Discharge characteristics in cesium-seeded argon

As part of a program investigating nonequilibrium MHD power generation, experiments were performed to study discharge characteristics in a cesium-seeded argon blowdown facility with a maximum capability in gas total temperature of 1500°K, Mach number M = 0.6 and applied magnetic field B = 22,500 gauss. The results show that an ionization instability can occur as the result of a slow ionization rate in a convective flowfield, and does not necessarily depend on the presence of a magnetic field. Discharge holding devices were fully capable of controlling the instability up to M = 0.6 with 5 = 0, but some effectiveness was lost with increasing P due to a dependence of the final channel nonequilibrium conductivity on the magnetic field and the electrode geometry without the need to consider nonuniform conductivity effects arising from discharge streamers or striations. In addition, measurements showed that an increasing magnetic field produced an increase in: the electron density recombination rate; the plasma breakdown voltage; and the plasma dissipation rate with respect to conductivity. There was also evidence of significant electron density relaxation during preionization.