国際発表 | 43rd APS Conference

Electron Cyclotron Current Drive by the Fundamental X-mode Waves Launched from the Low Field Side in JT-60U

Takahiro Suzuki, Syunsuke Ide, Yoshitaka Ikeda, Ken Kajiwara, Kenkichi Ushigusa and the JT-60 TEAM
Japan Atomic Energy Research Institute, Ibaraki, 311-0193, Japan

Abstract.
The first measurement of the current profile driven by the fundamental X-mode electron cyclotron (EC) waves launched from the low field side is presented. Such X-mode waves can couple to electrons with large velocity in a high temperature plasma due to the Doppler shift effect, in a properly low density condition. The 110 GHz EC waves of about 1MW are launched into the JT-60U tokamak, with changing power fraction of the O/X-mode component. The driven current (j_EC) profile is evaluated, considering transient toroidal electric field profile measured by the motional Stark effect (MSE) polarimetry.
In a higher density condition (line averaged electron density n_e of 1x10¹⁹/m³) above cyclotron cut-off, electron temperature increased much less than in the lower n_e condition; the slight increase in T_e is due to the absorption of O-mode waves. Comparison of increase in pressure showed that fraction of X-mode waves to the whole EC waves was about 71%. Both for the O-/X-mode injection into the lower n_e plasma, locations of the driven current measured by the MSE agreed with deposition locations determined by the increase in electron temperature by electron cyclotron emission (ECE). Center location of the measured j_EC by the O-mode was different from that of the linearlized Fokker-Planck calculation, but was closer to the calculation than that by the X-mode was. The EC driven current, and hence, the current drive (CD) efficiency  by the X-mode waves was consistent with the calculation, while that by the O-mode was larger than the calculation. Resulting  was almost same for both O- and X-mode, while calculation shows that X-mode waves drive current much effectively than the O-mode waves do. The experimental results are not recognized under the conventional propagation and absorption of the EC waves, especially for the X-mode.