Synthetic Nuclear Diagnostics for Inferring Plasma Properties of Inertial Confinement Fusion Implosions

TL;DR

This paper develops synthetic nuclear diagnostics based on simulations to analyze plasma properties in inertial confinement fusion implosions, providing new methods for inferring plasma parameters and asymmetries.

Contribution

It introduces a suite of synthetic diagnostics for ICF simulations, enabling novel plasma property inference and assessment of experimental techniques.

Findings

Neutron spectrum features can infer shell velocity.

Areal density asymmetries are detectable via downscatter spectrum slope.

Carbon gamma-ray imaging can visualize the ablator at high convergence.

Abstract

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, $\gamma$-ray time histories and carbon $\gamma$-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 $\gamma$-ray imaging could be used to image the ablator at high convergence ratio. Time histories of both the fusion and carbon $\gamma$ signals showed a greater time difference between peak intensities for the perturbed case when compared to a symmetric simulation.