Kernel Hilbert space template-matching techniques for simultaneous determination of neutron source location and identity with a volumetrically-sensitive moderating-type neutron spectrometer

Hand-held instrumentation that can provide real-time information regarding the location and identity (i.e., type/radioisotope and local surrounding/shielding) of neutron radiation sources, via free neutron measurements alone, are of interest to non-proliferation, water/oil-exploration and related neutron scattering applications. In a previous report, template-matching techniques in two- and three-spatial dimensions were introduced as methods for simultaneously determining the horizontal-planar location and the identity of neutron radiation sources with a new class of volumetrically-sensitive moderating-type neutron spectrometer. Although these methods were shown to be quite promising for this new class of instrumentation, there are three significant factors that negatively affect their performance in practice: (1) there are a large number of templates of interest for most practical applications; (2) many of these templates are very similar (i.e., highly correlated or strongly degenerate); and, (3) the measurement data is superposed with environmental neutron scattering effects. In this work, kernel Hilbert space transformations, that have been proposed to solve analogous problems in digital image processing applications, are employed to overcome the aforementioned difficulties encountered when analyzing spectroscopic neutron radiation measurements via template-matching techniques, and a novel kernel Hilbert space template-matching algorithm is introduced. Four variants of this improved technique are tested and compared via MCNP6 simulation for efficacy of localization and identification of neutron radiation sources with this new class of neutron spectrometer.