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A plasma is ignited by ECRH in the flaring magnetic field zone of a superconducting coil, the maximum central field flux density of which is 3 T. The electron temperature, measured by Langmuir probes, is about 5 eV, and the density 1011-1012 cm-3. In this paper we have used the ray tracing method in order to describe the propagation and absorption of the ordinary and extraordinary modes of the electromagnetic wave at 29 GHz frequency, from an emission point outside the cylindrical plasma, towards the electron cyclotron resonance zone, for several angles of incidence. Temperature effects as well as electron-neutral collisions have been taken into account in the dielectric tensor. The polarization of the extraordinary mode, which is the one being principally absorbed, is also investigated.

A method for determining the radial profile of the lower‐hybrid current drive in tokamaks using electron cyclotron attenuation of the O mode for frequencies ω near the cutoff frequency is discussed. The basic idea is that, for a given wave frequency, the cutoff plays the role of a spatial filter selecting a variable portion of the noninductive current. It is shown that the incremental attenuation resulting from a small increase of ω displays specific features related to the current density near the cutoff point. Using the relation between the wave damping and the current density, it is possible to determine the radial profile of the current drive from the wave attenuation measurements. A numerical application is also presented for plasma parameters in the reactor regime.

A method for measuring the radial profile of the lower‐hybrid‐driven current in a low‐density tokamak plasma using electron‐cyclotron wave attenuation is discussed. This diagnostic scheme is reminiscent of the transmission interferometry approach, commonly used in tokamaks to measure the plasma density, but now the wave amplitude instead of the phase is measured. Wave attenuation of the ordinary mode at ωp ≪ ω < ωc along vertical chords is measured; at these frequencies, the waves are absorbed by the superthermal tail sustained by lower‐hybrid waves and the local wave absorption coefficient is proportional to the noninductive current density. The radial profile of this current is obtained from Abel inversion. An application to the Tore Supra tokamak is presented.

Nonlinear drift-waves are experimentally studied in a cylindrical magnetized laboratory plasma. Low-dimensional chaotic regimes are controled using the time-delay autosynchronization method [K. Pyragas, Phys. Lett. A 170, 421 (1992)]. A significant reduction of spectral width in the power spectrum is obtained.

Resume La caracterisation des regimes dynamiques et des scenarios de bifurcations pour les systemes non lineaires spatialement etendus necessite l'utilisation de methodes specifiques de traitement du signal, qui se distinguent fondamentalement des methodes classiques generalement fondees sur les techniques de Fourier. En effet, ces methodes classiques, qui conviennent a l'analyse d'une evolution purement temporelle, sont mal adaptees a la caracterisation des signaux multivariables. Parmi les nouvelles techniques, la decomposition bi-orthogonale (ou BOD) est un outil particulierement efficace permettant l'analyse de la structure spatio-temporelle des signaux. Dans cette note, nous exposons le principe de la BOD et presentons un exemple d'application a la caracterisation des structures spatio-temporelles des ondes d'ionisation dans un plasma de decharge luminescente.

A transmission diagnostic system working in the frequency range 77–109 GHz has been implemented in the Tore Supra tokamak. It makes use of an ordinary mode launched along a vertical diameter, i.e., propagating along a nearly constant magnetic field. The purpose of the diagnostic is to measure electron cyclotron absorption (ECA) below the electron cyclotron frequency fc in the presence of the fast electron tails created during lower‐hybrid current drive. Transmission spectra measured by this method are compared with spectra obtained by Fokker‐Planck simulations and the relaxation properties of the tail are discussed.

Thyroiditis or Graves'disease and connective tissue diseases. Retrospective study of 100 cases. There were 40 cases of rheumatoid arthritis, 38 cases of systemic lupus erythematosus, 12 cases of systemic sclerosis and 10 cases of Sjogren's syndrome. Hashimoto's thyroiditis was diagnosed in 8 patients, chronic thyroiditis in 2 patients and Graves'disease in 3 patients.