Characteristics of halo current in KSTAR

Small Rogowski coils as halo current monitors (HCMs) are used to measure halo currents (HCs) flowing through the support structures for the divertors between plasma and the wall of the vacuum vessel during the vertical displacement events (VDEs) which cause plasma disruption in the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. The HC measurements are carried out during up / downward VDEs under the experimental conditions such as plasma current I_p0 = 0.2 - 1.0 MA, toroidal field B_T= 1.5 - 3.0 T. The maximum value of total halo current I_h,max is estimated up to 40 % of I_p0 in the operational range of I_p0 and B_T for elongated plasmas (κ ≥ 1.49). The dependences of I_h,max on plasma parameters (as plasma current, stored energy, plasma density, plasma shaping) are investigated. The toroidal peaking factor (TPF) is evaluated from the toroidal distribution of the local HC obtained at the inner /outer divertors. The maximum value of TPF x I_h,max / I_p0 is about 0.5. In this work, the KSTAR HCMs are briefly introduced, and results from the experimental investigations of the HCs during the campaign of 2014 in the KSTAR tokamak are presented. (author)