n alarm signal indicating the probable presence of an explosive in a particular object prior to the time the object exits the system.
It is yet another feature of the invention to provide an explosive detection system wherein complex and labor-intensive calibration procedures can be minimized, thereby allowing the system to be quickly installed and easily operated.
Still another feature of the invention provides a nitrogen image of the object under investigation. In one embodiment, the spatial resolution of this nitrogen image may be significantly enhanced through the use of X-ray radiography.
A further feature of the invention allows background noise at a specific point in the gamma ray spectrum to be removed, thereby greatly improving the sensitivity of the system to detecting gamma rays at that specific point.
It is another feature of the invention that additional elements, e.g., hydrogen, chlorine, may be identified within the object under investigation, and from that identification improved discrimination of contraband, e.g. explosives or drugs, can be obtained.
Another feature of the invention allows the detection system to learn patterns from examples and classify objects based on these learned patterns, without the need for programming or algorithmic development.
It is still a further feature of the invention to provide a detection system that is readily adaptable to detect a wide variety of different types of explosive or other materials, and/or to quickly correct itself in the event of misclassifying a particular object.
The above and other features and advantages of the present invention will be more apparent from the following description, drawings and appendices wherein:
FIG. 1 is a simplified schematic diagram of a nuclear-based explosive detection system;
FIG. 2A illustrates a perspective view of one embodiment of a luggage and parcel inspection system;
FIG. 2B illustrates the system of FIG. 1 with a shield portion of the system removed;
FIG. 3 illustrates one possible arrangement of a conveyer path for the system showing the positioning of a pair of thermal neutron sources and sets of inorganic scintillator detectors comprising a C-ring detector array;
FIG. 4 is a block diagram of the system showing the detection of particular gamma rays used in the detection of explosive material, with waveforms (a), (b) and (c) in FIG. 4 being representative of the signals at particular points in the system;
FIG. 5(a), (b) and (c) illustrate typical spatial profiles of nitrogen concentration for explosive and non-explosive materials;
FIG. 6 illustrates a typical thermal neutron activation gamma spectrum, and further illustrates the manner in which background noise form one area of the spectrum is subtracted from another area of the spectrum in order to remove background noise;
FIG. 7 schematically illustrates the neutron detection system of the present invention combined with an X-ray system;
FIG. 8 depicts a three layer back propagation network of a preferred ANS that may be used in analyzing the detector data of the present invention for the purpose of classifying whether the object under investigation carries explosives; and
FIG. 9 is a graph that compares the probability of detection and the probability of false alarms obtained with an explosive detection system using an ANS analysis of the detector data verses an explosive detection system using a more conventional discriminate analysis of the detector data.
The following description is of the best mode presently contemplated of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the appended claims.
Referring first to FIG. 1, a simplified schematic diagram of a nuclear-based explosive detection system 100 is illustrated. The system includes a radioactive source 102 that emits neutrons 106. The neutron source 102 may include a nozzle 104, or equivalent structure, that thermalizes