US3748472A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of measuring fast-neutron flux
Assignee: United States Atomic Energy Commission
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Filing: 1972-08-11
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Granted: 1973-07-24
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Expires: 1992-08-11
Abstract
Abstract This invention consists of a novel method for measuring the neutron flux of monoenergetic fast-neutrons in the 700-5,000 keV energy range. A shielded, planar lithium-drifted germanium detector is placed so as to view a fast-neutron source. A collimated beam of 700 to 5,000 keV monoenergetic fast-neutrons from the neutron source is impinged upon the Ge(Li) diode of the detector. The number of internal conversion electrons with an energy of 691 keV produced within the Ge(Li) diode due to neutron inelastic scattering are counted and then converted according to a predetermined efficiency ratio for the detector into a value for neutron flux, the number of internal conversion electrons emitted being proportional to the total number of neutrons incident on the detector.
Inventors
- 👤 D Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:09
CPC Classifications
G; G01; G01T; G01T3/00; G01T3/08
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
169 words
A method of measuring the neutron flux of 700 to 5,000 keV monoenergetic neutrons utilizing a planar lithium-drifted germanium detector, comprising shielding said detector; measuring the neutron efficiency ratio of said shielded detector for each of several fast-neutron energies in the 700 to 5,000 keV energy range; impinging a collimated beam of monoenergetic fast-neutrons having an energy of 700 to 5,000 keV upon the lithium-drifted germanium diode of said shielded detector, whereby internal conversion electrons are produced during the de-excitation of the 691 keV 0 first-excited energy state of the 72Ge isotope intrinsically present in said detector''s diode following excitation to said state by inelastic scattering of said impinging fast-neutrons; counting the number of internal conversion electrons produced within said detector''s diode; and determining the value of the neutron flux for said monoenergetic neutron beam from the number of said internal conversion electron counts in accordance with said previously determined efficiency ratio, said internal conversion electron count being proportional to the total number of neutrons incident on said detector.
Claim 2
Dependent Claim
90 words
The method according to claim 2 wherein said efficiency ratio is measured by impinging a beam of collimated monoenergetic fast-neutrons having a known energy within said 700 to 5,000 keV energy range upon the lithium-drifted germanium diode of said shielded detector, measuring simultaneously the number of neutrons incident on said detector''s diode and the number of internal conversion electrons being produced therein, and dividing said number of conversion electrons produced by said number of incident neutrons, repeating said measurements for each of several impinging fast-neutron energies within said energy range.
Claim 3
Dependent Claim
25 words
The method according to claim 2 wherein said internal conversion electron counts are corrected for neutron scattering within said shielding, background radiation and electronic dead-time.
Claim 4
Independent Claim
240 words
A method of measuring the neutron flux of 700 to 5,000 keV monoenergetic neutron utilizing a planar lithium-drifted germanium detector having a lithium-drifted germanium diode wherein approximately 27 percent of the germanium in said diode consists of the isotope 72Ge, comprising shielding said detector so as to insure that most of the neutrons with energies exceeding 691 keV which reach said detector are collimated unscattered neutrons, no portion of said detector diode being shielded from direct neutron flux; measuring the neutron efficiency ratio of said shielded detector for each of several fast-neutron energies in the 700 to 5,000 keV energy range; placing a monoenergetic fast-neutron source a measured distance from and in view of said detector diode; measuring the solid angle of said detector; impinging a beam of 700 to 5,000 keV monoenergetic fast-neutrons from said neutron source upon said shielded detector diode, whereby internal conversion electrons are produced during the de-excitation of the 691 keV 0 first-excited energy state of the 72Ge isotope following excitation to said state by inelastic scattering of said impinging fast-neutrons; counting the number of 691 keV internal conversion electrons produced within said diode per second; and determining the value of the neturon flux for said monoenergetic neutron beam in neutrons/second/steradian from the number of said internal conversion electron counts in accordance with said previously determined efficiency ratio, said internal conversion electron count being proportional to the total number of neutrons incident on said detector.
Claim 5
Dependent Claim
88 words
The method according to claim 5 wherein said efficiency ratio is measured by impinging a beam of collimated monoenergetic fast-neutrons having a known energy within said 700 to 5,000 keV energy range upon the diode of said shielded detector, measuring simultaneously the number of neutrons incident on said detector diode and the number of internal conversion electrons being produced therein, and dividing said number of conversion electrons produced by said number of incident neutrons, repeating said measurements for each of several impinging fast-neutron energies within said energy range.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-23 | 1977-01-22 | 1977-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-23 | 1981-01-22 | 1981-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-23 | 1985-01-22 | 1985-07-24 | $7700.00 | Window Closed / Lapsed |