Gyrokinetic electrostatic turbulence close to marginality in the Wendelstein 7-X stellarator
[1];
[2];
[5];
- Max-Planck-Institut für Plasmaphysik, Greifswald (Germany)
- Max-Planck-Institut für Plasmaphysik, Greifswald (Germany); Università Milano Bicocca, Milano (Italy); Universität Greifswald (Germany)
- Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain)
- Univ. of Oxford (United Kingdom)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
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.
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE; Euratom Research and Training Programme
- Grant/Contract Number:
- AC02-09CH11466; 101052200
- OSTI ID:
- 1883323
- Journal Information:
- Physical Review. E, Vol. 106, Issue 1; ISSN 2470-0045
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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