Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

A study on the x-ray scattering from solid density plasmas was presented. By applying spectrally resolved multi-keV scattering, the measurements of the microscopic properties of dense matter were demonstrated. The scattering spectra from solid density beryllium demonstrated the inelastic Compton-down shifted feature that is spectrally broadened when heating the solid density plasmas isochorically and homogeneously to temperatures of several times the Fermi energy.

Abstract:

We present the first spectrally resolved x-ray scattering measurements from solid-density plasmas. The scattering spectra show the broadened Compton down-shifted feature allowing us to determine the electron temperature and density with high accuracy. In the low temperature limit, our data indicate that the ionization balance reflects the electrons in the conduction band consistent with calculations that include quantum mechanical corrections to the interaction potential.

Abstract:

An innovative target design was used to perform the first studies of the propagation of very high current laser-produced electron beams in a regime relevant to the fast ignition scheme. Although it appears that (Weibel) and two-stream instabilities in plasmas where the beam density was close to the background plasma density-use of cone-guided schemes for fast ignition may be able to reduce the propagation distance of the electron beam and reduce the effect of these instabilities.

Abstract:

The process of fast ignition (FI) using various laser systems was analyzed. A Petta watt (PW) laser system was used to study the basic elements relevant to FI, which could also be injected to a compressed core. Using a spherical target inserted with a Au cone guide for the PW laser pulse, an imploded core was heated upto 1 keV resulting in neutron increase which is 1000 times more than that without heating pulse.

Abstract:

Laser-based shock experiments have been conducted in thin Si and Cu crystals at pressures above the published Hugoniot Elastic Limit (HEL) for these materials. In situ x-ray diffraction has been used to directly measure the response of the shocked lattice during shock loading. Static film and x-ray streak cameras recorded x rays diffracted from lattice planes both parallel and perpendicular to the shock direction. In addition, experiments were conducted using a wide-angle detector to record x rays diffracted from multiple lattice planes simultaneously. These data showed uniaxial compression of Si (100) along the shock direction and three-dimensional compression of Cu (100). In the case of the Si diffraction, there was a multiple wave structure observed. This is evaluated to determine whether there is a phase transition occurring on the time scale of the experiments, or the HEL is much higher than previously reported. Results of the measurements are presented. (C) 2003 American Institute of Physics.