A compact low energy proton source

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.