Generation of H^-, D^-ions on Composite Surfaces with Application to Surface/Plasma ion Source Systems

We review some salient features of the experimental and theoretical data pertaining to hydrogen negative ion generation on minimum work function composite surfaces consisting of Cs/ transition metal substrates. Cesium or hydrogen ion bombardment of a cesium-activated negatively biased electrode exposed to a cesium-hydrogen discharge results in the release of hydrogen negative ions. These ions originate through desorption of hydrogen particles by incident cesium ions, desorption by incident hydrogen ions, and by backscattering of incident hydrogen. Each process is characterized by a specific energy and angular distribution. The calculation of ion formation in the crystal selvage region is discussed for different approximations to the surface potential. An ab initio, all-electron, local density functional model for the composite surface electronics is discussed.