High-current ion beam from a moving plasma

High-current ion beams in the 10--20-keV range are extracted from a moving plasma. Current densities up to 2.5 A/cm2 are obtained at the plasma boundary, which is almost an order of magnitude larger than the Bohm current. Total currents of over 100 A are obtained from the plasma. Simple geometric focusing gives current densities approx.200 A/cm2 at the focus