Complete stabilization of a tearing mode in steady state high-beta(p) H-mode discharges by the first harmonic electron cyclotron heating/current drive on JT-60U

A tearing mode with m = 3 and n = 2, destabilized in the steady state high- Bp H-mode discharges with edge localized mode (ELM), was completely stabili zed by local heating and current drive using the 110 GHz first harmonic O-m ode electron cyclotron CEC) wave. Here, m and n are poloidal and toroidal m ode numbers, respectively. The optimum EC wave injection angle was determin ed by identifying the mode location from an electron temperature perturbati on profile and a safety factor profile. The optimum injection angle was als o determined by scanning a steerable mirror during a discharge. In a typica l discharge where the tearing mode is completely stabilized, the ratio of t he electron cyclotron heating power to the total heating power is 0.17, and the ratio of the EC driven current to the total plasma current is 0.02. St ored energy and neutron emission rate were higher for the case with EC wave injection than that without EC wave injection, which suggests that the red uction of the stored energy and the neutron emission rate was recovered by the tearing mode stabilization.