A Histogram-Difference Method for Neutron/Gamma Discrimination Using Liquid and Plastic Scintillators

This paper introduces a novel and extremely simple-and therefore, easily implemented in a fieldprogrammable gate array-method of neutron/gamma pulse discrimination called the histogram-difference method (HDM). Crucially, this method relies on the use of a "reference set" of gamma-only pulses from Na-22, Cs-137, and Co-60 sources and on features extracted from the pulses. The pulses from this reference set are compared to a set of an identical number of n+gamma pulses from a Cf-252 source. Not only can HDM determine the presence of neutrons in the 252Cf source, but it can also estimate the approximate percentage of neutron pulses from that source. The results reported in this paper are based on data from different radioactive sources and a standard scintillator for this type of research, namely, BC-501A. These results were confirmed using three other scintillators, one made in-house and two others that are commercially available, EJ-299-33 and EJ-200. Pulses were encoded using Q values, which are features extracted from the pulses, that is, (Q(total), Q(tail)) pairs in SR2. As control, we also encoded pulses as the root-mean-square (RMS) distances from the average pulse of all known. -only pulses and ran HDM using these pulse representations. The results are very similar to those obtained using a Q-value encoding of the pulses.