Gain and power in COILs - theory and experiment

Modeling of the gain and power in chemical oxygen-iodine lasers (COILs) and comparison with experimental studies are reported. The effect of mixing on the operation of the COIL is studied theoretically applying a simple one-dimensional leak flow tube model. Both the fraction of the dissociated iodine and the maximum gain are shown to be nonmonotonous functions of the iodine flow rate (nl₂). There is an optimal value of nl₂, depending on the (O₂(¹Δ)) 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 nl₂for which lasing is possible is less than 5% of the oxygen flowrate. This result is in agreement with experimental data and can not be explained by models based on the assumption of a premixed flow. Simple analytic expressions are derived for the optimal nl₂the characteristic length of iodine dissociation, the gain and the lasing power. The calculated gain and power are compared with available experimental results for a small scale supersonic COIL developed in our laboratory. The power is studied as a function of the molar flow rates of the various reagents. Good agreement is found between the experimental results and calculations.