Confinement Characteristics of 3D Magnetic Braking Discharges in KSTAR

We report an investigation of the confinement of magnetic braking experiments in KSTAR. A set of discharges are developed injecting neutral beams (NBs) that supply strong toroidal torques to produce fast rotating H-mode plasmas. We utilize non-axisymmetric (3D) magnetic field to drive toroidal rotation braking and electron cyclotron heating (ECH) to explore the lowest rotation level. In those discharges, toroidal rotation over a range of 120-300km/s is achieved at the core depending on the combination of NB, 3D field, and ECH. Improved energy confinement triggered by 3D field driven toroidal rotation braking is observed, where increase of stored energy by up to 15% is achieved in spite of increased particle transport by 3D magnetic field. ECEI measurement shows that broadband turbulent fluctuations of ~200kHz near the pedestal are largely mitigated and suppressed in the improved confinement phase. FIDA measurement indicates improved fast ion confinement during the same period. Confinement data are collected for magnetic braking H-mode plasmas in the range of plasma parameters of B$_{T}$=1.6-1.8T, I$_{P}$=500-700kA, and q$_{95}$=3.7-5.4. The analysis result will be presented with a focus on the correlation between the confinement and the toroidal rotation.