Table of contents

A simple MHD model of a plasma rotating through the periodic ripple of the toroidal magnetic field of a Tokamak is considered. It is shown that the plasma becomes unstable when the equilibrium toroidal rotation velocity exceeds the sound speed. The rippled field is equivalent to the magnetic 'wiggler' of a free electron laser. In the plasma case, long wavelength Alfven waves and short wavelength ion acoustic waves are excited.

Perturbed fluid quantities due to non-uniform laser illumination of a spherical target with scale-length variations of the order of the pellet radius, are analyzed. The model includes localized absorption at the critical surface, inverse Bremsstrahlung absorption and light refraction throughout the corona, and heat conduction restricted to one layer. Light self-focusing may substantially increase the perturbation amplitudes, which are also sensitive to laser wavelength.

Neoclassical bootstrap currents with well controlled central seed current drive in Tokamak plasmas are investigated analytically and numerically. The analytical current scaling predicts a strong bootstrap effect in hot, high density plasmas. The Troyon limit and safety factor profiles in various small seed current cases are considered to find the optimal conditions for a large bootstrap amplification. The Troyon limited bootstrap current is very insensitive to the detailed form of the pressure profile and the beta-limit is determined by the plasma geometry alone. Regarding the current seeding, high frequency methods, like beat-waves, are proposed, which are ideal for the localized central current drive.

In a DC neon discharge with moderately strong magnetic field, nonlinear drift waves are studied under the condition of strong dispersion. Forced harmonics and multimode spectra are observed and compared to theoretical expectations.

The minimum energy principle of Taylor is extended to the case where a vacuum layer is situated between a weakly resistive plasma and a perfectly conducting wall. The second variation of the magnetic energy is investigated with respect to both helical and symmetric perturbations. The stability results are compared to those in the literature.