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Electrostatic fluctuations have been measured in the scrape-off layer of ASDEX and W7-AS by Langmuir probes and by observation of H(alpha) light and light emitted from a fast Li atom beam with high spatial and temporal resolution. It is demonstrated that these fluctuations contribute a significant, if not dominant, fraction of the anomalous radial particle transport. The basic properties of the fluctuations are the same in both experiments. A model for an instability mechanism specific to the SOL is presented including density, temperature and electric potential fluctuations. From this model, mixing length estimates for the radial transport and resulting density and pressure gradients in the SOL are derived and compared to measurements in the mid-plane and in the divertor of ASDEX. Data from poloidal multi-pin probe arrays are decomposed into a sum of spatial temporal events by means of a fitting procedure. Centres of selected events serve as reference points for the analysis of the dynamics in their surroundings.

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Authors: ENDLER M ET AL., Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);TSOIS N, Demokritos, Athens (GR);ZOLETNIK S, KFKI Research Institute for Particle and Nuclear Physics, Budapest (HU)
Bibliographic Reference: Article: Physica Scripta, Vol. 51 (1995) pp. 610-616
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