Professor Justin Wark: Publications

Measurements of the XUV mass absorption coefficient of an overdense liquid metal

Journal of Physics B Atomic Molecular and Optical Physics 34:17 (2001) L565-L570

Authors:

E Wolfrum, AM Allen, I Al'Miev, TW Barbee, PDS Burnett, A Djaoui, C Iglesias, DH Kalantar, RW Lee, R Keenan, MH Key, CLS Lewis, AM Machacek, BA Remington, SJ Rose, R O'Rourke, JS Wark

Abstract:

The increase in the XUV mass absorption coefficient of liquid aluminium, produced by high-power-laser shock-compression, is measured using XUV laser radiography. At a photon energy of 63 eV a change in the mass absorption coefficient by up to a factor of ∼2.2 is determined at densities close to twice that of solid and electron temperatures of the order of 1 eV. Comparison with hydrodynamic simulations indicate that the absorption coefficient scales with density as ρ^1.3±0.2.

Detailed simulations of sonoluminescence spectra

Journal of Physics B Atomic Molecular and Optical Physics 34:16 (2001) L511-L518

Authors:

PDS Burnett, DM Chambers, D Heading, A Machacek, M Schnittker, WC Moss, P Young, S Rose, RW Lee, JS Wark

Abstract:

We present detailed simulations of the optical spectra emitted from an argon plasma whose conditions correspond to those thought to prevail within sonoluminescing bubbles. The model incorporates detailed atomic physics based on atomic data from the Opacity Project database, and includes bound-bound, bound-free and free-free transitions. Line broadening is treated using the modified semi-empirical method. The spectral model is used as a postprocessor of hydrodynamic simulations. While finding excellent agreement with the shape of experimental spectra, we calculate an intensity that is a factor of 100 greater than that in experiment. We also predict that whilst the majority of the optical emission corresponds to bound-free transitions, there remains the possibility of observing broad line emission in both the UV and IR regions of the spectrum.

Plasma-based studies on 4th generation light sources

AIP Publishing 581:1 (2001) 45-58

Authors:

RW Lee, HA Baldis, RC Cauble, OL Landen, JS Wark, A Ng, SJ Rose, C Lewis, D Riley, J-C Gauthier, P Audebert

High-speed optical and x-ray methods for evaluating laser-generated shock waves in materials and the corresponding dynamic material response

Proceedings of SPIE--the International Society for Optical Engineering SPIE, the international society for optics and photonics 4183 (2001) 556-565

Authors:

Dennis L Paisley, DC Swift, AC Forsman, George A Kyrala, RP Johnson, Justin S Wark, AM Allen, A Loveridge, Roger A Kopp

Probing impulsive strain propagation with X-ray pulses.

Phys Rev Lett 86:14 (2001) 3072-3075

Authors:

DA Reis, MF DeCamp, PH Bucksbaum, R Clarke, E Dufresne, M Hertlein, R Merlin, R Falcone, H Kapteyn, MM Murnane, J Larsson, T Missalla, JS Wark

Abstract:

Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation of a coherent acoustic pulse generated by ultrafast laser excitation. The surface and bulk components of the strain could be simultaneously measured due to the large x-ray penetration depth. Comparison of the experimental data with dynamical diffraction simulations suggests that the conventional model for impulsively generated strain underestimates the partitioning of energy into coherent modes.

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