Study Of Chemical Oxygen-Iodine Laser With Nitrogen Buffer Gas

In this paper, a study on a chemical oxygen-iodine laser using nitrogen buffergases (N₂-COIL) is described. The most important motivation for using nitrogen asthe COIL buffer gas is that it enables the use of a cryosorption pump as the vacuumpumping system, and besides, it can greatly reduce the cost of COIL systems forindustrial applications.The COIL device was designed based on theoretical analysis, and wasexperimentally investigated. The reactive flow field in the supersonic nozzle andcavity was simulated using CFD (Computational Fluid Dynamics) method. Someimportant conclusions was reached as following:1. A chemical efficiency of 22.7%, and a nozzle flux of 75W/cm² was obtained.The performance of the COIL using nitrogen buffer gases is comparative withthat of the COIL using helium buffer gases. The use of nitrogen instead of helium fordiluting the COIL active medium proved to be feasible if the COIL device isredesigned.2. The singlet oxygen generator with a large specific area and a small reactivevolume is essential for a COIL using nitrogen buffer gases. A Square-pipe array jettype singlet oxygen generator (SPJSOG) was used. Measurements showed that theSPJSOG during normal operations could provide a singlet oxygen yield Y ≥65% , achlorine utilization U ≥85% and a relative water vapor concentrationw=[H₂O]/([O₂]+[Cl₂]) ≤0.1.3. It was found that a nozzle bank with a designed Mach number of 2.5 and asubsonic I₂-O₂ mixing length of 4mm was well suited to provide supersonic activemedium for a COIL with nitrogen buffer gas. Experiments and CFD simulationshowed that the small signal gain was larger than 1×10^-2 cm^-1.The N₂-COIL device in our laboratory was successfully connected withcryosorption pump and tested.In addition, in this paper, some investigations on N2-COIL with high totalpressure are also described. The ejector-type nozzle can increase the total pressure ofgas in the cavity up to 100×133Pa with a 2.6 Mach number.