Turbulence mitigation in maximum-J stellarators with electron-density gradient

TitleTurbulence mitigation in maximum-J stellarators with electron-density gradient
Publication TypeJournal Article
Year of Publication2022
AuthorsJ.H.E. Proll, G.G. Plunk, B.J. Faber, T. Görler, P. Helander, I.J. McKinney, M.J. Pueschel, H.M. Smith, P. Xanthopoulos
JournalJournal of Plasma Physics
Volume88
Issue1
Pagination905880112
Date Published02/2021
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).

DOI10.1017/S002237782200006X
Division

FP

Department

PMT

PID

56b59ba74a6482235e8dfb23d8bfcac1

Alternate TitleJ. Plasma Phys.
LabelOA

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