H-extraction from a magnetic multipole source: the effect of cathode area

Publisher Website
Google Scholar
Abstract
Measurements are made of the extracted H- ion current from a magnetic multipole volume source operating CW. Ion currents up to 44 mA have been achieved using a 16 mm diameter extraction aperture. The transported ion beam current is dependent on both the number of filaments in the source and the filament diameter. The authors present data which show that this dependency, at least for this source, is due largely to the cathode structures acting as an ion collector. As the cathode area is increased, the fraction of discharge current comprising collected ions is increased. In this source as much as 28% of the arc current may be ions drawn from the plasma. Thus comparisons at the same arc current for different cathode areas are not made with the same emitted electron current from the cathodes and hence not at the same plasma conditions. This has important implications for the arc efficiency of such discharges.
Keywords

This publication has 6 references indexed in Scilit: