Modeling of Magnetized-ICF Experiments at the NIF

Conventional inertial confinement fusion (ICF) at the National Ignition Facility (NIF) uses a high-energy laser to drive a cylindrical hohlraum, producing an x-ray bath which ablates a high-density-carbon (HDC) shell; this spherically implodes the fusion fuel to sufficient conditions for laboratory fusion gain and ignition. One approach proposed to more robustly ignite the capsule and reach higher fusion yield is to apply an axial magnetic field (of order 10-50 T) to the implosion, which is compressed in the capsule to magnetize the electrons. Magnetization of the central hot-spot suppresses thermal losses, shown in NIF experiments with a 26 T applied field to increase the ion temperature by 40% and the fusion yield by 3x [J.D. Moody et al., Phys. Rev. Lett. 2022]. These magnetized-ICF NIF experiments, which use a D­₂ gas-filled capsule with HDC ablator (called a Symcap), have measured yields and radial temperature profile shapes inconsistent with standard post-shot radiation-magneto-hydrodynamics simulations and analytic hot-spot models. In this presentation, we describe a new hot-spot model for magnetized-ICF which explains that the change in temperature profile shape is a consequence of anisotropic and inhomogeneous magnetized thermal conduction. This model is contrasted against the NIF experiments and radiation-hydrodynamics simulations, suggesting that experimental neutron yields may be largely degraded by an asymmetric x-ray drive and high-Z material mixing into the hot-spot.