Extraction characteristics of hydrogen-like helium ions in a magnetized sheet plasma

Abstract

The extraction of He^- ions from a magnetized sheet plasma source is reported. Optimum detection and extraction of He⁺ ions were conducted using an ExB probe as a mass analyzer. The effect of the probe's extraction potential, its position relative to the center of the core plasma, gas filling pressure and discharge conditions in the production and extraction of He⁺ ions were investigated. The He⁺ ion current density yield of 8 μA/cm² was optimum at plasma discharge current of 1.5 A within the vicinity of 5 to 7 cm from the sheet plasma core. Investigations also show the predominance of He⁺⁺ species. At higher pressures, the formation of molecular helium ions He₂⁺ was observed. He⁺ yield decreased as discharge current was increased; this is especially evident at the peripheral region. Two configurations of the plasma, sheet and cylindrical were compared in terms of He⁺ yield. Results indicated the sheet configuration produced a higher yield by one order of magnitude.