ExB Flow Velocity Prediction with Microwave Imaging Reflectometer in KSTAR L-mode Plasmas

Abstract

Turbulence driven by micro-instabilities is considered to be a major source of anomalous transport in fusion plasmas, and the ExB flow shear is known for suppression of the micro-instability driven turbulence and for transport barrier formation. This is why the measurement of the radial electric field or ExB flow velocity is important in turbulence and transport studies. The ExB flow velocity were estimated from the measured apparent poloidal rotations of ion-scale density fluctuations in the laboratory frame with the microwave imaging reflectometer (MIR) system in KSTAR. The apparent poloidal velocity is close to the ExB flow velocity when the intrinsic phase velocity of dominant density turbulence is negligible compared to the apparent poloidal velocity. Details of the ExB flow velocity estimation from the apparent velocity and the result for neutral beam heated L-mode plasmas will be presented. For validation of the MIR measurement, the measured apparent poloidal velocities were compared with the results from a nonlinear gyro-kinetic simulation performed with GTS. *Work supported by NRF Korea under grant no. NRF-2014M1A7A03029865.