Experimental Observation of the rf-Driven Current by the Lower-Hybrid Wave in a Tokamak

It is observed that the waves launched from a phased array antenna of four waveguides couple effectively with electrons under the condition of $\frac{{\ensuremath{\omega}}_{0}}{{\ensuremath{\omega}}_{1h}(0)}\ensuremath{\gtrsim}2.0$. This coupling generates a rf-driven current, rather than heating of the bulk electrons, and the current/rf-power ratio of 110 A/kW was obtained with a rf power of 125 kW radiated into a plasma which included appreciable suprathermal electrons.