Initiation of plasma current with the assistance of electron cyclotron waves in the WT-3 tokamak

Abstract

In the WT-3 tokamak, the toroidal plasma current is started and ramped up to 6.3 kA by the electron cyclotron (EC) wave alone, without ohmic heating (OH) power. After generation of the plasma current by the EC wave, the OH current can be started up with a very low ohmically induced electric field, i.e. <0.32 V/m, which is extremely small compared with that (2.5 V/m) in an OH discharge with the assistance of EC resonance preionization. The low value of the starting loop voltage is in accordance with the requirements of the ITER design. It is demonstrated that the loop voltage and the flux of the OH transformer can be reduced considerably when the EC power is used for preionization and startup of the toroidal current before initiation of an OH discharge in tokamaks