US Patent 7470900 Compensating for field imperfections in linear ion processing apparatus

An electrode structure for manipulating ions includes a main electrode and a compensation electrode. An outer surface of the main electrode includes a curved section that includes an apex. An aperture is generally disposed at the apex and extends along a radial center line from the outer surface through a thickness of the main electrode. The compensation electrode is disposed at the radial center line and at a tangent line tangent to the apex. Another electrode structure includes a plurality of main electrodes defining an interior space, and one or more compensation electrodes disposed in the interior space. RF signals may be applied to the main electrodes and to the compensation electrode.