Ion funnels and systems incorporating ion funnels

An ion transport system comprises: (I) an ion transfer tube extending between an atmospheric-pressure ionization chamber and a partially evacuated chamber; and (II) an ion funnel within the chamber comprising: (1) an exit electrode that has an exit aperture configured to deliver the gas and charged particles to a high-vacuum chamber; and (2) a funnel portion comprising a plurality of plate electrodes configured as a stack, each electrode comprising a respective aperture, wherein an aperture diameter of each of the plurality of electrodes is greater than or equal to three times an inter-electrode pitch and wherein no DC electrical potential gradient is applied between the exit electrode and an adjacent one of the plurality of plate electrodes.