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SUPERSONIC NOZZLE BEAMS - SOME RECENT EXPERIMENTAL RESULTS.
VIRGINIA UNIV CHARLOTTESVILLE
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The application of molecular beam techniques to a study of the collision processes important in gas dynamics and aerothermochemistry is described. Emphasis is placed on the characteristics of molecular beams formed by a nozzle source. It is shown that the available intensities from nozzle beams are substantially larger than those from classical effusive sources, the spread in molecular velocities in nozzle beams is much more narrow than the corresponding spread in effusion beams, and the nozzle beam energy is larger than that of the effusion beam at the same source temperature. Experimental results are presented which show that nozzle beam energies in excess of 1 evparticle can be produced by aerodynamic acceleration of heavy molecules in a light gas with the binary gas mixture in the nozzle source near room temperature. The effects of binary mixture mass ratio, source temperature, and specific heat ratio on the attainable beam energy are shown to be adequately described by a simple theory based on the isentropic expansion of a pure gas having a molecular weight corresponding to the concentration-weighted mean for the mixture. The use of nozzle beams as probes and the use of beam velocity analysis are shown to represent a powerful method for the study of relaxation rates of various kinds e.g., in the exhaust nozzles of various propulsion systems. Author
APPROVED FOR PUBLIC RELEASE