Plasma parameters and weakly non-ideal behaviour of a high density, super-atmospheric 2 kA cascade arc in argon

Experimental results are reported for simultaneous pressure and current pulses up to 14 bar and 2200 A superimposed on an atmospheric pressure 60 A DC cascade arc. A current density over 10/sup 8/ A/m/sup 2/, previously 10/sup 7/ A/m/sup 2/ (power density 10/sup 12/ W/M/sup 3/, previously 10/sup 10/ W/m/sup 3/) has been obtained. The electron temperature of the thermal plasma was deduced from the end-on measured radiance of argon lines, and the electron density from the absolute continuum emission. The values found for the quantities mentioned during the quasi-stationary phase of the current pulse, lasting ~1 ms, were 27000 K and 3*10/sup 23/ m/sup -3/, respectively, at a pressure of ~1.5 bar (ionization degree 100%), and 18000 K and >10/sup 24/ m/sup -3/, respectively, for a pressure of 14 bar (ionization degree 60%). These values satisfy the LTE relation. Deviations from the Spitzer conductivity have been observed in this weakly non-ideal plasm