US4297615A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High current density cathode structure
Assignee: University of California, San Diego
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Filing: 1979-03-19
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Granted: 1981-10-27
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Expires: 1999-03-19
Abstract
Abstract A lanthanum hexaboride element, typically of cylindrical configuration, is mounted within a high plasma density cathode enclosure. An inlet is provided to supply gas to the cathode enclosure in the vicinity of the lanthanum hexaboride cathode element, and the element is heated to electron-emitting temperature. A plasma utilization chamber is coupled to receive an electron or plasma stream from the cathode enclosure through an aperture of a suitable size to maintain a relatively high plasma density within the cathode enclosure. The plasma density within the cathode enclosure is preferably above the critical level required for high current emission from the lanthanum hexaboride cathode structure. For example this may be in the order of 3.5 times 10 12 electrons per cubic centimeter for a current density of 10 amperes per square centimeter. The lanthanum hexaboride cathode element is supported on notched graphite rings, and the cathode enclosure is made of tungsten. Exceedingly high currents, of the order of 1000 amperes, and high current densities of the order of 5,000 amperes per square centimeter can be obtained from the exit aperture.
Inventors
- 👤 Dan M. Goebel
- 👤 James T. Crow
- 👤 A. Theodore Forrester
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:06
CPC Classifications
H; H01; H01J; H01J1/00; H01J1/02; H01J1/13; H01J1/14; H01J1/148; H01J27/00; H01J27/02; G; G21; G21B; G21B1/00; G21B1/11; H01J1/20; H01J1/22; H05; H05H; H05H2240/00; Y; Y02; Y02E; Y02E30/00; Y02E30/10
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
179 words
A system including a compact cathode assembly having high electron emission current densities for producing a dense gas plasma, comprising: a high plasma density cathode enclosure; inlet means connected to said cathode enclosure for supplying gas to said cathode enclosure; a low plasma density utilization chamber coupled to receive plasma from said cathode enclosure through a restricted opening between said enclosure and said chamber; a cathode element of lanthanum hexaboride having an emitting surface exposed within said cathode enclosure; means for heating said lanthanum hexaboride element to an elevated temperature from a surface of said lanthanum hexaboride away from the emitting surface, whereby contamination of said emitting surface is avoided; said system including means for establishing a high plasma density, in the order of 2×10 12 electrons per cubic centimeter or more, within said cathode enclosure, substantially higher than in said utilization chamber; power supply means for drawing current densities greater than five amperes per square centimeter from the emitting surface of said lanthanum hexaboride cathode; and means for mounting said lanthanum hexaboride cathode on carbon material support arrangements.
Claim 2
Independent Claim
179 words
A system including a compact cathode assembly having high electron emission current densities for producing a dense gas plasma, comprising: a high plasma density cathode enclosure; inlet means connected to said cathode enclosure for supplying gas to said cathode enclosure; a low plasma density utilization chamber coupled to receive plasma from said cathode enclosure through a restricted opening between said enclosure and said chamber; a cathode element of lanthanum hexaboride having an emitting surface exposed within said cathode enclosure; means for heating said lanthanum hexaboride element to an elevated temperature from a surface of said lanthanum hexaboride away from the emitting surface, whereby contamination of said emitting surface is avoided; said system including means for establishing a high plasma density, in the order of 2×10 12 electrons per cubic centimeter or more, within said cathode enclosure, substantially higher than in said utilization chamber; power supply means for drawing current densities greater than five amperes per square centimeter from the emitting surface of said lanthanum hexaboride cathode; and means for mounting said lanthanum hexaboride cathode on carbon material support arrangements.
Claim 3
Dependent Claim
19 words
A system as defined in claim 1 wherein said cathode element is a hollow cylinder of solid lanthanum hexaboride.
Claim 4
Dependent Claim
26 words
A system as defined in claim 2 wherein said inlet means includes means for supplying gas to the inside of said cylinder, at one end thereof.
Claim 5
Dependent Claim
30 words
A system as defined in claim 3 wherein said opening is substantially aligned with said cylinder and is spaced away from said cylinder in the opposite direction from said inlet.
Claim 6
Dependent Claim
33 words
A system as defined in claim 1 including means for establishing a plasma density within said cathode enclosure above the critical level permitting cathode electron current densities of 20 amperes per square centimeter.
Claim 7
Dependent Claim
17 words
A system as defined in claim 1 wherein the walls of said cathode enclosure are of tungsten.
Claim 8
Dependent Claim
31 words
A system as defined in claim 1 wherein said cathode element is a hollow cylinder of solid lanthanum hexaboride and wherein notched carbon rings are provided for physically mounting said cylinder.
Claim 9
Dependent Claim
34 words
A system as defined in claim 1 wherein means are provided for producing a current density of more than ten amperes per square centimeter from the emitting surface of the lanthanum hexaboride cathode element.
Claim 10
Dependent Claim
153 words
A compact cathode assembly having high electron emission current densities for producing a dense gas plasma, comprising: a high plasma density cathode enclosure, inlet means connected to said cathode enclosure for supplying gas to said cathode enclosure; a low plasma density utilization chamber coupled to receive plasma from said cathode enclosure through an aperture between said enclosure and said chamber; a lanthanum hexaboride cathode element having an electron emissivity of more than 10 amperes per square centimeter mounted within said cathode enclosure between said inlet means and said aperture; means for heating said cathode element to an elevated temperature without contaminating the electron emitting surface of said cathode element; and said system including means for providing a much higher plasma density within said cathode enclosure than in said utilization chamber, said higher plasma density being above the critical level required to support a cathode electron emission density of ten amperes per square centimeter.
Claim 11
Dependent Claim
153 words
A compact cathode assembly having high electron emission current densities for producing a dense gas plasma, comprising: a high plasma density cathode enclosure, inlet means connected to said cathode enclosure for supplying gas to said cathode enclosure; a low plasma density utilization chamber coupled to receive plasma from said cathode enclosure through an aperture between said enclosure and said chamber; a lanthanum hexaboride cathode element having an electron emissivity of more than 10 amperes per square centimeter mounted within said cathode enclosure between said inlet means and said aperture; means for heating said cathode element to an elevated temperature without contaminating the electron emitting surface of said cathode element; and said system including means for providing a much higher plasma density within said cathode enclosure than in said utilization chamber, said higher plasma density being above the critical level required to support a cathode electron emission density of ten amperes per square centimeter.
Claim 12
Dependent Claim
19 words
A system as defined in claim 9 wherein said cathode element is a hollow cylinder of solid lanthanum hexaboride.
Claim 13
Independent Claim
150 words
A system including a compact cathode assembly having high electron emission current densities for producing a dense gas plasma, comprising: a high plasma density cathode enclosure; inlet means connected to said cathode enclosure for supplying gas to said cathode enclosure; a hollow cylindrical cathode element of solid lanthanum hexaboride, said cathode element having an electron emitting surface; means including at least two carbon rings having inner and outer peripheral notches, for mounting said cylindrical cathode within said cathode enclosure; means for heating said lanthanum hexaboride element to an elevated temperature without contaminating said electron emitting surface; and said system including means for producing a current density of more than ten amperes per square centimeter at the surface of the lanthanum boride element, said means including means for establishing a plasma density within said cathode enclosure above the critical level permitting cathode electron current densities of ten amperes per square centimeter.
Claim 14
Independent Claim
150 words
A system including a compact cathode assembly having high electron emission current densities for producing a dense gas plasma, comprising: a high plasma density cathode enclosure; inlet means connected to said cathode enclosure for supplying gas to said cathode enclosure; a hollow cylindrical cathode element of solid lanthanum hexaboride, said cathode element having an electron emitting surface; means including at least two carbon rings having inner and outer peripheral notches, for mounting said cylindrical cathode within said cathode enclosure; means for heating said lanthanum hexaboride element to an elevated temperature without contaminating said electron emitting surface; and said system including means for producing a current density of more than ten amperes per square centimeter at the surface of the lanthanum boride element, said means including means for establishing a plasma density within said cathode enclosure above the critical level permitting cathode electron current densities of ten amperes per square centimeter.
Claim 15
Dependent Claim
17 words
A system as defined in claim 11 wherein the walls of said cathode enclosure are of tungsten.
Claim 16
Dependent Claim
24 words
A system as defined in claim 11 further comprising a low plasma density utilization chamber coupled to said cathode enclosure through a restricted aperture.
Claim 17
Dependent Claim
97 words
A cathode system comprising: a cathode element of lanthanum hexaboride having an electron emitting surface; means for heating said cathode to electron emitting temperatures without contaminating said electron emitting surface; means for establishing a gas plasma density in the vicinity of said electron emitting surface having an electron density in the order of 2×10 12 electrons per cubic centimeter or more; means for supporting said cathode with only carbonaceous material in engagement with said cathode; and power supply means for drawing current densities greater than 5 amperes per square centimeter from said emitting surface of said cathode.
Claim 18
Dependent Claim
97 words
A cathode system comprising: a cathode element of lanthanum hexaboride having an electron emitting surface; means for heating said cathode to electron emitting temperatures without contaminating said electron emitting surface; means for establishing a gas plasma density in the vicinity of said electron emitting surface having an electron density in the order of 2×10 12 electrons per cubic centimeter or more; means for supporting said cathode with only carbonaceous material in engagement with said cathode; and power supply means for drawing current densities greater than 5 amperes per square centimeter from said emitting surface of said cathode.
Claim 19
Dependent Claim
56 words
A cathode system as defined in claim 14 including means for establishing a plasma having an electron density near said cathode equal to or greater than 3.5×10 12 electrons per cubic centimeter, and power supply means for drawing current densities greater than 10 amperes per square centimeter from said emitting surface of said lanthanum hexaboride cathode.
Claim 20
Dependent Claim
42 words
A system as set forth in claim 1, 9, or 13 including means for providing a current density in the order of 2500 amperes per square centimeter or more at the opening or aperture between said cathode enclosure and the utilization chamber.
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) | 1984-10-26 | 1985-04-27 | 1985-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-26 | 1989-04-27 | 1989-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-26 | 1993-04-27 | 1993-10-27 | $7700.00 | Window Closed / Lapsed |