Volume and Surface-Enabled Volumne Negative Ion Sources

Abstract

H- volume sources and especially caesiated H- volume sources are important ion sources for generating high intensity proton beams, which then in turn generate large quantities of other particles. This paper discusses the physics and technology of the volume production and the caesium enhanced (surface) production of H- ions. Starting with Bacal’s discovery of the H- volume production, the paper briefly recounts the development of some H- sources, which capitalized on this process to significantly increase the production of H- beams. Another significant increase was achieved in the 1990s by adding cesiated surfaces to supplement the volume produced ions with surface produced ions as illustrated with other H- sources. Finally the focus turns to some of the experience gained when such a source was successfully ramped up in H- output as well as in duty factor to support the generation of 1 MW proton beams for the Spallation Neutron Source.