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Title: Radiation-hydrodynamic simulations of the impact of instabilities and asymmetries on inertial confinement fusion
Author: McGlinchey, Kristopher
ISNI:       0000 0004 6496 5098
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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In recent years, there has been significant progress towards achieving ignition from controlled thermonuclear fusion. Recent experiments at the National Ignition Facility have come close to achieving this, but the performance of experiments were compromised by perturbations affecting the implosion's symmetry. This thesis presents the implementation of a multigroup radiation transport algorithm into an existing hydrodynamics code, Chimera, and its application to Inertial Confinement Fusion (ICF) to investigate these perturbations. An idealised 1-dimensional implosion was simulated to explore how the shock timing and final drive affected the stagnation conditions of a capsule's implosion. The timing of the shocks played a critical role in controlling the adiabat of the implosion, with the initial shock being most important by setting the mass that enters the forming hotspot. Multidimensional simulations then evaluated how perturbations affected an implosion's performance. Hydrodynamic instabilities from harmonic and natural roughness seeds were imaged, and the requirements of a next generation imaging system derived. It was found that a new system will require a 10keV backlighter at a < 10 micron spatial and a < 20 ps temporal resolution. The radiation from the forming hot spot played an important role in fire polishing incoming instabilities, leading to a denser, cooler hot spot which lowered the yield by 50%. Large-scale asymmetries caused by radiation asymmetries prematurely ended the hotspot confinement due to imploding lobes of cold dense material, reducing the yield by 50%. Neutron detectors found a 10% variation in inferred ion temperature due to the residual flows induced. The tent scar had a small influence on the performance of a capsule, being confined largely to the surface. The combination of the tent and radiation asymmetries produced a highly perturbed implosion that performed better than the radiation asymmetry, but worse than the tent.
Supervisor: Chittenden, Jeremy Sponsor: Engineering and Physical Sciences Research Council ; Atomic Weapons Establishment
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral