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Measurement of electron temperature and number density in shock-tunnel flows. I - Development of free-molecular Langmuir probes.

1969; American Institute of Aeronautics and Astronautics; Volume: 7; Issue: 8 Linguagem: Inglês

10.2514/3.5415

1533-385X

Michael G. Dunn, John A. Lordi,

Atomic and Molecular Physics

Thin-wire Langmuir probes have been used to measure the electron temperature and electron density of the inviscid nozzle flow of a short-duration reflected-shock tunnel at conditions for which the flow was free molecular with respect to the probe diameter. Experiments were conducted at equilibrium reservoir conditions of 6850°K and 22 atm pressure in air; and at 8000°K and 9.35 atm pressure and at 6090°K and 10.4 atm pressure in argon. The electron densities were simultaneously measured using microwave interferometers and found to be in good agreement with the values obtained from the Langmuir probe. The experiments have confirmed the validity of Laframboise's theoretical predictions for ion collection, including that in the orbital-motion-limited region. The electron temperatures measured in both the air and argon plasmas were found to be significantly greater than the calculated heavyparticle translational temperature, although in all cases the Langmuir probe results indicated that the electron velocity distribution was Maxwellian.