Patent ID: 7468511

Claim:
A FAIMS cell, comprising: an outer electrode comprising a first electrode surface, the outer electrode being generally cylindrical; an inner electrode comprising a second electrode surface, the inner electrode being generally cylindrical, the second electrode surface disposed in a spaced-apart facing arrangement relative to the first electrode surface so as to define an ion separation region therebetween, the ion separation region extending along a lateral direction between first and second opposite lateral boundaries thereof, the second electrode surface adapted with a recessed channel extending around the perimeter of the inner electrode and extending along a defined direction of ion travel that is approximately perpendicular to the lateral direction, the recessed channel supporting focusing along the lateral direction of ions traveling through the ion separation region; a voltage source for applying a radio frequency (RF) asymmetric waveform (DV) and a direct current compensation voltage (CV) to at least one of the outer electrode and the inner electrode; and a protruding ridge extending inwardly from the outer electrode surface toward the inner electrode surface, the protruding ridge spaced-apart from and laterally aligned with the recessed channel.