Experimental assessment of temperature in plasma wall interaction

Abstract

The purpose of this paper is to study the temperature evolution during the interaction of a plasma with an insulating wall in polyethylene ((CH2) n ) and polyoxymethylene ((CH2O) n ). The plasma is initiated by means of a capacitor bank discharge in a copper fuse wire. Due to the energy release the ablation of the insulating wall produces some insulating vapours in addition to the copper vapours corresponding to the wire vaporization. Using neutral copper line intensity ratio assuming a Bo ltzmann distribution we obtain a temperature evolution from $\sim$ 11 000 K to $\sim$ 24 000 K in the first few hundreds microseconds of the discharge. For later times the copper lines are strongly self-absorbed and make impossible the diagnostic in a spectroscopic way. Hence the temperature is deduced from the comparison between the experimental and calculated electrical conductivity. So for the decrease of the current the temperature evolves from $\sim$ 21 000 K down to $\sim$ 6 000 K and depends on the p lasma density. The results and the reliability of the two methods are discussed.