Construction of negative-ion-based NBI system in Large Helical Device

A high-power negative-ion-based NBI system is now under construction for Large Helical Device (LHD). The neutral beam injection power and energy are designed to be 15 MW and 180 keV, respectively, for hydrogen, and the pulse duration is 10 sec. Two beamlines are installed to LHD, the injection direction of which is tangential and balanced with each other. Two large negative-ion sources are attached side-by-side to each beamline, which produce 180 keV-40 A of the negative ion beam. The prototype ion source has just started operation in the negative NBI test stand, and produced 106 keV-21 A of the negative ion beam. The fabrication of the beamline components and the power supplies have been almost finished. The installation to LHD starts in October and is completed in March, 1998. After the commissioning and the conditioning, the injection to LHD is scheduled in September, 1998.