Penning surface-plasma source scaling laws---theory and practice

The small-angle source (SAS), 4X source, and 8X source are Penning surface-plasma sources (SPS) that produce high-current, high-brightness H- ion beams for accelerator applications. It is desirable to achieve high duty-factor (df) operation, ultimately dc, with a Penning SPS. Two developments may make this goal possible. First, the H- beam-emission scaling from the SAS (the 1X device) to the 4X source, and from the 4X source to the 8X source, is more favorable than the scaling laws predict. Second, fringe-field separation of the e- and H- beams may make it possible to handle the power of the coextracted e- beam, especially since a collar arrangement reduces the e- loading. We compare our measured results with the predictions of the Penning SPS scaling laws. Particular attention is paid to the H- current and temperature scaling as well as the power efficiency