Patent ID: 9123517
Filing Date: 2015-09-01
Classification: H01J

Abstract:
1. An apparatus including an ion guide to confine ions radially therethrough, the ion guide having a plurality of circumferentially arranged elongated rods disposed about a common axis and forming a plurality of longitudinally traversing segments, where at least a first and a second subset of the segments have an equal number of elongated rods in a multiple of two and are physically configured in angular positions (θ) about said axis to receive a first and a second set of symmetric RF voltage waveforms (V) that are applied to the first and second subsets of segments in accordance with the relationship V=V 0 cos (nθ/2) and that produce multipolar field distributions of a given order (n) equal to or lower than the number of rods, respectively, where V 0 is the maximum voltage applied, where the first set of symmetric RF voltage waveforms produce a field distribution of a first order and the second set of symmetric RF voltage waveforms produce a field distribution of a second order that is different from the first order, where the ratio of the number of rods to the order of the field distribution produced thereby is an integer number, where the first subset of segments is positioned closest to an entrance end of the ion guide, and where the first order field distribution is of higher order than that of the second order field distribution.