Langmuir Probe and Microwave Technique for Ionized Flows

Electron number densities were measured behind the incident shock wave in a pressure-driven shock tube by a microwave resonant cavity technique and by electrostatic probes. The driven gas was air at initial pressures of 0.5 and 1 mm Hg, and the shock Mach number was varied from 7 to 10. Electron neutral collision frequency was also determined by the microwave technique. The experimental measurements were compared with other measurements and with theory.