Development of advanced diagnostics for high energy density plasmas

Thesis

The field of high-energy density physics explores the properties of matter at extreme conditions, crucial for both astrophysical insights and in the pursuit of fusion energy. However, the complexity of competing forces influencing material behaviour within this regime necessitates experimental validation of theoretical models. One powerful experimental technique capable of probing the equation of state is Thomson scattering.

This thesis investigates the use of Thomson scattering across diverse experimental setups in the high-energy density regime. Bayesian inference techniques are employed for inferring thermodynamic conditions from experimental observations. Firstly, the feasibility of using Thomson scattering to discern in-flight conditions within inertial confinement fusion implosions is presented. Spatially-integrated synthetic scattering spectra are generated to infer information about the inhomogeneous compressed shell under various adiabat capsule conditions. Secondly, a multi-messenger platform using velocimetry and in situ angularly and spectrally resolved X-ray scattering is fielded to measure the thermodynamic conditions and ion structure factor of warm dense matter silicon. The observed liquid scattering is used to infer the pressure, density and temperature state without relying on equation of state models. In addition, the measurements are sufficient to distinguish between and rule out some ion screening models. Finally, temporally-resolved optical Thomson scattering is utilised to characterise turbulent plasmas generated at two high-power laser facilities. These platforms aim to understand magnetic-field generation and amplification to reconcile observations in the universe. Perturbative heating effects induced by the Thomson probe are observed on one platform, affecting the inferred conditions and influencing the mechanisms driving magnetic field amplification. The results from these experiments demonstrate the power of Thomson scattering to benchmark theoretical modelling, in particular when used in conjunction with alternate in situ diagnostics.

Authors: Poole, H

• DOI: 10.5287/ora-vmogdevnp
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Thomson scattering; inertial confinement fusion; high-energy density physics
• Subjects: Inertial confinement fusion; Thomson scattering; High-density plasmas