Surface Ionization Ion Sources

Recent achievements with iridium surface ionization ion sources are discussed. These sources can be used to produce ion beams of elements with ionization potentials from 5-1/2 to 6 V, e. g., the IILA metals (Al, Ga, In and Tl), the rare earths, the heavier alkaline earths, and Li, in addition to the usual heavier alkalis. Ion beams of Li, Al, Ga, and In have been produced here. Ionization efficiencies, critical temperatures, current densities, and beam purities as measured by magnetic mass separation are discussed. An ion source design being employed for the IIIA metals is described briefly.