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Abstract

Tokamak-like plasmas are modelled by a periodic cylindrical system with magnetic shear and realistic density and temperature profiles. Linear electrostatic microinstabilities in such plasmas are studied by solving the eigenvalue problem starting from gyrokinetic theory. The actual eigenvalue equation is then of integral type. With this approach, finite Larmor radius (FLR) effects to all orders are taken into account. FLR effects provide for the only radial coupling in a cylinder and to lowest order correspond to polarization drift.
This effectively one-dimensional problem helped us to gain useful knowledge for solving gyrokinetic equations in a curved system. When searching for the eigenfrequencies of the global modes, two different methods have been tested and compared. Either the true eigenvalue problem is solved by finding the zeroes of the characteristic equation, or one considers a system driven by an antenna and looks for resonances in the power response of the plasma. In addition, mode structures were computed as well in direct as in Fourier space. The advantages and disadvantages of the these various approaches are discussed.
Ion temperature gradient (ITG) instabilities are studied over a wide range of parameters and for wavelengths perpendicular to the magnetic field down to the scale of ion Larmor radii. Flute instabilities driven by magnetic curvature drifts are also considered. Some of these results are compared with a time evolution PIC code. Such comparisons are valuable as the convergence of PIC results is often questioned. Work considering true toroidal geometry is in progress. .

Additional information

Authors: BRUNNER S, Ecole Polytechnique Fédérale de Lausanne, Centre de Recherche en Physique des Plasmas (CH);VACLAVIK J, Ecole Polytechnique Fédérale de Lausanne, Centre de Recherche en Physique des Plasmas (CH);FIVAZ M, Ecole Polytechnique Fédérale de Lausanne, Centre de Recherche en Physique des Plasmas (CH);APPERT K, Ecole Polytechnique Fédérale de Lausanne, Centre de Recherche en Physique des Plasmas (CH)
Bibliographic Reference: Article: Proceedings of the International Sherwood Fusion Theory Conference (1996) pp 2C13
Record Number: 199611219 / Last updated on: 1996-11-11
Category: PUBLICATION
Original language: en
Available languages: en