ION SOURCE FILTER

摘要

An ion source filter for use in the source region is disclosed. The ion source filter includes four rod electrodes having circular cross sections. The rod electrodes of the ion source filter are sized and positioned such that the ratio r/r0 of the rod radius to the inscribed circle radius is considerably reduced relative to conventional RF/DC mass filters. The reduced r/r0 geometry has been observed to lessen the diminishment of resolution with increasing pressure relative to prior art devices.

主权项

1. A source filter for a mass spectrometer, comprising:
four elongated rod electrodes extending between an inlet end and an outlet end, the rod electrodes each being circular in cross section, the rod electrodes being arranged into first and second electrode pairs, each electrode pair having two rod electrodes opposed across a central axis of the source filter; a voltage supply for applying oscillatory and resolving direct current (DC) voltages to the first and second electrode pairs; wherein, within a lateral cross-sectional plane located at any point along the central axis between the inlet end and the outlet end, each of the rod electrodes has a radius of r and has an inner face located as a distance r0 from the central axis, the value of r/r0 being less than or equal to unity.