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

Abstract

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 3×10¹⁵ 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.