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 field-programmable 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 γ-only pulses from
²²
Na,
¹³⁷
Cs, and
⁶⁰
Co 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 + γ pulses from a
²⁵²
Cf source. Not only can HDM determine the presence of neutrons in the
²⁵²
Cf 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 Sℝ
²
. As control, we also encoded pulses as the root-mean-square (RMS) distances from the average pulse of all known γ-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.