  A low energy proton source for non-neutral plasma experiments was developed.
Electrons from a hot filament ionize H$_2$ gas inside a geometrically
compensated Penning trap to produce protons via dissociative ionization. A
rotating wall electric field destabilizes the unwanted H$_2^+$ and H$_3^+$
generated in the process while concentrating protons at the center of the trap.
The source produces bunches of protons with relatively low ion contamination
(5.5% H$_2^+$ and 15.5% H$_3^+$), with energy tunable from 35 to 300 eV.
