Latest investigations on fluctuations, ELM filaments and turbulent transport in the SOL of ASDEX upgrade

H.W. Müller, J. Adamek, R. Cavazzana, G.D. Conway, C. Fuchs, J.P. Gunn, A. Herrmann, J. Horčaek, C. Ionita, A. Kallenbach, M. Koan, M. Maraschek, C. Maszl, F. Mehlmann, B. Nold, M. Peterka, V. Rohde, J. Schweinzer, R. Schrittwieser, N. VianelloE. Wolfrum, M. Zuin

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Abstract

This paper presents turbulence investigations in the scrape-off layer (SOL) of ASDEX Upgrade in ohmic, L-mode and H-mode discharges using electrostatic and electromagnetic probes. Detailed studies are performed on small scale turbulence and on ELM filaments. Simultaneous measurements of floating and plasma potential fluctuations revealed significant differences between these quantities. Large errors can occur when the electric field is extracted from floating potential measurements, even in ohmic discharges. Turbulence studies in ohmic plasmas show the existence of density holes inside the separatrix and blobs outside. Close to the separatrix a reversal of the poloidal blob propagation velocity occurs. Investigations on the Reynolds stress in the scrape-off layer (SOL) show its importance for the momentum transport in L-mode while its impact for momentum transport during ELMs in H-mode is rather small. In the far SOL the electron density and temperature were measured during type-I ELMy H-mode at ASDEX Upgrade resolving ELM filaments. Strong density peaks and temperatures of several 10 eV were detected during the ELM events. Additional investigations on the ions in ELM filaments by a retarding field analyser indicate ion temperatures of 50-80 eV. ELMs also expel current concentrated in filaments into the SOL. Furthermore, discharges with small ELMs were studied. In N2 seeded discharges the type-I ELM frequency rises and the ELM duration decreases. For discharges with small type-II ELMs the mean turbulent radial particle flux is increased over the mean particle flux in type-I ELM discharges at otherwise similar plasma parameters. © 2011 IAEA, Vienna.
Original languageEnglish
Article number073023
Pages (from-to)-
JournalNuclear Fusion
Volume51
Issue number7
DOIs
Publication statusPublished - Jul 2011
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Müller, H. W., Adamek, J., Cavazzana, R., Conway, G. D., Fuchs, C., Gunn, J. P., ... Zuin, M. (2011). Latest investigations on fluctuations, ELM filaments and turbulent transport in the SOL of ASDEX upgrade. Nuclear Fusion, 51(7), -. [073023]. https://doi.org/10.1088/0029-5515/51/7/073023