Turbulence mitigation in maximum-J stellarators with electron-density gradient
Author | |
Abstract |
In fusion devices, the geometry of the confining magnetic field has a significant impact on the instabilities that drive turbulent heat loss. This is especially true of stellarators, where the density-gradient-driven branch of the "trapped electron mode" (TEM) is predicted to be linearly stable if the magnetic field has the maximum-J property, as is very approximately the case in certain magnetic configurations of the Wendelstein 7-X experiment (W7-X). Here we show, using both analytical theory and simulations, that the benefits of the optimisation of W7-X also serve to mitigate ion-temperature-gradient (ITG) modes as long as an electron density gradient is present. We find that the effect indeed carries over to nonlinear numerical simulations, where W7-X has low TEM-driven transport, and reduced ITG turbulence in the presence of a density gradient, giving theoretical support for the existence of enhanced confinement regimes, in the presence of strong density gradients (e.g. hydrogen pellet or neutral beam injection). |
Year of Publication |
2022
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Journal |
Journal of Plasma Physics
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Volume |
88
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Issue |
1
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Number of Pages |
905880112
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Date Published |
02/2021
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DOI |
10.1017/S002237782200006X
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PId |
56b59ba74a6482235e8dfb23d8bfcac1
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Alternate Journal |
J. Plasma Phys.
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Label |
OA
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Journal Article
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