FREE-STREAM ELECTRON CONCENTRATION IN AN ARC-HEATED WIND TUNNEL AND CORRELATION OF LANGMUIR PROBE AND MICROWAVE INTERFEROMETER MEASUREMENTS

摘要

Langmuir probes and microwave interferometer studies were made in the free stream of a Mach 10 arc-heated wind tunnel using air and nitrogen as test media. Electron concentrations were measured from 1 x 10^ to 6 x 1010 electrons per cubic centimeter. The measured electron concentrations were compared with the finite-rate nonequilibrium calculations and were found to be about 1 order of magnitude greater for the case of air and several orders of magnitude for nitrogen. Several mechanisms are examined for the increased electron concentration. Correlation of the microwave interferometer and conical Langmuir probe measurements yielded results which agreed within a factor of 2. The mean electron temperature measured by the Langmuir probe was equal to the gas temperature at the throat of the nozzle.