[en] The optimum conditions for MHD power generation with only Joulean dissipation were derived from the thermodynamic First and Second Laws. The condition from the First Law was obtained by determining the optimum functional form of polytropic exponents against the load factor for a given interaction parameter. The other conditions from the Second Law were the spatial constancy of the ratio of magnetic body force to the static pressure for a compressible plasma and the spatial constancy of σu²B²/ρT for an incompressible plasma. The proposed optimum generator for a compressible plasma exhibited approximately 25% higher efficiency than that of the conventional constant velocity and constant magnetic field type generator for the moderate values of interaction parameters. Both the Faraday- and Hall-type generators exhibited the same load characteristics when the condition of minimum entropy increase was introduced. Thus optimal load factor giving the maximum thermal efficiency for the proposed optimum generator was V = 0.5. The introduction of non-adiabatic losses produced a slight shift of the optimal values of the load factor and hence reduced the efficiency. However, the efficiency was extensively recovered when the spatial constancy of σuB²/p was extended for the non-adiabatic case and exhibited the maximum at V = 0.5. (author)

[en] Simplified formulae were derived for the approximate evaluation of electrical performances of an MHD generator with nonuniform equilibrium plasma. In order to clarify the effectiveness of the properly shaped nonuniform magnetic induction of the type B varies as nsub(e), the transverse component Bsub(y) was included in the formulation of the theory. It was shown that the terminal characteristics of the generator, such as the internal resistance, the motional emf, the current and the output power could be improved significantly under the shaped Bsub(z) varies as nsub(e) type of applied magnetic induction for wide ranges of electrode- and insulator wall temperatures, channel sizes and averaged intensities of the magnetic induction. (author)

[en] The nonlinear oscillatory behaviors of plasma and internal trapped magnetic flux in a pinched plasma under a forced oscillating external magnetic field are analyzed numerically, and it is found three kinds of stable radial oscillation mode; T¹ and T² periodic modes and intermittent chaotic one exist. For the case that a small amplitude oscillatory field component whose frequency satisfies the nonlinear resonant condition to radial oscillation mode is added, the flux trapped inside plasma increases remarkably, and its quantity reaches a saturation level whose value is more than 2.5 times as large as value maintained with only a crowbar field. Matching conditions between plasma and magnetic field to control the trapped flux by the resonance effect are obtained. (author)

[en] The authors report on how they obtained in theory the potassium atom density from the temperature and optical thickness which they determined by the polarization line reversal method. In their results, the extremely large value they got, especially near the electrode, was considered to be due to the error arising from the experiments

[en] Electrical characteristics of a Faraday-type MHD generator with a transversally shaped field configuration (SFC) of magnetic induction were investigated experimentally by using shock heated plasma. The magnetic induction was sharply reduced near electrodes in order to minimize the electrical losses caused by the Hall effect and the conductivity nonuniformity in the boundary layer. The performance of the proposed generator was experimentally compared with that of the conventional type with a uniform field configuration. It was shown that the apparent conductivity, the output power, and the internal resistance were markedly improved in the SFC design, namely, by a factor of from about 1.5 to 2.0. The experimental characteristics agreed qualitatively with results of three-dimensional computer simulations. A possible arrangement of the superconducting coil for the generation of the SFC for a full-scale MHD generator channel was also proposed

[en] The seed material (potassium) atom density distribution plasma adjacent to the electrode in an MHD generator channel relates significantly to the occurrence and behavior of arcs on the electrode. The purpose of this study is to derive the distributions of seed atom density, seed ratio and temperature profile, when using potassium as the seed material, from optical thickness and temperatures measured by the light polarization line-reversal using the vibration mirror method

[en] The interactions of a compact toroid (CT) plasma with an external magnetic field and a tokamak plasma have been studied experimentally on the FACT and JFT-2M devices. Fast framing camera and soft X ray emission profile measurements indicate shift and/or reflection motions of the CT plasma. New electrostatic probe measurements indicate that the CT plasma reaches at least up to the separatrix for discharges with toroidal field strengths of 1.0-1.4 T and that there exists a trailing plasma behind the CT. A large amplitude fluctuation on the ion saturation current and magnetic coil signals is observed. Power spectrum analysis suggests that this fluctuation is related to magnetic reconnection between the CT plasmoid and the toroidal field. The CT, including much of the trailing plasma, may be able to move across the external magnetic field more easily in the drift region of the injector owing to the Hall effect. (author)