Combined electron cyclotron and lower hybrid current drive on WT-3 tokamak

The plasma current is ramped up by oblique injection of the electron cyclotron (EC) wave in the form of X-mode into a lower hybrid current drive (LHCD) plasma in the WT-3 tokamak (major radius R0=0.65 m, minor radius a=0.2 m and toroidal field Br (0)≤1.75 T). The current ramp-up is due to selective EC heating of tail electrons by the fundamental EC resonance at an upshift frequency due to the Doppler effect. Nearly the same current ramp-up rate is obtained for the same additional power injected by stepping up the LH power instead of EC power, while increment hard X-ray emission is larger in the EC case. This results suggests that the current is carried away by more energetic electrons in the EC case compared with the LH case. (author). 7 refs, 4 figs