Thermal neutron capture techniques, as embodied in Thermal Neutron Analysis (TNA(R)) devices, provide a powerful tool for counter terrorism and environmental demilitarization. The common objective in both applications is the detection of explosives via their unique elemental constituents. In TNA, the primary explosive signature is the nitrogen concentration. Hydrogen is a secondary one. However, useful tertiary signatures exist in the full gamma-spectrum reflecting the explosive material itself and its surrounding. All these signatures, or spectra features, are derived from the analysis of the gamma-ray spectra collected by NaI detectors With a good energy resolution. This approach to the generation of explosive, decision algorithms was incorporated in: Ancore's Small Parcel Explosive Detection System (SPEDS) and other systems. The application described in this paper was the inspection airline passenger carry-on items such as laptop computers, briefcases, liquid bottles, etc., for the presence of small explosives. The feature analysis and the resulting excellent receiver operator characteristics are shown in the paper. The SPEDS was able to automatically detect less than 100 g of explosives in carry-on items, with a low false alarm rate. (C) 2003 Elsevier Science B.V. All rights reserved.
