Thermal Laser Excitation by Supersonic Mixing in a Gas Dynamic Nozzle
ARMY MISSILE RESEARCH DEVELOPMENT AND ENGINEERING LAB REDSTONE ARSENAL AL PHYSICAL SCIENCES DIRECTORATE
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An arc-driven laser suitable for gas-dynamic and similar modes of operation is described. Inversion is obtained by rapid expansion of hot gas mixtures through a supersonic aerodynamic nozzle. Upper vibrational lasing levels are frozen at preexpansion conditions while the lower levels are characterized by conditions in the supersonic flow downstream of the nozzle. A population inversion exists for some distance downstream. Inversion is enhanced by the injection of additives to relax the lower levels at a faster rate. The system is so designed that the gases used, the mixture ratios, and the mass flow rates, as well as the specific enthalpy of the system, may be varied nearly independently. In addition, gases may be injected at various points along the flow, and the results of this feature is stressed. The laser has been operated under marginal gas-dynamic conditions with all component gases of a CO2 system premixed prior to expansion. However, most of the work presented deals with the injection of cold CO2 into the hot supersonic flow mixture immediately downstream of the nozzle throat. The report illustrates how parametric studies may be made of various aerodynamic systems. In particular, the effects of controlled amounts of impurities, such as those formed in various combustion processes, may be investigated.
- Lasers and Masers