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P: Plasmaphysik

P 13: Postersitzung I

P 13.11: Poster

Dienstag, 4. März 1997, 16:00–18:00, Foyer

Curvature and Local Shear Characteristics in Optimized Stellarators — •Carolin Nührenberg — IPP-EURATOM Association, Teilinstitut Greifswald, 17491 Greifswald, Germany

A computational study investigating the properties of non-local ballooning-type linear ideal MHD modes — determined by the CAS3D stability code [1] — and their driving terms is described here for two different types of 3D plasma configurations: the W7–X stellarator and a two-periodic quasi-axisymmetric case. The investigation of the competing driving forces may be based on the inspection of three functions — |B|, σ, and |∇ s|² —, since the magnetohydrostatic equilibrium relations for the magnetic field B in magnetic coordinates may be used to show that the geometry is, apart from the surface functions, completely determined by |B| and two other, independent quantities, one of which is chosen to be the odd function σ occurring in the local shear, the other the even function | ∇ s|², which is a measure for the spacing of the magnetic surfaces. Accordingly, the formulation of the ideal MHD energy principle in magnetic coordinates, which was used for the implementation of the CAS3D stability code, only involves these functions, so that the correlations between the perturbation properties and the physical driving forces can be made transparent.

[1] C. Schwab, Phys. Fluids B 5(9), 3195 (1993)