Arrangement for the mass-spectrometric detection of ions

Abstract

The arrangement is for the mass-spectrometric detection of ions in the presence of a disturbing background, and is of the type including a source of ions, a mass-spectrometric separating system, a detector for the presence of ions, and a focusing device for the ions interposed between the source and the detector. The focusing device comprises an asymmetric electrostatic focusing lens arrangement having semi-cylindrical electrodes defining a lens axis, an ion entrance aperture, and an ion exit aperture. In three embodiments of the electrostatic focusing lens, the ion entrance aperture is eccentric to the axis of the lens. In a fourth embodiment, the ion entrance and exit apertures are coaxial with the lens axis and a pair of intermediate electrodes define an ion aperture which is eccentric relative to the axis of the lens.

Dependencies are inferred from the claim text.