Plasma current sustainment and ramp-up by electron cyclotron waves in the WT-2 tokamak

By injecting RF power in the electron cyclotron(EC) range of frequency, the plasma current is sustained and ramped up after OH power is shut off. Here EC driven current is generated by EC heating of suprathermal electrons in the OH plasma. The plasma current is also generated in the RF discharge plasma at EC resonance (ECR plasma) in WT-2. Both in OH-produced and ECR-produced plasmas, the electron velocity distribution function is asymmetric with respect to the magnetic field. This asymmetry leads to an asymmetric EC heating generating the toroidal plasma current. The efficiency of EC current drive is obtained as η ∼ 1 x 10-4(1020 m-2kA/kW), which is small in comparison with the theoretical prediction. (author)