Nitrogen detection
OwnerLuis W. Alvarezinventor
Life of this patent
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Abstract
A method and apparatus for detecting concentrations of nitrogen between 20% and 30% by weight such as is common in explosives is disclosed. A microtron having an output electron beam at a level below 45 MeV is targeted onto a typically tungsten target to provide gamma radiation levels. Deflection magnets adjacent to the target deflect the electron beam of the microtron to cause it to scan. Articles placed on a container containing suspect nitrogen are systematically scanned and output gamma radiation of 511 keV detected from nitrogen. Nitrogen concentrations and consequently expected concealed explosives are easily mapped in two or three dimensions, quantitatively.
Claims12
Nitrogen concentration detection apparatus useful for the detection of nitrogen concentration in an article containing suspect nitrogen comprising:
- a source of x-ray energy exceeding 30.64 MeV, said x-rays causing the following reaction
- .sup.14 N(gamma, 2n).sup.12 N
- in nitrogen in said article but having insufficient energy to cause a significant reaction .sup.16 O(gamma, n.sup.3 H).sup.12 N, said significant reaction being that which would interfere with .sup.12 N production desired from interaction with .sup.14 N;
- at least two gamma ray detectors aligned near the path of said generated x-ray for detecting the 511 keV annihilation gamma radiation produced by the reaction of .sup.14 N(gamma, 2n).sup.12 N;
- and
- means for conveying said article proximate said x-ray source and said gamma ray detectors.
A method of scanning a series of conveyed articles for randomly placed nitrogen concentrations in the order of 20% to 30% by weight comprising the steps of:
- providing an x-ray source having x-rays exceeding 30.64 MeV in the range sufficient to cause a significant reaction
- .sup.14 N(gamma, 2n).sup.12 N
- but insufficient to cause a significant reaction
- .sup.16 O(gamma, n.sup.3 H).sup.12 N, said significant reaction being that which would interfere with .sup.12 N production desired from interaction with .sup.14 N;
- irradiating a suspect article to determine the presence of nitrogen with radiation sufficient to cause the reaction .sup.14 N(gamma, 2n).sup.12 N where gamma is x-radiation, and n is a neutron;
- detecting delayed annihilation radiation from said .sup.14 N(gamma, 2n).sup.12 N in the range of 511 keV on opposite sides of said articles for simultaneous scintillation events;
- and
- moving said article and beam relative to one another to quantitatively map said article in three dimensions, relative to its nitrogen content.
Nitrogen concentration detection apparatus comprising in combination:
- a high energy electron source having an output electron beam in the order of 35 MeV;
- a target for said high energy electron source to produce x-radiation in the range exceeding 30.64 MeV;
- deflection magnets adjacent said target for deflecting the electron beam of said microtron to cause said electron beam to scan;
- a conveyer suitable to transport an article containing suspect nitrogen through the path of said electron beam scan;
- and
- a stack of scintillation detectors for detecting the 511 keV annihilation gamma radiation produced by the reaction .sup.14 N(gamma, 2n).sup.12 N where:
- gamma is x-radiation;
- n is a neutron;
- and
- .sup.14 N and .sup.12 N are isotopes of nitrogen.
Nitrogen concentration detection apparatus useful for the tomographic mapping of nitrogen concentrations in an article containing suspect nitrogen comprising:
- a source of x-ray energy exceeding 30.64 MeV, said x-rays causing the following reaction
- .sup.14 N(gamma, 2n).sup.12 N
- in nitrogen in said article but having insufficient energy to cause a significant reaction .sup.16 O(gamma,n.sup.3 H).sup.12 N;
- said significant reaction being that which would interfere with .sup.12 N production derived from interaction with .sup.14 N
- means for conveying along a conveyor path said article by said scanning x-ray beam;
- and,
- means for scanning said source of x-rays across said article and said conveyor path;
- first and second linear arrays of annihilation radiation detectors aligned parallel to the path of said generated x-rays for detecting the 511 keV annihilation gamma radiation produced by the reaction of N(gamma, 2n).sup.12 N, one array disposed on one side of a said conveyor path and the other array disposed on the opposite side of said conveyor path whereby a tomographic plot of the nitrogen in said articles can be made.
Dependencies are inferred from the claim text.