Temperature Measurements of Nonequilibriurn High-temperature Plasmas by Means of N₂⁺ First Negative Bands

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The temperature measurements of nonequilibrium argon plasmas are made in a stacked plasma generator of arc discharge type. Intensity distributions of the N₂⁺ fisrt negative bands, which appear when a small amount of nitrogen gas is added to the plasmas, are measured and compared with computer-generated synthetic ones for determination of rotational and vibrational temperatures. The rotational temperature is well known to be substantially equal to gas temperature. The experiments are performed in a cylindrical positive column under the conditions of discharge currents 20 to 40 A and test section pressures 3.3 to 5.3 kPa. Measured temperatures, which extend up to about 9000 K, reasonably increase as the pressure and discharge current increase. It is also found that at lower pressures the rotational temperatures are much lower than the vibrational and electron temperatures, but they agree with one another at higher pressures, because thermal equilibrium is attained.