US4916356A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High emissivity cold cathode ultrastructure
Assignee: United States Department of the Air Force
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Filing: 1988-09-26
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Granted: 1990-04-10
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Expires: 2008-09-26
Abstract
Abstract A high emissivity cold cathode has alternating cylindrical tube layers, deposited by vapor deposition, of a refractory metal such as niobium and a refractory insulating material such as alumina. The metal layers have a thickness of less than or about 1,000 angstroms such that the electric field strength at the exposed end is sufficient, in combination with a low work function metal to emit electrons when a voltage of about 2,000 volts is applied.
Inventors
- 👤 Brian S. Ahern
- 👤 David W. Weyburne
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 22:44
CPC Classifications
H; H01; H01J; H01J1/00; H01J1/02; H01J1/30; H01J1/304
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
173 words
A high emissivity cold cathode, said high emissivity cold cathode comprising: a central rod, said central rod being made of a refractory and insulating material; a metal cylindrical tube, said tube being deposited by vapor deposition onto said central rod, said tube being made of a refractory metal, said tube having a wall thickness of less than or about 1,000 angstroms wherein the exposed top edge radius (r) is of a dimension to obtain an electric field strength of about 2 to 5×10 7 volts per centimeter for spontaneous electron emission therefrom, said field strength (E) given by E=kV/r where V is the applied voltage and k is a constant; an insulator cylindrical tube, said insulator cylindrical tube being vapor deposited on said metal cylindrical tube, said insulator cylindrical tube being made of a refractory material, said insulation cylindrical tube having a thickness of about 20 times that of said metal cylindrical tube, and additional tubes being deposited thereon in an alternating manner until a determined diameter of said cold cathode is obtained.
Claim 2
Dependent Claim
173 words
A high emissivity cold cathode, said high emissivity cold cathode comprising: a central rod, said central rod being made of a refractory and insulating material; a metal cylindrical tube, said tube being deposited by vapor deposition onto said central rod, said tube being made of a refractory metal, said tube having a wall thickness of less than or about 1,000 angstroms wherein the exposed top edge radius (r) is of a dimension to obtain an electric field strength of about 2 to 5×10 7 volts per centimeter for spontaneous electron emission therefrom, said field strength (E) given by E=kV/r where V is the applied voltage and k is a constant; an insulator cylindrical tube, said insulator cylindrical tube being vapor deposited on said metal cylindrical tube, said insulator cylindrical tube being made of a refractory material, said insulation cylindrical tube having a thickness of about 20 times that of said metal cylindrical tube, and additional tubes being deposited thereon in an alternating manner until a determined diameter of said cold cathode is obtained.
Claim 3
Dependent Claim
21 words
A high emissivity cold cathode as defined in claim 1 wherein said central rod has a diameter of about 0.050 inch.
Claim 4
Dependent Claim
25 words
A high emissivity cold cathode as defined in claim 1 wherein said insulating material is selected from the group comprising oxides, borides, nitrides and carbides.
Claim 5
Dependent Claim
24 words
A high emissivity cold cathode as defined in claim 1 wherein said metal cylindrical tube has a thickness from 500 to about 1,000 angstroms.
Claim 6
Dependent Claim
22 words
A high emissivity cold cathode as defined in claim 1 wherein said insulating cylindrical tube has a thickness of about 20,000 angstroms.
Claim 7
Dependent Claim
21 words
A high emissivity cold cathode as defined in claim 1 wherein said metal is niobium and said insulating material is alumina.
Claim 8
Dependent Claim
40 words
A high emissivity cold cathode as defined in claim 1 wherein said refractory metal is an alloy having a low work function and said refractory material of said insulator cylindrical tube is an insulating material of high dielectric breakdown strength.
Claim 9
Dependent Claim
27 words
A high emissivity cold cathode as defined in claim 7 wherein said alloy is lanthanum hexaboride, LaB 6 , and said insulating material is boron nitride, BN.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-04-09 | 1993-10-09 | 1994-04-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-04-09 | 1997-10-09 | 1998-04-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-04-09 | 2001-10-09 | 2002-04-10 | $7700.00 | Window Closed / Lapsed |