Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session C3: X-ray Diffraction/Scattering I |
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Chair: Paulo Rigg, Los Alamos National Laboratory Room: Fairmont Orchid Hotel Plaza I |
Monday, June 25, 2007 1:45PM - 2:00PM |
C3.00001: X-ray scattering measurements from solid density plasmas Siegfried Glenzer, Paul Neumayer, Otto Landen The development of spectrally resolved x-ray scattering for accurate measurements of densities and temperatures in solid-density plasmas has enabled new applications to characterize shock-compressed matter. The first proof-of-principle experiments on the Omega laser facility at the Laboratory for Laser Energetics have employed isochorically heated solid-density beryllium targets. In backscattering geometry, Compton scattering measurements have been shown to provide information on temperature and the ionization state from the spectral broadening and relative intensity of the inelastic scattering spectrum, respectively. In the forward scattering regime, the collective plasmon oscillations have been observed providing the local electron density from the frequency shift of the plasmon peak from the incident probe x-ray energy. These results indicate that the simultaneous application of forward (collective) and backward (non-collective) scattering will allow accurate measurements of the compressibility of warm dense matter. New experimental results important for applications to shock-compressed matter will be discussed. [Preview Abstract] |
Monday, June 25, 2007 2:00PM - 2:30PM |
C3.00002: In-situ probing of lattice response in shock compressed materials using x-ray diffraction Invited Speaker: Diagnostics which can probe the lattice response during shock compression offer insight into many key features of the physical phenomena which govern material response. An in-depth analysis of diffraction images of the alpha to epsilon transition in shock compressed single crystal iron offers insight into the transition mechanism of the lattice due to compression along the 100 principal axes. These single crystal diffraction techniques integrate well with molecular dynamics simulations, and have been shown to offer insight into the atomistics of the shock process. The recent development of polycrystalline diffraction techniques offers similar levels of insight into materials which are more complicated by their nature of having grains of multiple orientations, but are more representative of commonly used materials. This work was conducted under the auspices of the U.S. DOE by the UC LLNL and LANL under Contract No. W-7405-Eng-48. Additional support was provided by LDRD program Project No. 06-SI-004 at LLNL. [Preview Abstract] |
Monday, June 25, 2007 2:30PM - 2:45PM |
C3.00003: Real time x-ray diffraction measurements in shocked solids at the Advanced Photon Source Y.M. Gupta, S.J. Turneaure, K. Perkins, K. Zimmerman, C.S. Yoo, G.W. Collins, G. Shen The Advanced Photon Source provides a number of benefits (high photon numbers, pulsed time structure, and flexible beam properties) to examine the real time x-ray diffraction response of shocked crystals. However, shock wave experiments at a synchrotron facility pose a number of operational challenges, including the coupling of a shock wave driver to the beam line, and appropriate synchronization/gating of detectors. This talk will describe experimental plans and developments underway to utilize either a monochromatic or white beam for x-ray measurements in shocked solids. A compact launcher to achieve impact velocities of $\sim $1km/s will be presented. Results of ambient measurements, in preparation for the shock experiments planned this summer, will be presented. Work supported by DOE. [Preview Abstract] |
Monday, June 25, 2007 2:45PM - 3:00PM |
C3.00004: Temperature Measurements of Shocked Crystals by Use of Nanosecond X-ray Diffraction William Murphy, Andrew Higginbotham, Justin Wark, Nigel Park Over the past few years we have been pioneering the use of sub-nanosecond X-ray diffraction to determine the phase and compression of shocked crystals. It is well known that the deviation of atoms from their ideal lattice sites due to thermal motion reduces the integrated intensity within diffraction peaks - the so-called Debye-Waller effect, and thus it is pertinent to investigate whether line ratios might be sufficiently sensitive to be used as a viable temperature diagnostic. Clearly the matter is not completely straight-forward, as the Debye frequency of a solid also varies under compression. In our initial investigations we have calculated the ratios of intensities of high-order reflections assuming various forms of the Gruneisen parameter, and have also compared these results with those obtained from Molecular Dynamics simulations. We also note that under isentropic compression high order reflections monotonically increase in intensity. Given the photon energies of nanosecond X-ray pulses that can currently be produced, we comment on the experimental feasibility of the technique. [Preview Abstract] |
Monday, June 25, 2007 3:00PM - 3:15PM |
C3.00005: Measurement of shock wave density using quantitative x-ray phase contrast imaging Damien Hicks, Jon Eggert, Peter Celliers, Hye-Sook Park, Sebastien Le Pape, Pravesh Patel, Brian Maddox, Gilbert Collins, Thomas Boehly, Benjamin Barbrel Determining the density in a shock wave at multi-Mbar pressures using traditional impedance matching methods suffers from the dual problems of increasing uncertainty in the material standard and the increasing precision required to measure shock velocities. We present results from laser-driven shock wave experiments employing a technique designed to achieve \textit{direct} density measurements of a shock wave. Point projection of a laser-plasma x-ray source is used to produce a phase contrast image snapshot of an expanding shock wave. Using an iterative algorithm to determine the propagation of refracted x rays at the shock front, the resulting optical depth of the image is tomographically inverted to determine the shock density. By simultaneously measuring the shock velocity using VISAR, absolute equation-of-state points are determined. This technique has been extended to produce phase contrast images of shocks in aluminum using high-energy, short-pulse laser-produced x rays. This work was performed under the auspices of the US DOE by LLNL under Contract No. W-7405-ENG-48 and by the University of Rochester under Cooperative Agreement No. DE-FC03-92SF19460. \newline [Preview Abstract] |
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