Microinstabilities in Advanced Tokamak and Stellarator Geometries
Doktorsavhandling, 2008

The anomalous particle and heat transport observed in magnetically confined plasmas is generally attributed to plasma turbulence driven by short-scale instabilities, called microinstabilities. Understanding the stability limits of microinstabilities and their dependency on the equilibrium configuration is of paramount importance in the effort to predict the performance of future fusion devices such as the International Thermonuclear Experimental Reactor (ITER). The present thesis investigates the linear stability properties of simple electron drift waves, ion-temperature-gradient (ITG) modes, collisionless trapped electron (TE) modes and resistive edge modes in the electrostatic limit in realistic advanced toroidal geometries. The magnetic field equilibria under study are that of an ITER-like tokamak and Wendelstein 7-X (W7-X) stellarator, and are computed using the variational moments equilibrium code (VMEC). The instability-models are formulated in the ballooning mode representation and the drift wave problem is set as an eigenvalue equation along a field line. The derived eigenvalue problem is solved numerically in the magnetic field equilibria using a standard shooting code technique and applying Wentzel-Kramers-Brillouin (WKB) type boundary conditions. Correlations of the mode stability and the mode structure with various equilibrium quantities, such as density gradient, electron/ion temperature gradients, temperature ratios, wave vector, magnetic field, magnetic field line curvature, and local/global magnetic shear, are investigated. The results are also compared with earlier tokamak and stellarator studies.

tokamaks

microinstabilities

fusion plasmas

ITG

drift waves

stellarators

EA-salen, Hörsalsvägen 11, Chalmers University
Opponent: Professor Per Helander, Stellarator Theory Devision, Max-Planck-Institut für Plasmaphysik, Greifswald, Germany.

Författare

Ansar Mahmood

Chalmers, Signaler och system

Unstable ion-temperature-gradient modes in an advanced tokamak plasma

Plasma Physics and Controlled fusion,; Vol. 48(2006)p. 1019-

Artikel i vetenskaplig tidskrift

Electron drift waves in an advanced tokamak plasma

Physica Scripta,; Vol. 73(2006)p. 648-

Artikel i vetenskaplig tidskrift

Resistive edge mode instability in stellarator and tokamak geometries

Physics of Plasmas,; Vol. 15(2008)p. 092507-

Artikel i vetenskaplig tidskrift

Ämneskategorier

Fusion, plasma och rymdfysik

ISBN

978-91-7385-210-4

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 2891

EA-salen, Hörsalsvägen 11, Chalmers University

Opponent: Professor Per Helander, Stellarator Theory Devision, Max-Planck-Institut für Plasmaphysik, Greifswald, Germany.