Mechanical design and fabrication of a barium surface conversion H/sup -/ ion source

The details of a prototype surface conversion ion source, designed for continuous operation are described. The source consists of an annular, convectively water-cooled, magnetic multi-cusp driver chamber separated by a magnetic field from an inner chamber. A barium-coated spherically contoured disc-shaped converter in the inner chamber produces a stream of H/sup -/ ions focused at the exit aperture. The converter is electrically biased up to 300 V negative with respect to the source potential. Jacketed, water-cooled permanent magnets near the source exit deflect electrons out of the beam path. Techniques for fabrication and maintenance of a clean barium metal surface are also discussed.<>