Thermal plasma diagnostic methods based on the analysis of large spectral regions of plasma radiation

A new diagnostic method to evaluate thermal plasma temperature is investigated. This method in principle consists of using the relative and absolute dependences on temperature of the emitted plasma radiation in various spectral regions. The technique needs a preliminary study to calculate these relations and we present the basis of these calculations. This method is applied to argon plasma at atmospheric pressure and can be performed using either a 3-colour camera or a low resolution spectrometer. An experimental study was carried out to validate the methods. The set-up is composed of a wall-stabilized arc and a multichannel spectrometer. Values of temperature obtained by the new method are compared with the literature and the classical measurements based on the absolute line intensity method. We limit our work to spectral regions between 300 and 1100 nm, and between 5000 and 25 000 K. Experimental results are presented and discussed for argon plasma showing the influence of line self-absorption on the results obtained by various methods.