Suppression of runaway current by electrode biasing and limiter biasing on J-TEXT

Abstract The avoidance of runaway electrons (REs) generated during plasma disruption is of great concern for the safe operation of tokamak devices. Experimental study on the suppression of runaway current by electrode biasing (EB) and limiter biasing (LB) has been performed on J-TEXT tokamak, which could be an alternative way to suppress the runaway current. The experimental results show that the higher the voltage value, the smaller the runaway current in both electrode biasing and limiter biasing experiments. The runaway current can be completely suppressed at electrode biased voltage of +450 V and limiter biased voltage of +300 V. The comparison of the energy spectra during the runaway plateau phase shows that the maximum energy max(ERE) and radiation temperature THXR of hard X-rays (HXR) are significantly reduced after the application of +200 V limiter biased voltage. The electric field generated by the biased voltage may be the key factor to suppress the runaway current, and the measured radial electric field increases obviously after the voltage applied. This may result in the increase of the loss of REs to realize the suppression of runaway current.