横磁界中のAr・KやN_2・Kプラズマの衝撃波管実験
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概要
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It has been found that the ionization relaxation time in Ar-K and N_2-K plasmas may be offset by heating the driven section of the conventional pressure-driven shock tube. Precursor electrons were observed 30cm ahead of the shock front by the axially distributed electrical floating probes. With nine pairs of Faraday-type electrodes and four floating probes the electrical conductivity was found to be two orders of magnitude greater than the equilibrium value, when the gas had an impurity level of less than 100ppm. At the same time, the momentum-transfer collision-cross-sections of electron for Ar, K and N_2 were found to be 0.8, 250 and 6(A^2) respectively from measurements of the Hall parameter and using a bulk plasma diagnostic analysis. The cross-section for Ar is higher than the value form DC discharges because of the strong dependence on the electron energy. An alternative method of non-equilibrium MHD power generation is proposed for both closed and cycles, in which the long lived electronic and vibrational excited N_2 are produced by an auxiliary discharge and gradually transfer their energy to ionize the K as the plasma passes though the generator. The shock tube studies determined the relaxation tie of the electrical conductivity to be about 5 msec, as the conductivity decreased to approximately 10mhsd/m in Ar-N_2-K plasma and 1 in N_2-K or at 1500゜K. This is in reasonable agreement with the theory, although the reaction cross-section were unknown precisely.
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