Optical measurements of gas temperatures in Ar/CO$_{2}$ arc plasma

This paper presents an experimental study of the temperatures on DC vertical short free arc in Ar and Ar/CO$_{2}$ mixtures by employing optical interferometry and optical emission spectroscopy. The arc plasma burns between two tungsten vertical electrodes with a gap of 10 mm put in a chamber filled with argon or an argon/carbon dioxide mixture at atmospheric pressure. Two optical windows allow to observe the arc plasma in the chamber. Electrical power is delivered by a DC high voltage (10 kV) with a current intensity chosen from 0,1A up to 0.3 A. By employing optical interferometry, acquired interferograms were treated using Fast Fourier Transform and Abel inversion to obtain the radial distribution of the plasma index refraction. Temperature profiles were then obtained from Gladstone-Dale relation, taking in account the plasma composition versus temperature. The experimental spectrums of the Swan band of C$_{2}$ molecule have been recorded and a code of calculation has been created to simulate molecular spectra of the radical C$_{2}$. Finally rotational temperatures have been determined by comparison between experimental and calculated spectra and then temperature profiles have been obtained and compared with those obtained by optical interferometry.