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We describe laboratory experiments to generate x-ray photoionized plasmas ofrelevance to accretion-powered x-ray sources such as neutron star binaries andquasars, with significant improvements over previous work. We refer to a keyquantity, the photoionization parameter, defined as xi = 4{\pi}F/n_e where F isthe x-ray flux and n_e the electron density. This is usually meaningful in asteady state context, but is commonly used, in the literature, as a figure ofmerit for laboratory experiments that are, of necessity, time dependent. Wedemonstrate that we can achieve values of xi >100 erg-cm s-1 using laser-plasmax-ray sources, in the regime of interest for several astrophysical scenarios.In particular, we show that our use of a keV line source, rather than thequasi-blackbody radiation fields normally employed in such experiments, hasallowed generation of a ratio of inner-shell to outer-shell photoionizationexpected from a blackbody source with ~keV spectral temperature. This is a keyfactor in allowing experiments to be compared to the predictions of codesemployed to model astrophysical sources. We compare calculations from ourin-house plasma modelling code with those from Cloudy and find moderately goodagreement for the time evolution of both electron temperature and averageionisation. However, a comparison of code predictions of a K-beta argon X-rayspectrum with experimental data reveals that our Cloudy simulationoverestimates the intensities of more highly ionised argon species. This is nottotally surprising as the Cloudy model was generated for a single set of plasmaconditions, while the experimental data are spatially integrated.

Generation of photoionized plasmas in the laboratory of relevance to accretion-powered x-ray sources using keV line radiation