Frequency redistribution effect on emissivity and intensity of Ge²²⁺ and C⁵⁺ X-ray lasers

Abstract
This work concerns the effect of frequency redistribution on X-ray laser beams. The redistribution function, calculated by extending the frequency fluctuation model to 2-photon processes, shows coherent scattering and a redistributed contribution. The spectral emissivity, corrected in order to account for this effect, is calculated for X-ray lasers, the amplifier plasma being composed either of neon-like germanium ions or hydrogen-like carbon ions. The coupled radiative transfer equation and population equations are solved consistently, and the intensity of the X-ray laser output is given for two 3p-3s lines (19.6 and 23.6 nm) of neon-like germanium. We also study the variation with plasma length (i.e. line intensity) of the emissivity of the C⁵⁺ Balmer-[MAHT] lasing line. The physical conditions of the calculations are obtained from a modelling of experiments conducted at the Rutherford Appleton Laboratory.