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Plasma Turbulence studied by means of Correlation-ECE in the TEM domain in TCV

Plasma Turbulence studied by means of Correlation-ECE in the TEM domain in TCV Electron temperature fluctuations in the TEM domain have been measured in TCV using the correlation-ECE diagnostics [1]. Significant broadband electron temperature fluctuations are found radially extending between 0.3<ρ<0.7 on the equatorial LFS. Their amplitude decreases with collisionality (with increasing density in OH discharges), in qualitative agreement with predictions from local, linear gyrokinetic GS2 calculations. Thus the mixing length heat diffusivity calculated from GS2 decreases with collisionality, as does the measured heat diffusivity from power balance [2]. This diagnostics allows now the study at the microscopic, turbulence level, of the previously found heat transport triangularity scaling [3], linked to changes of the resonance of TE with the TEM [4]. The decrease of transport when going from positive to negative triangularity found in TCV L-mode can now be investigated and compared to gyrokinetic predictions of instabilities or turbulence (linear/non-linear, local/global). TEM features, like the orientation of the potential cells, predicted to change with plasma shape, up/down-asymmetries, can now be measured through the correlation lengths along a horizontal line of sight, or obliquely, using a mobile mirror arrangement (ECRH launcher in reception mode). [1] V.S. Udintsev et al., Fusion Science and Technology 52 (2007) 161. [2] V.S. Udintsev, E. Fable et al., in preparation. [3] Y. Camenen et al. Nucl., Fusion 47 (2007) 510. [4] A. Marinoni et al., Plasma Phys. Control. Fusion 51 (2009) 055016. 1 present address ITER-IO, Cadarache, St Paul-lez-Durance, F 2 present address CFSA, Dept of Physics, University of Warwick, UK This work was supported in part by the Swiss National Science Foundation.

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