The diameter and length of both cathodes and the anode has a significant effect on plasma formation and runout velocity. Another factor is that the rods have a taper, and may not be precisely perpendicular to the base. This angle is to help impart angular momentum, with the Blake Coil as a backup.
I know I’d rather manufacture a single tubular cathode than 16 or more tapered ones. The biggest design challenge right now is the computer simulation software.
