Gyrokinetic simulation of turbulenct transport with magnetic island in KSTAR tokamak

Global gyrokinetic simulations with kinetic electrons are performed to study microturbulence in the presence of magnetic islands with self-generated ExB shear flow in the KSTAR tokamak with resonant magnetic perturbation (RMP). Magnetic equilibrium with the islands generated by RMP coils is obtained from M3D-C1 MHD simulations of the discharge #19118. Simulations show that microturbulence is dominated by Ion temperature gradient (ITG) instability. The simulations with islands show distinct turbulence properties compared to that in simulations without islands. The turbulence fluctuation is greatly suppressed within the island region, and consequently, larger transport levels are found near the X-points of the island compared to the O-points. A vortex flow, an ExB flow around the islands by electrostatic potential with the same helicity as the magnetic island , is nonlinearly generated and regulates the ITG turbulence across the islands. The transport is modulated by the vortex flow frequency with a geodesic acoustic mode (GAM) oscillation. The transport varies in toroidal direction, and the maximum transport happens when the X-points are located at outer mid-plane.