Method and apparatus for sampling a plasma into a vacuum chamber
US4501965A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 14, 1983 |
| Grant date | Feb 26, 1985 |
| Priority date | — |
| Expiry date | Jan 14, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05H1/46
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A plasma is generated within an induction coil and the plasma is sampled through an orifice into a vacuum chamber for mass analysis of trace ions in the plasma. Arcing at the orifice is prevented by grounding the induction coil at or near its center, thus eliminating ultraviolet noise and reducing average ion energies and ion energy spread, as well as preventing destruction of the orifice. The elimination of arcing at the orifice allows the use of a sharp edge orifice structure to prevent formation of a cool boundary layer over the orifice and also permits direct sampling of the plasma. The direct sampling and the lack of cooling prevent recombination and reaction of the ions with oxygen and improve the response to elements of high ionization potential, increasing the desired ion signal and greatly reducing the presence of oxides which would otherwise complicate the spectrum.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.