Contraband detection system using direct imaging pulsed fast neutrons
First Claim
1. Contraband detection apparatus comprising:
- means for irradiating an object under investigation with a collimated pulsed beam of fast neutrons having a pulse width of less than 5 nanoseconds;
first detecting means for detecting gamma rays emitted from said object as a result of interactions between a neutron from said pulsed beam of fast neutrons and an atomic nucleus within said object;
identifying means for identifying a particular atomic element which gives rise to a particular detected gamma ray;
locating means for determining the approximate location within said object of the origin of each gamma ray detected by said detecting means without the necessity of detecting associated particles; and
second detection means responsive to said irradiating means, identifying means and locating means for detecting a distribution and concentration of at least one atomic element within said object indicative of the presence of contraband.
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Accused Products
Abstract
A system and method for detecting contraband generates a highly collimated beam of pulsed fast neutrons, having a pulse width on the order of a nanosecond, and an energy of 5 to 9 MeV. An object under investigation is scanned with the collimated pulsed beam. The neutrons in the beam cause (n, γ) reactions in a limited object volume or voxel, defined by the intersection of the collimated beam and the scanned object. The highly penetrating fast neutrons produce nuclear reactions with the atomic elements present within the object, causing gamma rays to be emitted. By measuring the approximate time of flight of the neutron pulse, a determination is made as to the particular voxel from which the gamma ray originated. The energy of the detected gamma rays identifies the particular elements from which the gamma rays originated. Thus, e.g., the carbon, nitrogen, oxygen, and chlorine content, which elements are commonly found in contraband, of a particular voxel can be determined directly and precisely. This voxel content information may be combined from a substantial sample of the voxels that make up the object to provide a direct indication of the elemental content of the object, and hence whether contraband is present or absent within the object.
109 Citations
26 Claims
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1. Contraband detection apparatus comprising:
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means for irradiating an object under investigation with a collimated pulsed beam of fast neutrons having a pulse width of less than 5 nanoseconds; first detecting means for detecting gamma rays emitted from said object as a result of interactions between a neutron from said pulsed beam of fast neutrons and an atomic nucleus within said object; identifying means for identifying a particular atomic element which gives rise to a particular detected gamma ray; locating means for determining the approximate location within said object of the origin of each gamma ray detected by said detecting means without the necessity of detecting associated particles; and second detection means responsive to said irradiating means, identifying means and locating means for detecting a distribution and concentration of at least one atomic element within said object indicative of the presence of contraband. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A contraband detection system comprising:
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means for generating a recurring short pulse of less than five nanoseconds of directed fast neutrons; means for scanning an object under investigation for the presence of contraband with said recurring short pulse of directed fast neutrons, each of said fast neutrons possibly reacting with a particular atomic nucleus present within said object, thereby generating gamma rays having an energy characteristic of the particular atomic nucleus with which said fast neutrons react; means for detecting the gamma rays produced by neutrons in reaction with atomic nuclei, said detection means including means for detecting the energy of a particular gamma ray and the time of its detection relative to the time of generation of said short pulse of fast neutrons; and means for determining a particular volume element, or voxel, within said object from which a particular detected gamma ray originated without the necessity of detecting associated particles, such as alpha particles, that may be generated by the means for generating the fast neutrons, said detected gamma ray thereby providing a direct indication of the particular atomic nucleus in said particular voxel;
the particular atomic nuclei, present in a sample of the voxels within said object providing a direct indication of the abundances and distributions of particular elements within said object;
a prescribed abundance and distribution of particular elements within said object providing a direct indication of the presence of contraband within said object. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A system for detecting contraband comprising:
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(a) means for scanning an object under investigation with a pulsed beam of highly collimated fast neutrons by controllably directing said pulsed beam at a prescribed volume of said object, said pulsed beam of highly collimated fast neutrons having a pulse width of less than 5 nanoseconds; (b) means for detecting gamma rays having prescribed energies emitted from said prescribed volume of said object as a result of interactions between pulsed fast neutrons from said pulsed beam of fast neutrons and atomic nuclei of particular elements within said object, said prescribed energies corresponding to atomic elements commonly found in contraband; and (c) means responsive to said detecting means for ascertaining whether a distribution and concentration of at least one atomic element indicative of contraband exists within said prescribed volume, said means performing its contraband detecting function without the necessity of detecting associated particles, such as alpha particles, that may be generated coincident with the pulsed fast neutrons. - View Dependent Claims (21, 22)
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23. A method of detecting contraband comprising the steps of:
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(a) directing a pulsed beam of fast neutrons, laterally limited, towards an object under investigation said pulsed beam having a pulse width of less than 5 nanoseconds; and (b) detecting gamma rays having prescribed energies emitted from a prescribed volume of said object as a result of interactions between pulsed fast neutrons from said pulsed beam of fast neutrons and atomic nuclei of a particular elements within said prescribed volume, said prescribed energies corresponding to atomic elements commonly found in contraband. - View Dependent Claims (24, 25, 26)
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Specification