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US4194115A
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Method and means for helium/hydrogen ratio measurement by alpha scattering
Assignee: National Aeronautics and Space Administration
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Filing: 1978-11-07
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Granted: 1980-03-18
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Expires: 1998-11-07
Abstract
Abstract Apparatus and method for determining helium to hydrogen ratios in a gaseous sample by measurement of forward scattering products due to alpha particle collisions with helium and hydrogen contained within the gaseous sample. More specifically, an apparatus is disclosed in which a gaseous sample, contained within an enclosure, is bombarded by alpha particles created by a self contained radioactive source. Baffles are positioned in the enclosure so that only scattering products falling within a predetermined forward scattering angular range can impact a detector assembly. In an embodiment scattered particles are detected by two detectors mounted in tandem, the first completely blocking the second detector with respect to incident scattering products. This embodiment is based on the principle that scattering products have a forward scattering angle θ greater than 15 degrees due to alpha particle/hydrogen collisions comprise only recoil protons. For a given kinetic energy, recoil protons will penetrate farther into silicon detector material than will scattering products from alpha particle/helium collisions. Thus, an apparatus according to the teachings of the invention identifies alpha particle/hydrogen or alpha particle/helium collisions primarily by whether scattering product impacts occur simultaneously in both the first and second detectors or occur only in the first detector. Relative magnitudes of the two pulses can be used to further discriminate against other effects such as noise and cosmic ray events.
Inventors
- 👤 with respect to an invention of Frosch Robert A. Administrator of the National Aeronautics and Space Administration
- 👤 A. Bruce Whitehead
- 👤 Thomas A. Tombrello
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 23:08
CPC Classifications
G; G01; G01N; G01N23/00; G01N23/20; G01N23/201
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
121 words
An apparatus for providing data useful in a determination of the ratio of helium to hydrogen in a gaseous sample; comprising: a source for directing alpha particles into said gaseous sample; isolation means for isolating scattering products contained within a predetermined forward scattering angular range, said scattering products resulting from collisions between said alpha particles and said gaseous simple; detection means for detecting said isolated scattering products; first identification means for identifying said detected isolated scattering products resulting from alpha particle/hydrogen collisions; and second identification means for identifying said detected isolated scattering products resulting from alpha particle/helium collisions whereby the ratio of helium to hydrogen is determinable from the ratio of the products of said second and first identification means, respectively.
Claim 2
Independent Claim
121 words
An apparatus for providing data useful in a determination of the ratio of helium to hydrogen in a gaseous sample; comprising: a source for directing alpha particles into said gaseous sample; isolation means for isolating scattering products contained within a predetermined forward scattering angular range, said scattering products resulting from collisions between said alpha particles and said gaseous simple; detection means for detecting said isolated scattering products; first identification means for identifying said detected isolated scattering products resulting from alpha particle/hydrogen collisions; and second identification means for identifying said detected isolated scattering products resulting from alpha particle/helium collisions whereby the ratio of helium to hydrogen is determinable from the ratio of the products of said second and first identification means, respectively.
Claim 3
Dependent Claim
99 words
The apparatus of claim 1 in which said isolation means comprises: an elongated enclosure containing said gaseous sample and having said alpha particle source located at one end and said detection means at the other end; a plurality of baffles extending inwardly from said enclosure inner walls; and a blocking shield spaced-apart from said detection means and positioned to block a straight-line path from said alpha particle source to said detection means, said blocking shield and said baffles being located so that only scattering products within said predetermined forward scattering angular range can be detected by said detection means.
Claim 4
Dependent Claim
177 words
The apparatus of claim 2 in which said predetermined forward scattering angular range is between approximately 30 and 60 degrees, further comprising: said detection means comprising a first surface barrier detector and a second surface barrier detector, said first and second detectors being mounted in tandem and positioned so that said first detector faces into said enclosure, said first detector being chosen to have a thickness sufficiently great to absorb substantially all of the energy of scattering products due to alpha particle/helium collisions and to pass a portion of the energy of scattering products due to alpha particle/hydrogen collisions, said second detector being chosen to have a thickness sufficiently great to absorb the energy of alpha particle/hydrogen scattering products not absorbed by said first detector; said first identification means for identifying scattering products resulting from alpha particle/hydrogen collisions comprises means to identify substantially simultaneous output pulses from said first and second detectors; and said second identification means for identifying scattering products resulting from alpha particle/helium collisions comprises means to identify output pulses from said first detector only.
Claim 5
Dependent Claim
43 words
The apparatus of claim 3 in which said alpha particle source is Polonium 214, said first detector is a totally depleted gold-silicon surface barrier detector approximately 35 microns thick, and said second detector is a gold-silicon surface barrier detector approximately 100 microns thick.
Claim 6
Dependent Claim
19 words
The apparatus of claim 2 further comprising means to measure the pressure of said gaseous sample within said enclosure.
Claim 7
Independent Claim
279 words
An apparatus for providing data useful in a determination of the ratio of helium to hydrogen in a gaseous sample, comprising: a source for directing alpha particles into said gaseous sample whereby said alpha particles will collide with said helium and hydrogen; means for isolating scattering products due to collisions between said alpha particles and said gaseous sample to scattering products which occur within a predetermined forward scattering angular range; means for detecting said isolated scattering products comprising a first surface barrier detector and a second surface barrier detector, said first and second detectors being mounted in tandem and positioned so that said first detector is impacted first by said isolated scattering products, said first detector being chosen to have a thickness sufficiently great to absorb substantially all of the energy of isolated scattering products due to alpha particle/helium collisions and to pass a portion of the energy of isolated scattering products due to alpha particle/hydrogen collisions, said second detector being chosen to have a thickness sufficiently great to absorb the energy of isolated scattering products due to alpha particle/hydrogen collisions not absorbed by said first detector; first means for counting each isolated scattering product having a kinetic energy within a predetermined range that impacts said first detector but not said second detector thereby identifying an alpha particle/helium collision; and second means for counting each scattering product having a kinetic energy sufficiently great to pass through said first detector and being at least partially absorbed by said second detector thereby dentifying an alpha particle/hydrogen collision whereby the ratio of helium to hydrogen is determinable from the ratio of the products of said first and second means for counting, respectively.
Claim 8
Independent Claim
279 words
An apparatus for providing data useful in a determination of the ratio of helium to hydrogen in a gaseous sample, comprising: a source for directing alpha particles into said gaseous sample whereby said alpha particles will collide with said helium and hydrogen; means for isolating scattering products due to collisions between said alpha particles and said gaseous sample to scattering products which occur within a predetermined forward scattering angular range; means for detecting said isolated scattering products comprising a first surface barrier detector and a second surface barrier detector, said first and second detectors being mounted in tandem and positioned so that said first detector is impacted first by said isolated scattering products, said first detector being chosen to have a thickness sufficiently great to absorb substantially all of the energy of isolated scattering products due to alpha particle/helium collisions and to pass a portion of the energy of isolated scattering products due to alpha particle/hydrogen collisions, said second detector being chosen to have a thickness sufficiently great to absorb the energy of isolated scattering products due to alpha particle/hydrogen collisions not absorbed by said first detector; first means for counting each isolated scattering product having a kinetic energy within a predetermined range that impacts said first detector but not said second detector thereby identifying an alpha particle/helium collision; and second means for counting each scattering product having a kinetic energy sufficiently great to pass through said first detector and being at least partially absorbed by said second detector thereby dentifying an alpha particle/hydrogen collision whereby the ratio of helium to hydrogen is determinable from the ratio of the products of said first and second means for counting, respectively.
Claim 9
Dependent Claim
108 words
The apparatus of claim 6 in which said predetermined forward scattering angular range is between approximately 30 and 60 degrees, said first detector is a totally depleted gold-silicon surface barrier detector approximately 35 microns thick, said second detector is a gold-silicon surface barrier detector at least 100 microns thick, said means for isolating comprising; an enclosed chamber containing said sample gas, said alpha particle source and said means for detecting; and a plurality of baffles located within said chamber and positioned to allow forward scattering products within said predetermined angular range to impact said means for detecting and to block scattering products not within said predetermined angular range.
Claim 10
Dependent Claim
14 words
The apparatus of claim 7 in which said alpha particle source is Polonium 214.
Claim 11
Independent Claim
96 words
A method for developing data useful in determining the ratio of helium to hydrogen in a gaseous sample comprising the steps of: directing alpha particles into said gaseous sample; isolating scattering products due to collisions between said alpha particles and said gaseous sample that are within a predetermined forward scattering angular range; detecting said isolated scattering products; and identifying said detected isolated scattering products due to alpha particle/helium collisions and said isolated scattering products due to alpha particle/hydrogen collisions whereby the ratio of helium to hydrogen can be determined from the products of said identifying step.
Claim 12
Independent Claim
96 words
A method for developing data useful in determining the ratio of helium to hydrogen in a gaseous sample comprising the steps of: directing alpha particles into said gaseous sample; isolating scattering products due to collisions between said alpha particles and said gaseous sample that are within a predetermined forward scattering angular range; detecting said isolated scattering products; and identifying said detected isolated scattering products due to alpha particle/helium collisions and said isolated scattering products due to alpha particle/hydrogen collisions whereby the ratio of helium to hydrogen can be determined from the products of said identifying step.
Claim 13
Dependent Claim
120 words
The method of claim 9 in which said predetermined forward scattering angular range is between approximately 30 and 60 degrees, said identifying step further comprising the steps of: counting each detected scattering product having a kinetic energy within a predetermined voltage range that impacts a first detector of a detecting means comprising said first detector and a second detector mounted behind and in tandem with said first detector, but does not have sufficient energy to pass through said first detector, thereby identifying an alpha particle/helium collision; and counting each detected scattering product having a kinetic energy sufficiently great to pass through said first detector and be at least partially absorbed by said second detector thereby identifying an alpha particle/hydrogen collision.
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) | 1983-03-18 | 1983-09-17 | 1984-03-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-03-18 | 1987-09-17 | 1988-03-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-03-18 | 1991-09-17 | 1992-03-18 | $7700.00 | Window Closed / Lapsed |