Construction of negative-ion-based neutral beam teststand for Large Helical Device (LHD)

Abstract

A test stand for the negative-ion-based NBI (neutral beam injector) for the LHD, currently under construction, has neutral beam capabilities of 2.5 MW at a beam energy of 125 keV (H/sup 0/)/250 keV (D/sup 0/) and pulse duration of 10 s. Components being developed are as follows: (1) a large and high current negative ion source which is immersed in vacuum and composed of a compact modular ion source; (2) a beam dump to remove high heat flux up to 1.6 kW/cm/sup 2/; (3) a high-pumping-speed (450 m/sup 3//s) cryopump; (4) a 250-kV power supply system using a GTO (gate turn-off thyristor); and (5) a controller system to vary the beam energy within 0.5 s.<>