TIME-DEPENDENT ANALYSIS OF SPATIALLY-RESOLVED FLUCTUATIONS OBSERVED BY MICROWAVE-SCATTERING ON TEXTOR

A 2 mm microwave scattering system was used on TEXTOR to observe densi ty microfluctuations with good space and time resolution. In ohmic hea ting conditions, a turbulent sawtooth precursor was discovered and stu died in detail near the q = 1 surface, the large fluctuation spike occ urring at the sawtooth crash was precisely located in the mixing regio n, and it was shown that a turbulence pulse propagates together with t he outgoing heat pulse. In sawteeth-free neutral beam injection heatin g discharges, evidence of a toroidal Doppler effect was collected sugg esting short parallel wavelength fluctuations near the magnetic axis. In sawtoothing neutral beam injection discharges, a strong transition of the MHz fluctuation levels during the sawtooth development appears as new evidence of the link between confinement and fluctuations.