Features of the Uramoto-type sheet plasma as a possible negative ion source

Abstract

The Uramoto-type sheet plasma, which has a unique magnetic field geometry, has been investigated with both Langmuir and JAERI probes [Rev. Sci. Instrum. 62, 772 (1991)]. In these investigations, the plasma potential was found to decrease while the extracted negative hydrogen ion currents increased in the cold region of the plasma. The extracted negative hydrogen ion current also increased as the plasma potential decreased at the same location when the chamber was biased more negative. These features are very favorable for negative ion generation since the destruction of negative hydrogen ions in the extraction region of the source can be minimized resulting in larger negative hydrogen ion currents at constant discharge power. An extracted negative hydrogen ion current density of 3 mA/cm2 was obtained in a 150 V–10 A discharge.