Improvement in brightness of multicusp-plasma ion source

Abstract

The beam brightness of a multicusp-plasma ion source has been substantially improved by optimizing the source configuration and extractor geometry. The current density of a 2 keV He+ beam extracted from a 7.5-cm-diameter source operating at 2.5 kW rf power is ∼100 mA/cm2, which is ∼10 times larger than that of a beam extracted from a 5-cm-diameter source operating at 1 kW rf power. A smaller focused beam spot size is achieved with a counter-bored extractor instead of a conventional (“through-hole”) extractor, resulting another order of magnitude improvement in beam current density. Measured beam brightness can be as high as 440 A/cm2Sr, which represents a 30 times improvement over prior work.