Greifswald 2009 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 9: Poster: Niedertemperaturplasmen

P 9.12: Poster

Dienstag, 31. März 2009, 17:30–19:30, Foyer des IfP

Analysis of the constriction of the dc positive column in argon — •Mykhaylo Gnybida, Detlef Loffhagen, and Dirk Uhrlandt — INP Greifswald, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany

The dc positive column in argon plasmas at conditions of the glow-to-arc transition has been studied by means of fluid modeling. The self-consistent model comprises the particle balance equations for electrons, atomic and molecular ions, three excited argon atoms and two excited molecular species, the balance equation of the mean electron energy and the heavy particle temperature in the plasma, Poisson’s equation for the space-charge potential, and a current balance determining the axial electric field. 33 reactions are included in the collisional-radiative model. The electron transport and rate coefficients are applied in dependence on the mean energy of the electrons and the gas temperature. Different assumptions concerning the electron energy distribution function have been considered. In particular, the impact of using a Maxwellian distribution and solutions of the 0D electron Boltzmann equation with and without consideration of electron-electron collisions, respectively, is analysed. The model calculations have been carried out for a discharge tube with a radius of 1 cm at currents between 0.6 and 70 mA and pressures between 100 and 500 Torr. The model predictions are compared with experimental data and the nonlocal features of the mean electron energy balance are discussed.