Mechanisms of COIL operation: Experiment and modeling

Spatial distributions of the gain, temperature and I₂ across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit nozzle supersonic chemical oxygen-iodine laser (COIL) as a function of the iodine and secondary nitrogen flow rate and jet penetration parameter. The mixing efficiency for supersonic injection of iodine (∼ 0.85) is found to be much larger than for transonic injection (∼ 0.5), the maximum values of the gain being ∼ 0.65%/cm for both injection schemes. Spatial distributions of the gain corresponding to the maximum power are found. A simple one-dimensional model is developed for the fluid dynamics and chemical kinetics in the COIL. Two different I₂ dissociation mechanisms are tested against the performance of a COIL device in our laboratory. The two mechanisms chosen are the celebrated mechanism of Heidner and the newly suggested mechanism of Heaven. The gain calculated using Heaven's dissociation mechanism is much lower than the measured one. Employing Heidner's mechanism, a surprisingly good agreement is obtained between the measured and calculated gain and temperature over a wide range of flow parameters.