US4501965A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for sampling a plasma into a vacuum chamber
Assignee: DONALD JAMES DOUGLAS
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Filing: 1983-01-14
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Granted: 1985-02-26
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Expires: 2003-01-14
Abstract
Abstract A plasma is generated within an induction coil and the plasma is sampled through an orifice into a vacuum chamber for mass analysis of trace ions in the plasma. Arcing at the orifice is prevented by grounding the induction coil at or near its center, thus eliminating ultraviolet noise and reducing average ion energies and ion energy spread, as well as preventing destruction of the orifice. The elimination of arcing at the orifice allows the use of a sharp edge orifice structure to prevent formation of a cool boundary layer over the orifice and also permits direct sampling of the plasma. The direct sampling and the lack of cooling prevent recombination and reaction of the ions with oxygen and improve the response to elements of high ionization potential, increasing the desired ion signal and greatly reducing the presence of oxides which would otherwise complicate the spectrum.
Inventors
- 👤 Donald J. Douglas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:24
CPC Classifications
H; H01; H01J; H01J49/00; H01J49/02; H01J49/06; H01J49/067; H01J49/10; H01J49/105; H05; H05H; H05H1/00; H05H1/24; H05H1/46
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
113 words
Apparatus for sampling a plasma into a vacuum chamber comprising: (a) means for generating a plasma, including an electrical induction coil having first and second terminals and at least one turn between said first and second terminals, said turn defining a space within said coil for generation of said plasma, (b) a vacuum chamber including an orifice plate defining a wall of said vacuum chamber, (c) said orifice plate having an orifice therein located adjacent said space for sampling a portion of said plasma through said orifice into said vacuum chamber, (d) and circuit means connected to said coil between said terminals to reduce the peak to peak voltage swing in said plasma.
Claim 2
Dependent Claim
113 words
Apparatus for sampling a plasma into a vacuum chamber comprising: (a) means for generating a plasma, including an electrical induction coil having first and second terminals and at least one turn between said first and second terminals, said turn defining a space within said coil for generation of said plasma, (b) a vacuum chamber including an orifice plate defining a wall of said vacuum chamber, (c) said orifice plate having an orifice therein located adjacent said space for sampling a portion of said plasma through said orifice into said vacuum chamber, (d) and circuit means connected to said coil between said terminals to reduce the peak to peak voltage swing in said plasma.
Claim 3
Dependent Claim
13 words
Apparatus according to claim 1 wherein said coil includes a plurality of turns.
Claim 4
Dependent Claim
29 words
Apparatus according to claim 2 wherein said circuit means includes means for holding the potential at a point in said coil between said terminals at a substantially constant value.
Claim 5
Dependent Claim
10 words
Apparatus according to claim 3 wherein said value is ground.
Claim 6
Dependent Claim
18 words
Apparatus according to claim 3 wherein said point is located at or near the centre of said coil.
Claim 7
Dependent Claim
18 words
Apparatus according to claim 4 wherein said point is located at or near the centre of said coil.
Claim 8
Dependent Claim
32 words
Apparatus according to claim 2 wherein said circuit means includes a tap connected to said coil between said terminals thereof, said tap being located at or near the centre of said coil.
Claim 9
Dependent Claim
15 words
Apparatus according to claim 7 wherein said tap is clamped to a substantially fixed potential.
Claim 10
Dependent Claim
10 words
Apparatus according to claim 8 wherein said potential is ground.
Claim 11
Dependent Claim
26 words
Apparatus according to claim 3 and including mass analyzer means located within said vacuum chamber for analyzing ions sampled into said vacuum chamber from said plasma.
Claim 12
Dependent Claim
26 words
Apparatus according to claim 9 and including mass analyzer means located within said vacuum chamber for analyzing ions sampled into said vacuum chamber from said plasma.
Claim 13
Dependent Claim
33 words
Apparatus according to claim 3 wherein said orifice plate includes a conical wall extending outwardly from said plate towards said space, said conical wall having a sharp outer edge which defines said orifice.
Claim 14
Dependent Claim
33 words
Apparatus according to claim 9 wherein said orifice plate includes a conical wall extending outwardly from said plate towards said space, said conical wall having a sharp outer edge which defines said orifice.
Claim 15
Dependent Claim
56 words
Apparatus according to claim 3 wherein said orifice plate includes a conical wall extending outwardly from said plate towards said space, said conical wall having a sharp outer edge which defines said orifice, said apparatus further including mass analyzer means located within said vacuum chamber for analyzing ions sampled into said vacuum chamber from said plasma.
Claim 16
Dependent Claim
56 words
Apparatus according to claim 9 wherein said orifice plate includes a conical wall extending outwardly from said plate towards said space, said conical wall having a sharp outer edge which defines said orifice, said apparatus further including mass analyzer means located within said vacuum chamber for analyzing ions sampled into said vacuum chamber from said plasma.
Claim 17
Independent Claim
69 words
A method of sampling a plasma into a vacuum chamber comprising: (a) applying a high frequency electrical current to a coil to generate a plasma within said coil, (b) reducing the peak to peak voltage variations is said plasma by limiting the voltage variations in said coil at a position between the ends thereof, and (c) directing a portion of said plasma through an orifice into said vacuum chamber.
Claim 18
Independent Claim
69 words
A method of sampling a plasma into a vacuum chamber comprising: (a) applying a high frequency electrical current to a coil to generate a plasma within said coil, (b) reducing the peak to peak voltage variations is said plasma by limiting the voltage variations in said coil at a position between the ends thereof, and (c) directing a portion of said plasma through an orifice into said vacuum chamber.
Claim 19
Dependent Claim
29 words
A method according to claim 16 wherein said step (b) comprises holding the potential in said coil at a position between the ends thereof at a substantially constant value.
Claim 20
Dependent Claim
12 words
A method according to claim 17 wherein said value is substantially ground.
Claim 21
Dependent Claim
18 words
A method according to claim 17 wherein said position is at or near the center of said coil.
Claim 22
Dependent Claim
19 words
A method according to claim 17 wherein said position is within one-quarter turn from the center of said coil.
Claim 23
Dependent Claim
31 words
A method according to claim 17 wherein said position is at or near the center of said coil and including the step of analyzing ions in said portion of said plasma.
Claim 24
Dependent Claim
35 words
A method according to claim 17 wherein said position is at or near the center of said coil and including the step of analyzing with a mass analyzer ions in said portion of said plasma.
Claim 25
Dependent Claim
60 words
A method according to claim 17 wherein said position is at or near the center of said coil and including the step of analyzing ions in said portion of said plasma, said method further including the step of preventing substantial cooling of said plasma over said orifice to reduce recombination and reaction of said ions in said plasma with oxygen.
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) | 1988-02-26 | 1988-08-27 | 1989-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-26 | 1992-08-27 | 1993-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-26 | 1996-08-27 | 1997-02-26 | $7700.00 | Window Closed / Lapsed |