Power dependence of chemical oxygen-iodine lasers on iodine dissociation

The loss of O₂(¹Δ) during iodine dissociation in the chemical oxygen-iodine laser (COIL) is one of the main factors affecting the output power. Analytical expression is obtained for the number of O₂(¹Δ) molecules, N, lost in the region of I₂ dissociation per one molecule of Iz. This expression yields N = 4-6, in agreement with numerical calculations and experimental measurements. It is shown that some effective number N₁ < N should be used rather than N to calculate the power. Analytical expression for the 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 increases. Therefore, maximum power is achieved at low values of the iodine flow rate when iodine is not completely dissociated before the resonator and when the small signal gain in the resonator region is less than its maximum achievable value. Numerical modeling of the RADICL (supersonic COIL) is carried out. The values of the O₂(¹Δ) yield and of the mixing rate are estimated to reach an agreement between the calculated and the measured dependencies of the power on the iodine flow rate.