Patent ID: 8124930

Claim:
An ion transport apparatus, comprising: an ion entrance end; an ion exit end disposed at a distance from the ion entrance end along a longitudinal axis; an ion entrance section extending along the longitudinal axis from the ion entrance end toward the ion exit end; an ion exit section extending along the longitudinal axis from the ion exit end toward the ion entrance end; and a plurality of electrodes arranged along the longitudinal axis wherein at least portions of the electrodes are disposed at a radial distance in a transverse plane orthogonal to the longitudinal axis, the plurality of electrodes including a plurality of first electrodes circumscribing an interior space in the ion entrance section and a plurality of second electrodes circumscribing an interior space in the ion exit section, wherein the plurality of electrodes is configured for applying an RF electrical field that varies along the longitudinal axis such that at the ion entrance end, the RF electrical field comprises a first RF electrical field comprising a major first multipole component of 2n 1 poles where n 1 ≧3/2, and at the ion exit end the RF electrical field comprises a second RF electrical field comprising predominantly a second multipole component of 2n 2 poles where n 2 ≧3/2 and n 2 <n 1 .