With the advent of high-energy-density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, millimeter-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly suitable to this class of experimental astrophysics include the study of opacities relevant to stellar interiors, equations of state relevant to planetary interiors, strong shock-driven nonlinear hydrodynamics and radiative dynamics relevant to supernova explosions and subsequent evolution, protostellar jets and high Mach number flows, radiatively driven molecular clouds and nonlinear photoevaporation front dynamics, and photoionized plasmas relevant to accretion disks around compact objects such as black holes and neutron stars.

/pdf/experimental-astrophysics-with-high-power-lasers-and-z-2ws0p4rgie.pdf

Experimental astrophysics with high power lasers and Z pinches

Accurate x-ray scattering techniques to measure the physical properties of dense plasmas have been developed for applications in high energy density physics. This class of experiments produces short-lived hot dense states of matter with electron densities in the range of solid density and higher where powerful penetrating x-ray sources have become available for probing. Experiments have employed laser-based x-ray sources that provide sufficient photon numbers in narrow bandwidth spectral lines, allowing spectrally resolved x-ray scattering measurements from these plasmas. The backscattering spectrum accesses the noncollective Compton scattering regime which provides accurate diagnostic information on the temperature, density, and ionization state. The forward scattering spectrum has been shown to measure the collective plasmon oscillations. Besides extracting the standard plasma parameters, density and temperature, forward scattering yields new observables such as a direct measure of collisions and quantum effects. Dense matter theory relates scattering spectra with the dielectric function and structure factors that determine the physical properties of matter. Applications to radiation-heated and shock-compressed matter have demonstrated accurate measurements of compression and heating with up to picosecond temporal resolution. The ongoing development of suitable x-ray sources and facilities will enable experiments in a wide range of research areas including inertial confinement fusion,more » radiation hydrodynamics, material science, or laboratory astrophysics.« less

X-ray Thomson scattering in high energy density plasmas

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

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

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)

The K-shell spectroscopy code FLY and its predecessors have been employed to study hot dense plasmas for decades. FLY has provided a basis for studies of K-shell ions up to Z=26, where its ease of use, PC application base, and synthetic spectral production have made it attractive to both experimentalists and modelers. However, the application has been focused on K-shell ions where less ionized species are represented as a ground state only. To attempt to make this simple model predict the ionization and recombination through the less ionized stages, we extend the model to include kinetics models for all ion stages. The emphasis of this extension is not to provide detailed spectra or population for the L- or M-shell, but to provide a K-shell model with enhanced accuracy in those cases where ionization and recombination through the L- and M-shell are important. This work is a first step in generating an application that will allow detailed analysis of sub-picosecond self-consistent velocity distribution and population kinetics solutions. We will discuss the extensions and provide examples. Finally, we will outline the progress towards the eventual goal of the self-consistent solution.

W L. Morgan

Papers

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

FLYCHK: an extension to the K-shell spectroscopy kinetics model FLY.