Inverse ion diode experiment

An experimental test has been performed of a novel ion diode intended for inertial confinement fusion applications. The diode is a small thin-walled evacuated glass sphere (nicknamed a ''light bulb'') which is irradiated by relativistic electron beams transported to the sphere via plasma channels. The virtual cathode formed by the electrons in the light bulb accelerates ions radially inwards from the walls of the sphere. The ions are focused on a levitated central target. Qualitative aspects of one-dimensional theoretical analyses of the light bulb are supported by the experimental results reported here. However, the overall ion beam generation efficiency in the experiment is evidently substantially below that of the simple theory, probably owing to two-dimensional effects