Plasma Parameters and Weakly Non-Ideal Behaviour of a High Density, Super-Atmospheric 2kA Cascade Arc in Argon

Abstract

Abstract 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 108 A/m2, previously 107 A/m2 (power density 1012W m3, previously 1010W/m3) 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 · 1023 m-3, respectively, at a pressure of ~ 1.5 bar (ionization degree 100%), and 18000 K and > 1024 m-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 plasma. In general, the high ionized thermal plasma studied with its composition of neutral, singly ionized and doubly ionized argon atoms can serve as a useful medium for spectroscopic studies of highly ionized systems and as a valuable source of radiation in the visible a well as in the near and far ultraviolet parts of the spectrum.