ABSTRACT
Proper interpretation of results of spectroscopic temperature measurements must be based on realistic physical model of state of the gas. the core of the problem in diagnostics is the correct judgment on whether conditions of Local Thermodynamic Equilibrium (LTE) exist. For an arc plasma jet, special attention must be paid to distinguish the states of LTE and PLTE(Partial LTE). One reliable method of checking is to compare the results of spectroscopic measurements with those of probe measurements. For the arcjet, it is important to select proper thermodynamic model and corresponding diagnostic techniques according to the nature of the problem. Experimental results show that, the phenomena in arcjets are not quite the same as those in the arc column, and the conclusions related to diagnostics of the arc column must not be applied directly to the arcjet without careful scrutiny.
