Electrodynamic on funnels confine, guide, or focus ions in gases using the Dehmelt potential of oscillatory
electric field. New funnel designs operating at or close to atmospheric
gas pressure are described. Effective on focusing at such pressures is enabled by fields of extreme amplitude and frequency, allowed in microscopic gaps that have much higher
electrical breakdown thresholds in any gas than the macroscopic gaps of present funnels. The new microscopic-gap funnels are useful for
interfacing atmospheric-pressure
ionization sources to
mass spectrometry (MS) and on mobility separation (IMS) stages including differential IMS or FAIMS, as well as IMS and MS stages in various configurations. In particular, “wedge” funnels comprising two planar surfaces positioned at an angle and wedge funnel traps derived therefrom can compress on beams in one dimension, producing narrow belt-shaped beams and laterally elongated cuboid packets. This beam profile reduces the
ion density and thus space-charge effects, mitigating the adverse
impact thereof on the resolving power, measurement accuracy, and
dynamic range of MS and IMS analyzers, while a greater overlap with coplanar light or particle beams can benefit spectroscopic methods.