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Title: Ignition and burn in perturbed inertial confinement fusion hotspots
Author: Tong, Jon King
ISNI:       0000 0004 9350 7459
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2019
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This work explores how perturbations affect the performance of inertial confinement fusion hotspots through the inhibition of ignition and the effect on burn propagation post-ignition. To model this, a 3D Monte-Carlo charged particle transport module has been developed for the radiation-magnetohydrodynamics code Chimera. The behaviour of the hotspot and the hotspot power balance in three alpha-heating regimes - self-heating, robust ignition and propagating burn - are explored in 1D through hydrodynamic scaling with capsule size and laser energy, demonstrating strong alpha-heating effects on the hydrodynamic evolution. The hotspot’s definition affects calculated hotspot parameters, particularly in weak alpha-heating regimes where the boundary between the hotspot and the shell is less well-defined. The impact of perturbations on the hotspot was explored using idealised spike and bubble perturbations. Less efficient PdV heating of the hotspot reduces the strength of the alpha-heating bootstrap. The spike significantly increased heat flow out of the hotspot from thermal conduction and alpha-heating; due to larger temperature gradients and surface area around the spike, and the closer proximity of cold, dense material to the primary fusion regions respectively. The bubble’s effect on the hotspot power losses was minimal, but re-expansion into the bubble reduced confinement and truncated burn. 3D implosions based on National Ignition Facility Highfoot and High-Density Carbon (HDC) designs were perturbed using short-wavelength multi-mode and long-wavelength radiation asymmetry perturbations and scaled with capsule size and laser energy. The multi-mode yield increased faster with scale factor due to more synchronous P dV compression producing higher temperatures, and therefore stronger alpha-heating bootstrapping. Significant yield degradation for the Highfoot design resulted in only modest improvements in yield from scaling, whereas the less degraded HDC design demonstrated non-linear yield scaling. Perturbed implosions in the propagating burn regime exhibited fire-polishing due to thermal conduction and alpha-heating, in addition to "aneurysm"-like loss of confinement.
Supervisor: Chittenden, Jeremy Sponsor: Atomic Weapons Establishment
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available