Electron gun with magnetic immersion double condenser lenses
US8314401B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 1, 2010 |
| Grant date | Nov 20, 2012 |
| Priority date | — |
| Expiry date | May 17, 2031 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/1405
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An electron gun comprises an electron emitter, an electrode surrounding the electron emitter, an extraction electrode, and a double condenser lens assembly, the double condenser lens assembly comprising a magnetic immersion pre-condenser lens and a condenser lens. In combination with a probe forming objective lens, the electron gun apparatus can provide an electron beam of independently adjustable probe size and probe current, as is desirable in electron beam applications. The electron emitter is immersed in the magnetic field generated by a magnetic type pre-condenser lens. When activated, the pre-condenser lens collimates the beam effectively to increase its angular intensity while at the same time enlarging the virtual source as compared with non-immersion case, due to geometric magnification and aberrations of its lens action. The pre-condenser lens is followed by a condenser lens. If the condenser lens is of the magnetic type, its peak magnetic field is far enough away and thus its action does not significantly affect the size of the virtual source. Independent adjustment of the lenses, combined with suitable selection of final probe forming objective aperture size, allows var…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.