Measurement of current driven by electron cyclotron waves in JT-60U

Abstract

Localized driven current profile by electron cyclotron (EC) waves is measured on the JT-60U tokamak, considering transient inductive current. The inductive current is derived from temporal evolution of internal magnetic field, which is evaluated by reconstructions of MHD equilibria with a spline function of total current and with motional Stark effect polarimetry. The analysis clearly shows that the EC-driven current is in a thin layer of about 10% of the minor radius of the plasma. The determined EC-driven current agrees with the one calculated by ray tracing and Fokker-Planck codes. The analysis shows the change in driven current profile when the deposition location of EC waves is changed. The current drive efficiency is about 5×1018 A W-1 m-2 at an electron temperature of 7 keV.