Explosive detection method and apparatus using selective gamma ray resonance absorption
First Claim
1. A method of detecting the presence of a compound containing both nuclei of a first kind which exhibit NMR (nuclear magnetic resonance) behavior and nuclei of a second kind which exhibit NQR (nuclear quadrupole resonance) comprising the steps of:
- subjecting a first material known to contain said compound to radiation;
subjecting said first material known to contain said compound to a magnetic field;
measuring a reference change in the absorption and/or transmission of said radiation through said first material in the presence and in the absence of said magnetic field;
subjecting a second material suspected of containing said compound to radiation;
subjecting said second material suspected of containing said compound to a magnetic field;
measuring a test change in the absorption and/or transmission of said radiation through said second material in the presence and in the absence of said magnetic field;
comparing said test change with said reference change; and
using the results of the said comparing step to determine the presence or absence of said compound in said second material.
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Abstract
An apparatus and method for determining the presence of certain elements or compounds within an object, wherein the object under examination contains both nuclei of a first type which exhibit nuclear magnetic resonance and nuclei of a second type which exhibit nuclear quadrupolar resonance. The apparatus and method involve subjecting the object to a magnetic field and to a radiation beam whose characteristics in the presence of a magnetic field and in the absence of a magnetic field can be measured. The radiation transmission and/or absorption "fingerprint" of a particular substance is experimentally determined and recorded in the presence of a magnetic field calculated to optimize a cross coupling between nuclei of the first (NMR) type and nuclei of the second (NQR) type. This reference is then utilized later as a basis on which to identify an unknown compound exhibiting the same radiation absorption and/or transmission characteristics in response to the same or similar magnetic field intensity. Specific types of radiation and specific magnetic field intensities are pre-selected as optimizing the detectability of specific NMR/NQR element pairs.
48 Citations
9 Claims
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1. A method of detecting the presence of a compound containing both nuclei of a first kind which exhibit NMR (nuclear magnetic resonance) behavior and nuclei of a second kind which exhibit NQR (nuclear quadrupole resonance) comprising the steps of:
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subjecting a first material known to contain said compound to radiation; subjecting said first material known to contain said compound to a magnetic field; measuring a reference change in the absorption and/or transmission of said radiation through said first material in the presence and in the absence of said magnetic field; subjecting a second material suspected of containing said compound to radiation; subjecting said second material suspected of containing said compound to a magnetic field; measuring a test change in the absorption and/or transmission of said radiation through said second material in the presence and in the absence of said magnetic field; comparing said test change with said reference change; and using the results of the said comparing step to determine the presence or absence of said compound in said second material.
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2. A method for determining the presence of specific elements and/or compounds within an object comprising the steps of:
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subjecting said object to electromagnetic or particulate radiation; measuring first characteristics of electromagnetic or particulate radiation absorbed and/or transmitted by said object; subjecting said object to a magnetic field of a specific intensity predetermined to create a change in said radiation absorbed and/or transmitted by said object if said specific elements and/or compounds are present; measuring second characteristics of electromagnetic or particulate radiation absorbed and/or transmitted by said object; comparing the second measured characteristics of radiation absorbed and/or transmitted with the first measured characteristics of said radiation absorbed and/or transmitted, and identifying a change between said measured characteristics; comparing said change between said measured characteristics with predetermined radiation changes characteristic of said specific elements and/or compounds; and using the results of the said comparing step to identify elements and/or compounds; wherein said magnetic field of a specific intensity has been predetermined to effect a cross coupling between nuclei of a first element exhibiting nuclear magnetic resonant behavior and nuclei of a second element exhibiting nuclear quadrupole resonant behavior. - View Dependent Claims (3, 4, 5)
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6. An apparatus for determining the presence of specific elements and/or compounds within an object comprising:
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a radiation source, said radiation source directing radiation at said object; a radiation detector, said radiation detector detecting radiation from said object; an electromagnet capable of generating a varying magnetic field about said object; means for detecting a change in said radiation detected from said object, both in the presence of said magnetic field and in the absence of said magnetic field; means for storing reference characteristic changes in said radiation previously identified with said specific elements and/or compounds; and means for correlating said change in said radiation with said reference characteristic identifying said specific elements and/or compounds as being present within said object. - View Dependent Claims (7, 8, 9)
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Specification