Present status of the negative ion based neutral beam injector for JT-60U

Abstract

The negative ion based neutral beam injector heating system for JT-60U has contributed to core plasma heating and noninductive current drive experiments on JT-60U. For increasing further the beam power and beam pulse duration, the serious issue is improvement of source plasma nonuniformity in the ion source. Various countermeasures have been devised to solve the nonuniformity. The first is to adjust the spatial distribution of the arc discharge through regulating the arc current limiting resistors to be connected in series to each of the filament groups. The second is to change the arc discharge mode through controlling the filament temperature. These measures have been found to be very effective.