Ion-source and low-energy beam-transport issues with the front-end systems for the Spallation Neutron Source

H- ions are being used in high-energy accelerators and spallation neutron-sources because of the efficiency with which they can be converted into protons at high energy, a mechanism utilized in schemes that provide injection into a ring by means of charge. This paper discusses new trends and recent developments in the field of H- plasma generators, extraction systems, and Low-Energy Beam-Transport (LEBT) systems, with emphasis on low-emit-tance systems delivering beams in the 50-mA range.