Optical-field induced gas mixture breakdown for recombination X-ray lasers

A spatially resolved analytic model is used to calculate the distribution of optical-field ionisation and heating including both above-threshold ionisation and inverse bremsstrahlung electron heating mechanisms. A 1D Lagrangian hydrodynamics model is subsequently used as a postprocessor to simulate the recombination phase with both plasma effects and atomic kinetics included. Calculation of gain coefficients for pure lasant and mixed species targets are presented, and important parameters examined. Both pure nitrogen (247 Angstrom) and argon (232 Angstrom) targets produce low gain, however hydrogen doping significantly enhances the gain particularly in argon up to values as high as 300 cm(-1). Lithium (135 Angstrom) and neon (98 Angstrom) are shown to be ineffective even with doping, due to severe electron heating. Low saturation intensities (similar to 10(7) W cm(-2)) are found for argon and nitrogen limiting the output X-ray pulse energy available. (C) 1997 Elsevier Science B.V.