Equilibrium βlimits in classical stellarators
Abstract
Here, a numerical investigation is carried out to understand the equilibrium βlimit in a classical stellarator. The steppedpressure equilibrium code is used in order to assess whether or not magnetic islands and stochastic fieldlines can emerge at high β. Two modes of operation are considered: a zeronetcurrent stellarator and a fixediota stellarator. Despite the fact that relaxation is allowed, the former is shown to maintain good flux surfaces up to the equilibrium βlimit predicted by idealmagnetohydrodynamics (MHD), above which a separatrix forms. The latter, which has no ideal equilibrium βlimit, is shown to develop regions of magnetic islands and chaos at sufficiently high β, thereby providing a ‘nonideal βlimit’. Perhaps surprisingly, however, the value of β at which the Shafranov shift of the axis reaches a fraction of the minor radius follows in all cases the scaling laws predicted by idealMHD. We compare our results to the HighBetaStellarator theory of Freidberg and derive a new prediction for the nonideal equilibrium βlimit above which chaos emerges.
 Authors:

 MaxPlanckInstitut fur Plasmaphysik, Greifswald (Germany)
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Publication Date:
 Research Org.:
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1414936
 Grant/Contract Number:
 AC0209CH11466
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Journal of Plasma Physics
 Additional Journal Information:
 Journal Volume: 83; Journal Issue: 06; Journal ID: ISSN 00223778
 Publisher:
 Cambridge University Press
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; fusion plasma; plasma confinement
Citation Formats
Loizu, Joaquim, Hudson, S. R., Nuhrenberg, C., Geiger, J., and Helander, P. Equilibrium βlimits in classical stellarators. United States: N. p., 2017.
Web. doi:10.1017/S0022377817000861.
Loizu, Joaquim, Hudson, S. R., Nuhrenberg, C., Geiger, J., & Helander, P. Equilibrium βlimits in classical stellarators. United States. doi:10.1017/S0022377817000861.
Loizu, Joaquim, Hudson, S. R., Nuhrenberg, C., Geiger, J., and Helander, P. Fri .
"Equilibrium βlimits in classical stellarators". United States. doi:10.1017/S0022377817000861. https://www.osti.gov/servlets/purl/1414936.
@article{osti_1414936,
title = {Equilibrium βlimits in classical stellarators},
author = {Loizu, Joaquim and Hudson, S. R. and Nuhrenberg, C. and Geiger, J. and Helander, P.},
abstractNote = {Here, a numerical investigation is carried out to understand the equilibrium βlimit in a classical stellarator. The steppedpressure equilibrium code is used in order to assess whether or not magnetic islands and stochastic fieldlines can emerge at high β. Two modes of operation are considered: a zeronetcurrent stellarator and a fixediota stellarator. Despite the fact that relaxation is allowed, the former is shown to maintain good flux surfaces up to the equilibrium βlimit predicted by idealmagnetohydrodynamics (MHD), above which a separatrix forms. The latter, which has no ideal equilibrium βlimit, is shown to develop regions of magnetic islands and chaos at sufficiently high β, thereby providing a ‘nonideal βlimit’. Perhaps surprisingly, however, the value of β at which the Shafranov shift of the axis reaches a fraction of the minor radius follows in all cases the scaling laws predicted by idealMHD. We compare our results to the HighBetaStellarator theory of Freidberg and derive a new prediction for the nonideal equilibrium βlimit above which chaos emerges.},
doi = {10.1017/S0022377817000861},
journal = {Journal of Plasma Physics},
number = 06,
volume = 83,
place = {United States},
year = {2017},
month = {11}
}
Web of Science
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