| Plasma wall interaction (PWI) driven relaxation oscillations are investigated in the steady state discharge for 5 hours. The oscillation frequency was about 10-3 Hz and each perturbation lasted for ~ 300 s. The heat load, recycling flux and impurity influx were varied from a few % to several tens of % . The largest variation of 70% was seen on the Mo XIII, although the influx of Mo I was only 20%. Although the input rf power is kept constant during the discharge, the coupling between the rf and plasma was increased by ~ 10%. The current drive efficiency is decreased by 24 % in spite of current ramp. The toroidal and poloidal profiles of the recycling flux were also changed. During the last relaxation phase, the plasma was finally terminated. The current reduction (> 4 kA) was not recovered by intense local perturbation of the recycling superposed on the relaxation oscillation. |
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