Work function dependence of surface produced H− in the presence of a plasma

The maximum H− flux from a negatively biased ‘‘converter cathode’’ occurs at the work function minimum. A cesiated hydrogen plasma produces a partially‐cesiated surface at the converter. The cesium coverage can be controlled by the cesium partial pressure, the bias on the converter surface is measured by the photo‐electric effect, using a bright light source and a series of fliters. The angular dependence is measured by rotating the converter.