Electron sources having shielded cathodes

Details Electron sources having shielded cathodes Electron sources having shielded cathodes

1997-05-27

1999-04-27

Patel, Nimeshkumar D.

Electric lamp and discharge devices

Photosensitive

Photocathode

313530, 313541, 313539, 313544, H01J 4006

Patent

active

058982698

ABSTRACT:
An electron beam source includes a cathode having an electron emission surface including an active area for emission of electrons and a cathode shield assembly including a conductive shield disposed in proximity to the electron emission surface of the cathode. The shield has an opening aligned with the active area. The electron beam source further includes a device for stimulating emission of electrons from the active area of the cathode, electron optics for forming the electrons into an electron beam and a vacuum enclosure for maintaining the cathode at high vacuum. The cathode may be a negative electron affinity photocathode formed on a light-transmissive substrate. The shield protects non-emitting areas of the emission surface from contamination and inhibits cathode materials from contaminating components of the electron beam source. The cathode may be moved relative to the opening in the shield so as to align an new active area with the opening. Getter materials and sources of activation material may be incorporated into the shield assembly.

REFERENCES:
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patent: 4820927 (1989-04-01), Langner et al.
patent: 4868380 (1989-09-01), Booman et al.
patent: 4906894 (1990-03-01), Miyawaki et al.
patent: 4970392 (1990-11-01), Oettinger et al.
patent: 5039862 (1991-08-01), Smith et al.
patent: 5594296 (1997-01-01), Mitsutake et al.
Colin A. Sanford, Doctoral Thesis, Cornell University Dept. of Electrical Engineering May (1990), Entitled: Laser Pulsed GaAs Negative Electron Affinity Photocathodes for Electron Beam Instrumentation.

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