Professor Justin Wark: Publications

X-ray laser peels and cores atoms

Nature Springer Nature 466:7302 (2010) 35-36

Electronic structure of an XUV photogenerated solid-density aluminum plasma.

Phys Rev Lett 104:22 (2010) 225001

Authors:

SM Vinko, U Zastrau, S Mazevet, J Andreasson, S Bajt, T Burian, J Chalupsky, HN Chapman, J Cihelka, D Doria, T Döppner, S Düsterer, T Dzelzainis, RR Fäustlin, C Fortmann, E Förster, E Galtier, SH Glenzer, S Göde, G Gregori, J Hajdu, V Hajkova, PA Heimann, R Irsig, L Juha, M Jurek, J Krzywinski, T Laarmann, HJ Lee, RW Lee, B Li, K-H Meiwes-Broer, JP Mithen, B Nagler, AJ Nelson, A Przystawik, R Redmer, D Riley, F Rosmej, R Sobierajski, F Tavella, R Thiele, J Tiggesbäumker, S Toleikis, T Tschentscher, L Vysin, TJ Whitcher, S White, JS Wark

Abstract:

By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have created highly excited exotic states of matter in solid-density aluminum samples. The XUV intensity is sufficiently high to excite an inner-shell electron from a large fraction of the atoms in the focal region. We show that soft-x-ray emission spectroscopy measurements reveal the electronic temperature and density of this highly excited system immediately after the excitation pulse, with detailed calculations of the electronic structure, based on finite-temperature density functional theory, in good agreement with the experimental results.

The strength of single crystal copper under uniaxial shock compression at 100 GPa.

J Phys Condens Matter 22:6 (2010) 065404

Authors:

WJ Murphy, A Higginbotham, G Kimminau, B Barbrel, EM Bringa, J Hawreliak, R Kodama, M Koenig, W McBarron, MA Meyers, B Nagler, N Ozaki, N Park, B Remington, S Rothman, SM Vinko, T Whitcher, JS Wark

Abstract:

In situ x-ray diffraction has been used to measure the shear strain (and thus strength) of single crystal copper shocked to 100 GPa pressures at strain rates over two orders of magnitude higher than those achieved previously. For shocks in the [001] direction there is a significant associated shear strain, while shocks in the [111] direction give negligible shear strain. We infer, using molecular dynamics simulations and VISAR (standing for 'velocity interferometer system for any reflector') measurements, that the strength of the material increases dramatically (to approximately 1 GPa) for these extreme strain rates.

Measurement of the dynamic response of compressed hydrogen by inelastic X-ray scattering

Journal of Physics Conference Series 244:PART 4 (2010)

Authors:

K Falk, AP Jephcoat, BJB Crowley, RR Fäustlin, C Fortmann, FY Khattak, AK Kleppe, D Riley, S Toleikis, J Wark, H Wilhelm, G Gregori

Abstract:

Measurement of the dynamic properties of hydrogen and helium under extreme pressures is a key to understanding the physics of planetary interiors. The inelastic scattering signal from statically compressed hydrogen inside diamond anvil cells at 2.8 GPa and 6.4 GPa was measured at the Diamond Light Source synchrotron facility in the UK. The first direct measurement of the local field correction to the Coulomb interactions in degenerate plasmas was obtained from spectral shifts in the scattering data and compared to predictions by the Utsumi-Ichimaru theory for degenerate electron liquids. © 2010 IOP Publishing Ltd.

Plasma emission spectroscopy of solids irradiated by intense XUV pulses from a free electron laser

High Energy Density Physics 6:1 (2010) 109-112

Authors:

TWJ Dzelzainis, J Chalupsky, M Fajardo, R Fäustlin, PA Heimann, V Hajkova, L Juha, M Jurek, FY Khattak, M Kozlova, J Krzywinski, RW Lee, B Nagler, AJ Nelson, FB Rosmej, R Soberierski, S Toleikis, T Tschentscher, SM Vinko, JS Wark, T Whitcher, D Riley

Abstract:

The FLASH XUV-free electron laser has been used to irradiate solid samples at intensities of the order 1016 W cm-2 at a wavelength of 13.5 nm. The subsequent time integrated XUV emission was observed with a grating spectrometer. The electron temperature inferred from plasma line ratios was in the range 5-8 eV with electron density in the range 1021-1022 cm-3. These results are consistent with the saturation of absorption through bleaching of the L-edge by intense photo-absorption reported in an earlier publication. © 2009 Elsevier B.V. All rights reserved.

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