The dispersion relation of electrothermal waves in a nonequilibrium MHD plasma

The work described concerns the experimental verification of the dispersion relation of electrothermal waves. The theoretical derivation of this relation differs from the usual approach because the experiment requires an analysis in terms of real frequesncy and complex wave number. In the experiment value of electron temperature up to 2400 K and electron density up to 7 x 1019m-3 can be realized. The properties of the heavy particle gas do not have to be characteristic for the situation in a closed cycle MHD generator because electrothermal waves are essentially a property of the electron gas only. The waves are excited artificially in the stable regime so that they are damped which sets high requirements on the measuring technique. The ratio of the amplitudes at two successive double probes is measured as well as the phase shift between the two signals. The experimental results are discussed and compared with the theoretical predictions. (Auth.)