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 C2: Equation of State II: Very High Pressure |
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Chair: Neal Bourne, University of Manchester, Dawn Flicker, Sandia National Laboratories Room: Grand F |
Monday, June 15, 2015 11:15AM - 11:30AM |
C2.00001: Hugoniot and opacity measurements of polystyrene and carbon up to 80 TPa from radiography of converging shocks at the National Ignition Facility A.L. Kritcher, T. Doeppner, D.C. Swift, B. Bachmann, D. Kraus, J. Hawreliak, J. Gaffney, G. Collins, S. Glenzer, D. Chapman, S.D. Rothman, S. Rose, R.W. Falcone Converging shocks were induced with hohlraum-driven x-ray radiation on spherical samples of poly alpha-methyl styrene and diamond. The time-history of density profiles through the sample was measured by x-ray radiography using a laser-heated backlighter and a streak camera, viewing a diameter across the sample through slots in the hohlraum wall. Profile-matching in radius and time was used to increase the accuracy of density inferred from the transmission. The shock temperature reached several hundred eV, causing ionization which significantly reduced the opacity to the 9 kV x-ray energy. The opacity change at the shock was inferred from the change in apparent mass inside a radiographic marker layer. The speed and compression of the shock were measured from the density profiles. The shock pressure increased with convergence, so a range of Hugoniot states was obtained from each experiment. Shock states were measured between 10 and 80 TPa. [Preview Abstract] |
Monday, June 15, 2015 11:30AM - 11:45AM |
C2.00002: Shock wave equation of state experiments at multi-TPa pressures on NIF P.M. Celliers, D.E. Fratanduono, J.L. Peterson, N.B. Meezan, A.J. MacKinnon, D.G. Braun, M. Millot, J. Fry, K.J. Boehm, G.W. Collins, A. Nikroo, P. Fitzsimmons The National Ignition Facility provides an unprecedented capability to generate steady, planar, ultra-high pressure shock waves (around 10 TPa) in solid samples. Building on successful laser shock equation of state experiments performed on a variety of other laser facilities, we have designed and fielded experiments to perform impedance match experiments on samples of C, Be, quartz and CH, in the range of 3 to 7 TPa. The experiments use a line-imaging VISAR as the primary diagnostic to measure the shock velocity in an Al reference standard and in an array of the four samples. Initial tests with the line-imaging VISAR show that the NIF is capable of driving shocks that are steady for several ns, with smooth planar breakout patterns over a 2 mm diameter spot. Initial results will be discussed. [Preview Abstract] |
Monday, June 15, 2015 11:45AM - 12:00PM |
C2.00003: Absolute Hugoniot measurements of polystyrene between 3 and 12 TPa using radiography of a converging shock at the National Ignition Facility T. Doeppner, A.L. Kritcher, D.C. Swift, B. Bachmann, J. Hawreliak, G.W. Colllins, S. Glenzer, S.D. Rothman, D. Kraus, R.W. Falcone A converging shock was induced with hohlraum-driven soft x-ray radiation on a solid, spherical sample of poly alpha-methyl styrene. The time-history of density profiles through the sample was measured by x-ray radiography using a laser-heated backlighter and a streak camera, viewing a diameter across the sample through slots in the hohlraum wall. Profile-matching in radius and time was used to increase the accuracy of density inferred from the transmission. The speed and compression of the shock were measured from the density profiles. The shock pressure increased with convergence, so a range of Hugoniot states was obtained from a single experiment. Using a laser power based on the early part of a ``high foot'' pulse from ignition experiments, the low end of the pressure range was brought down to 2 TPa, overlapping states accessible by experiments in plane geometry, and ensuring that the opacity of the compressed sample was the same as for unshocked material, simplifying the analysis. Shock states were measured up to 12 TPa, when the shock was close to the center of the sample. This is several times higher than has been obtained by other methods and is an absolute measurement. [Preview Abstract] |
Monday, June 15, 2015 12:00PM - 12:15PM |
C2.00004: New Hugoniot measurements on LiF and diamond from laser-driven compression Federica Coppari, Amy Lazicki, Dayne Fratanduono, Peter Celliers, Richard London, David Erskine, Damian Swift, Jon Eggert, Gilbert Collins, Heather Whitley, John Castor, Joe Nilsen The measurement of materials' equations of state (EOS) is relevant to a variety of applications, ranging from material science to geophysics and planetary science. EOS measurements along a shocked state (Hugoniot) are particularly useful for developing and benchmarking models because they yield data from well-defined thermodynamic states. Impedance-matching (IM) techniques, which are most often used to determine the shock state at multi-megabar pressure, rely on the accuracy of the impedance matching standard. We present new Hugoniot measurements of LiF from 15-30 Mbar, using the recently refined quartz standard, extrapolated to the pressures we achieved in our experiments. We also present the concept and initial experimental results for establishing diamond as an absolute (reference-free) impedance-matching standard up to tens of megabars, using symmetric impact of laser-accelerated diamond flyer plates on diamond windows, and our plans for extending the technique to perform higher-accuracy EOS measurement on opaque materials. [Preview Abstract] |
Monday, June 15, 2015 12:15PM - 12:30PM |
C2.00005: Probing the Release of Shocked Material Danae Polsin, Thomas Boehly, Steven Ivancic, Michelle Gregor, Chad McCoy, Phillip Nilson, Dayne Fratanduono, Peter Celliers The behavior of shocked material as it releases to lower pressures is important for equation of state experiments and inertial confinement fusion research. We present results of experiments that used a 10-ps, 266-nm probe beam to image the release plumes of various target material shocked to multi-megabar pressures by the OMEGA-EP laser. Simultaneous VISAR measurement provide the initial shocked state from which these material release. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Monday, June 15, 2015 12:30PM - 12:45PM |
C2.00006: Measuring preheat in laser-drive aluminum using VISAR Hua Shu In this paper, we systematically study preheating in laser-direct-drive shocks by using a velocity interferometer system for any reflector (VISAR). Using the VISAR we measured free surface velocity histories of Al samples over time, 10--70 $\mu $m thick, driven directly by a laser at different frequencies (2$\omega$ - 3$\omega )$. Analyzing our experimental results, we concluded that the dominant preheating source was X-ray radiation. We also discussed how preheating affected the material initial density and the measurement of Hugoniot data for high-Z materials (such as Au) using impedance matching. To reduce preheating, we proposed and tested three kinds of targets. [Preview Abstract] |
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