Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session T1: X-ray Free Electron Lasers and Materials II |
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Chair: Raymond Smith, Lawrence Livermore National Laboratory, Bob Nagler, SLAC National Accelerator Laboratory Room: Grand E |
Thursday, June 18, 2015 11:15AM - 11:45AM |
T1.00001: Ultra-Fast Structural Studies of Shock-Induced Phase Transitions in Bismuth Invited Speaker: Malcolm McMahon The study of structural phase transitions via dynamic compression has a long and illustrious history. But, due to the absence of suitably bright x-ray sources, it is only relatively recently that the structures of some of these high-pressure phases have been determined. Over the last 25 years, static compression studies have revealed the great structural complexity that exists in many high-pressure phases, and DFT calculations predict that such complexity will continue to pressures as yet unattainable experimentally. Are these same complex structures formed on shock timescales, and, if so, can we determine their structures with certainty via x-ray diffraction? The recent advent of x-ray free electron lasers (XFELs) now provides us with x-ray sources that are ideally suited to structural studies of shock-compressed matter on nanosecond timescales. In this talk I will describe results from recent experiments on the MEC beamline at the LCLS on diffraction studies of the phase transitions in bismuth, and look forward to what will be possible in the Euro-XFEL after its start-up in 2017. [Preview Abstract] |
Thursday, June 18, 2015 11:45AM - 12:00PM |
T1.00002: In situ x-ray diffraction of shock-driven deformation and phase transformation in titanium Cynthia Bolme, Amy Lazicki, Don Brown, Arianna Gleason, Ellen Cerreta, Ben Morrow, Suzanne Ali, Damian Swift, Bob Nagler, Eric Galtier, Eduardo Granados, Despina Milathianaki, Phil Heimann Titanium alloys are employed in demanding engineering applications due to their high strength-to-weight ratio and their resistance to corrosion. Pure titanium and titanium with high levels of oxygen impurities were studied under laser-driven shock compression at the Matter in Extreme Conditions endstation at the Linac Coherent Light Source. In situ x-ray diffraction data were acquired during compression, showing the lattice-level response of titanium as it underwent plastic deformation and phase transformation. The kinetics of these processes and the influence of oxygen impurities on the deformation behavior will be presented. [Preview Abstract] |
Thursday, June 18, 2015 12:00PM - 12:15PM |
T1.00003: Investigations into uniaxial deformation of textured polycrystalline targets using X-ray diffraction David McGonegle, Despina Milathianaki, Bruce Remington, Justin Wark, Andrew Higginbotham Most dynamic compression experiments make use of targets with some degree of texture, however, little attention has been paid to how this affects {\it in situ} diffraction patterns. This preferred grain orientation results in variation in intensity around the Debye-Scherrer ring, and is often ignored by integrating data azimuthally. However, we demonstrate that this variation provides important information about reorientation of the crystal lattice, which is unobtainable with traditional powder diffraction. In particular we describe how to obtain the orientational relationship between two phases within a phase transition, as well as how to distinguish between competing plasticity mechanisms, such as slip and twinning. The geometries we propose are ideal for study by 4th generation sources such as LCLS. [Preview Abstract] |
Thursday, June 18, 2015 12:15PM - 12:30PM |
T1.00004: Spatially-resolved X-ray Scattering off shock-compressed carbon at the LCLS Ulf Zastrau The diversity of the electronic properties of carbon makes it of key interest to the material science community; nowhere is this more evident than in the myriad potential applications of structured allotropes like grapheme and nano tubes. By contrast, at the high pressures typical of planetary and stellar interiors, the behavior of carbon is poorly understood with large uncertainties in the conductivity and even the material phase. There is growing evidence of the abundance of diamond in the interiors of the ice giant planets Uranus and Neptune; the conductivity of which could potentially influence models for the origin of the unusual magnetic fields of these planets. In laboratory experiments, practical issues with gradients in the temperature and density of shock compressed matter have hindered accurate measurement and further from distinguishing theoretical models. Here, we present spatially resolved x-ray scattering experiments using LCLS free electron laser to examine and understand the gradients of thermal properties under dynamic shock loading. We employed curved mosaic and perfect imaging crystals. Compared with hydro-dynamic simulations, we present time-resolved data on plasmon dispersion, axial compression gradients and finally carbon melting at shock coalescence. [Preview Abstract] |
Thursday, June 18, 2015 12:30PM - 12:45PM |
T1.00005: The High Energy Density science instrument at the European XFEL, Hamburg, Germany: a new platform for shock compression research Karen Appel, Motoaki Nakatsutsumi, Gerd Priebe, Alexander Pelka, Ian Thorpe, Thomas Tschentscher The \underline {High Energy Density science instrument} (HED) at the European XFEL, Hamburg, Germany will provide unique experimental possibilities for the investigation of near solid material driven to extreme states and will also establish a new platform to study materials response to shock compression. HED is located at the SASE2 undulator, which provides up to 27000 pulses per second with about 10$^{\mathrm{12}}$ photons per pulse, photon energies between 3 and 24 keV and pulse lengths of 2 -- 100 fs. Self-seeding is foreseen, as well as natural bandwidth (BW) SASE radiation. In addition, energy BW of 10$^{\mathrm{-4}}$ and 10$^{\mathrm{-6}}$ will be available through monochromators. Focussing is based on CRL optics, which will allow to provide beam sizes of 2 $\mu $m, 10-20 $\mu $m and 150 -- 260 $\mu $m at the sample position. Samples will be driven to extreme states by different types of optical lasers (either 200 kHz/3 mJ/15 fs, 10 Hz/100 TW/30 fs or 10 Hz/100J/ns), the pump-probe FEL beam (delays of up to 2 -23 ps for 5 -20 keV using a split-and-delay unit) and pulsed magnetic fields (up to 50 T). Pump probe experiments can be performed at adapted repetition rates (4.5 MHz, 1 -- 10 Hz, single shot). X-ray techniques comprise diffraction, imaging and spectroscopic methods. User operation is planned for fall 2017. We will present the science case of HED, the current layout and present ideas on first shock compression experiments. [Preview Abstract] |
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