Shaped electron emission from single crystal lanthanum hexaborid

Details Shaped electron emission from single crystal lanthanum hexaborid Shaped electron emission from single crystal lanthanum hexaborid

1981-05-26

1984-08-28

Chatmon, Saxfield

Electric lamp and discharge devices

Electrode and shield structures

Point source cathodes

313346R, 252521, 445 50, H01J 116, H01J 1910

Patent

active

044685866

ABSTRACT:
The shape of an electron beam emitted from an LaB.sub.6 single crystal cathode can be controlled directly by shaping the cathode tip itself. The LaB.sub.6 cathode is provided with a flat top surface which is substantially perpendicular to the emitted beam direction and which corresponds in shape to the shape of the beam desired. For a square beam the flat top surface is square in shape. The size of the shaped top surface and operating conditions are arranged such that emission of electrons occurs over substantially the entire shaped top surface with minimum emission from side regions of the tip adjacent to this shaped surface. In order to maximize emission from the shaped top surface, a crystallographic orientation is selected such that the shaped top surface exposes a relatively low work function crystal plane. Emission from side regions of the tip adjacent to the shaped high emission surface may be reduced by orienting such side regions very obliquely to the emitted beam axis. The side regions may also be flat surfaces, in which case emission from these flat side surfaces may be reduced by orienting the flat side surfaces such that they expose relatively high work function crystal plane.

REFERENCES:
patent: 3631290 (1971-12-01), Loeffler
patent: 4054946 (1977-10-01), Ferris et al.
patent: 4055780 (1977-10-01), Kawai et al.
patent: 4363995 (1982-12-01), Takigawa et al.

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