Observation of MHD Effects with Non-Equlibrium Ionization in Cold Supersonic Air Flows

Abstract

An earlier experimental investigation has been performed using short duration, high repetition rate, high voltage (2 ns, 100 kHz, ~10 kV/cm) pulses to ionize a Mach 3 air flow. The wind tunnel was placed in a 5 Tesla magnetic field. In this paper these results, are further interpreted with the help of modeling. A cold, supersonic, non-equilibrium plasma was created. Peak electron densities between 5×10 11 and 10 12 per cm 3 were reached in the experiments. The electrical properties of the resultant MHD channel were investigated. Power extraction via MHD effects was demonstrated in the cold, supersonic, unseeded air flow. The Hall parameter was estimated from the electrical properties of the MHD channel. Modeling predictions were found to be in very good agreement with experimentally measured Faraday current between the pulses. Modeling showed that between pulses the electrons have low energy, electron and ion currents are comparable, and the cathode fall is very small.