The 100 GHz-band gyrotron (high-power RF tube) was developed to obtain an output of 1 MW at JAERI, the first in the world, and its development has been successfully in progress. Our purpose of the present work is to demonstrate that magnetic oscillations are suppressed by injecting RF waves from gyrotrons locally into plasma interiors where magnetic oscillations take place. The 110 GHz ECRF (electron cyclotron range of frequency) device including the antenna with a steerable mirror to control the injection direction of RF waves has been installed in JT-60 (Fig. 3-4 and 3-5).
Figure 3-6 shows the result of experiments, where an ECRF power of 1. 6 MW was injected into JT-60 plasmas at the time of 7. 5 s. Before 7. 5 s, magnetic oscillations inside plasmas were observed by magnetic probes. When ECRF power was injected into the local area of the plasma interior with magnetic oscillations by adjusting its injection direction, EC-driven local plasma current stabilized the magnetic oscillations, which were decreased to noise levels after 8 s (Fig. 3-6).
This method of suppressing magnetic oscillations by ECRF waves, which will be applicable also for ITER, is being further investigated in JT-60. |
