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P: Plasmaphysik

P 14: Poster: Niedertemperaturplasmen / Plasmatechnologie 6, Diagnostik 4

P 14.6: Poster

Samstag, 5. März 2005, 14:45–16:45, Poster HU

Higher order Chapman-Enskog electrical conductivities of Hg, Na, and rare-gas plasmas — •Martin Wendt, Manfred Kettlitz, and Hartmut Schneidenbach — INP Greifswald, Friedrich-Ludwig-Jahn-Str. 19, 17489 Greifswald

We investigate the influence of the approximation order N of the Chapman-Enskog method on the electrical conductivity σ(N) which is a key parameter in HID-lamp modelling [1]. Devoto demonstrated that this method converges rather slowly for Argon at low temperatures where electron-atom collisions dominates [2]. This slow convergence is associated with the Ramsauer-minimum in the electron-atom cross section of rare-gases. We give detailed numerical results of σ(N)/σ(N−1) for all rare-gases (except Rd) and some rare-gas/metal plasmas. We conclude that for He and Ne, that do not show an equally sharp Ramsauer-minimum as Ar, Kr and Xe, σ(N) converges rapidly below 8000 K (σ(3)/σ(2)<1.03 for He, σ(4)/σ(3)<1.05 for Ne). For Ar, Kr and Xe which have a more pronounced Ramsauer-minimum the convergence is slower. For Ar only σ(5)/σ(4) is below 1.10 for all T>2000 K. For Kr and Xe one still gets maxima of 1.18 and 1.22 in σ(6)/σ(5) at 3750 and 4200 K, respectively. The conductivities are used to validate the temperature profiles coming from a fit of the sodium D lines in an HID-lamp with a NaI-Xe fill.

[1] S. Chapman, T. G. Cowling, "The Mathematical Theory of Non-Uniform Gases", Cambr. University Press (1953)
[2] R. S. Devoto, Phys. Fluids, 9 (1966) 1230.