Electron gun having magnetic collimator
US6392333B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 5, 1999 |
| Grant date | May 21, 2002 |
| Priority date | — |
| Expiry date | Mar 5, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/06316
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An enhanced electron source in most respects similar to a standard cathode assembly for an electron gun includes an electron emitter surrounded by a suppressor electrode, the emitted electrons passing through an extractor electrode. Additionally, the suppressor electrode includes a small ring shaped permanent magnet surrounding the opening in the suppressor electrode through which the emitter tip protrudes. The resulting magnetic field is aligned with the beam axis, and includes a tail which forms a very short focal length magnetic lens immediately following the emitter tip. This magnetic field collimates the electron beam before it enters the downstream electrostatic gun lens, thus increasing the effective angular intensity of the cathode assembly. The aberrations of this collimating lens are very low so that its useful brightness is not reduced. Also the influence of guns lens aberrations is reduced because a smaller aperture angle in the gun lens may be used to obtain higher beam current.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.