Synthetic Diagnostic Signatures of Burn Truncation within Simulations of ICF Implosions

The 3D radiation hydrodynamics code Chimera is used to run simulations aiming to investigate possible yield degradation mechanisms in ICF experiments. By modelling the observable signals measured in experiments, synthetic diagnostics can probe simulations in an analogous way to their experimental equivalents. This allows current and novel analysis techniques to be investigated with full knowledge of the capsule properties for comparison.

Drive asymmetries and capsule defects cause current ICF experiments to exhibit yields below those expected from an idealised symmetric implosion. By considering these perturbations in isolation and in combination, the effect on nuclear observations can be simulated. These observations include neutron imaging and spectroscopy as well as fusion and Carbon γ ray time histories and imaging. For drive asymmetries, correlations between the burn width, time between bang time and stagnation and the mechanical work timescale are found. For capsule defects these correlations are broken.

Signatures of burn truncation can also be observed in the residual fluid velocity of both the hotspot and the dense DT shell. Spectral measurements of the DT primary and backscattered neutrons can be used to infer both hotspot and shell fluid velocities around bang time.