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  • Letter
  • Open Access

Coarse-grained gyrokinetics for the critical ion temperature gradient in stellarators

G. T. Roberg-Clark*, G. G. Plunk, and P. Xanthopoulos

  • Max-Planck-Institut Für Plasmaphysik, D-17491 Greifswald, Germany

  • *gar@ipp.mpg.de
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Phys. Rev. Research 4, L032028 – Published 15 August, 2022

DOI: https://doi.org/10.1103/PhysRevResearch.4.L032028

Abstract

We present a modified gyrokinetic theory to predict the critical gradient that determines the linear onset of the ion temperature gradient (ITG) mode in stellarator plasmas. A coarse-graining technique is applied to the drift curvature, entering the standard gyrokinetic equations, around local minima. Thanks to its simplicity, this novel formalism yields an estimate for the critical gradient with a computational cost low enough for application to stellarator optimization. When comparing against a gyrokinetic solver, our results show good agreement for an assortment of stellarator designs. Insight gained here into the physics of the onset of the ITG-driven instability enables us to devise a compact configuration, similar to the Wendelstein 7-X device, but with almost twice the ITG linear critical gradient, an improved nonlinear critical gradient, and reduced ITG mode transport above the nonlinear critical gradient.

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Outline

Information

Phys. Rev. Research 4, L032028– Published 15 August, 2022
  • Received 14 March 2022
  • Revised 2 June 2022
  • Accepted 19 July 2022
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

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