MICROWAVE DIAGNOSTICS OF ARC-HEATED NITROGEN AND AIR PLASMAS.
NORTHWESTERN UNIV EVANSTON ILL GAS DYNAMICS LAB
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Electrical properties of arc-heated nitrogen and simulated air plasma flows were studied using microwave diagnostic techniques. The plasmas were produced by running nitrogen through a commercial plasma jet with a supersonic nozzle attached downstream. Oxygen is mixed with the nitrogen plasma just upstream of the throat of the supersonic nozzle in order to produce the simulated air plasma. Electron densities and collision frequencies were determined from measurements of the phase shift and attenuation of E-band microwaves transmitted through the plasma. The microwave frequencies used were 76.9 and 82.4 kMc and for both air and nitrogen plasmas the following properties were determined electron density, attenuation constant, and collision frequency. These properties are presented as functions of hgas, a measure of the electrical power input to the plasma, which ranged up to 36 kilowatts. The experimental results are compared with available theoretical predictions and qualitative agreement is found. Author
- Plasma Physics and Magnetohydrodynamics