Major results from the stellarator Wendelstein 7-AS

M. Hirsch, J. Baldzuhn, C. Beidler, R. Brakel, R. Burhenn, A. Dinklage, H. Ehmler, M. Endler, V. Erckmann, Y. Feng, J. Geiger, L. Giannone, G. Grieger, P. Grigull, H. J. Hartfuß, D. Hartmann, R. Jaenicke, R. König, H. P. Laqua, H. Maaßberg & 9 others K. McCormick, F. Sardei, E. Speth, U. Stroth, F. Wagner, A. Weller, A. Werner, H. Wobig, S. Zoletnik

Research output: Contribution to journalArticle

119 Citations (Scopus)

Abstract

Wendelstein 7-AS was the first modular stellarator device to test some basic elements of stellarator optimization: a reduced Shafranov shift and improved stability properties resulted in β-values up to 3.4% (at 0.9 T). This operational limit was determined by power balance and impurity radiation without noticeable degradation of stability or a violent collapse. The partial reduction of neoclassical transport could be verified in agreement with calculations indicating the feasibility of the concept of drift optimization. A full neoclassical optimization, in particular a minimization of the bootstrap current was beyond the scope of this project. A variety of non-ohmic heating and current drive scenarios by ICRH, NBI and in particular, ECRH were tested and compared successfully with their theoretical predictions. Besides, new heating schemes of overdense plasmas were developed such as RF mode conversion heating - Ordinary mode, Extraordinary mode, Bernstein-wave (OXB) heating - or 2nd harmonic O-mode (O2) heating. The energy confinement was about a factor of 2 above ISS95 without degradation near operational boundaries. A number of improved confinement regimes such as core electron-root confinement with central Te ≤ 7 keV and regimes with strongly sheared radial electric field at the plasma edge resulting in Ti ≤ 1.7 keV were obtained. As the first non-tokamak device, W7-AS achieved the H-mode and moreover developed a high density H-mode regime (HDH) with strongly reduced impurity confinement that allowed quasi-steady-state operation (τ ≈ 65 τE) at densities (at 2.5 T). The first island divertor was tested successfully and operated with stable partial detachment in agreement with numerical simulations. With these results W7-AS laid the physics background for operation of an optimized low-shear steady-state stellarator.

Original languageEnglish
Article number053001
JournalPlasma Physics and Controlled Fusion
Volume50
Issue number5
DOIs
Publication statusPublished - May 1 2008

Fingerprint

stellarators
Heating
heating
optimization
Impurities
Plasmas
Degradation
degradation
impurities
quasi-steady states
detachment
Physics
Electric fields
Radiation
Electrons
shear
Computer simulation
harmonics
physics
electric fields

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Condensed Matter Physics
  • Nuclear and High Energy Physics

Cite this

Hirsch, M., Baldzuhn, J., Beidler, C., Brakel, R., Burhenn, R., Dinklage, A., ... Zoletnik, S. (2008). Major results from the stellarator Wendelstein 7-AS. Plasma Physics and Controlled Fusion, 50(5), [053001]. https://doi.org/10.1088/0741-3335/50/5/053001

Major results from the stellarator Wendelstein 7-AS. / Hirsch, M.; Baldzuhn, J.; Beidler, C.; Brakel, R.; Burhenn, R.; Dinklage, A.; Ehmler, H.; Endler, M.; Erckmann, V.; Feng, Y.; Geiger, J.; Giannone, L.; Grieger, G.; Grigull, P.; Hartfuß, H. J.; Hartmann, D.; Jaenicke, R.; König, R.; Laqua, H. P.; Maaßberg, H.; McCormick, K.; Sardei, F.; Speth, E.; Stroth, U.; Wagner, F.; Weller, A.; Werner, A.; Wobig, H.; Zoletnik, S.

In: Plasma Physics and Controlled Fusion, Vol. 50, No. 5, 053001, 01.05.2008.

Research output: Contribution to journalArticle

Hirsch, M, Baldzuhn, J, Beidler, C, Brakel, R, Burhenn, R, Dinklage, A, Ehmler, H, Endler, M, Erckmann, V, Feng, Y, Geiger, J, Giannone, L, Grieger, G, Grigull, P, Hartfuß, HJ, Hartmann, D, Jaenicke, R, König, R, Laqua, HP, Maaßberg, H, McCormick, K, Sardei, F, Speth, E, Stroth, U, Wagner, F, Weller, A, Werner, A, Wobig, H & Zoletnik, S 2008, 'Major results from the stellarator Wendelstein 7-AS', Plasma Physics and Controlled Fusion, vol. 50, no. 5, 053001. https://doi.org/10.1088/0741-3335/50/5/053001
Hirsch M, Baldzuhn J, Beidler C, Brakel R, Burhenn R, Dinklage A et al. Major results from the stellarator Wendelstein 7-AS. Plasma Physics and Controlled Fusion. 2008 May 1;50(5). 053001. https://doi.org/10.1088/0741-3335/50/5/053001
Hirsch, M. ; Baldzuhn, J. ; Beidler, C. ; Brakel, R. ; Burhenn, R. ; Dinklage, A. ; Ehmler, H. ; Endler, M. ; Erckmann, V. ; Feng, Y. ; Geiger, J. ; Giannone, L. ; Grieger, G. ; Grigull, P. ; Hartfuß, H. J. ; Hartmann, D. ; Jaenicke, R. ; König, R. ; Laqua, H. P. ; Maaßberg, H. ; McCormick, K. ; Sardei, F. ; Speth, E. ; Stroth, U. ; Wagner, F. ; Weller, A. ; Werner, A. ; Wobig, H. ; Zoletnik, S. / Major results from the stellarator Wendelstein 7-AS. In: Plasma Physics and Controlled Fusion. 2008 ; Vol. 50, No. 5.
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AU - Dinklage, A.

AU - Ehmler, H.

AU - Endler, M.

AU - Erckmann, V.

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