Characteristics of Tearing Modes in Steady State High Be H-mode Discharges in JT-60U

In the steady state high Bo mode discharges in JT-60U, long sustainment of the beta plasma is limited by the occurrence of tearing modes with low toroidal and poloidal mode numbers. In this paper, characteristics of the tearing modes are described mainly from the viewpoint of the experimental results. It is found that the characteristics are similar to those of the neoclassical tearing mode. Tearing mode stabilization experiments have been carried out since 1999 by local heating and current drive using the newly installed electron cyclotron wave injection system. Although decrease in magnetic perturbations and electron temperature perturbations was observed, complete stabilization was not successful.