Abstract
Water vapor is produced in the singlet oxygen generator of a supersonic flow chemical oxygen-iodine laser as an undesirable by-product. Since the water vapor deactivates the excited iodine atoms very efficiently, it is removed using a water vapor trap before the singlet oxygen is mixed with the iodine. However, part of the water vapor passes through the trap, mixes with the iodine and expands through the supersonic nozzle. 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 instantaneously and the flow is one-dimensional. The condensation causes a reduction in water vapor concentration and, in this respect, the deactivation of the excited iodine atoms is suppressed. However, the latent heat released into the flow greatly suppresses the cooling in the supersonic expansion. As a result, the small signal gain coefficient is lowered considerably. However, the scattering and the absorption of the laser beam by the water droplets are negligibly small compared to the amplification.
