Theoretical modeling of iodine dissociation in coils

The losses of O₂(¹Δ) during iodine dissociation in the chemical oxygen iodine laser (COIL) are shown to be one of the main factors affecting the lasing power. Analytical expression is obtained for the number of O₂(¹Δ) molecules, N, lost in the region of 12 dissociation per one molecule of I₂. This expression yields N = 5 - 7, in agreement with numerical calculations and experimental measurements. It is shown that some effective number N₁ < N should be used instead of N to calculate the lasing power. Analytical expression for the lasing power is obtained taking into account the O₂(¹Δ) losses in the dissociation region. It is shown that N increases and the power decreases when the dissociation fraction F is increased. Therefore maximum power is achieved at low values of the iodine flow rate when iodine is not completely dissociated before the resonator and the small signal gain in the resonator region is less than the maximum gain. Numerical modeling of the RADTCL (the supersonic COIL developed in Phillips Laboratory) is performed. The values of the rate constants of the reactions responsible for iodine dissociation are specified to reach an agreement between the calculated and measured dependences of the power on the iodine flow rate.