H/sup -/ ion source with high duty factor

The small-angle source (SAS) and 4X source are Penning surface-plasma sources (SPS) that produce high-brightness H/sup -/ ion beams for accelerator applications. However, electrode cooling considerations have limited the duty factor for pulsed operation to 1 to 3% and the maximum cw H/sup -/ beam to 2 to 4 mA. The addition of some active cooling to the 4X source has allowed pulsed operation at 6% duty factor for arc parameters sufficient to produce approx. 100 mA of H/sup -/ beam. More vigorous cooling, now being added, should allow production of cw H/sup -/ beams up to 20 to 40 mA. The cooled electrodes were designed using the predictions of TOPAZ2D, a 2-D transient, conductive heat-transfer code. The latest results, along with the possibility of producing even larger cw II/sup -/ beam currents, will be discussed.