Ultraviolet Raman spectroscopy of N 2 in a recombining atmospheric pressure plasma
Abstract
We report ultraviolet spontaneous Raman scattering measurements of temperature in a recombining nitrogen plasma. The plasma source is an atmospheric pressure RF torch facility. A N2/ Ar mixture is injected into the torch and heated to approximately 6800 K at the torch exit. Raman scattering measurements are in agreement with optical emission spectroscopy measurements of temperature at the torch exit. A 15 cm water-cooled tube is then mounted at the torch exit to rapidly cool the gas and produce a recombining plasma. Raman scattering measurements indicate a temperature of approximately 3300 K at the tube exit, significantly lower than previous emission spectroscopy estimates. The Raman measurements were confirmed via separate Rayleigh scattering measurements. The lack of agreement between emission spectroscopy, which only yields information on excited states, and Raman scattering measurements shows that the plasma is far from equilibrium at the exit of the recombining tube. These experiments provide a basis for studying recombining plasmas which, among other applications, are important for atmospheric reentry applications and plasma processing.
Domains
PlasmasOrigin | Files produced by the author(s) |
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