Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

We present simplified expressions for the dynamic structure factor, or form factor S(k, omega), which is the quantity describing the inelastic x-ray scattering cross section from a dense plasma or a simple liquid. Our results, based on the random phase approximation (RPA) for the treatment on the charged particle coupling, are compared with analytical expressions for the free electron dynamic structure factor which include effects of strong coupling in both classical and degenerate plasmas. We will show that these modifications introduce minimal corrections to the RPA for typical conditions found in recent non-collective x-ray Thomson scattering experiment on solid density isochorically heated laser plasmas. On the other hand, strong collective scattering may exhibit significant deviations from the RPA. The results shown in this work can be applied to interpreting future x-ray scattering in warm dense plasmas occurring in inertial confinement fusion experiments or for the modelling of solid density matter found in the interior of planets.

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.