EXPERIMENTAL INVESTIGATIONS OF GASDYNAMIC N₂/CO₂ MIXING LASERS

Abstract
N₂/CO₂ mixing lasers with thermal excitation of the N₂ in arc-heaters and with screen nozzles for the expansion and mixing process are investigated. Results obtained with two devices having different cross-sections of the laser channel are compared. For equal operating conditions the small signal gain is well correlated by a normalized distance downstream of the nozzle exit plane. The distribution of gain along the flow direction is mainly determined by the stagnation temperature, the ratio of N₂/CO₂ and the presence of He. Values of small signal gain up to 3 % cm^-1 are achieved. The effect of replacing N₂ by CO is studied in detail. The observed reduction of laser performance depends on the ratio of N₂/CO/CO₂ but is almost independent of stagnation temperature. In addition, preliminary experiments aiming at the substitution of N₂ by air yield a specific laser energy of 5 J/g.