Professor Justin Wark

Abstract:

The temporal coherence properties of the X-ray pulse from a Free Electron Laser (FEL) will be altered during the process of dynamical diffraction from a perfect crystal. We present simulations of this process based on time-dependent dynamical diffraction theory. In addition, we present simulations of the diffraction of chirped X-ray pulses, demonstrating methods of pulse recompression by use of strained crystals.

Abstract:

The present book is a teaching text designed to introduce the fundamentals of thesubject of statistical mechanics.

Abstract:

Experiments have been developed using high powered laser facilities to study the response of materials in the solid state under extreme pressures and strain rates. Details of the target and drive development required for solid-state experiments and results from two separate experiments are presented. In the first, thin foils were compressed to a peak pressure of 180 GPa and accelerated. A pre-imposed modulation at the embedded Rayleigh-Taylor unstable interface was observed to grow. The growth rates were fluid-like at early time, but suppressed at later time. This result is suggestive of the theory of localized heating in shear bands, followed by conduction of the heat into the bulk material, allowing for recovery of the bulk material strength. In the second experiment, the response of Si was studied by dynamic x-ray diffraction. The crystal was observed to respond with uni-axial compression at a peak pressure 11.5-13.5 GPa. (C) 2000 American Institute of Physics. [S1070-664X(00)94505-1].