High Density current Drive Experiments on JFT-2M

概要

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Current drive experiment by 200 MHz fast waves have been carried out to investigate a feasibility of the fast wave current drive (FWCD) in hot and dense plasmas. Four phased loop antenna arry is employed to excite traveling fast waves. The wavenumber spectrum has a peak at N_z=4 with Δ N_z=4 when Δ φ=π/2. Typical loading resistance of the antenna is about 1-1.5 Ω at n_e=2×10^<19>m^<-3>, and increases with the density as well as that of ICRF loop antenna. Wehn the fast wave is applied to the ohmic plasma with T_<eo>=1 keV and n_e>1×10^<19>m^<-3>, where the lower hybrid resonance layer locates at the plasma edge, remarkable increase of the electron temperature is observed at the plasma center. The increment of T_e depends on the antenna phasing. Effective heating is obtained at Δ φ=π where V_<ph>/V_<te>=3-4. A noticeable loop voltage drop is observed only at Δ φ=π. When the 2nd harmonic ECH is applied to heat the plasma up to 1.5 keV, the region where the loop voltage drops is expanded into Δ φ=2π/3. This result indicates that the fast wave with higher phase velocity becomes to be absorbed effectively with increasing T_e. Linear theory predicts that sufficient absorption at Δ φ=π/2 requires the electron temperature of 3 keV at the plasma center and the plasma current of several tens kA will be generated by an rf power of 500 kW.
核融合科学研究所の論文