Effects of shock waves on the performance of a cw supersonic HF chemical laser

Abstract

The effects of oblique shock waves on the gain and the output power of a cw supersonic HF chemical laser are theoretically investigated. A one-dimensional model is used to solve the flow of a premixed H2–SF6–He or H2–F2–He mixture through the resonator, allowing the presence of oblique shock waves in the flow. It is shown that a shock wave significantly affects the laser performance due to the gas compression at the shock front and due to acceleration of the chemical and energy transfer processes. It was found that immediately behind the shock front the gain coefficients and the photon energy sharply increase and further downstream they fall off rapidly, thus the profiles of the gain and radiation flux become narrower along the flow direction. Integration of the radiation flux along the cavity coordinate reveals that in some cases the total available power is significantly higher than the available power obtained in the undisturbed flow. For HF lasers pumped by the chain reactions it was found that choking occurs over a wide range of flow parameters including very weak shock waves. This is due to the large amount of heat released by the exothermic reactions.