Method and apparatus for producing an electron beam from a therm

Details Method and apparatus for producing an electron beam from a therm Method and apparatus for producing an electron beam from a therm

1984-02-08

1985-07-09

Moore, David K.

Electric lamp and discharge devices

Electrode and shield structures

Cathodes containing and/or coated with electron emissive...

313310, 313300, 313308, 445 50, 445 51, H01J 114

Patent

active

045284741

ABSTRACT:
Disclosed is a method and apparatus for producing a high electron beam current having a low energy spread at a high brightness of the beam and a uniform intensity distribution. The electron beam is extracted from an emission current which consists of used emission current and unused emission current. The used emission current has a uniform intensity distribution. The apparatus produces a negligibly small unused emission current by using both a frustum shaped cathode and a multi-electrode. The cathode comprises a thermoelectron emissive material having a low work function and one or more thin layers which cover the side surface of the cathode. A material of the outermost thin layer has a high work function. The multi-electrode consists of the cathode, a first grid electrode, a second grid electrode and an anode electrode. The used emission current is generated from the top surface of the cathode. The unused emission current that is generated from the side surface of the cathode is negligibly small. The top surface is immersed into a strong accelerating electric field. By adjusting the field at the top surface, an emission current density from the top surface can be varied in the range of one to several hundred times of the saturation current density at an operating temperature. Methods for manufacturing the cathode are provided.

REFERENCES:
patent: 3384776 (1968-05-01), Houston
patent: 3534455 (1970-10-01), Bondley
patent: 3656020 (1972-04-01), Cronin
patent: 3697321 (1972-10-01), Eckert et al.
patent: 4288717 (1981-09-01), Tanji et al.
patent: 4346325 (1982-08-01), Nakasuji et al.
patent: 4468586 (1984-08-01), Hohn

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