Gain coefficient and vibrational temperature measurements in shock tube driven CO2-GDL, CO2+N2+He, and CO2+CO(N2)+H2 mixtures

It is shown how CO2 upper and lower laser level temperatures (populations) can be determined, thereby obtaining comprehensive information on population inversion generation in CO2 lasers. Underlying the method is a simultaneous measurement of the intensities in corresponding vibrational rotational bands of CO2-laser active medium emitting molecules. Measurements are made of the radiation intensities in 4.3-micron and 2.7-micron CO2 bands in a CO2 gasdynamic laser using CO2 and N2 + He mixtures. Calculations are performed of the vibrational temperatures of the 00(0)1 and 10(0)0 vibrational levels of CO2 and of the small-signal gain coefficient on the 00(0)1-10(0)0 laser transition, K(0). The results show a faster relaxation of the CO2 upper laser level than predicted by the theoretical calculation. Performance optimization is then determined of a CO2 gasdynamic laser using a CO2 + N2 + H2 mixture with a hydrogen content of 50 percent. For a stagnation temperature of 1100-1200 K and a pressure of 1.5 + 20 atm, a maximum gain coefficient of 0.5/m (sufficient for generation) is obtained.