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In the supersonic COIL the power output and the laser performance strongly depend on mixing conditions of the gas flows. For the 10 kW COIL of DLR, the effects of the gas mixing on the laser power have been experimentally investigated to work out the relations between maximum laser power and the corresponding optimum mixing conditions. For this purpose, optimally diluted iodine jets have been matched to different molar flow rates of singlet delta oxygen. These energetic considerations have been complemented by the investigation of the power dependence on fluid mechanic aspects.

In a stable resonator configuration, the output power and the power density distribution of a chemical oxygen-iodine laser (COIL) were measured for various outcoupling geometries: Diaphragms with slit apertures of various size were introduced intracavity in front of the outcoupling mirror. The slit was placed at different positions along the flow axis. Furthermore, outcoupling mirrors of various reflectivity were used. For all experimental conditions the measured power density distribution at the outcoupling mirror reveals strong symmetry effects: The beam patterns are always symmetric to the resonator axis. The beam shape and the beam size are defined by the hardware aperture that is nearest to the resonator axis. As a function of the slit width, the laser output power saturates well before the aperture of the resonator is fully opened. Fifty percent of the maximum output power were achieved at a width of 6 mm only. Good agreement is found between the measured data and theoretical calculations, when taking into account the specific flow conditions. The data highlight the significance of deactivation processes and the strong iodine repumping mechanism within the cavity. For standard operating conditions a Rigrod type analysis reveals a small signal gain that is nearly constant throughout the cavity exceeding 1.3% cm-1. The outcoupling reflectivity for the maximum power output was found at a value of about 94%. These experimental data agree well with a simplified analytic model for gain saturation and power extraction as derived by G. D. Hager et al.

The design of an optimized resonator for a supersonic chemical oxygen iodine laser (COIL) requires detailed information of the saturated gain distribution. By using diaphragms with slit apertures of various sizes at different positions in a stable resonator configuration it was possible to work out detailed information on the coupling characteristics and the influence of iodine repumping and deactivation processes. The measurements were performed at the DLR Lampoldshausen 10 kW supersonic COIL. A high Fresnel number stable resonator is coupled to the active medium and extends about 40 mm downstream from the exit plane of the expansion nozzle array. Apertures with slit widths ranging from 14% to 100% of the full resonator width were introduced into the cavity directly in front of the outcoupling mirror at a fixed z-position of 17 mm downstream of the nozzle exit. The center of another aperture with a fixed slit width of 10 mm could be positioned in flow direction from near the nozzle exit plane to about 29 mm downstream. The optical alignment was controlled with respect to the laser beam size and power density distribution at the outcoupling mirror. As a function of slit aperture the laser output power saturates well before the aperture of the resonator is fully opened. The experimental results are compared with calculations based on the theoretical model of Hager et al. Measured pressure values along the flow direction from the nozzle exit plane to well beyond the laser cavity show a strong dependence on position and width of the diaphragm, resulting from deactivation of unexploited singlet delta oxygen. After taking these pressure effects into account good agreement is found between theory and experiment. The data highlight the significance of deactivation processes for the achievable output power.

The DLR successfully operates a supersonic chemical oxygen iodine laser (COIL) at power levels of up to 8 kW. We address substantial discrepancies between the measured oxygen yield and its theoretically deduced value. This major issue cannot be resolved by using the well-known heuristic model for COIL performance evaluation. Therefore, a new approach derived from a comprehensive enthalpy flow model is presented and validated. We conclude that the experimental yield value is consistent with the new model whereas the theoretical yield is largely overestimated.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The German Aerospace Research Establishment (DLR) is routinely operating its supersonic chemical oxygen-iodine laser (COIL). Meanwhile over 200 single tests have been performed at run times extending to 1 minute. Power levels of 5 KW have been exceeded. Parametric studies were performed resulting in chemical generator efficiencies of about 43% for the baseline operation with high power output. The BHP molarity was found as one of the most important parameters for a stable and reproducible operation. Yield measurements revealed lower numbers than expected from theoretical calculations. The paper gives an overview of the COIL device and discusses the experimental and calculated results of the investigations.

For a rotating disk type generator the dependencies of utilization and yield on the generator operating mode are experimentally investigated. The fundamental effects of rotational speed, reduced gas volume, gas flow and liquid phase composition on the efficiency of singlet delta oxygen generation are discussed together with theoretically predicted generator performace from literature.