Multispectral X-ray Tomography of ICF Implosions

Multispectral x-ray tomography characterizes the hydrodynamic state of an inertial confinement fusion (ICF) implosion near peak x-ray emission, providing a 3D view of hot-spot morphology and degradation mechanisms. In the presented method, the per-voxel fields Te and n² are reconstructed jointly through a multiplicative splitting of the emissivity forward model, regularized by a second-derivative penalty and a progressively relaxed maximum-entropy penalty. With this splitting, the otherwise linear tomography problem becomes nonlinear in the joint unknowns and is solved by a preconditioned Gauss-Newton scheme with Levenberg-Marquardt damping. From the resulting fields, we extract the hot-spot volume and mass together with the low-mode (l ≤ 4) asymmetry of the density, temperature, and pressure, yielding quantities that can be compared directly against radiation-hydrodynamics simulations and used to test specific degradation hypotheses. Combined with neutronics data, the method opens a new route to disentangling shell and ablator instabilities, mix, and residual kinetic energy in ICF implosions.