Portable nuclear moisture-density gauge with low activity nuclear sources
First Claim
1. A portable low activity nuclear measuring gauge for measuring the density and moisture characteristics of a test material, comprisinga low activity neutron radiation source for emitting fast neutrons into the test material,thermal neutron detector means mounted in predetermined spaced relationship to said neutron source for detecting thermal neutrons which have been moderated by neutron moderating elements, such as hydrogen, present in the test material and for generating a signal representative of the moisture content of the test material,a low activity gamma radiation source for emitting gamma radiation into the test material,gamma radiation detector means mounted in predetermined spaced relationship to said gamma radiation source for detecting gamma radiation which is emitted from the gamma radiation source and which passes through the test material and for generating an uncorrected signal which is representative of the density of the test material plus error due to extraneous background radiation,means operatively connected to said thermal neutron detector means for generating a correction signal which is a function of said moisture signal and which represents the amount of gamma radiation emitted from said test material resulting from the (n, γ
- ) neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, in the test material; and
means for applying said correction signal to said uncorrected density signal to obtain a corrected density signal which is unaffected by background gamma radiation caused by the presence of neutron capture elements, such as hydrogen, in the test material.
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Abstract
The nuclear moisture-density gauge of the present invention employs a low activity neutron radiation source and a low activity gamma radiation source. In order to achieve more accurate density measurements at the relatively low count rates which results from the use of a low activity gamma source, the present invention is provided with means for generating a correction signal which is a function of the moisture content of the test material and which represents the amount of gamma radiation emitted from the test material resulting from the neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, present in the test material. This correction signal is applied to the uncorrected density signal obtained from the gauge to thereby obtain a corrected density measurement which is unaffected by background gamma radiation caused by the presence of neutron capture elements in the test material. The gauge is also provided with means for correcting naturally occurring background gamma radiation from the test material.
58 Citations
10 Claims
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1. A portable low activity nuclear measuring gauge for measuring the density and moisture characteristics of a test material, comprising
a low activity neutron radiation source for emitting fast neutrons into the test material, thermal neutron detector means mounted in predetermined spaced relationship to said neutron source for detecting thermal neutrons which have been moderated by neutron moderating elements, such as hydrogen, present in the test material and for generating a signal representative of the moisture content of the test material, a low activity gamma radiation source for emitting gamma radiation into the test material, gamma radiation detector means mounted in predetermined spaced relationship to said gamma radiation source for detecting gamma radiation which is emitted from the gamma radiation source and which passes through the test material and for generating an uncorrected signal which is representative of the density of the test material plus error due to extraneous background radiation, means operatively connected to said thermal neutron detector means for generating a correction signal which is a function of said moisture signal and which represents the amount of gamma radiation emitted from said test material resulting from the (n, γ - ) neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, in the test material; and
means for applying said correction signal to said uncorrected density signal to obtain a corrected density signal which is unaffected by background gamma radiation caused by the presence of neutron capture elements, such as hydrogen, in the test material. - View Dependent Claims (2, 3, 4, 5)
- ) neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, in the test material; and
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6. A method of measuring the density of a test material using a low activity gamma radiation source in the presence of a neutron radiation source, comprising:
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directing fast neutrons from a neutron radiation source into the test material, detecting neutrons which have been moderated and thermalized by neutron moderating elements present in the test material and generating a signal representative of the moisture content of the test material, directing gamma radiation from a gamma radiation source into the test material, detecting gamma radiation emitted from the gamma radiation source and which passes through the test material and generating an uncorrected signal which is representative of the density of the test material plus error due to extraneous background radiation, generating a correction signal which is a function of said moisture signal and which represents the amount of gamma radiation emitted from said test material resulting from the (n, γ
) neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, in the test material, andapplying said correction signal to said uncorrected density signal to obtain a corrected density signal which is unaffected by background gamma radiation caused by the presence of neutron capture elements in the test material. - View Dependent Claims (7, 8, 9, 10)
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Specification