Island divertor studies on W7-AS

F. Sardei, Y. Feng, P. Grigull, G. Herre, D. Hildebrandt, J. V. Hofmann, J. Kisslinger, R. Brakel, J. Das, J. Geiger, O. Heinrich, G. Kühner, H. Niedermeyer, D. Reiter, M. Richter-Glötzl, A. Runov, R. Schneider, U. Stroth, H. Verbeek, F. WagnerR. Wolf

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Basic topological features of the island divertor concept for low shear stellarators are discussed with emphasis on the differences to tokamak divertors. Extensive measurements of the edge structures by two-dimensional plasma spectroscopy and by target calorimetry are in excellent agreement with predicted vacuum and equilibrium configurations, which are available up to central β values of ∼ 1%. For this β value the calculated field-line pitch inside the islands is twice that of the corresponding vacuum case. Video observations of the strike points indicate stability of the island structures for central β values up to ∼ 3.7%. The interpretation of the complex island divertor physics of W7-AS has become possible by the development of the three-dimensional plasma transport code EMC3 (Edge Monte Carlo 3D), which has been coupled self-consistently to the EIRENE neutral gas code. Analysis of high density NBI discharges gives strong indications of stable high recycling conditions for n̄c ≥ 1020 m-3. The observations are reproduced by the EMC3/EIRENE code and supported by calculations with the B2/EIRENE code adapted to W7-AS. Improvement of recycling, pumping and target load distribution is expected from the new optimized target plates and baffles to be installed in W7-AS.

Original languageEnglish
Pages (from-to)135-148
Number of pages14
JournalJournal of Nuclear Materials
StatePublished - 11 Feb 1997
Externally publishedYes


  • 3D model
  • Divertor plasma
  • Plasma density diagnostic
  • Plasma temperature diagnostic
  • W7-AS


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