Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator

S. Zoletnik, M. Anton, M. Endler, S. Fiedler, M. Hirsch, K. McCormick, J. Schweinzer

Research output: Contribution to journalArticle

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Abstract

The fluctuation of electron density in the scrape-off layer (SOL) and edge plasma regions of the Wendelstein 7-AS stellarator [H. Renner et al., Plasma Phys Controlled Fusion 31, 1579 (1989)] is investigated by the beam emission spectroscopy technique, observing fluctuations in the Li(2p) line emission intensity of a 50 keV accelerated Li beam. A recently developed numerical technique enables correct reconstruction of correlation functions (and as a consequence, fluctuation amplitudes as well) of the electron density fluctuations from correlations of beam light fluctuations. Depending on the plasma electron density, the radial range of the measurement is either limited to r/a>0.9 (at the highest densities) or can extend to about r/a>0.3 at the lowest densities. As the technique is nonperturbing to the plasma, several hundred shots were analyzed and a catalog of the observed phenomena was established. The results always show a change in the properties of the fluctuations at approximately the last closed flux surface. This observation might indicate differences in the turbulence drive in the SOL and the edge plasma. However, one cannot exclude that the same turbulence phenomenon results in different density fluctuations in the two regions due to the different magnetic topologies. The relevance of the observed phenomena to anomalous transport is discussed.

Original languageEnglish
Pages (from-to)4239-4247
Number of pages9
JournalPhysics of Plasmas
Volume6
Issue number11
Publication statusPublished - Nov 1999

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stellarators
turbulence
controlled fusion
light beams
shot
catalogs
topology
spectroscopy

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Condensed Matter Physics

Cite this

Zoletnik, S., Anton, M., Endler, M., Fiedler, S., Hirsch, M., McCormick, K., & Schweinzer, J. (1999). Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator. Physics of Plasmas, 6(11), 4239-4247.

Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator. / Zoletnik, S.; Anton, M.; Endler, M.; Fiedler, S.; Hirsch, M.; McCormick, K.; Schweinzer, J.

In: Physics of Plasmas, Vol. 6, No. 11, 11.1999, p. 4239-4247.

Research output: Contribution to journalArticle

Zoletnik, S, Anton, M, Endler, M, Fiedler, S, Hirsch, M, McCormick, K & Schweinzer, J 1999, 'Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator', Physics of Plasmas, vol. 6, no. 11, pp. 4239-4247.
Zoletnik S, Anton M, Endler M, Fiedler S, Hirsch M, McCormick K et al. Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator. Physics of Plasmas. 1999 Nov;6(11):4239-4247.
Zoletnik, S. ; Anton, M. ; Endler, M. ; Fiedler, S. ; Hirsch, M. ; McCormick, K. ; Schweinzer, J. / Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator. In: Physics of Plasmas. 1999 ; Vol. 6, No. 11. pp. 4239-4247.
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