Recent Progress in Negative-Ion-Based Neutral Beam Injection Experiment
Since the negative-ion-based neutral beam injection into JT-60U plasmas (N-NBI: designed parameters of 500 keV and 10 MW with two ion sources), the performance on beam power and pulse length is being progressed together with its application to current drive experiment using the high energy beams.
In late 1996 fiscal year, the profile of currents driven by the energetic beams from N-NBI was for the first time identified from multi-channel motional Stark effect spectroscopy measurements, which reasonably agrees with the theoretical prediction using the ACCOME code (see below). The establishment of evaluation scheme for the current drive performance associated with the energetic beams would significantly contribute to ongoing ITER Physics R&D activities in addition to further progress in N-NBI experiments hereafter. Moreover, recent achievements of 3.2 MW/source of power at 350 keV of beam energy and a pulse length up to ~2 s are promising for early demonstration of the full injection performance.
