Transmission–resolution curves for a quadrupole mass spectrometer with separated rf and dc fields in the entrance aperture

Abstract

The use of an entrance aperture which spatially separates the rf and dc fringe fields in a quadrupole mass filter is shown to improve the transmission–resolution characteristics. We have measured transmission–resolution curves at 28 amu for a quadrupole mass spectrometer with and without a field separating entrance aperture as described by Fite. The aperture design improves the resolution at near unity transmission, the ultimate resolution, and the absolute transmission of the mass filter.