Greifswald 2009 – scientific programme

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P: Fachverband Plasmaphysik

P 7: Theorie/Modellierung I

P 7.12: Talk

Tuesday, March 31, 2009, 16:20–16:35, HS Biochemie (groß)

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

The glow-to-arc transition of the positive column of a dc discharge in argon in the course of the constriction has been investigated on basis of a self-consistent fluid model. The model consists of the coupled solution of the time-dependent balance equations for the charge carrier and excited species densities, the mean electron energy and the gas temperature in the plasma, and a current balance determining the axial electric field. Assuming an axially and azimuthally homogeneous plasma in cylindrical geometry, the radial structure is taken into account and Poisson’s equation for the space-charge potential is solved in addition. The electron transport and rate coefficients are adapted as functions of the electron mean energy, the gas temperature and the ionization degree and they have been determined from solving the steady-state, spatially homogeneous electron Boltzmann equation including electron-electron collisions. Investigations have been performed for currents from 0.6 to 70 mA and pressures from 100 to 500 Torr. The predicted voltage-current characteristics and electron density profiles are used to identify the transition from glow to constricted mode of the argon discharge. Good agreement with experimental data and results of other models has been obtained.