Gyrokinetic electrostatic turbulence close to marginality in the Wendelstein 7-X stellarator

Alessandro Zocco, Linda Podavini, José Manuel Garcìa-Regaña, Michael Barnes, Felix I. Parra, A. Mishchenko, Per Helander

Research output: Contribution to journalArticlepeer-review

Abstract

The transition from strong (fluidlike) to nearly marginal (Floquet-type) regimes of ion-temperature-gradient (ITG) driven turbulence is studied in the stellarator Wendelstein 7-X by means of numerical simulations. Close to marginality, extended (along magnetic field lines) linearly unstable modes are dominant, even in the presence of kinetic electrons, and provide a drive that results in finite turbulent transport. A total suppression of turbulence above the linear stability threshold of the ITG modes, commonly present in tokamaks and known as the "Dimits shift,"is not observed. We show that this is mostly due to the peculiar radial structure of marginal turbulence, which is more localized than in the fluid case and therefore less likely to be stabilized by shearing flows.

Original languageEnglish (US)
Article numberL013202
JournalPhysical Review E
Volume106
Issue number1
DOIs
StatePublished - Jul 2022

All Science Journal Classification (ASJC) codes

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Condensed Matter Physics

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