Patent ID: 8546755

Claim:
An ion mobility spectrometer or separator comprising: a first ion guide section comprising a first plurality of electrodes having at least one aperture through which ions are transmitted in use; a second ion guide section comprising a second plurality of electrodes having at least one aperture through which ions are transmitted in use, wherein said first and second ion guide sections comprise stacked ring ion guides; a first transfer section connecting said first ion guide section with said second ion guide section, wherein ions are transmitted radially, in use, in said first transfer section from said first ion guide section into said second ion guide section; and a first transient DC voltage means arranged and adapted to apply one or more transient DC voltages or potentials or one or more transient DC voltage or potential waveforms to at least some of said first plurality of electrodes in order to urge, force, drive or propel at least some ions along at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the length of said first ion guide section; or a second transient DC voltage means arranged and adapted to apply one or more transient DC voltages or potentials or one or more transient DC voltage or potential waveforms to at least some of said second plurality of electrodes in order to urge, force, drive or propel at least some ions along at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the length of said second ion guide section; wherein ions are transmitted in use in a first direction through said first ion guide section and in a second direction through said second ion guide section, wherein said first direction is substantially different to or counter to said second direction.