Detection of nitrogen in explosives
First Claim
1. An apparatus for scanning an object to determine the concentration and position of nitrogen in the object comprising:
- a housing having a cavity for receiving an object to be scanned and means for passing the object through said cavity;
means for producing a thermal neutron flux within said cavity, said thermal neutron flux causing high energy gamma rays to be emitted from said object as the object passes through said cavity in response to reactions with nitrogen contained in said object;
means for sensing the amount of thermal neutrons within said cavity;
means for adjusting the thermal neutron flux within said cavity in response to the amount of thermal neutrons to maintain a predetermined thermal neutron flux density within said cavity;
at least one primary radiation detector within the cavity for detecting the high energy gamma rays emitted by the object as the object passes said radiation detector(s) and for producing output signals representative of the position and energy of said gamma rays; and
means for processing and analyzing said output signals for determining the concentration and position of nitrogen in said object.
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Accused Products
Abstract
An apparatus and method for scanning an object for nitrogen for detecting the presence of explosives in luggage, parcels and the like. The object is placed in a cavity in which a thermal neutron flux is produced by introducing fast neutrons in the presence of a nuclear moderating material. A reaction between the thermal neutrons and the nitrogen contained in the object causes gamma rays to be emitted which are detected and transmitted to processing electronics to determine the concentration and position of nitrogen in the object. Thermal neutrons sensors are located within the cavity to monitor the amount of thermal neutrons and adjust the thermal neutron flux within the cavity in order to maintain an optimal thermal neutron flux density within the cavity. The adjustment may be effectuated by adjusting the accelerating potential of a neutron accelerator or by adjusting the position of a neutron moderator for use with an isotopic neutron source.
81 Citations
32 Claims
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1. An apparatus for scanning an object to determine the concentration and position of nitrogen in the object comprising:
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a housing having a cavity for receiving an object to be scanned and means for passing the object through said cavity; means for producing a thermal neutron flux within said cavity, said thermal neutron flux causing high energy gamma rays to be emitted from said object as the object passes through said cavity in response to reactions with nitrogen contained in said object; means for sensing the amount of thermal neutrons within said cavity; means for adjusting the thermal neutron flux within said cavity in response to the amount of thermal neutrons to maintain a predetermined thermal neutron flux density within said cavity; at least one primary radiation detector within the cavity for detecting the high energy gamma rays emitted by the object as the object passes said radiation detector(s) and for producing output signals representative of the position and energy of said gamma rays; and means for processing and analyzing said output signals for determining the concentration and position of nitrogen in said object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A directional channeling detector for detecting the presence and location of radiation emitted from an object comprising:
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means for converting the radiation into electrons; a channeling crystal coupled to said converting means for producing channeling radiation in response to electrons travelling through said crystal at a direction substantially parallel to a plane of the crystal lattice; an electron detector for producing a first signal in response to an electron passing through said crystal; and a channeling radiation detector for producing a second signal in response to channeling radiation emitted by said crystal. - View Dependent Claims (26, 27)
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28. A method of scanning an object for nitrogen and determining the location and concentration of nitrogen in the object, comprising:
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placing an object to be scanned in a cavity; producing a thermal neutron flux within said cavity causing gamma rays to be emitted from said object in response to reactions with nitrogen contained in said object; sensing the amount of thermal neutrons within said cavity; adjusting the thermal neutron flux within said cavity in response to the amount of thermal neutrons; detecting said gamma rays and producing output signals indicative of the position and energy of said gamma rays; and analyzing said output signals to determine the concentration and position of nitrogen in the object. - View Dependent Claims (29)
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30. An apparatus for scanning a subject to determine the distribution of nitrogen in the subject comprising:
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a housing having a cavity for receiving a subject to be scanned and means for passing the subject through said cavity; means for causing gamma rays to be emitted from the subject due to the presence of nitrogen within the subject; at least one radiation detector having a conversion foil for converting gamma rays into electrons, a channeling crystal coupled to said conversion foil for producing channeling radiation in response to electrons travelling through said crystal substantially parallel to a plane of the crystal lattice, an electron detector for producing first signals in response to electrons passing through said crystal lattice and a solid state channeling radiation detector for producing second signals representative of the position and concentration of nitrogen contained in the subject; and means for processing said first and second signals to determine the distribution of nitrogen in the subject. - View Dependent Claims (31, 32)
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Specification