Method and apparatus for focussing and declustering trace ions
US4121099A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 25, 1977 |
| Grant date | Oct 17, 1978 |
| Priority date | — |
| Expiry date | Apr 25, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J49/0422
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for focussing and declustering trace ions travelling from a gas through an orifice into a vacuum chamber and to a mass analyzer in the vacuum chamber. Advantage is taken of the free jet expansion of the gas into the vacuum chamber by applying an electric focussing field in a specific region of the free jet. The region is selected sufficiently close to the orifice that the gas density limits the kinetic energy spread which the ions can acquire under the applied field, typically to 2 ev or less, while the early focussing increases the available ion signal. Declustering can be collision induced in the region by providing a field in the region sufficient to impart an internal energy of between 0.1 and 1.5 ev to ions in the region. The kinetic energy which the ions can acquire under the applied field is still limited by the density of the gas in the free jet, so that the kinetic energy spread which the ions can acquire is still limited. Preferably the focussing and declustering fields are produced by a single conical tapered lens element located at distance X.sub.l from the orifice, where ##EQU1## and D is the orifice diameter, for atmospheric pressure and room te…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.