H−Formation in a Barium-Seeded Hydrogen Discharge

It has been found that the ${\mathrm{H}}^{-}$ output current from a multicusp source can be substantially increased if the hydrogen plasma is seeded with cesium or barium. Experimental results demonstrate that, for a pure-hydrogen discharge, the ${\mathrm{H}}^{-}$ ions extracted from a multicusp source are indeed produced in the plasma volume. However, if barium is mixed with hydrogen in the source discharge, the majority of the ${\mathrm{H}}^{-}$ ions are generated on the anode walls.