Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

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



T.J. Langford, E J. Beise, H Breuer, Craig Heimbach, G Ji, Jeffrey S. Nico


We present the development of a segmented fast neutron spectrometer (FaNS-2) based upon plastic scintillator and He-3 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-3 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-252 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.
Journal of Instrumentation


neutron spectrometer, monoenergetic neutrons, He-3, Singular Value Decomposition


Langford, T. , Beise, E. , Breuer, H. , Heimbach, C. , Ji, G. and Nico, J. (2016), Development and characterization of a High Sensitivity Segmented Fast Neutron Spectrometer (FaNS-2), Journal of Instrumentation (Accessed October 3, 2023)
Created January 14, 2016, Updated October 12, 2021