Experimental study of the interactions between intense X-rays and solid matter illustrate the generation of a solid-density plasma governed by electron–ion collisions; these results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological samples, material science investigations, and the study of matter in extreme conditions. With the advent of free-electron lasers, the high intensities previously only achievable with optical lasers can be produced at X-ray wavelengths. This opens new opportunities for theory and experiment. Here, Vinko et al. report the first detailed study of intense X-ray radiation interacting with solid density matter, carried out on the Linac Coherent Light Source free-electron laser at the SLAC National Accelerator Facility in California. They observe the generation of a solid-density plasma and establish that collisions have a pivotal role. The results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological samples and materials science investigations. Matter with a high energy density (>105 joules per cm3) is prevalent throughout the Universe, being present in all types of stars1 and towards the centre of the giant planets2,3; it is also relevant for inertial confinement fusion4. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities5,6. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser7, high-intensity radiation (>1017 watts per cm2, previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated8. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 106 kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray–matter interactions, and illustrate the importance of electron–ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.

Creation and diagnosis of a solid-density plasma with an X-ray free-electron laser

The characteristics of 22–40keV Kα x-ray sources are measured. These high-energy sources are produced by 100TW and petawatt high-intensity lasers and will be used to develop and implement workable radiography solutions to probe high-Z and dense materials for the high-energy density experiments. The measurements show that the Kα source size from a simple foil target is larger than 60μm, too large for most radiography applications. The total Kα yield is independent of target thicknesses, verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter Kα radiation. One-dimensional radiography experiments using small-edge-on foils resolved 10μm features with high contrast. Experiments were performed to test a variety of small volume two-dimensional point sources such as cones, wires, and embedded wires, measured photon yields, and compared the measurements with predictions from hybrid-particle-in-cell simulations. In addition to high-energy, high-resolution backlighte...

/pdf/high-energy-ka-radiography-using-high-intensity-short-pulse-51ll2v098v.pdf

High-energy Kα radiography using high-intensity, short-pulse lasersa)

http://www.prism-cs.com/Software/Spect3D/SPECT3D_RPHDMpaper_2007.pdf

SPECT3D - A Multi-Dimensional Collisional-Radiative Code for Generating Diagnostic Signatures Based on Hydrodynamics and PIC Simulation Output

Advances in NLTE modeling for integrated simulations

The role of a detailed configuration accounting (DCA) atomic physics package in explaining the energy balance in ignition-scale hohlraums

https://digital.library.unt.edu/ark:/67531/metadc874703/m2/1/high_res_d/881067.pdf

M.H. Chen

Papers

FLYCHK: Generalized population kinetics and spectral model for rapid spectroscopic analysis for all elements

Extension of atomic configuration sets of the Non-LTE model in the application to the Kα diagnostics of hot dense matter

A fast method to generate collisional excitation cross-sections of highly charged ions in a hot dense matter