Determination of the electron temperature of a shocktunnel-produced Ar-Cs plasma by the line reversal method using non-resonance lines of Cs

Abstract

It is shown that the influence of the temperature boundary layer on the measured population temperature of Cs, of a shocktunnel-produced, low-temperature Ar-Cs plasma, can be neglected in measurements where the line reversal method is used with non-resonance lines of Cs. Owing to Ar-Cs collisions and radiation losses, a decrease in population density of the levels concerned in the transition occurs. This decrease is calculated in comparison with LTE and results in a population temperature of Cs which is less than 8 per cent lower than the electron temperature. Because of a test time of 5 msec in our shocktunnel experiment, use is made of a chopper to measure the radiation intensity of the plasma and the radiation intensity of the reference source in interaction with the plasma alternately. From these two radiation intensities and the radiation intensity of the reference source, we calculate the population temperature of Cs and the ratio of the concentration of Cs-atoms and the concentration of Ar-atoms, which is called the seed ratio. Comparison of the measured population temperature and the calculated electron temperature at a gas temperature and pressure of 2000 K and 5 atm, respectively, shows agreement within 10 per cent.