Ion beam apparatus and a method for neutralizing space charge in an ion beam
US6515408B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 15, 2001 |
| Grant date | Feb 4, 2003 |
| Priority date | — |
| Expiry date | Feb 15, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/0041
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A source of thermionic electrons is provided inside the flight tube of a magnet, especially an analysing magnet, and extends along the beam flight path. This allows space charge to be neutralised along the beam's axis in spite of severely restricted electron mobility in this direction owing to the presence of substantially transverse magnetic field. Thermionically emitted electrons may contribute directly to the neutralisation of space charge in positive ion beams, or, in the case of negative ion beams, indirectly by ionizing residual or deliberately introduced neutral gas atoms or molecules. Examples are described and claimed in which the source is arranged outside the nominal beam envelope in the flight tube, but linked to the beam by magnetic flux generated in the flight tube. This reduces erosion of the source by the beam and so reduces beam contamination. In these examples, an important feature is the provision of electron repellers to reflect electrons back and forth across the beam. Alternative arrangements are described and claimed in which the source is positioned inside the beam. The thermionic electron source may comprise an array of filaments, and preferably is negative…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.