Generation of rf-Driven Currents by Lower-Hybrid-Wave Injection in the Versator II Tokamak

Experimental verification of lower-hybrid rf current drive in the Versator II tokamak is presented. The experiments show that efficient current drive exists only in low-density discharges (${\overline{n}}_e\lesssim 6\times {10}^{12}$ ${\mathrm{cm}}^{-3\mathrm{}}$) in the "slide-away" regime where a preformed suprathermal electron tail exists prior to the application of the rf power.