Mass spectrometer

A method of mass analysing ions comprising:

• providing an ion guide comprising a plurality of electrodes;
• applying a first AC or RF voltage to at least some of said plurality of electrodes such that a plurality of first axial time averaged or pseudo-potential barriers, corrugations or wells are created along at least a portion of the axial length of said ion guide;
• driving or urging ions along at least a portion of the axial length of the ion guide by 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;
• and
• applying a second AC or RF voltage to one or more of said plurality of electrodes such that one or more second axial time averaged or pseudo-potential barriers, corrugations or wells 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.

A method of mass analysing ions comprising:

• providing an ion guide comprising a plurality of electrodes, said plurality of electrodes comprising electrodes having an aperture through which ions are transmitted;
• applying a first AC or RF voltage to at least some of said plurality of electrodes so that axially adjacent groups of electrodes are supplied with opposite phases of said first AC or RF voltage and wherein 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
• reversing the polarity of said first AC or RF voltage applied to one or more axially adjacent groups of electrodes such that 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.

A method of mass analysing ions comprising:

• providing an ion guide comprising a plurality of electrodes, said plurality of electrodes comprising electrodes having an aperture through which ions are transmitted;
• applying a first AC or RF voltage to at least some of said plurality of electrodes so that axially adjacent electrodes or axially adjacent groups of electrodes are supplied with opposite phases of said first AC or RF voltage and wherein 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;
• applying one or more transient DC voltages or potentials or one or more transient DC voltage or potential waveforms to said plurality of electrodes in order to drive or urge ions along at least a portion of the axial length of said ion guide;
• reversing the polarity of said first AC or RF voltage applied to a pair of axially adjacent electrodes or a pair of axially adjacent groups of electrodes such that 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;
• and
• progressively decreasing in a linear, stepped or other manner the amplitude of said first AC or RF voltage so as to progressively reduce the amplitude of said one or more second axial time averaged or pseudo-potential barriers, corrugations or wells.

A method of guiding ions or mass analysing ions comprising:

• providing an ion guide or mass analyser comprising a plurality of electrodes;
• applying a n-phase AC or RF voltage to said plurality of electrodes wherein n≧2;
• maintaining a first phase relationship or first aspect ratio between, at or of said plurality of electrodes;
• and
• changing the phase relationship or aspect ratio between, at or of a sub-set of said plurality of electrodes so that a second different phase relationship or second aspect ratio is maintained between, at or of said sub-set of electrodes so as to create one or more axial time averaged or pseudo-potential barriers, corrugations or wells along at least a portion of the axial length of said ion guide or mass analyser.