportional counters. It was designed to measure both the flux and spectrum of fast neutrons in the energy range of few MeV to 1 GeV. FaNS-2 utilizes capture-gated spectroscopy to identify neutron events and reject backgrounds. Neutrons deposit energy in the plastic scintillator before capturing on a He nucleus in the proportional counters. Segmentation improves neutron energy reconstruction while the large volume of scintillator increases sensitivity to low neutron fluxes. A main goal of its design is to study comparatively low neutron fluxes, such as cosmogenic neutrons at the Earth's surface, in an underground environment, or from low-activity neutron sources. In this paper, we present details of its design and construction as well as its characterization with a calibrated Cf source and monoenergetic neutron fields of 2.5 MeV and 14 MeV. Detected monoenergetic neutron spectra are unfolded using a Singular Value Decomposition method, demonstrating a 5% energy resolution at 14 MeV. Finally, we discuss plans for measuring the surface and underground cosmogenic neutron spectra with FaNS-2.