An ion separation apparatus comprises: (a) first and second ion carpets, each comprising: a substrate having first and second faces; and a set of electrodes disposed on or beneath the first face, wherein a configuration of a first plurality of the set of electrodes defines at least one group of circle sectors; (b) an ion exit aperture passing through one ion carpet; and (c) one or more power supplies configured to provide radio frequency voltages to a first subset of the electrodes of each ion carpet, to provide electrical potential differences across electrodes of the first subset of electrodes of each ion carpet, and to provide time-varying voltages to the first plurality of electrodes of each ion carpet that migrate through the sectors as a traveling wave, wherein the ion carpets are disposed parallel to one another with a gap therebetween, the first faces facing one another across the gap.