Resolving the uncertainties of non-axisymmetric fields in tokamaks

Recent study suggests that KSTAR could be a benefactor of the extremely low level of intrinsic error field in n$=$1 resonant magnetic perturbation (RMP) driven edge localized modes (ELM) control [1]. Specifically, when the $n=$1 RMP currents increases in order to suppress/mitigate ELMs, a kink-resonant mode-locking is not usually invoked in KSTAR, unlike in other devices [2]. Besides we have discovered that the mid-plane RMP appeared much more effective than the off-midplane RMPs in affecting the ELMs with strong density pump-outs and enhanced ELM frequency. Presently, the enhanced understanding of non-axisymmetric field in tokamaks has been in great need, in particular, for the ITER RMP requirements [3]. As the prevailing design of in-vessel RMP coils in ITER is similar to that in KSTAR, we are keen to resolve the uncertainties of the non-axisymmetric fields on transport and stability, and their limits, contributing directly to ITER and beyond. \\[4pt] [1] Y. In \textit{et al}, NF (2015)\\[0pt] [2] Y.M. Jeon \textit{et al}, PRL(2012)\\[0pt] [3] A. Loarte \textit{et al}, NF (2014)