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We present measurements of the spectrally-resolved X-rays emitted from solid-density magnesium targets of varying sub-μm thicknesses isochorically heated by an X-ray laser. The data exhibit a largely thickness-independent source function, allowing the extraction of a measure of the opacity to K-shell X-rays within well-defined regimes of electron density and temperature, extremely close to local thermodynamic equilibrium (LTE) conditions. The deduced opacities at the peak of the K-α transitions of the ions are consistent with those predicted by detailed atomic-kinetics calculations.

The advent of the 4th generation X-ray sources paves the way for a new phase of experimental investigation of Hot-Dense plasmas. At the Linac Coherent Light Source (LCLS), pulses of keV X-rays, shorter than 100 fs, and with intensities up to 1018 W·cm-2, are routinely produced, allowing for the production of uniform samples of solid-density plasmas. The simple single-photon X-ray absorption mechanism can be easily modelled, so that the plasma conditions can be accurately retrieved, without relying on diagnostic techniques that are not benchmarked in this high density regime. The work presented here describes the results of the first experiment where the LCLS interacts with a solid Al target, isochorically heating it at temperatures up to 190 eV. The system is described by the SCFLY non-LTE model, where the density and temperature are computed self consistently, as a consequence of the detailed atomic processes, rather than imposed by the user. The approximations affecting the simulations are discussed in detail. The code is first validated, by modelling the charge state distribution measured in a previous experiment (L. Young et. al), where the LCLS interacts with a Ne gas, a simplified (collisionless) problem. Then it is used to model the K-alpha spectroscopic data obtained for Al. The plasma evolution, explained by SCFLY simulations, is found to be primarily determined by collisions, whose visible effects on the experimental spectra are discussed. By varying the wavelength of the laser and observing the change in the K-alpha fluorescence, the K-edges for different ions in the plasma were determined, leading to a charge resolved measurement of continuum lowering in the HDM system. The results disagree with the widely used Stewart-Pyatt model, with the disagreement increasing for higher charge states, but are consistent with the older Ecker-Kroell model. These results have profound implications for dense plasma modelling.

We present simulations of the time and space-resolved transmission of a solid-density aluminium plasma as it is created and probed with the focussed output of an x-ray free-electron-laser with photon energies ranging from the K-edge of the cold material (1560 eV) to 1880 eV. We demonstrate how information about the temporal evolution of the charge states within the system can be extracted from the spatially resolved, yet time-integrated transmission images. We propose that such time-resolved measurements could in principle be performed with recently developed split-and-delay techniques.

A novel approach to ICF called shock ignition, that relies on delivery of a very strong shock created by a laser pulse at intensities around 10 16 W cm-2, is investigated. In this context, an experiment using two beams from the Prague Asterix Laser System with time duration of 300 ps was performed at the PALS laboratory. The first beam at low intensity was used to create extended preformed plasma, and the second one to create a strong shock. Several diagnostics were used to characterize the preformed plasma and the interaction of the main pulse with the target. © 2011 Institute of Thermomechanics AS CR, v.v.i.

A 250-TW laser system (FLAME - Frascati laser for acceleration and multidisciplinary experiments) is now in its commissioning phase in a new laboratory at LNF-INFN in the framework of the PLASMONX (Plasma acceleration and monochromatic X-ray generation) project. The laser will deliver < 25 fs duration pulses with an energy up to 6J, at a 10Hz repetition rate. An ad hoc target area has also been designed and is currently being set up, allowing the first test experiments of electron laser wakefield acceleration to be carried out over the next few months in a safe, radiation-protected environment. An overview of the main features of the laser system and target area is given, along with a survey of the design and set-up of the self-injection test experiment, which is expected to reach the production of sub-GeV electron bunches. © 2010 Taylor and Francis.

By the year 2010 a new laser will be operational at the CNR Campus in Pisa. The laser system will deliver two beams each one providing 1-ns 50-joule pulses of high optical quality and full control of phase. The major feature of the system is its spectral and time shape flexibility ranging from narrowband single mode operation to broadband operation with pulse tailoring. According to previous experiments and recent simulations, these features could critically determine the laser-pellet coupling in the different approaches to laser fusion. The physics involved in the different coupling processes is still not fully investigated experimentally. The BLISS laser, combined with the rest of the ILIL experimental facility, including ultrafast optical probing, time resolved optical X-ray diagnostics and particle detection could contribute to this investigation with ad hoc small scale experiments. The main features of the innovative BLISS laser front end for broadband operation are shown, together with the amplification chain and the main features of the experimental installation. Data from simulations providing a useful input for future experiments are also presented. BLISS is expected to contribute to the preparatory phase of the large scale European HiPER project. © 2010 American Institute of Physics.