Electron-beam-irradiated discharges considered for initiating high-pressure pulsed chemical lasers

Abstract

Volumetric irradiation by a short-pulse electron beam has been used to trigger long-duration spatially uniform electric discharges in gas mixtures of He and F2 or SF6. Uniform energy deposition to 300 J/liter has been observed for atmospheric F2–He mixtures at nominal electron-beam currents of 3 A/cm2 and discharge currents up to 20 A/cm2. Operation suitable for efficient initiation of pulsed HF/DF chain lasers appears possible over a wide range of E/N and mixture ratios, limited by breakdown at large E/N and negligible field enhancement at low E/N. Approximate analytical plasma models are presented and used in conjunction with time-resolved afterglow current measurements to obtain rate constants for F−-ion F2+−ion recombination and F2+−ion electron recombination. Estimates of F2 dissociation fractions achieved in the experiments imply the possibility of scalable and efficient initiation of pulsed chemical lasers with such discharges.