Optically-ionized plasma recombination x-ray lasers

摘要

Design studies for recombination x-ray lasers based on plasmas ionized by high intensity, short pulse optical lasers are presented. Transient lasing on n = 3 to n = 2 transitions in Lithium-like Neon allows for moderately short wavelengths ((le) 100(angstrom)) without requiring ionizing intensities associated with relativistic electron quiver energies. The electron energy distribution following the ionizing pulse affects directly the predicted gains for this resonance transition. Efficiencies of 10(sup (minus)6) or greater are found for plasma temperatures in the vicinity of 40 eV. Simulation studies of parametric heating phenomena relating to stimulated Raman and Compton scattering are presented. For electron densities less than about 2.5 (times) 10(sup 20) cm(sup (minus)3) and peak driver intensity of 2 (times) 10(sup 17) W/cm(sup 2) at 0.25 (mu)m with pulse length of 100 fsec, the amount of electron heating is found to be marginally significant. For Lithium-like Aluminum, the required relativistic ionizing intensity gives excessive electron heating and reduced efficiency, thereby rendering this scheme impractical for generating shorter wavelength lasing ((le) 50(angstrom)) in the transient case. Following the transient lasing phase, a slow hydrodynamic expansion into the surrounding cool plasma is accompanied by quasi-static gain on the n = 4 to n = 3 transition in Lithium-like Neon. Parametric heating effects on gain optimization in this regime are also discussed. 18 refs., 6 figs.