The BNL toroidal volume H- source

The BNL toroidal volume H/sup -/ ion source, in pulsed operation, is now producing up to 35 mA with an electron to H/sup -/ ratio of less than five, and a ratio of less than three for currents up to 20 mA. This improvement came about by increasing the strength of the conical filter field. The source has also been operated steady state at low arc currents, where up to 6 mA of H/sup -/ was extracted. The electron to H/sup -/ ratio is 2-3 times larger for DC operation. For DC currents up to 5 mA, the arc power efficiency was 5 mA/kW. Pulsed performances with Ta and W filaments were very similar, except for the large gas pumping observed with the Ta filament. In DC operation, the Ta filament performed somewhat better than W. Extraction from seven apertures having a total area of 1 cm/sup 2/ produced the same results as a single 1 cm/sup 2/ aperture.<
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