Claims
- 1. A grid-controlled electron source comprising, a thermionic cathode having an electron-emissive surface, a multi-apertured insulative layer, and a multi-apertured control grid overlaying said electron emissive surface, said control grid comprising a multi-apertured conductive layer which is electrically isolated from said thermionic cathode by said insulative layer, said insulative layer being bonded to said control grid, the surface of said conductive layer distal said cathode being coated with a layer of boron nitride whereby the flow of thermionic electrons from said thermionic cathode can be controlled by applying a selected potential difference between said cathode and said conductive layer, and thermionic electron emission from said grid is inhibited by said boron nitride layer.
- 2. The electron source of claim 1, wherein said control grid includes clamp means to bias said control grid against said electron-emissive surface of said cathode.
- 3. The electron source of claim 1 wherein said multi-apertured conductive layer is a layer of carbon.
- 4. The electron source of claim 3 wherein said layer is made of pyrolytic graphite.
- 5. The electron source of claim 1 wherein said boron nitride layer has a thickness of 1 micron or less.
- 6. The source of claim 1, in which said insulative layer comprises boron nitride.
- 7. The source of claim 1 wherein said insulative layer comprises a barrier layer attached directly to said electron-emissive surface.
- 8. The source of claim 7 in which said barrier layer is a metal bonded to said electron-emissive surface.
- 9. The structure of claim 7 in which said barrier layer is a layer of a stable form of carbon.
- 10. A grid-controlled electron source comprising:
- a cathode capable of emitting thermionic electrons;
- a control grid adjacent and insulated from said cathode, having a surface distal said cathode and capable of emitting thermionic electrons; and
- a layer of boron nitride coating said surface, said layer being sufficiently thin to inhibit the emission of thermionic electrons from said surface, and to not behave as a pure insulator.
- 11. The electron source of claim 10 in which said layer of boron nitride is of the order of one micron in thickness.
- 12. The electron source of claim 10 in which said control grid comprises graphite.
- 13. The electron source of claim 10 in which said control grid comprises tungsten.
- 14. The electron source of claim 10 in which said control grid comprises molybdenum.
- 15. The electron source of claim 10 in which said thermionic cathode includes barium.
- 16. The source of claim 1 in which said insulative layer comprises boron nitride.
- 17. A thermionic bonded-grid-controlled electron source providing suppression of thermionic emission by said grid, comprising:
- a thermionic cathode having an electron-emissive surface;
- a multi-apertured conductive grid overlaying said electron emissive surface;
- an insulative member interposed between said emissive surface and said conductive member;
- a barrier layer interposed between said insulative member and said emissive surface;
- and a boron nitride layer coating the surface of said conductive layer distal said cathode, said layer being much less thick than said insulative member to preclude said layer from behaving as a pure insulator, said layer inhibiting thermionic emission by said conductive layer, said cathode, grid, insulative member and barrier layer comprising a bonded unit,
- whereby thermionic electron emission from said cathode may be controlled by application of a selected potential between said conductive layer and said cathode, minimal cathode-to-grid spacing is provided, while thermionic emission from said grid is inhibited.
- 18. A source as in claim 17, in which said boron nitride is no more than approximately 1 micron in thickness, while said insulative member is of the order of 50 microns in thickness.
- 19. A source as in claim 17 in which said insulative member is boron nitride.
- 20. A source as in claim 17 in which said grid comprises graphite.
- 21. The electron source of claim 1 wherein said thermionic cathode, conductive layer and insulative layer comprise a bonded unit.
BACKGROUND OF THE INVENTION
Government Contract -- This invention was reduced to practice under U.S. Army Electronics Command Contract No. DAAB07-76-C-1379.
US Referenced Citations (11)