Spectroscopy of x-ray laser media

For this thesis, experiments using spectroscopic methods and simulations have been undertaken to understand different x-ray laser media. H-like carbon and Li-like titanium and calcium recombination laser schemes have been investigated with the aim of producing shorter wavelength x-ray lasers using moderate driving laser energy. New Ne-like germanium collisional x-ray lasers have been developed using pre-pulse and multi-pulse laser driving configurations which reduce the required driving laser energy and increase the x-ray laser output. Lasing and resonance line output for these experiments is simulated in this work. The experimental resonance line spectrum from H- and He- like carbon ions has been modelled. The temperature of the Li-like Ti and Ca x-ray laser media has been measured using the relative Li-like dielectronic satellite lines and He-like intercombination line intensities. It is shown that these lines are optically thin and in coronal equilibrium. Time- and space integrated Ne-like and F- like Ge resonance lines intensities have been calculated and compared with experimental spectra. Spectral lines emitted from He-like, Li-like and Be-like Ti and Ca and Ne-like and F-like Ge x-ray laser media have been modelled using the hydrodynamic and atomic physics code EHYBRID. Artificial spectra which can be compared with time- and space-averaged experimentally obtained spectra are presented. Additional coding was added to EHYBRID so that the emission from j,k,l,m,a,b,c,q,r,s,t lines of satellites near the He- like Ti resonance lines and similarly the emission from 3s-2p, 3d-2p resonance lines of Ne- and F-like Ge could be evaluated. Overall good agreement with the experimental spectra has been obtained indicating that EHYBRID models well the plasma expansion, ionic populations and x-ray laser gain. Resonance lines are often optically thick since they have strong absorption oscillator strengths. The absorption of resonance lines emitted from the lower lasing level can reduce the population inversion of both collisional and recombination x-ray lasers and needs to be taken into account for the correct evaluation of emitted spectra. An escape factor approximation has been developed in this thesis assuming absorption and emission decay exponentially with distance from the target surface. The escape factor calculation has been used in the modelling of the Ne-like Ge, Li-like Ti and Ca x-ray laser media.