A compact neutron spectrometer system

A portable neutron spectrometer, nSpec, has been developed for passive interrogation of fast neutrons (> 1 MeV) from neutron sources. The design of the system includes four EJ-301 liquid scintillation cells, a custom stand, and tungsten caps for gamma-ray shielding. Data acquisition settings were optimized to provide a dynamic range of up to 15 MeV neutron energy. The detector response matrix was characterized using a time-of-flight method based on gamma-ray tagged neutron emission from 252Cf. The spectrum unfolding was characterized using measured and simulated spectra of AmBe and 252Cf with the GRAVEL and MLEM methods. Monte Carlo methods were used to examine the uncertainty propagation and determine sufficient counts for a measurement.