High gain CO chemical laser produced in a shock tunnel

Experimental theoretical results are presented of small signal gain in a CO chemical laser produced in a shock tunnel. The thermal dissociation of CS2 into CS + S is effected by a reflected shock wave. The dissociated products, diluted in Ar, expand through a supersonic nozzle having an area ratio of 40 into a combustion chamber. At the nozzle exit, molecular oxygen is injected supersonically. The two streams mix and combustion occurs where vibrationally excited CO is produced by the CS + O - CO (v) + S reaction. Gain measurements of the P7(14) line are made at distances of 5.5 and 11.5 cm downstream of the oxygen injection point, the stagnation pressure being 25 atm. The stagnation temperatures are varied in the range of 2500-4600 K and mixtures of CS2:Ar between 5:95 and 30:70 are tested. A maximum gain of 8% per cm is observed for CS2:Ar = 20:80 at a stagnation temperature of about 4000 K and a distance of 11.5 cm. A semiempirical model describing the fuel-diluent expansion through the supersonic nozzle and the fuel-oxidizer mixing process is then developed.