2nd Harmonic ECCD experiment using 84 GHz EC-wave in LHD

摘要

Second harmonic electron cyclotron current drive (ECCD) experiments were performed in Large Helical Device (LHD) to investigate the characteristics of the EC-driven current and its profile, and to investigate the possibility of controlling the current and rotational transform profiles by ECCD. By a scanning of EC-wave beam direction, a systematic change of plasma current is observed, and the direction of the plasma current is reversed by a reversal of the beam direction. Motional Stark Effect (MSE) measurement revealed tentative behavior of plasma current profile. At the early phase of ECCD, the EC driven current at the plasma core is mostly cancelled by counter current driven by an inductive electromagnetic force. It takes a few seconds for the inductive electromagnetic force to disappear, and the total plasma current gradually approaches to a constant value