Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

A scheme for artificially collimating fast-electron beams produced in high intensity (>1019Wcm-2) laser-solid interactions is proposed. The scheme uses a laser pulse at the relativistic threshold (1018Wcm-2) that precedes the high intensity pulse to pregenerate a collimating magnetic field. This concept is supported by analytical calculations and numerical calculations performed using a novel hybrid-Vlasov-Fokker-Planck code called LEDA. This scheme may be highly useful for fast ignition inertial confinement fusion. © 2008 The American Physical Society.

Abstract:

Metal foil targets were irradiated with 1μm wavelength (λ) laser pulses of 5 ps duration and focused intensities (I) of up to 4×1019Wcm-2, giving values of both Iλ2 and pulse duration comparable to those required for fast ignition inertial fusion. The divergence of the electrons accelerated into the target was determined from spatially resolved measurements of x-ray Kα emission and from transverse probing of the plasma formed on the back of the foils. Comparison of the divergence with other published data shows that it increases with Iλ2 and is independent of pulse duration. Two-dimensional particle-in-cell simulations reproduce these results, indicating that it is a fundamental property of the laser-plasma interaction. © 2008 The American Physical Society.

Abstract:

The understanding of energy transport by fast electrons generated in intense laser-plasma interactions is crucial for the successful applications of petawatt-class laser systems. I will describe recent experiments that have investigated these properties in detail. © 2008 OSA.

Abstract:

One of the grand challenges of contemporary physics is understanding strongly interacting quantum systems comprising such diverse examples as ultracold atoms in traps, electrons in high-temperature superconductors and nuclear matter. Warm dense matter, defined by temperatures of a few electron volts and densities comparable with solids, is a complex state of such interacting matter. Moreover, the study of warm dense matter states has practical applications for controlled thermonuclear fusion, where it is encountered during the implosion phase, and it also represents laboratory analogues of astrophysical environments found in the core of planets and the crusts of old stars. Here we demonstrate how warm dense matter states can be diagnosed and structural properties can be obtained by inelastic X-ray scattering measurements on a compressed lithium sample. Combining experiments and ab initio simulations enables us to determine its microscopic state and to evaluate more approximate theoretical models for the ionic structure. © 2008 Macmillan Publishers Limited. All rights reserved.