Sensitivity Analysis of a Chemical Laser System

* A new technique of sensitivity analysis has been applied to the Kerber-Emanuel-Whittier model of a pulse mode hydrogen fluoride chemical laser, so as to determine which parameter uncertainties most critically influence the model's ability to predict laser performance. The particular parameters directly considered were thirteen rate constants out of a set of 68 rate constants in the model, and also the initial concentration of fluorine atoms that start the chain processes which lead to population inversion. In an indirect sense, all 68 rate constants have been studied, because of empirical relations between various sets of constants controlling the formation rates of the excited vibrational states of the hydrogen fluoride molecule. The study covers the time period from 0.1 to 4.0 microseconds following initiation, and presently considers only zero power operation. Future work will treat the finite power case. The study demonstrates how the. parameter uncertainties influence the predictions of the model. It shows that only a small subset, four in number, of all the parameters, have uncertainties which cause significant variance in the predictions. That is to say, the performance of the system, in the time range studied, is almost totally independent of the uncertainties in most of the rate constants. Most prominent at early times (0.1 ysec to 1.0 Msec) are the influences of the chain processes H + F. $ HF(v) + F and F + H2{0) t HF(v) + H. Most prominent at later times (> 1 ysec) is the influence of the VT transfer process HF(v) + HF(v') t HF(v-l) + HF(v'). The initial concentration of F atoms, as generated by flashlamp discharge, is also found to be an important parameter of the system, both at early times (< 1 ysec) and again at later times (> 3 ysec). ■.MiuaMaitoriiUiMttillMllill tm ^t^mmum^m w im** mmm^^rmmmmmmmmmmmmmmm W mmm 1 ■■UPlllJILIIIIIilJUIJJ "T