Absolute Electron Density Measurement Techniques in Hypersonic Wakes

New techniques have been evolved for the application of Langmuir probes to the measurement of electron densities in the wakes of hypersonic projectiles flown in ballistic ranges. These techniques concern probe cleanliness, minimization of flow disturbance, minimization of reflected shocks, and the effect of plasma potential. Electron density level estimates obtained with the probes in sphere wakes were in good agreement with electron density estimates derived from simultaneous measurements with a microwave interferometer.