Experimental investigation of toroidal eddy current in the in-vessel components during plasma disruption in the KSTAR tokamak

•Evaluation of toroidal eddy current during plasma disruption.•Validation of the eddy current in the outer part of the in-vessel components.•Eddy currents during plasma disruptions at low and high field sides.•Eddy current in the counter-Ip direction during vertical displacement event. The total toroidal eddy current in the in-vessel components evaluated from the difference between a discrete and continuous Rogowski coil measurements in the KSTAR tokamak was previously reported in [1]. For the eddy currents evaluated from 305 disrupted plasma discharges, it is found that while the peaked value of the eddy current linearly correlates with the value of plasma current Ip, it weakly depends upon the current quench rate. In addition, the eddy currents in the inner and outer parts of the in-vessel components during plasma disruption are assessed from two different Rogowski coil measurements, and the eddy current in the inner part decays faster than one in the outer part. The eddy current in the outer part is validated by comparing it with the eddy current directly measured at the gap resistors in the passive stabilizer. While the eddy currents in the two parts are comparable for plasma disruption at the high field side, the eddy current in the outer part is quite large for the disruption at the low field side. The magnitude of the eddy current at the same side where the disruption occurs is higher than that at the other side. The eddy current in the counter-Ip direction is always detected during the vertical displacement event and its maximum value linearly correlates with the vertical growth rate.