Extended magneto-hydrodynamic effects in indirect-drive inertial confinement fusion experiments
File(s)
Author(s)
Walsh, Christopher
Type
Thesis
Abstract
A 3-D extended-magnetohydodynamic code has been developed and applied to studying inertial confi nement fusion (ICF) implosions. The research is split into two areas: estimating the effect of magnetic fields spontaneously generated during standard experiments; understanding how externally applied magnetic fi elds could be used to impact
fusion performance. Self-generated magnetic fields are estimated to reach 10,000T in the fuel of implosions on the National Ignition Facility (NIF). A combination of high and low modes are found to result in the greatest magnetisations, with the high-modes generating the large fields and the low-modes pushing these fields deep into the hot-spot core. Thermal conductivities are reduces to as low as 10% of the value used if magnetic fields are ignored, greatly moticvating the widespread use of magnetohydrodynamic codes for the design and post-shot analysis of ICF experiments. Intricate interplay between magnetic transport terms is also found, with both the Nernst term and Righi-Leduc heat-flow playing crucial roles. Nernst moves the magnetic fields towards the hot-spot edge, lowering magnetisations, while Righi-Leduc greatly reduces the thermal ablative stabilisation of the perturbations. Overall, hot-spot energy containment is found to be largely unchanged by the magnetic fields for the perturbation scenarious considered, although the hot-spot is more deformed. Previous work used 2-D simulations to predict that application of an external magnetic field would bring current high-performing NIF experiments into the ignition regime [1]. The enclosed research builds in this by investigating 3-D extended-MHD behaviour with realistic perturbation sources. Particular focus is given to the impact of magnetic fields on implosion symmetry. Thermal ablative stabilisation modifications dependent on the perturbation type are observed, as well as vortex stabilisation by magnetic tension and the first estimates for the consequences of Righi-Leduc, cross-gradient-Nernst and Biermann Battery terms. Validation of the model by comparison with direct-drive experiments [2,3] is also presented.
fusion performance. Self-generated magnetic fields are estimated to reach 10,000T in the fuel of implosions on the National Ignition Facility (NIF). A combination of high and low modes are found to result in the greatest magnetisations, with the high-modes generating the large fields and the low-modes pushing these fields deep into the hot-spot core. Thermal conductivities are reduces to as low as 10% of the value used if magnetic fields are ignored, greatly moticvating the widespread use of magnetohydrodynamic codes for the design and post-shot analysis of ICF experiments. Intricate interplay between magnetic transport terms is also found, with both the Nernst term and Righi-Leduc heat-flow playing crucial roles. Nernst moves the magnetic fields towards the hot-spot edge, lowering magnetisations, while Righi-Leduc greatly reduces the thermal ablative stabilisation of the perturbations. Overall, hot-spot energy containment is found to be largely unchanged by the magnetic fields for the perturbation scenarious considered, although the hot-spot is more deformed. Previous work used 2-D simulations to predict that application of an external magnetic field would bring current high-performing NIF experiments into the ignition regime [1]. The enclosed research builds in this by investigating 3-D extended-MHD behaviour with realistic perturbation sources. Particular focus is given to the impact of magnetic fields on implosion symmetry. Thermal ablative stabilisation modifications dependent on the perturbation type are observed, as well as vortex stabilisation by magnetic tension and the first estimates for the consequences of Righi-Leduc, cross-gradient-Nernst and Biermann Battery terms. Validation of the model by comparison with direct-drive experiments [2,3] is also presented.
Version
Open Access
Date Issued
2018-04
Date Awarded
2018-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Chittenden, Jeremy
Sponsor
CIFS
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)