Experimental assessment of temperature in plasma wall interaction
Résumé
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 Boltzmann distribution we obtain a temperature evolution from about 11 000 K to about 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 about 21 000 K down to about 6 000 K and depends on the plasma density. The results and the reliability of the two methods are discussed.