Image correction of ablator instability collapse over time

One obstacle to attaining serviceable inertial confinement fusion (ICF) and improving energy yield is the presence of voids within the ablator material of fusion capsules. Hydrodynamic instabilities arising from voids and other imperfections during ICF experiments disrupt uniform compression as the shockwave progresses, reducing yield. We seek to experimentally image the void-shock evolution of these instabilities to identify the mechanisms that prevent compression symmetry, allowing us to develop strategies for enhancing uniformity and maximizing energy yield. In our proof-of-principle experiment, 40-um diameter hollow silicon-dioxide shells were used as surrogate voids and placed inside ablator-like material. The X-ray free-electron laser (XFEL) of the Matter in Extreme Conditions (MEC) instrument at the Linac Coherent Light Source (LCLS) compressed the sample with a shockwave and imaged its collapse via long-pulse laser. This yielded 2D X-ray phase-contrast images showing void collapse and shockwave evolution. We applied flat-field correction methods, including image registration and principal component analysis (PCA), to mitigate noise due to X-ray beam profile variations and lens artifacts. The resulting images experimentally confirmed the similarity of particular features in the xRAGE simulations and will allow for better phase retrieval and areal density calculations. Experimentally imaging hydrodynamic instability progression during shockwave compression furthers understanding of the effect of ablator imperfections on the ICF process, enabling us to increase yield through improved xRAGE models and experimental setup.