Figure 1.

(a) 3D mechanical drawing of an ion sponge with three trapping layers. Ions detected with three electron multipliers. (b) Schematic configuration of a single trapping unit, with a square ring electrode and two cross end-cap electrodes, and simulated electric field. (c) Photo of an ion sponge with four trapping layers. (d) Schematic configuration of 1 trap layer and geometries (e) without and (f) with a shift of the cross end-cap electrodes off the center of the square hole. (g) Schematic instrument setup for testing, with a DAPI interface for directly introducing ions from ion sources in an ambient environment.