Time- and space-resolved spectroscopic studies of electrical breakdowns in an argon-hydrogen mixture

Emission spectra from a 6-A 250-ns cable discharge between gold electrodes in a mixture of 90% Ar+10% H2 at atmospheric pressure have been obtained both with and without time resolution as a function of position in the gap. The Stark broadening of the hydrogen Hβ line and of Ar II lines has been used to estimate the electron density in the gap which is observed to exceed 1018 cm−3 during the first 100 ns of the discharge. A quasi-steady-state is observed after approximately 100 ns until current extinction, during which time the Ar II populations are given by Boltzmann statistics with a temperature of ∼20 000 °K. The results of the time-integrated and time-resolved studies are compared to provide information about the effects of spatial and temporal integrations on measured parameters. The qualitative features of the spectra together with estimates of the plasma equilibration time indicate that it may be possible to use a local thermodynamic equilibrium (LTE) model of the plasma to quantiatively study the electrode erosion process.