The purpose of this research is to characterize the thermochemical states of CO2 and CO2-N2 arc plasma flows via temperature measurements. To do this, radiation from the stagnation streamline around a disk model is measured using the newly developed multipoint spectroscopic measurement system and temperatures are deduced by applying the spectrum fitting method to the measured spectra. It is found that the vibrational temperature is nearly constant and higher than the rotational temperature along the stagnation streamline, showing the vibrational nonequilibrium process. The rotational temperature is also nearly constant and does not increase in the shock layer. This may be caused by the fact that measured temperatures are averaged temperatures along the line-of-sight (LOS). In conclusion, the thermochemical states of CO2 and CO2-N2 arc plasma flows are vibrational nonequilibrium states in the free stream region. However, the thermochemical state in the shock layer cannot be clarified accurately using LOS averaged temperatures. In the future, LOS effects should be examined using spectroscopic measurements along a radial direction.

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