Production and acceleration of pulsed kiloampere currents of H− and subkiloampere currents of C−, F−, I−, and Pb− ions

Abstract

Experiments on acceleration of various negative ions in a high-power coaxial diode with magnetic insulation are described. Various methods of initiating cathode plasma for H− production were tried: surface discharge of a dielectric by the prepulse in two cathode configurations and laser illumination of a dielectric cathode. A new more universal method of cathode plasma initiation was developed, allowing us to produce various species of negative ions including metallic ones. Rather rare plasma was injected from a plasma gun at the outer surface of the anode. This plasma penetrates partially into the diode through holes, and positive ions are extracted and accelerated by the negative prepulse or/and main voltage pulse of the diode and bombard the cathode surface. The energy deposition and cathode plasma parameters can be easily varied by orders of magnitude by changing near anode plasma density (by varying charging voltage of plasma gun and time delay between plasma gun pulse and prepulse and main voltage pulse of the diode) and ion acceleration voltage. Up to 30 A/cm2 of H− ion current density was recorded, as well as about 1 A/cm2 for C−, 0.3 A/cm2 for F−, and 0.1 A/cm2 for I− and Pb−.