Patent ID: 7982183

Claim:
An ion transfer arrangement for transporting ions between a relatively high pressure region and a relatively low pressure region, comprising: an electrode assembly defining an ion transfer channel having a longitudinal axis, the electrode assembly including a first plurality of electrodes extending along the longitudinal axis a first distance D 1 , and a second plurality of electrodes extending along the longitudinal axis a second distance D 2 >D 1 and being arranged in alternating relation with the said first plurality of electrodes; and means for supplying a DC voltage of a first polarity +V 1 to the first plurality of electrodes and for supplying a DC voltage −V 2 (|V 1 |>|V 2 |) of a second polarity, relative to the average voltage distribution in the longitudinal direction of the electrode assembly, to the second plurality of electrodes; wherein the period, H, between successive electrodes in the first plurality of electrodes is selected so that ions having a velocity, S, within the ion transfer channel experience an effective frequency νeff within the ion transfer channel (νeff=S/H) within the radio frequency part of the electromagnetic spectrum.