Top: comparison of the calculated FoVs (side view) of the STEP MC (solid line) and IC (dashed line). Bottom: side view of example 200 keV electron trajectories. The apertures are schematically sketched in light grey, the magnets in a darker grey. The pinhole has a beige coloration while the segmented detector is coloured reddish. We note that the figure is true to scale. A slight asymmetry of ion trajectories in the magnet head is taken into account by shifting the corresponding magnet-head pinhole by 0.25 mm in +z direction.