Hannah Poole

University of Oxford

Hannah is currently a PhD Graduate student at the University of Oxford working with Professor Gianluca Gregori within the Atomic and Laser Physics department. Her research, which focuses on the development of advanced diagnostics for high energy density plasmas, involves close collaboration with the Laboratory of Laser Energetics (LLE) at the University of Rochester. Hannah has worked as a principal investigator at LLE’s OMEGA laser facility, conducting experiments ranging from generating and diagnosing turbulent plasmas to measuring the liquid structure of warm dense matter. Her primary interest is the use of scattering techniques, such as optical Thomson scattering and X-ray diffraction, to understand the complexities of matter under extreme conditions. This extends to investigating the feasibility of using X-ray scattering on inertial confinement fusion implosions. Prior to embarking on her PhD research, Hannah worked as a Graduate Scientist at First Light Fusion. There her work focused on developing new techniques to achieve fusion, operating a two-stage light gas gun and updating and running an X-pinch to provide complimentary X-ray radiography to experiments.

Abstract:
Using X-ray Thomson scattering to diagnose the plasma conditions of DT cryogenic implosions

In the pursuit of carbon-neutral energy, a critical milestone has been achieved: fusion ignition via inertial confinement fusion (ICF) demonstrated at the National Ignition Facility (NIF) [1].The success of the ICF campaign hinges on carefully designed capsules capable of compressing the deuterium-tritium (DT) fuel to temperatures and electron densities on the order of 1 keV and1026 cm−3, respectively. The development of these capsules requires accurate hydrodynamic simulations with detailed knowledge of the materials’ equation of state (EOS) under such extreme conditions [2]. However, uncertainty in the material’s EOS persists due to the need for quantum mechanical treatment of the degenerate electrons, moderate strongly coupled ions, and many-particle correlations. To overcome this challenge, experimental validation of the physical properties within these dense plasmas is crucial. Over the past few decades, there has therefore been a push to develop new diagnostics capable of benchmarking and refining these models. One such technique is multi-keV spectrally resolved X-ray Thomson scattering (XRTS) [3].

Here I present a feasibility study that explores the potential of spatially-integrated, spectrally-resolved XRTS to diagnose the temperature, density, and ionisation of compressed DT shells in cryogenic DT implosions. The synthetic scattering spectra were generated using 1-D implosion simulations from the LILAC code [4] that were post processed with the X-ray Scattering (XRS) model which is incorporated within SPECT3D [5]. To extract the most probable plasma conditions, the multi-parameter space is explored by employing Bayesian inference, via Markov-Chain Monte Carlo(MCMC). The scattering spectra from two extreme adiabat capsule conditions were analysed and the plasma properties within both compressed DT shells were effectively resolved. To incorporate the realistic inhomogeneity within the compressed shell, this analysis is extended to 2-D simulations of the cryogenic implosions. The 2-D simulations are able to capture some of the hydrodynamic instabilities that can severely affect the overall ICF target performance. This work highlights the promising capabilities of XRTS as a diagnostic tool for ICF research.

This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award No. DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority.

References:
[1] Abu-Shawareb et al., Physical Review Letters, 129, 075001 (2022).
[2] Gaffney et al., High Energy Density Physics 28, 7 (2018)
[3] Poole et al., Phys. Plasmas, 29, 072703 (2022)
[4] Delettrez et al., Phys. Rev. A, 36, 3926 (1987)
[5] Golovkin et al., High Energy Density Phys. 9, 510 (2013)