Current Drive Performance by Neutral Beam Injection and Electron Cyclotron Wave
K. Ushigusa
Japan Atomic Energy Research Institute Naka Fusion Research Establishment 801-1 Naka-machi, Naka-gun, Ibaraki-ken 311-0193 JAPAN
Abstract.
Multi- MW injections of current drive (CD) power such as 100GHz band of electron cyclotron (EC) waves and negative ion based neutral beams (N-NB) have been extending their current drive performance in toroidal plasmas. In addition to the development of current drivers, establishment of a technique to identify the small fraction of non-inductively driven current based on Mortional Stark effect measurement has greatly contributed to understand physics of CD performance. These progress on NBCD and ECCD are reviewed in this paper.
Recent experimental results are summarized in Fig.1 where the current drive efficiencies (a figure of merit : = neRpICD/PCD) is plotted against the driven current. The shadow area in Fig.1 indicates the region of JT-60 LHCD. N-NBCD experiments has shown the beam driven current of ~1MA and =1.55x1019m-2A/W, while driven current of 0.35MA and efficiency of 0.68x1019m-2A/W is obtained in ECCD experiments. Both CD methods are approaching a level for a practical use in magnetic fusion reactor.. Experimentally observed CD characteristics such as the driven current, its profile and its parameter dependence for both methods will be reviewed. Important applications of these CD methods in recent experiments will be also summarized to obtain the prospect in a future magnetic fusion reactor.
Fig. 1 The CD efficiency versus the driven current