Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase
Name
1.5098761.pdf
Description
Published version
Size
5.48 MB
Format
Adobe PDF
Checksum (MD5)
9171169612877f975485a2f040e59582
Author(s)
Wolf, R. C.
Alonso, A.
Äkäslompolo, S.
Baldzuhn, J.
Beurskens, M.
Beidler, C. D.
Biedermann, C.
Bosch, H.-S.
Bozhenkov, S.
Brakel, R.
Date Issued
August 2019
Journal
Physics of Plasmas
Publisher
AIP Publishing
Citation
Wolf, R. C. et al. "Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase." Physics of Plasmas 26, 8 (August 2019): 082504 © 2019 Author(s)
Version
Final published version
Abstract
Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future stellarator power plant. Plasma operation started in 2015 using a limiter configuration. After installing an uncooled magnetic island divertor, extending the energy limit from 4 to 80 MJ, operation continued in 2017. For this phase, the electron cyclotron resonance heating (ECRH) capability was extended to 7 MW, and hydrogen pellet injection was implemented. The enhancements resulted in the highest triple product (6.5 × 1019 keV m-3 s) achieved in a stellarator until now. Plasma conditions [Te(0) ≈ Ti(0) ≈ 3.8 keV, τE > 200 ms] already were in the stellarator reactor-relevant ion-root plasma transport regime. Stable operation above the 2nd harmonic ECRH X-mode cutoff was demonstrated, which is instrumental for achieving high plasma densities in Wendelstein 7-X. Further important developments include the confirmation of low intrinsic error fields, the observation of current-drive induced instabilities, and first fast ion heating and confinement experiments. The efficacy of the magnetic island divertor was instrumental in achieving high performance in Wendelstein 7-X. Symmetrization of the heat loads between the ten divertor modules could be achieved by external resonant magnetic fields. Full divertor power detachment facilitated the extension of high power plasmas significantly beyond the energy limit of 80 MJ.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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Creative Commons Attribution 4.0 International license
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DOI of Published Version
https://doi.org/10.1063/1.5098761
