Barlow, Duncan (2021) Inertial confinement fusion : energy transport and shock ignition. PhD thesis, University of Warwick.

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Abstract

From hydrodynamics alone, shock ignition (SI) achieves the largest fusion energy output per energy input, using current inertial confinement fusion (ICF) facilities (Betti et al. [2007]). This gain margin is critical if ICF is to be used for energy generation. The National Ignition Facility (NIF, Miller et al. [2004]) is the world's largest laser facility, with a 1:8MJ laser energy. It has not yet achieved ignition and although not designed to work in the same direct drive configuration as SI there are simulations showing an alignment called polar direct drive (PDD) could be used to ignite an implosion (Anderson et al. [2013]). Strong shock experiments intended to investigate the fundamental principles of SI have shown that hot electrons generated from laser plasma instabilities (LPI) can degrade shock creation (Theobald et al. [2012]; Nora et al. [2015]), but LPI are a phenomenon that do not scale (Rosenberg et al. [2018]) and so further investigation is required at SI relevant plasma conditions.

SI simulations require accurate hydrodynamics, a laser driver, energy transport and a kinetic model of hot electrons. Odin uses arbitrary Lagrangian-Eulerian (ALE) methods to accurately capture the hydrodynamics.

This thesis introduces a diffusion operator to model energy transport, as well as, a simplified laser driver and a full 3D Monte-Carlo scattering model of hot electrons. This thesis presents Odin's use in support of two of the first experiments that characterize the hot electron populations at SI intensities and plasma conditions. The NIF strong shock solid target (SSS) experiment uses PDD to observe a hot electron population with a temperature 56keV and a cumulative energy of 35kJ (an instantaneous energy fraction at ncrit=4 of 0:2) for a SI laser pulse. The Omega laser (Laboratory for Laser Energetics, Boehly et al. [1997]), with total energy < 40kJ, was used in a novel geometry to achieve SI plasma conditions and laser intensities which resulted in a hot electron population with an observed 40keV temperature and energy fraction 0:025 at ncrit=4. The disparity in observed conversion fractions is an open problem for SI requiring more experimental investigation. Simulation for this thesis demonstrates that the NIF SSS population would lead to preheat near the maximum tolerable limit and require mitigation strategies (Rosenberg et al. [2018]) while the Omega conical target would cause only a minor deleterious effect.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Laser plasmas, Laser-plasma interactions, Plasma instabilities, Hydrodynamics
Official Date:	2021
Dates:	Date Event 2021 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Arber, T. D.
Sponsors:	Engineering and Physical Sciences Research Council ; Atomic Weapons Establishment (Great Britain) ; Collaborative Computational Project for Plasma Physics
Format of File:	pdf
Extent:	xxii, 124 leaves : illustrations
Language:	eng

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