Local Heating and Current Drive using the Fundamental O-mode EC wave on JT-60U.
KEN KAJIWARA, AKIHIKO ISAYAMA, TAKAHIRO SUZUKI, SHUNSUKE IDE, ATSUSI KASUGAI, KOJI TAKAHASHI, YOSHITAKA IKEDA, TSUNEYUKI FUJII
Japan Atomic Energy Research Institute
Abstract.
In JT-60U, a 3 MW-level ECRF system using 3 gyrotrons was completed in March 2000. The frequency of 110 Ghz was selected to launch a fundamental O-mode from the low field side. The toroidal injection angle is fixed about 15/FONT> to drive plasma current and poloidal injection angle can be steered using a mirror for deposition control. Up to now, the power of ~ 1.5 MW x 3 second (~ 2.2 MW at gyrotrons) was successfully injected to study the local electron heating and current drive. The mode purity can be controlled by rotatable grooved mirrors that generate adequate elliptical polarization. The correlation between the O-mode purity and the increase of electron temperature was clearly obtained at ne0 > 0.8 x 1019m-3, while weak dependence of electron heating on mode purity was observed at low density (~ 0.3 x 1019m-3) due to the Doppler effect of fundamental X-mode absorption with toroidal oblique angle. A strongly peaked Te profile with Te0 > 10keV at ne0 ~ 1 x 1019m-3 was obtained for 1 s with the injected power of ~ 1.5MW when the O-mode purity is adjusted more than 80%. Impact on sawtooth activity, both suppression and enhancement depending on ECW deposition and direction of EC driven current to the plasma current, was observed. In view of local current drive, changes in MSE signals were observed.