Difference of co-extracted electron current and beam acceleration in a negative ion source with hydrogen-isotope ions

Abstract Improvement of the performance on a hydrogen/deuterium negative ion source for nuclear fusion device is reported. In particular, suppression co-extracted electron current, I e , an important issue to ensure stable beam acceleration. has been confirmed by optimizing magnetic field deflection magnet in extraction grid. Two other new methods reduction were validated. The first was fence whose rods set between rows apertures plasma and current ratio, approximately /I acc greatly improved from 0.7 0.25 deuterium. second outer iron yoke which enhanced flux density 19% inside arc discharge chamber. using decreased 0.1 compared with normal filter deuterium operation. These attempts have total injection power 8.4 MW three based NBIs.