Driving Iron plasmas to stellar core conditions using extreme x-ray radiation

Abstract We report here on experiments where we have created and diagnosed exactly solid-density iron plasmas at temperatures in excess of 10 million Kelvin (～ 1 keV) and electron densities greater than 2×10 24 cm −3 . This has been achieved by focusing the sub-100-femtosecond output of the Linac Coherent Light Source (LCLS) x-ray laser at photon energies between 7100 and 9000 eV onto solid iron foils at intensities in excess of 10 20 Wcm −2 . The path that these plasmas take through electron density/ temperature space as they are heated traverses conditions comparable to those within the cores of stars on the main sequence ranging from 0.1 to 100 solar masses, as shown in Fig. 1, and approaches temperatures of relevance to emission seen from Galaxy clusters (1). Comparison of the x-ray emission from these hot, dense, iron plasmas with detailed atomic-kinetics calculations reveals a rich array of physics including confirmation of the charge states produced, the effects of the high electron density on the position of the continuum, and a measure of the impact of the dense nature of the plasma on collisional ionisation rates.