Correlation of H/sup -/ density and work function of a plasma electrode in H/sub 2/+alkali (Rb, Cs) plasma

Abstract

The work function of the plasma electrode of an H/sup -/ ion source was measured photoelectrically in H/sup 2/ plasma, which contains vapor of an alkali metal. The measured work function was correlated with the H/sup -/ density obtained by a laser photodetachment technique. As the work function of the plasma electrode was reduced due to rubidium injection, the ratio of H/sup -/ density to electron density, n/n/sub e/ increased gradually. The n/n/sub e/ ratio became maximum when the work function reached the minimum value. The same result was obtained in the case of cesium injection.