Electron sources having shielded cathodes
US5898269A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 27, 1997 |
| Grant date | Apr 27, 1999 |
| Priority date | — |
| Expiry date | May 27, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/31754
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.