Studies of current profile optimization and influence of electron heating towards advanced tokamak operation on JT-60U

Experimental results of studies towards steady state operation of an advanced tokamak on JT-60U are presented. Especially, issues that are related to a current profile and internal transport barriers (ITBs) with emphasis on fusion relevant conditions are discussed. The major results are; 1) High confinement improvement at high normalized density regime which is expected in the ITER steady state operational scenario was obtained in a reversed magnetic shear (RS) plasma under full non inductive current drive (CD). In the discharge, capability of active current profile control was demonstrated. 2) Influence of dominant electron heating on the ITBs was investigated, and it was found that in RS plasmas the confinement improvement by the ITBs could be maintained in the dominant electron heating regime. On the other hand, it was found in positive shear plasmas that the Ti ITB could be degraded by dominant electron heating. (author)