Heating and current drive by electron cyclotron waves in JT-60U

Results of studies on heating and current drive by the electron cyclotron (EC) waves in JT-60U are presented. Electron temperature up to 26keV was achieved by injecting EC waves in the center of a reversed shear plasma produced by the lower hybrid (LH) waves. The electron temperature Te exceeds 24keV in a wide range of minor radius (ρ<0.3, where (ρ is the normalized minor radius). ECCD (Current Drive) efficiency ηCD was examined at high Te up to 21keV without using LH waves. The CD efficiency increases with Te, but there is discrepancy from linear dependence on Te in a high Te regime of 10-20keV. Dependence of normalized CD efficiency ζ=e3ηCD/ε2kTe on deposition location was also studied to optimize the CD efficiency, since trapped particle effect, which depends strongly on deposition location, is expected to reduce ζ. The effect was detected from significant decrease in ζ in the lower magnetic field deposition, which is consistent with linearized Fokker- Planck calculation. (author)