LH Transition and rotation studies under non-axisymmetric magnetic fields in KSTAR

A thorough study of LH transition under the influence of non-axisymmetric field (NF) has been conducted in KSTAR. It shows that LH power threshold depends on the resonant NFs and the line-averaged density-LH power threshold curve agrees well with the power law scaling [Martin, JOP(2008)] as the resonant NF ($\delta $B/B$^{\mathrm{n=1}})$ applied up to 2.7x10$^{\mathrm{-4\thinspace }}$in KSTAR which has a low intrinsic error field. However, LH power threshold is independent of non-resonant NFs with n$=$1 and n$=$2 which reduced only toroidal rotation by 30{\%} in L-mode The rotation pedestal during LH transition with both co- and counter-NBI heating appears saturated at a critical level of edge rotation [Ko, NF (2015)] which is dependent of LH power threshold However, the core rotation increased with the stored energy in the co-NBI with and without NFs while it is saturated in counter-NBI plasma. In co-NBI heated H-mode, the pedestal width of rotation is 5 cm with wide that of ion temperature (2 cm). On the other hand, in counter-NBI heated H-mode, the rotation pedestal width (2 cm) appeared as similar as that of ion temperature. The newly diagnosed results of rotation in KSTAR seemingly pose a variety of physics questions.