H- surface converter source development at Los Alamos

Production of H^- ions by the surface conversion process is being pursued at the Los Alamos Neutron Science Center (LANSCE) as part of an upgrade project to provide higher currents and enhanced flexibility for injecting a 800 MeV H^- beam into the proton storage ring (PSR). An eventual goal of 40-mA H^- current at 80 keV beam energy with 0.13 πmm-mrad (1 rms normalized) emittance at 12% duty factor (120 Hz, 1 ms) is desired. To attain this goal, two types of surface converter sources are being investigated in which H^- ions are extracted either radially or axially through a line-cusp magnetic field. The radial source produces 18 mA H^- in a 28-day run cycle for LANSCE production while the axial source has been developed to the desired 40 mA current. However, an emittance growth of factor 2-3 accompanied the increased axial source current. The axial source development program includes electron suppression, increased beam current, and 80-keV beam emittance measurements. The current understanding of the emittance growth mechanism will be discussed.