Investigation of the effect of electron cyclotron heating on runaway generation in the KSTAR tokamak

Wave enhanced runaway generation is expected to play an important role in the conversion of plasma current into runaway current during major disruptions. The fast electrons created by electron cyclotron heating (ECH) were used to study this issue in KSTAR. It is found that the fast electrons driven by ECH can enhance runaway production in the flat top phase with high loop voltage. The runaway current in disruptions was not enhanced by the ECH produced fast electron population due to the strong magnetic fluctuations which inhibited the generation of runaway electrons. It is found that a complete loss of existing REs during thermal quench has occurred in KSTAR limiter configuration discharges. -- Highlights: → The effect of ECH on runaway generation has been investigated in KSTAR. → Wave enhanced runaway generation plays a role in flat top phase in KSTAR. → While the ECH didn't enhance runaway generation in disruptions in KSTAR. → The existing runaway electrons were completely lost during thermal quench.