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 density microfluctuations with good space and time resolution. In ohmic heating conditions, a turbulent sawtooth precursor was discovered and studied in detail near the q = 1 surface, the large fluctuation spike occurring at the sawtooth crash was precisely located in the mixing region, and it was shown that a turbulence pulse propagates together with the outgoing heat pulse. In sawteeth-free neutral beam injection heating discharges, evidence of a toroidal Doppler effect was collected suggesting 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.