the ANS computations can be quickly performed, with many of the computations being performed in parallel.
Another implementation involves modeling the ANS using software. A suitable modeling program that simulates an ANS network on a conventional IBM PC/AT or compatible computer, for example, is commercially available from Science Applications International Corporation (SAIC), San Diego, CA 92121 under the name of "ANSim." By using the ANSim program, an IBM PC/AT or compatible computer, and related equipment as detailed in applicants' prior application, Ser. No. 07/367,534, which application is incorporated herein by reference, it is thus possible to readily model the ANS portions of the present invention.
In conclusion, the present invention is directed to an explosive detection system using neutrons from a source to impinge on a object potentially containing explosive material and with the neutrons reacting with the nitrogen or other elements contained in the object to produce gamma rays. The gamma rays are detected by suitable detectors, such as inorganic scintillators, and in a preferred embodiment, the scintillators are arranged so as to surround the object to provide for detection of a two dimensional slice or plane of the object under observation. A neutron detector may also be used to measure neutron flux in the same vicinity as the gamma ray detectors. The object is moved continuously through the ring of detectors so that successive slices or planes provide for the build up of a three dimensional profile of the nitrogen bearing material within the object under observation. The three dimensional profile may then be used to determine the concentration and distribution of the nitrogen (or other element, or combinations of elements) bearing material and to make a determination whether such nitrogen (or other element) bearing material has a profile likely to be an explosive material, or other contraband, as manifest, e.g., by a high nitrogen, chlorine and/or hydrogen density. This determination is enhanced by correlating the elemental density image thus obtained with an X-ray image of the same object. In one embodiment, the determination is further facilitated through the use of an Artificial Neural System, or equivalent parallel distributed network. Use of an ANS advantageously results in a PD for the system that is increased and/or a PFA of the system that is decreased over that which is achievable using conventional standard decision analysis.
In one embodiment, the inorganic scintillator is sodium iodide, and two oppositely disposed C-ring detectors having their open ends facing each other are used to provide for a complete profile of each slice or plane along all four sides. In addition, the gamma ray detectors may be formed of sets of detectors in rows and columns to increase the detection capability by receiving additional gamma rays produced by the interaction of the thermal neutrons and nitrogen in the cavity. The present invention, therefore, provides for a greater resolution and efficiency in the detection of potentially explosive material and, because this is accomplished in a fast period of time, also provides for an adequate throughput of the luggage or parcels through the detection system.
While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the allowed claims. For example, instead of using a TNA-based system to probe or scan the luggage or parcels in order to cause the characteristic gamma rays to be emitted from the materials contained within the luggage or parcels, other equivalent or similar systems could be used. For example, an FNA (fast neutron activation) system could be used. So long as gamma rays or other indicia representative of the composition of the materials within the parcel or luggage are generated, and so long as a suitable detection system or mechanism is used to quantitativ