2007 Volume 2 Pages 022
In our recent experiment, it was found that intense negative ion beams could be extracted from high-density and high-electron temperature plasmas under a Cesium seeded condition. This indicates that such plasmas contribute to the surface production of negative ions, and that the negative ion production exceeds the destruction process via electron detachment. Thus, it has been suggested that highly ionized and dissociated plasmas are suitable for the surface production of negative ions. This paper reports the results of specific experiments to confirm the negative ion production in plasmas with high-electron temperature. In these experiments, high electron temperature plasmas were produced by (1) placing filaments (acting as cathodes) near the extraction area, and (2) reducing the magnetic filter strength, both to allow fast electrons access to the beam extraction area. The results support the production of high-density H- ions even in plasmas with high-electron temperature. Also included is a discussion on the surface production mechanism of negative ions under a Cs-seeded condition.
