Intense ion beam from a magnetically insulated diode with magnetically controlled gas-breakdown ion source

Abstract

A magnetically insulated diode with an active anode source has been developed which produces a high-quality intense ion beam. The anode plasma of annular shape is produced independently of the main diode power pulse by the inductive breakdown of a radially expanding gas cloud supplied by a fast puff valve and nozzle configuration. The diode was developed on a 1010-W pulsed power generator that typically produces 150-kV, l-μs pulses. Prompt ion beam turn-on was attained in this diode when an adequate delay between pulsing the plasma source and delivering the diode power pulse was chosen. The neutral atom density in the diode accelerating gap was sufficiently low that the presence of the neutrals did not limit the beam pulse duration. When the puff valve was filled with H2 gas, a pure proton beam was produced, within the 20% uncertainty of the measurement technique. Proton beam pulses longer than 1 μs and current densities higher than 100 A/cm2 at 70–150 keV were generated.