ECRF Experiments for Local Heating and Current Drive in JT-60U

An ECRF program has been started to study the local heating and current drive in JT-60U. The frequency of 110GHz was adopted to couple the fundamental O-mode from low field side with an oblique toroidal injection angle for current drive. Experiments were performed at the injection power of ~1.5 MW by using three gyrotrons, each of which has generated the output power up to ~0.8 MW for 3 seconds. A strongly peaked Te profile was observed and the central electron temperature increased up to ~15 keV when the O-mode was absorbed on axis. The local electron heating clarified the significant difference on the heat pulse propagation between in the plasmas with the internal transport barrier (ITB) and without ITB. The driven current estimated by the Motional Stark Effect (MSE) diagnostic showed that the EC driven current was ~0.2MA at the local electron temperature and density of Te ~6 keV, ne~0.7x10 19 m. The measured driven current near the axis was consistent with the theoretical prediction using a Fokker Planck code. In the case of co-ECCD, the sawteeth activity in NB heated plasma was completely suppressed for 1.5 s with the deposition at the inversion radius, while the sawteeth was enhanced for counter-ECCD at the same deposition condition.