Ion transfer apparatus

Abstract

An ion transfer apparatus for transferring ions from an ion source at an ion source pressure, which ion source pressure is greater than 500 mbar, along a path towards a mass analyser at a mass analyser pressure that is lower than the ion source pressure. The apparatus includes a plurality of pressure controlled chambers, wherein each pressure controlled chamber in the ion transfer apparatus includes an ion inlet opening for receiving ions from the ion source on the path and an ion outlet opening for outputting the ions on the path. The plurality of pressure controlled chambers are arranged in succession along the path from an initial pressure controlled chamber to a final pressure controlled chamber, wherein an ion outlet opening of each pressure controlled chamber other than the final pressure controlled chamber is in flow communication with the ion inlet opening of a successive adjacent pressure controlled chamber. The ion transfer apparatus is configured to have, in use, at least one pair of adjacent pressure controlled chambers for which a ratio of pressure in an upstream pressure controlled chamber to pressure in a downstream pressure controlled chamber is set such that there is substantially subsonic gas flow in the downstream pressure controlled chamber.