Aachen PK 2003 – wissenschaftliches Programm

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P: Plasmaphysik

P 17: Poster III

P 17.5: Poster

Donnerstag, 20. März 2003, 17:30–19:15, Foyer

Theoretical investigations of the plasma composition of an electrical discharge in SF₆ — •Sergej Gortchakov^1,2, Yuri Bychkov², Sonja Yampolskaya², and Arkady Yastremsky² — ¹Institut für Niedertemperatur-Plasmaphysik, 17489 Greifswald, Germany — ²Institute of High Current Electronics, 634055 Tomsk, Russia

Electrical discharges in SF₆ and its mixtures are mainly used as an active medium of pulsed chemical HF lasers. Despite of the progress in development of these lasers, some physical phenomena occurring in the discharge plasma are studied insufficiently. Investigations of e-beam pumped systems have demonstrated an effect of e-beam cutoff caused by the decrease of the plasma conductivity due to accumulation of negative charge carriers through the conversion of thermal electrons into the SF_n⁻ ions in attachment processes. Experimentally detected effects in discharge excited systems - unipolarity of the discharge current, high value of the residual voltage, and peculiarities of the discharge contraction process - indicate that the growth of discharge current density accelerate such conversion. As a result the density of negative ions is higher than that of the electrons. In order to investigate the dynamics of charge carrier production and their loss in discharge excited systems a self-consistent numerical model has been developed. Results of simulations of a homogeneous discharge in SF₆ and a comparison with experimental data are presented and discussed.