An end to end model was developed to predict the performance of a rotating disk Chemical Oxygen Iodine Laser (COIL). The model includes coupled routines to model the singlet oxygen generator (500) including ducting and cold trap, the nozzle, and the laser cavity and resonator. The SOG model is based on a quasi one dimensional two phase wetted wall approach. It includes an effective resistance chlorine/oxygen mass transfer model, a local basic hydrogen peroxide (BHP) HOj diffusion model including property variations both in the flow direction and within the film, thermal analysis for both the liquid and gas phases, and evaluation of O('A) detachment yield, surface deactivation, and gas phase deactivation. A mass addilion routine based on variable specific heat and molecular weight influence coefficients is used to establish nozzle initial conditions. The results ofthe mass addition calculation are used iteratively to assess SOG stagnation pressure and if necessary SOG calculations are repeated. The primary and secondary streams are then separated into a number of stream tubes. The scale of the piiinary and secondary stream tubes is determined by the specified mixing scale and their stoichiometries by the initial flows. Mixing is assessed based on an approximate bimolecular diffusion coefficient analysis. Concurrent calculations are made to evaluate the effects of area expansion and chemistry. Once the calculation reaches the mirror location the computations can be perfonned iteratively with either a roof-top or Fabry Perot resonator to achieve selfconsistency between the mode characteristics and gain medium. The model is described and representative results presented.
Results of an experimental investigation of phase conjugation by stimulated Brillouin scattering (SBS) at 1.053 pm using a focused beam geometry with very long pulse lengths (pulse length > 6700 phonon lifetimes) are reported.Scanning of the beam through the SBS medium is proposed as a means of suppressing the undesirable effects of processes which can compete with the SBS in the long -pulse regime. Data taken with and without beam scanning indicate that high -quality phase conjugation can be achieved by SBS using focused beams with arbitrarily long pump pulses.
A sensitive F2 absorption diagnostic technique was used to determine F2 densities in the flow of a 10.2-cm-long combustion-driven chemical-laser nozzle. The diagnostic device was demonstrated to be readily transportable and operable in a combustion-driven chemical-laser field environment. Cold- and hot-flow measurements up to 970 K plenum temperature (i.e., no F2 dissociation cases) were in agreement; hence, the measurement technique appears to be reliable. The use of C2H4 as a combustor fuel did not result in particulate absorption or scattering of sufficient magnitude to affect the measurement. The flow dissociation level (α) was ≳0.8 for this nozzle. The measurement sensitivity achieved in these tests was ΔI/I0=6×10−4, which corresponds to an F2 density of 6.76×10−6 mole/l (i.e., 0.127 Torr F2 at 300 K) for a 10.2-cm path length.
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