Production of Pulse Intense Ion Beam of the Current Density over a Hundred Times Larger than the Child-Langmuir Limit by Magnetieally-Insulated Ion Diode

Abstract

An intense high-density pulsed proton beam (∼200 A/cm2 at the anode surface, an energy of ∼80 keV, and a diode voltage pulse length of 500 ns) was produced by a cylindrical magnetically-insulated ion diode operated in the long-pulse mode. The ion current density was over 80-to 160-times larger than the Child-Langmuir limit on the anode flashboard. A measurement of the high-energy electrons leaked along the insulation magnetic field indicated that the actual diode gap was \\lesssim2 mm while the gap length in a vacuum was 7.5 mm. The microwave emission (∼2.45 and ∼50 GHz) wascoincident with ion beam production. These observations suggest that the anode plasma expansion to the cathode during a long pulse and a virtual cathode movement towards the anode due to field fluctuations in the gap were responsible for a strongly enhanced ion beam generation.