Simple models for mode-1 perturbed volume ignition fuel collapse

First Light Fusion are a privately funded company developing novel IFE target designs driven by strong shocks. These targets consist of a spherical fuel region embedded within an ‘amplifier’. The amplifier is a proprietary hydrodynamic system which converts non-spherical input to a spherically converging output and amplifies the pressure through spatial and temporal convergence of the shock.

A number of random degrading processes lead to a mode-1 perturbed fuel collapse in the amplifier system. This is investigated using a perturbed 2D axisymmetric simulation approach based on the Revolver concept [Molvig et al. 2016]. A scan varying the fuel radius, pusher thickness, fuel density and pusher kinetic energy is used to generate a statistical fit between the unperturbed simulation parameters, the magnitude of the perturbation, and the reduction in neutron yield relative to the unperturbed case.

A simple model is formulated from a time-delayed Guderley converging shock to predict the perturbed inner pusher shape at the point of maximum pusher kinetic energy. This will subsequently be coupled to a model of the perturbed stagnation, such as the asymmetric-piston model [Hurricane et al. 2020], generating a semi-analytic prediction of design choices’ sensitivity to mode-1 perturbations.