Simulation of the Population Inversion at Hydrogen-Like F IX and Li III Ion Transitions in a Recombining Laser Plasma

摘要

Spatial distributions of the intensities and inversion factor of the FIX ion lines of the Lyman series are studied as functions of the irradiation conditions. Laser plasma was produced by the first-harmonic radiation from a Nd laser (10-35 J, 0.6 ns) focused on a flat solid target. It is shown that, for moderate intensities (≈10~(14) W/cm~2), the use of phase plates, which smooth spatial beam inhomogeneities on the target, results in an appreciable increase in size of the emission region of recombining FIX ions. The experimental data are compared with calculations by the "Ion" computer code. Experiments on forming an extended active medium for lasing at the 4-3 transition of the hydrogen-like lithium ion are numerically simulated. This transition, having a wavelength of 208 nm in the UV spectral region, affords the inversion pickup using a resonator with available highly reflecting Al + MgF_2 mirrors.