Patent ID: 7919747

Claim:
A mass analyser comprising: an ion guide comprising a plurality of electrodes; means for applying a first AC or RF voltage to at least some of said plurality of electrodes such that, in use, a plurality of first axial time averaged or pseudo-potential barriers, corrugations or wells having a first amplitude are created along at least a portion of the axial length of said ion guide; and means for driving or urging ions along at least a portion of the axial length of said ion guide, wherein said means for driving or urging ions comprises means for applying one or more transient DC voltages or potentials or one or more DC voltage or potential waveforms to at least some of said electrodes; said mass analyser further comprising: means for applying a second AC or RF voltage to one or more of said plurality of electrodes such that, in use, one or more second axial time averaged or pseudo-potential barriers, corrugations or wells having a second amplitude are created along at least a portion of the axial length of said ion guide, wherein said second amplitude is different from said first amplitude.