Low activity nuclear density gauge
First Claim
1. A nuclear gauge for measuring the density of a material, said gauge comprising:
- a gauge housing having a surface adapted to be positioned on a surface of the material sample;
at least one gamma radiation source within said gauge housing having a characteristic primary energy and having a total activity of no more than 100 microcuries, said at least one source being positioned for emitting gamma radiation through said housing surface and into an underlying material sample;
at least one energy selective gamma radiation detector mounted within the gauge housing in spaced apart relation with respect to said at least one gamma radiation source, said gamma radiation detector being operable for producing signals representing the energy level of detected gamma radiation; and
density calculating means connected to said detector and operable for calculating a value for the density of the material sample based upon detected signals having an energy level within a predetermined portion of the energy spectrum of the gamma radiation detected by said at least one detector.
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Abstract
A nuclear density gauge and test method is provided for measuring density material in a relatively thin zone beneath a surface of the material. The gauge comprises a gauge housing and a substantially planar base on said gauge housing adapted to be positioned on a surface of the material sample. A gamma radiation source having a characteristic primary energy and an activity of no more than 100 microcurie is mounted within the housing and cooperates with the base for emitting gamma radiation through the base and into an underlying material sample. An energy selective gamma radiation detector is mounted within the gauge housing and in laterally spaced apart relation from the gamma radiation source. The gamma radiation detector is operable for quantifying the energy level of the detected gamma radiation. Shielding is provided within the gauge housing between the source and the detector for preventing gamma radiation from passing directly from said source to the detector. An analyzer is connected to the detector for detecting gamma radiation counts in a predetermined energy spectrum having a lower limit of 0.1 MeV or greater and an upper limit which is less than the characteristic primary energy of said source. The density of the sample is calculated based upon the gamma radiation counts obtained by the analyzer within the predetermined energy spectrum.
27 Citations
51 Claims
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1. A nuclear gauge for measuring the density of a material, said gauge comprising:
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a gauge housing having a surface adapted to be positioned on a surface of the material sample;
at least one gamma radiation source within said gauge housing having a characteristic primary energy and having a total activity of no more than 100 microcuries, said at least one source being positioned for emitting gamma radiation through said housing surface and into an underlying material sample;
at least one energy selective gamma radiation detector mounted within the gauge housing in spaced apart relation with respect to said at least one gamma radiation source, said gamma radiation detector being operable for producing signals representing the energy level of detected gamma radiation; and
density calculating means connected to said detector and operable for calculating a value for the density of the material sample based upon detected signals having an energy level within a predetermined portion of the energy spectrum of the gamma radiation detected by said at least one detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A nuclear gauge for measuring the density of a material, said gauge comprising:
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a gauge housing;
a base on said gauge housing adapted to be positioned on a surface of the material sample;
at least one gamma radiation source within said gauge housing having a characteristic primary energy and having a total activity of no more than 100 micro curies, said at least one source being positioned for emitting gamma radiation through said base and into an underlying material sample;
at least one energy selective gamma radiation detector mounted within the gauge housing in spaced apart relation with respect to said at least one gamma radiation source, said gamma radiation detector being operable for producing signals representing the energy level of detected gamma radiation;
shielding within said gauge housing and located between said at least one source and said at least one detector for blocking gamma radiation from passing directly from said source to said detector;
an analyzer operatively connected to said detector for receiving said signals therefrom, said analyzer including means for classifying and accumulating signals in one or more channels over the energy spectrum of the detected gamma radiation; and
density calculating means connected to said analyzer and operable for calculating a value for the density of the material sample based upon the accumulated signals in one or more of said channels selected to represent a predetermined portion of the energy spectrum of the gamma radiation detected by said at least one detector. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A nuclear gauge for measuring the density of a material, said gauge comprising:
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a gauge housing;
a base on said gauge housing adapted to be positioned on a surface of the material sample;
at least one gamma radiation source within said gauge housing having a characteristic primary energy and having a total activity of no more than 100 microcuries, said at least one source being positioned for emitting gamma radiation through said base and into an underlying material sample;
at least one energy selective gamma radiation detector mounted within the gauge housing in spaced apart relation with respect to said at least one gamma radiation source, said gamma radiation detector being operable for producing signals representing the energy level of detected gamma radiation;
shielding within said gauge housing and located between said at least one source and said detector for blocking gamma radiation from passing directly from said source to said detector;
an analyzer operatively connected to said detector for receiving said signals therefrom, said analyzer including means for classifying and accumulating signals in one or more channels over the energy spectrum of the detected gamma radiation;
background radiation detection means connected to said analyzer and operable for calculating a value representing the ambient background gamma radiation, density calculating means connected to said analyzer and operable for calculating a value for the density of the material sample based upon the accumulated signals in one or more of said channels selected to represent a predetermined portion of the energy spectrum of the gamma radiation detected by said at least one detector, and wherein said density calculating means also cooperates with said background radiation detection means for calculating a value for the density of the material sample which is corrected for ambient background radiation; and
stabilization means associated with said analyzer for correcting for temperature sensitivity of said detector, said stabilization means including means responsive to reference signals in at least one other selected channel of said analyzer, said at least one other selected channel representing an energy level outside of said predetermined portion of the energy spectrum. - View Dependent Claims (31, 32, 33)
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34. A nuclear gauge for measuring the density of a material, said gauge comprising:
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a gauge housing;
a base on said gauge housing having a lower surface adapted to be positioned on an exposed upper surface of the material sample;
at least one gamma radiation source having a characteristic primary energy and a total activity of no more than 100 microcurie, said at least one source being mounted within said housing and cooperating with said base for emitting gamma radiation through the base and into an underlying material sample;
a sodium iodide crystal gamma radiation detector mounted within the gauge housing and in spaced apart relation from said gamma radiation source, a photomultiplier tube operably connected to said sodium iodide crystal detector and being operable for generating an electrical signal proportional to the energy of the gamma radiation detected by said sodium iodide detector;
shielding within said gauge housing and located between said source and said detector for shielding gamma radiation from passing directly from said source to said detector;
an analyzer connected to said photomultiplier tube and operable for detecting gamma radiation counts in one or more channels over the energy spectrum of the detected gamma radiation; and
density calculating means connected to said analyzer and operable for calculating a value for the density of the material sample based upon the accumulated signals in one or more of said channels selected to represent a predetermined energy spectrum having a lower limit of 0.1 MeV or greater and an upper limit which is less than the characteristic primary energy of said source. - View Dependent Claims (35, 36, 37, 38, 39)
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40. A method for measuring the density of a material, comprising:
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directing gamma radiation into the material from at least one source having a characteristic primary energy and a total activity of no more than 100 microcuries;
detecting gamma radiation which has interacted with and been backscattered by the material and quantifying the energy levels of the detected gamma radiation;
selecting gamma radiation counts having an energy level within a predetermined portion of the energy spectrum of the detected gamma radiation; and
calculating a value for the density of the sample based upon the selected gamma radiation counts within said predetermined portion of the energy spectrum. - View Dependent Claims (41, 42, 43, 44)
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45. A method for measuring the density of a material, comprising:
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directing gamma radiation into the material from at least one source having a characteristic primary energy and a total activity of no more than 100 microcurie;
detecting gamma radiation which has interacted with and been backscattered by the material and generating signals representing the energy level of the detected gamma radiation;
classifying the signals according to their energy level and accumulating signal counts in respective channels of an analyzer;
selecting accumulated signals in one or more selected channels of the analyzer representing a predetermined portion of the energy spectrum of the detected gamma radiation; and
calculating a value for the density of the sample based upon the selected accumulated signals; and
,displaying a calculated density value for the material. - View Dependent Claims (46, 47)
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48. A nuclear gauge for measuring the density of a material, said gauge comprising:
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a gauge housing;
a base gauge housing having a lower surface adapted to be positioned on an underlying surface of the material sample;
at least one gamma radiation source within said gauge housing having a characteristic primary energy, said at least one source being positioned for emitting gamma radiation through said base and into an underlying material sample;
at least one energy selective gamma radiation detector mounted within the gauge housing in spaced apart relation with respect to said at least one gamma radiation source, said gamma radiation detector being operable for producing signals representing the energy level of detected gamma radiation;
shielding within said gauge housing and located between said at least one source and said detector for blocking gamma radiation from passing directly from said source to said detector;
a multichannel analyzer operatively connected to said detector for receiving said signals therefrom, said analyzer including means for classifying and accumulating signals in a plurality of discrete channels, each channel corresponding to a portion of the energy level spectrum of the detected gamma radiation;
density calculating means connected to said analyzer and operable for calculating a value for the density of the material sample based upon the accumulated signals in one or more of said channels selected to represent a predetermined portion of the energy spectrum of the gamma radiation detected by said at least one detector, stabilization means associated with said analyzer for correcting for temperature sensitivity of said detector, said stabilization means including means responsive to reference signals in at least one other selected channel of said analyzer, said at least one other selected channel representing an energy level outside of said predetermined portion of the energy spectrum. - View Dependent Claims (49, 50, 51)
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Specification