EFFECTS OF WATER-VAPOR CONDENSATION ON THE PERFORMANCE OF SUPERSONIC-FLOW CHEMICAL OXYGEN-IODINE LASER

Water vapor is produced in the singlet oxygen generator of a supersoni c flow chemical oxygen-iodine laser as an undesirable by-product. Sinc e the water vapor deactivates the excited iodine atoms very efficientl y, it is removed using a water vapor trap before the singlet oxygen is mixed with the iodine. However, part of the water vapor passes throug h the trap, mixes with the iodine and expands through the supersonic n ozzle. In the present study, a condensation model is proposed and the effect of the water vapor condensation due to the supersonic expansion is simulated numerically assuming that the mixing takes place instant aneously and the flow is one-dimensional. The condensation causes a re duction in water vapor concentration and, in this respect, the deactiv ation of the excited iodine atoms is suppressed. However, the latent h eat released into the flow greatly suppresses the cooling in the super sonic expansion. As a result, the small signal gain coefficient is low ered considerably. However, the scattering and the absorption of the l aser beam by the water droplets are negligibly small compared to the a mplification.