Talbot diagnostics with the MXI at LCLS: High-fidelity description of shock-compressed foams

Novel facility capabilities enable experimental platforms to explore new physics regimes. Measurement innovation is key to better describing Matter in Extreme Conditions (MEC); high-resolution probing supports model validation, providing deeper understanding of plasma processes. Shock compression plays a profound role in astrophysics, materials, high energy density, and planetary science. Accurate probing is challenging due to steep density gradients within small scales. Thus, coherent sources such as X-ray Free Electron Lasers are a powerful tool to improve transparent media visualization (e.g., turbulent 3D structure and plasma flow contours) in combination with advanced refraction-based x-ray phase-contrast. We describe a grating-based phase-contrast imaging platform (~200ns, <ps) at the Linac Coherent Light Source MEC X-ray Imager. Enhanced contrast was obtained with 8.3keV Talbot interferometry by leveraging its inherent phase change sensitivity and 2D electron density was retrieved with TNT, a dedicated post-processing tool. In recent MEC experiments, we investigated laser-mediated (>10¹³W/cm²) Multi-Mbar compression in low-density aerogel and additively manufactured foams, seeking to extend shock dynamics description to non-homogeneous media, testing target density and design (e.g., lattice structure, interfaces). Shocked material density distribution captured development and evolution of distinct features with remarkable sensitivity. The shock front position was determined with sub-µm resolution, enabling instantaneous shock speed measurements along the shock tube. The data are in good agreement with hydrodynamic simulations, providing insights into mechanisms for shock formation and evolution. In aerogels, shock front density maps revealed a low-density region ahead of >4x compression, where densities <10²⁴cm^-3 were measured. In modulated targets, distinct instability features were resolved with sub-µm scale at ~2x10²¹cm^-2 areal density, enabling growth rate measurements. In additively manufactured foams, 3D printed structures seem to dominate shock dynamics, with exact mechanisms yet to be determined. It was shown that the MEC Talbot platform can be a valuable tool to systematically investigate plasma dynamics through high-fidelity probing