Device and method for low-uncertainty and high-efficiency neutron time-of-flight spectrometry

Abstract

Neutron detection systems demand precise knowledge of detection efficiency. The goal of this work is to assess the suitability of a neutron detection concept to perform neutron spectrometry by time-of-flight with low systematic uncertainty while attaining high detection efficiency. The device is based on a neutron-to-gamma converter, made of a highly pure 10B disk, coupled to a gamma detector. The behavior of the whole detection system, using the neutron field generated by the 7Li(p,n)7Be reaction at near-threshold energies is studied. Neutron energies ranging from 1 keV up to 250 keV were used. The distribution of TOF events at proton energy equal to 2018 keV was measured and the conversion to neutron spectrum is reported. At around 30 keV of neutron energy, a comparison to a commercially available 6Li-glass scintillator is performed in terms of detection efficiency. An almost three times higher count rate was observed in our detector compared to the commercial one. Using the covariance information on neutron cross section to generate a set of perturbed cross section data, detection efficiency uncertainty ranging from 0.8% to 2.3% was estimated.