| CPC G01N 27/623 (2021.01) [H01J 49/0422 (2013.01)] | 19 Claims |

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1. An ion mobility analyser comprising:
an ion guide defining an ion drift channel extending in an axial direction, the ion guide comprising: first and second electrode assemblies provided on opposing sides of the ion drift channel, each of the first and second electrode assemblies extending in the axial direction and in a transverse direction which is transverse to the axial direction, wherein the first and second electrode assemblies are spaced apart on opposing sides of the ion drift channel by a first distance at a narrowest point along the axial direction, wherein a cross section of the ion drift channel normal to the axial direction extends in the transverse direction a second distance that is greater than the first distance;
a source of gas flow configured to direct a laminar gas flow in the axial direction through the ion guide; and
one or more power supplies configured to apply voltages to electrodes of the first and second electrode assemblies to create a quasi-potential that is substantially constant along the transverse direction such that ions are free to distribute along the transverse direction of the ion guide, and to create a DC potential gradient along the axial direction of the ion guide.
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