Device for detecting nitrogenous, phosphoric, chloric and oxygenous substances
First Claim
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1. Apparatus for detecting nitrogenous, phosphoric, chloric and oxygenous substances contained in an object, said apparatus comprising:
- nuclear activating means (1, 1.1, 3,
5) for causing at least one of said nitrogenous, phosphoric, chloric or oxygenous substances to emit positron radiation by exposing said object to radiation at a first energy level;
activity measuring means (8) for recording positron-electron annihilation radiation generated within said object;
means for determining a first activity density distribution within said object on the basis of coincidence measurements made by said activity measuring means within said object at said first energy level;
X-ray means (7) for detecting projections created by absorption of radiation within said object, said X-ray means having means for detecting at least two different energy levels of X-rays;
means (11) for determining a three dimensional absorption density distribution, comprising at least two absorption values for each of a multiplicity of points within said object, based on said projections detected by said X-ray means at each of said at least two different energy levels of X-rays;
means (11) for comparing said at least two absorption values at respective points within said object and for discriminating at least two atomic number ranges for substances at points within said object to determine an atomic number and absorption density distribution within said object; and
means (11) for correlating said activity density distribution and said atomic number and absorption density distribution and for constructing a corrected three dimensional activity density distribution within said object.
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Abstract
A device for detecting nitrogenous, phosphoric, chloric and/or oxygenous substances inside an object, particularly of explosives or addictive substances in pieces of luggage. A nuclear activating device stimulates the emission of positron radiation from nitrogen, phosphorous, chlorine and/or oxygen, and an activity measuring device records positron-electron annihilation radiation.
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Citations
17 Claims
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1. Apparatus for detecting nitrogenous, phosphoric, chloric and oxygenous substances contained in an object, said apparatus comprising:
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nuclear activating means (1, 1.1, 3,
5) for causing at least one of said nitrogenous, phosphoric, chloric or oxygenous substances to emit positron radiation by exposing said object to radiation at a first energy level;activity measuring means (8) for recording positron-electron annihilation radiation generated within said object; means for determining a first activity density distribution within said object on the basis of coincidence measurements made by said activity measuring means within said object at said first energy level; X-ray means (7) for detecting projections created by absorption of radiation within said object, said X-ray means having means for detecting at least two different energy levels of X-rays; means (11) for determining a three dimensional absorption density distribution, comprising at least two absorption values for each of a multiplicity of points within said object, based on said projections detected by said X-ray means at each of said at least two different energy levels of X-rays; means (11) for comparing said at least two absorption values at respective points within said object and for discriminating at least two atomic number ranges for substances at points within said object to determine an atomic number and absorption density distribution within said object; and means (11) for correlating said activity density distribution and said atomic number and absorption density distribution and for constructing a corrected three dimensional activity density distribution within said object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for detecting nitrogenous, phosphoric, chloric and/or oxygenous substances inside an object, comprising the steps of:
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activating at least one of nitrogen, phosphorous, chlorine atoms and oxygen atoms by means of gamma radiation, to cause said atoms to emit positron radiation; measuring positron-electron annihilation radiation generated inside the largest part of a solid angle surrounding the object; examining the object by means of an X-ray radiation with at least two different energy levels; determining an atomic number and absorption density distribution from measured absorption values of several projections of the object; and calculating a three-dimensional activity density distribution from the measured values according to said measuring step, taking into account the detailed atomic number and absorption density distribution.
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Specification