Energy analysis of H− ions from a hollow-discharge duoplasmatron

Abstract

Energy spectra of H⁻ ions from a HDD source operating in mixtures of helium, hydrogen, and cesium reveal that negative ions are generated by a volume process and by a surface process. A marked difference was observed in the pressure dependence of the low‐ and high‐energy groups, corresponding to the volume and the surface processes, respectively. The active surfaces could be identified. Some evidence that, besides collisional attachment processes, ion‐molecular reactions have an influence on the yield of H⁻ ions in volume reactions could be found.