Investigation of the LH wave energy conversion and current drive efficiency in the HT-7 tokamak

Abstract Lower hybrid current drive (LHCD) plasmas in the presence of DC electric filed have been investigated based on Karney–Fisch theory in the HT-7 tokamak. The relatively small scatter in the experimental data with various values of waveguide phasing and lower hybrid power, when plotted in the Karney–Fisch diagram, confirms that a reasonable theoretical interpretation is possible for the HT-7 data. The full non-inductively current drive efficiencies are obtained by fitting the experimental data to the theoretical curve. The efficiency strongly depends on the lower hybrid wave phase velocity.