The "wire" ion source

[Carl Willis]

For the purpose of establishing the wire discharge, all that matters is that the wire is positively charged relative to the outer cylindrical surface. The potential relative to any external point of reference is irrelevant.

You can certainly extract ions over the entire 360-degree azimuthal range, provided you provide the necessary mechanical support for the extraction grid (or slits) and you keep any external fields from penetrating too far into the trapping region.

-Carl