Collisionless microinstabilities in stellarators. II. Numerical simulations

Journal Article · Sun Dec 15 00:00:00 EST 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4846835· OSTI ID:22218345

Proll, J. H. E.; Xanthopoulos, P.; Helander, P. ^[1]

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1. Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstraße 1, 17491 Greifswald, Germany and Max-Planck/Princeton Research Center for Plasma Physics, 17491 Greifswald (Germany)

Microinstabilities exhibit a rich variety of behavior in stellarators due to the many degrees of freedom in the magnetic geometry. It has recently been found that certain stellarators (quasi-isodynamic ones with maximum-J geometry) are partly resilient to trapped-particle instabilities, because fast-bouncing particles tend to extract energy from these modes near marginal stability. In reality, stellarators are never perfectly quasi-isodynamic, and the question thus arises whether they still benefit from enhanced stability. Here, the stability properties of Wendelstein 7-X and a more quasi-isodynamic configuration, QIPC, are investigated numerically and compared with the National Compact Stellarator Experiment and the DIII-D tokamak. In gyrokinetic simulations, performed with the gyrokinetic code GENE in the electrostatic and collisionless approximation, ion-temperature-gradient modes, trapped-electron modes, and mixed-type instabilities are studied. Wendelstein 7-X and QIPC exhibit significantly reduced growth rates for all simulations that include kinetic electrons, and the latter are indeed found to be stabilizing in the energy budget. These results suggest that imperfectly optimized stellarators can retain most of the stabilizing properties predicted for perfect maximum-J configurations.

• OSTI ID: 22218345
• Journal Information: Physics of Plasmas, Vol. 20, Issue 12; Other Information: (c) 2013 Euratom; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
APPROXIMATIONS
BOLTZMANN-VLASOV EQUATION
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DEGREES OF FREEDOM
DOUBLET-3 DEVICE
ELECTRON TEMPERATURE
G CODES
ION TEMPERATURE
NUMERICAL ANALYSIS
PLASMA
PLASMA CONFINEMENT
PLASMA SIMULATION
TEMPERATURE GRADIENTS
TRAPPED ELECTRONS
TRAPPED-PARTICLE INSTABILITY
WENDELSTEIN-7 STELLARATOR