Plasma-fluid behavior of a less divergent disk magnetohydrodynamic Generator using helium-cesium

We describe the plasma-fluid behavior and performance of a less divergent disk-shaped radial-flow magnetohydrodynamic (MHD) generator using cesium-seeded helium (He-Cs) and compare it to a cesium-seed argon (Ar-Cs) generator. The less divergent generator using He-Cs provides a high isentropic efficiency of 45% and an enthalpy extraction ratio of 15.9%. The generator performance using He-Cs peaks at a low seed fraction of 1.7/spl times/10/sup -4/, which was reduced by a factor of four compared to the Ar-Cs generator. The proper He-Cs operation doubles the Hall parameter (3.7) but reduces the electrical conductivity to one-quarter in comparison with the Ar-Cs generator. The electron temperature of the He-Cs plasma is no more than 4000 K in a wide seed fraction range; this suggests that the plasma is in a fully ionized seed condition. Thus, the He-Cs plasma forms a stable and homogeneous structure without any specific nonuniformity. Although radiation from the He-Cs plasma is perturbed, its characteristic frequency is high (from 60 to 90 kHz). In contrast, the Ar-Cs plasma forms a localized structure at low seed fractions and a dense concentric circular structure at high seed fractions.