Observation of the Generalized Neoclassical Toroidal Viscosity Offset Rotation Profile in KSTAR*

A beneficial effect of Neoclassical Toroidal Viscosity [1] that may be important in slowly rotating plasmas as expected in ITER is the inherent or ``offset'' rotation created by an applied 3D field. Past experiments and associated theory have only considered that the NTV offset rotation can occur in the direction opposite to the plasma current. More recently, the NTV offset rotation profile, V$_{\mathrm{0}}^{\mathrm{NTV}}$, was directly measured and studied in the KSTAR tokamak that has shown for the first time strong, controlled rotation in the co-I$_{\mathrm{p}}$ direction at high electron temperature. This result is expected from generalized NTV theory that allows for electron and ion torques. A field with dominant n $=$ 2 component was applied to produce V$_{\mathrm{0}}^{\mathrm{NTV}}$. Rotation in the plasma outer region exceeded 12 krad/s, quite significant compared to projections for ITER of approximately 2 krad/s in the pedestal region. Also, the V$_{\mathrm{0}}^{\mathrm{NTV}}$ rotation profile shear is 15 times greater than measured in the intrinsic rotation profile (without 3D field). Experiments at higher T$_{\mathrm{e}}$ produced the strong co-rotation and rotation shear while higher density and lower T$_{\mathrm{e}}$ reduced these characteristics. [1] K.C. Shaing, K. Ida, S.A. Sabbagh, Nucl. Fusion \textbf{55} (2015) 125001. $^{\mathrm{\ast }}$Supported by US DOE Contracts DE-FG02-99ER54524 and DE-SC0016614.