Ion Gate

A method of controlling transmission of an ion beam through an ion gate in a mass spectrometer, wherein the ion gate comprises:

• a first electrode assembly comprising a plurality of guide electrodes aligned along a central axis, wherein:
• the plurality of guide electrodes are arranged to define a multipole ion guide from a first end of the first electrode assembly to a second end of the first electrode assembly, wherein at least one guide electrode is continuous from the first end of the first electrode assembly to the second end of the first electrode assembly;
• and
• the ion guide is configured to receive an ion beam at the first end;
• and
• a second electrode assembly comprising at least one gating electrode that intersects a guide electrode, wherein the at least one gating electrode is positioned:
• adjacent to the first electrode assembly;
• outside of the confinement volume;
• and
• between the first end of the electrode assembly and the second end of the first electrode assembly;
• the method comprising:
• applying RF voltages to the plurality of guide electrodes to define a confinement volume for the ion beam, wherein the confinement volume is centered about the central axis;
• allowing transmission of the ion beam by applying a passing DC voltage to the at least one gating electrode such that the ion beam is transmitted along the ion guide;
• and
• preventing transmission of the ion beam by applying a gating DC voltage to the at least one gating electrode such that the ion beam is prevented from transmission along the ion guide.