[en] The generation mechanism and the evolution of the magnetic fields in the laser plasma for radiative fluxes of the laser up to 10¹⁴ W/cm² Nd are studied

[en] Abstracts for 12 of the 15 included papers were entered into EDB. Abstracts for the remaining three papers appeared previously in EDB

[en] The minimum energy principle of Taylor is extended to the case where a vacuum layer is situated between the weakly resistive plasma and the perfectly conducting wall. The second variation is investigated for periodic perturbations (m and/or k≠0) as well as for symmetric perturbations (m=k=0). A necessary and sufficient criterion for stability is derived by means of the Rayleigh ratio method and turns out to be identical with the result of the resistive mode analysis. Stability diagrams λ vs k are presented. A new instability region at m=1 is found at negative values of k, already present when λ is small. The symmetric mode becomes more unstable as the vacuum layer grows thicker. 11 refs.; 7 figs.; 92 schemes

No abstract available

[en] The first part of this lecture discusses the influence of current profiles and noncircular cross-sections on the maximum β obtainable in a Tokamak from the MHD equilibrium point of view. The second part treats limitations on such MHD equilibria resulting from various MHD instabilities like external and internal kinks, localized and nonlocalized modes- and axisymmetric instabilities

[en] The suppression of the vertical instability by passive annular conductors is analyzed on the basis of the linearized 2-D equations of ideal MHD. The effect of a multisection construction of the conductors along the toroidal direction on the stability of the plasma column is studied. It is shown for the particular case of the INTOR reactor that a small number (Napprox.4) of correctly positioned conductors of reasonable size can suppress the vertical instability

[en] In the first part, an illustrative survey of operating tokamak devices is given. The ohmic heating of tokamak plasmas is reviewed, and the limitations imposed by MHD instability phenomena are described. A modification of the MHD theory, including finite-resistivity effects, appears to give a reasonable fit of experimental results. The combined requirements of ohmic heating, MHD stability, and radiation cooling define the experimental parameters of present-day tokamak devices. In the second part, the experimental results on energy and particle confinement in tokamaks are reviewed. MHD-instability effects on confinement can be distinguished when they are strong, but information on microscopic loss mechanism is still rudimentary. Under the constraint of dominant ohmic heating, the true physical scaling laws of the tokamak transport coefficients cannot be determined. Non-ohmic heating methods, notably neutral-beam injection, are now proving sucessful and should improve our knowledge of tokamak confinement physics. Non-ohmic heating combined with refinements in tokamak geometry offers the prospect of attaining practical tokamak reactor parameters

[en] This paper describes the electromagnetic analysis of vertical instability tests performed in JET. These and related mechanical studies are aimed at establishing safe operating limits. (author). 7 refs.; 7 figs

[en] The condition for a resonant diocotron instability in a column of non-neutral plasma is generalized to include the effect of plasma inertia. Near the Brillouin limit, for modes with large azimuthal mode number, instability is shown to occur for a nonzero plasma density at the resonant surface, regardless of the density gradient. In the presence of inertia the existence of another singularity is pointed out. Its effect on stability is shown to be small near the Brillouin limit for modes with large azimuthal mode number. For certain values of the number density below the Brillouin limit this singularity can exist in the region of large plasma density, for a density profile close to a step function profile, and is shown to resonantly drive an instability if the average plasma density decreases radially outward at the resonant surface. copyright 1995 American Institute of Physics

[en] An experimental study of the gross MHD stability properties of Spheromak plasmas in the Proto S-1 A/B device is presented. Utilizing the previously demonstrated S-1 slow formation technique, plasmas have been produced which exhibit the predicted tilting instability in a regime of slightly negative field index. A relatively simple passive coil system suggested by numerical stability studies has proven to be effective in stabilizing the observed tilting mode