CO gasdynamic laser measurement in a shock tunnel

The small signal gain measurements of a CO gasdynamic shock tube driven laser (GDL) is presented. The low signal TEM(00) single frequency continuous wave laser beam is passed through the nozzle of a shock tunnel, and its intensity is amplified by the radiative properties of the CO/N2/Ar expanding mixture. The various mixtures were brought to stagnation temperatures of 1850-3500 K and pressures of 17-50 atm which supplied the expanding gas for the measured amplification of the GDL's beam. Maximum small signal gain normalized to the stagnation pressure is found between 2500-2800 K, and the highest values were obtained with a 10% CO/90% Ar mixture (0.005%/cm per atm). The experimental data were correlated with numerical calculations based on a model that describes the vibrational energy level population in the CO and N2 molecules. Good agreement was obtained.