Dissociation efficiency of electron-beam-triggered discharges for initiating atmospheric-pressure H2-F2 lasers

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Abstract
Time‐resolved uv absorption measurements of the rate of F2 disappearance have been compared with a theoretical pulsed chemical laser code to infer electrical dissociation efficiencies of electron‐beam‐irradiated discharges. The results indicate that a 400‐keV, 50‐nsec e‐beam of A/cm2 dissociates approximately 0.3% of the reactants initially present in dilute F2/H2 mixtures, producing four chain carriers per ionizing collision. With the addition of a discharge field at 80% of the self‐breakdown limit, initial reactant dissociation increases to approximately 1.1%, corresponding to 15 chain carriers per ionizing event and a dissociation efficiency of 7.5%. An earlier analytical plasma model of reactant dissociation that has been generalized to account for the presence of Ar and H2 suggests that heating of the negative ions of fluorine, leading to electron detachment in heavy‐particle collisions and direct electron‐impact dissociation of reagents by slow electrons become dominant mechanisms with the application of a strong undervolted field. In general, the approximate plasma analysis is shown to yield results that are in qualitative agreement with the experimental data.

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