INVESTIGATION OF THE 2ND-HARMONIC ELECTRON-CYCLOTRON CURRENT DRIVE EFFICIENCY ON THE T-10 TOKAMAK

Experiments on second harmonic electron cyclotron current drive were d one on the T-10 tokamak using four gyrotrons. Total powers up to 1.2 M W at a frequency of 140 GHz were injected. Current generation by elect ron cyclotron (EC) waves was demonstrated in the experiments. The effi ciency eta of current generation and its dependence on plasma paramete rs were measured and it was shown that the efficiency is a nonlinear f unction of input power, more closely predicted by Fokker-Planck calcul ations than by linear theory. The interaction of EC waves with the tai l of the electron distribution was shown to be important. It was also found that current density profile redistribution played an important role in the plasma behavior.