MODELING OF MIXING IN CHEMICAL OXYGEN-IODINE LASERS - ANALYTIC AND NUMERICAL-SOLUTIONS AND COMPARISON WITH EXPERIMENTS

The processes of iodine dissociation, population inversion, and lasing in the chemical oxygen-iodine laser (COIL) are affected by the mixing between the flows of oxygen and injected iodine. The effect of mixing on the operation of the COIL is studied theoretically applying a simple one-dimensional leaky stream tube model and the results are compared to available experimental data. The model enables the calculation of the iodine dissociation and the gain along the flow and of the lasing power, as a function of the iodine flow rate (nI2), the yield of singlet oxygen [O2(1DELTA)] and the pressure in the cavity. Both the fraction of the dissociated iodine and the maximum gain are shown to be nonmonotonous functions of nI2. There is an optimal value of nI2, depending on the O2(1DELTA) yield, the gas velocity, and the temperature in the cavity, for which the gain achieves its maximum and the iodine dissociation length its minimum. The model shows that the maximum nI2 for which lasing is possible is less than 5% of the oxygen flow rate. This result is in agreement with experimental data and cannot be explained by models based on the assumption of a premixed flow. Simple analytic expressions are derived for the optimal nI2, the characteristic length of iodine dissociation, the gain, and the lasing power. The calculated gain and lasing power are compared with available experimental results for both subsonic and supersonic COILs.