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Abstract. The turbulence characteristics were investigated by means of correlation reflectometry and Langmuir probes. The ECRH discharges show the distinct transition from the core turbulence, having complex structure, to the unstructured one at periphery. It is explained as the transition from ITG/TEM to the resistive interchange instability. The core turbulence includes the “broad band”, “quasi-coherent” feature, arising due to the excitation of rational surfaces with high poloidal m-numbers, “low frequency”, looking like “streamers” and oscillations at 20 – 30 kHz, having properties of “zonal flows”. In OH discharges the turbulence rotates like rigid body with constant angular velocity equal to that of m=2 mode rotation over all plasma radii in OH discharges. The decrease of the mean core turbulence wavelength, impurities peaking and decrease of ion heat conductivity were observed under transition of the OH discharge from SOC to IOC phase after gas puff cut off. The change of poloidal asymmetry was also registered. Significant variation of the turbulence characteristics were measured at the start of the central ECRH and after fast edge cooling by carbon flake. In all cases the change of the core turbulence were interpreted as interplay between ITG and DTEM instabilities.
IAEA 2003
