Development of a 500 keV, 22 A D- ion source for the neutral beam injector for JT-60U

The first results of the performance test of the large negative ion source for a JT-60U negative-ion-based neutral beam injector (N-NBI) are presented. The ion source consists of a cesium seeded multicusp plasma generator, where negative ions are produced via volume and surface processes, a 110 cmX45 cm multiaperture extractor, and a three-stage electrostatic accelerator. After negative ion production and voltage holding tests in test stands, the ion source was installed in the N-NBI system and the full power test began. Up to now, the ion source has produced 400 keV, 5.9 A (2.4 MW) D- ion beams, the world highest D- current and beam power, with a pulse duration of 0.1 s. (C) 1996 American Institute of Physics.