Pre-magnetisation of inertial confinement fusion implosions on the National Ignition Facility has the potential to raise current high-performing targets into the ignition regime [Perkins et al. "The potential of imposed magnetic fields for enhancing ignition probability and fusion energy yield in indirect-drive inertial confinement fusion," Phys. Plasmas 24, 062708 (2017)]. A key concern with this method is that the application of a magnetic field inherently increases asymmetry. This paper uses 3-D extended-magnetohydrodynamics Gorgon simulations to investigate how thermal conduction suppression, the Lorentz force, and a-particle magnetisation affect three hot-spot perturbation scenarios: a cold fuel spike, a time-dependent radiation drive asymmetry, and a multi-mode perturbation. For moderate magnetisations (B 0 ¼ 5 T), the single spike penetrates deeper into the hot-spot, as thermal ablative stabilisation is reduced. However, at higher magnetisations (B 0 ¼ 50 T), magnetic tension acts to stabilise the spike. While magnetisation of a-particle orbits increases the peak hot-spot temperature, no impact on the perturbation penetration depth is observed. The P4-dominated radiation drive asymmetry demonstrates the anisotropic nature of the thermal ablative stabilisation modifications, with perturbations perpendicular to the magnetic field penetrating deeper and perturbations parallel to the field being preferentially stabilised by increased heat-flows. Moderate magnetisations also increase the prevalence of high modes, while magnetic tension reduces vorticity at the hot-spot edge for larger magnetisations. For a simulated high-foot experiment, the yield doubles through the application of a 50 T magnetic field-an amplification which is expected to be larger for higher-performing configurations.

We present 3D radiation-hydrodynamics simulations of indirect-drive inertial confinement fusion experiments performed at the National Ignition Facility (NIF). The simulations are carried out on two shots from different NIF experimental campaigns: N130927 from the high foot series and N161023 from the ongoing high density carbon series. Applying representative perturbation sources from each implosion, synthetic nuclear diagnostics are used to post-process the simulations to infer the stagnation parameters. The underlying physical mechanisms that produce the observed signatures are then explored. We find that the radiation asymmetry and tent scar perturbations extend the nuclear burn width; this is due to an asymmetric stagnation of the shell that causes the delivery of mechanical PdV work to be extended compared to an idealised implosion. Radiation asymmetries seed directed flow patterns that can result in a difference in the inferred ion temperature ranging from 80 eV to 230 eV depending on the magnitude and orientation of the asymmetry considered in the simulation; the tent scar shows no such temperature difference. For N130927, radiation asymmetries dominate the yield and inferred ion temperature and the tent scar has the largest influence on the neutron burnwidth. For N161023, the fill tube decreases the burn width by injecting mix into the hot spot, leading to a smaller hot spot and increased energy losses. Both the radiation asymmetry and the fill tube generate directed flows that lead to an anisotropic inferred temperature distribution. Through existing and novel synthetic neutron imaging techniques, we can observe the hot spot and shell shape to a degree that accurately captures the perturbations present.

We present simulations of ignition and burn based on the Highfoot and High-Density Carbon indirect drive designs of the National Ignition Facility for three regimes of alpha-heating -self-heating, robust ignition and propagating burn -exploring hotspot power balance, perturbations and hydrodynamic scaling. A Monte-Carlo Particle-in-Cell charged particle transport package for the radiation-magnetohydrodynamics code Chimera was developed for this purpose, using a linked-list type data structure.The hotspot power balance between alpha-heating, electron thermal conduction and radiation was investigated in 1D for the three burn regimes. The impact of perturbations on this power balance is explored in 3D using a single Rayleigh-Taylor spike. Heat flow into the perturbation from thermal conduction and alpha-heating increases by factors of ∼2 − 3, due to sharper temperature gradients and increased proximity of the cold, dense material to the main fusion regions respectively. The radiative contribution remains largely unaffected in magnitude.Hydrodynamic scaling with capsule size and laser energy of different perturbation scenarios (a short-wavelength multi-mode and a low-mode radiation asymmetry) is explored in 3D, demonstrating the differing hydrodynamic evolution of the three alpha-heating regimes. The multi-mode yield increases faster with scale factor due to more synchronous P dV compression producing higher temperatures and densities, and therefore stronger bootstrapping of alphaheating. Effects on the hydrodynamic evolution are more prominent for stronger alpha-heating regimes, and include: reduced perturbation growth due to ablation from both fire-polishing and stronger thermal conduction; sharper temperature and density gradients at the boundary; and increased hotspot pressures which further compress the shell, increase hotspot size and induce faster re-expansion. The faster expansion into regions of weak confinement is more prominent for stronger alpha-heating regimes, and can result in loss of confinement.

The solar wind impinging on the dayside magnetosphere compresses the magnetospheric field lines and enhances the equatorial magnetic field magnitude (Mead & Beard, 1964;Northrop, 1966; Roederer, 1970). Close to the magnetopause, the equatorial field strength can consequently exceed the field strength at a given particle's mirror point which causes drift orbits in the outer magnetosphere to bifurcate as particles become temporarily trapped within high-latitude pockets of magnetic field minima. Entering and exiting these non-dipolar regions has been associated with non-conservation of the particles second adiabatic invariant (Antonova et al., 2003) which, combined with conservation of the first adiabatic invariant, leads to radial transport across the magnetic field. It is therefore necessary to account for this phenomenon to understand and predict the dynamics of the outer radiation belt and its source populations.The early works of Shabansky and Antonova (1968) and Shabansky (1972) identified the phenomenon of drift orbit bifurcations (DOBs) and described how this can affect particles on both open and closed field lines. Early observations of enhanced energetic proton and electron fluxes in the high-latitude part of the trapping region were identified by several early satellite missions (

A suite of synthetic nuclear diagnostics has been developed to post-process radiation hydrodynamics simulations performed with the code Chimera. These provide experimental observables based on simulated capsule properties and are used to assess alternative experimental and data analysis techniques. These diagnostics include neutron spectroscopy, primary and scattered neutron imaging, neutron activation, γ-ray time histories and carbon γ-ray imaging. Novel features of the neutron spectrum have been analysed to infer plasma parameters. The nT and nD backscatter edges have been shown to provide a shell velocity measurement. Areal density asymmetries created by low mode perturbations have been inferred from the slope of the downscatter spectrum down to 10 MeV. Neutron activation diagnostics showed significant aliasing of high mode areal density asymmetries when observing a capsule implosion with 3D multimode perturbations applied. Carbon γ-ray imaging could be used to image the ablator at high convergence ratio. Time histories of both the fusion and carbon γ signals showed a greater time difference between peak intensities for the perturbed case when compared to a symmetric simulation.