Rf gas plasma source development for heavy ion fusion

Abstract

Presently the Heavy Ion Fusion Virtual National Laboratory is researching ion sources and injector concepts to understand how to optimize beam brightness over a range of currents (50–2000 mA argon equivalent). One concept initially accelerates millimeter size, milliamp beamlets to 1 MeV before merging them into centimeter size, ampere beams. Computer simulations have shown the final brightness of the merged beams is dominated by the emittance growth of the merging process, as long as the beamlets’ ion temperature is below a few electron volts. Thus, a radio frequency multicusp source capable of high current density can produce beams with better brightness compared to ones extracted from a colder source with a large aperture and lower current density. Initial experiments with such a source have successfully demonstrated simultaneously high current density, ∼100 mA/cm2, and fast turn on, ∼1 μs. Results from these experiments are presented as well as progress and plans for the next set of experiments for these sources.