Analytic modeling of electrically excited D2/HCl and HCl laser experiments

An analytic capability has been developed to model two types of laser experiments: (1) a D2/HCl EDL and (2) an e-beam sustainer discharge HCl laser. For the former device, a discharge in D2/inert gas mixtures provides excitation of the vibrational mode of D2. This gas is then supersonically expanded and HCl injected. The gases mix and flow into a cavity where vibrational energy transfer pumps the HCl. Complete modeling of this sequence of steps has been achieved. The relevant electron impact rate constants for D2 (and H2) as well as the vibrational energy transfer rate constants for the D2/HCl molecular system were selected from available data and theory. Comparison of the results of this model with data from the NRL EDL experiment were in qualitative agreement. A conceptual design of a next generation experiment was performed and indicates the requirement for an e-beam sustainer discharge operating at about one atmosphere plenum pressure. A D2/HCl EDL is predicted to be feasible. In the second experiment, HCl/inert gas mixtures are directly excited by a pulsed, high current e-beam sustainer discharge. The discharge conditions were modeled by developing a set of electron impact cross sections for HCl. The results of model calculations indicate that for the conditions of the NRL experiment, sufficient atoms may be generated in the discharge to prevent attainment of high gain. Definitive modeling of the atom generation is not possible at present.