Improved confinement by non-axisymmetric magnetic field in KSTAR*

Non-axisymmetric (3D) magnetic field induces a variety of plasma responses impacting on the pedestal stability, toroidal plasma rotation, and MHD activities. Thanks to flexibility of the 3D magnetic field coils, KSTAR tokamak has demonstrated 3D field capabilities for control of transport and stability of thermal and supratheramal plasmas in the core, edge, and SOL regions. In this presentation, we report the observation of improved confinement in the magnetic braking experiment on KSTAR. The improved confinement is achieved with reduced toroidal plasma rotation by non-axisymmetric magnetic field induced toroidal rotation braking along with significant reduction of edge localized modes (ELMs). Modifications in multi channel transport raise fast ion slowing-down time and improve neutral beam deposition, leading to improved fast ion confinement. We show that modifications of radial electric field and E×B shear flow by magnetic braking provoke an enhanced pedestal to sustain thermal confinement against degradation in the typical 3D field experiment.