Extraction and propagation of rotating intense proton beams from a magnetically insulated diode

A magnetically insulated parallel-plate geometry was used to produce intense rotating beams of protons. It is shown that even though the diode is not in equilibrium with respect to the drifting electrons, a decrease in the perveance by more than a factor of 40 could be produced by the application of the field. Operation of the diode is accompanied by strong bursts of microwave radiation. Efficiencies over 50% were achieved in accordance with theory. Ion current-density enhancements above the Child-Langmuir limit that appear directly attributable to drifting electron space-charge effects were observed. Typically, more than 3 x 1015 protons were extracted per pulse. Space-charge neutralization of the extracted beam appears complete and inductive electron backcurrents were not detected. The beam propagates in accordance with geometric predictions and at least 67% of the beam completes one revolution. A field reversal factor of 1.5% (ΔB=140 G) was obtained. It is shown that this injector can easily be scaled to the parameters needed to produce a self-contained ion ring