The Ion Current Density on the Surface of a Spherical Probe in a Flowing High Pressure Plasma

The positive ion current density on the surface of a spherical probe immersed in a flowing flame plasma has been measured under thin sheath conditions. The hydrodynamic Reynolds number ranged from 96 to 720. No pronounced real fluid effects have been observed in the current density although the probe is observed by Schlieren photography to exhibit boundary layer separation and wake formation. In spite of the real fluid behavior of the plasma fluid, the thin sheath theory describes the current density distribution on the probe surface very effectively. This is attributed to the formation and entrainment of a shielding layer of fluid, voided of charge during its passage through the sheath.