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Abstract

The temporal increase of low frequency plasma turbulence during ICRF heating has been recently studied for plasma conditions (using carbon limiters) where the radiated power losses in the centre of the discharge have been much less than the auxiliary heating power. The observed correlation between the temporal evolution of turbulence and central electron temperature is the purpose of this research note. The measured density fluctuations, [deltan**2], are approximately constant during the ohmic phase, and with auxiliary r.f. heating, increase progressively and reach a new level. This increased level of turbulence depends on r.f. power and antenna position, scales as the square root of the r.f. power, and is stronger for a low field side antenna. These variations are systematic. For usual shots, the central electron temperature T-eo increases at the beginning of the r.f. excitation, and then saturates and remains almost constant. The evolution of the turbulence also reaches progressively a higher level; the main remark about these variable evolutions is that the higher the level of turbulence, the stronger the decrease of T-eo. The discussion of these findings leads to the conclusion that these r.f. heating experiments show a connection between an increase of the density fluctuations and the deterioration of confinement which can be attributed mainly to an increase of anomalous electron energy transport.

Additional information

Authors: TFR GROUP CEA, FONTENAY-AUX-ROSES (FRANCE) TRUC LABORATOIRE PMI, ECOLE POLYTECHNIQUE, PALAISEAU (FRANCE) , CEA, FONTENAY-AUX-ROSES (FRANCE);LABORATOIRE PMI, ECOLE POLYTECHNIQUE, PALAISEAU (FRANCE)
Bibliographic Reference: PLASMA PHYSICS AND CONTROLLED FUSION VOL. 27 (1985), NO. 9, PP. 1057-1061
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