Electropolishing of Copper Targets for Inertial Fusion: Experimental and Simulation Study on Surface Finish and Shape Stability

Electropolishing (EP) is a key enabling technique used to fabricate ultrasmooth surfaces in inertial confinement fusion (ICF) targets. However, the coupled effects of material removal, thermal fields, and surface morphology on dimensional stability and laser-driven performance remain poorly understood. This study investigates the EP of copper targets in a phosphoric acid–glycerol electrolyte via experiments, COMSOL Multiphysics simulations, and FLASH radiation–hydrodynamics modeling. The results reveal that thin foils are highly susceptible to warping due to the interplay of nonuniform material dissolution, the edge-enhanced current density, and thermally induced stress gradients. A stable diffusion-controlled polishing regime is identified, under which surface asperities are preferentially removed, resulting in a reduction in roughness from ~ 48 nm to ~ 5 nm at ~ 55 °C, a 3:1 acid-rich electrolyte, and ~ 1.2 V. More importantly, a cross-scale correlation between surface morphology and laser ablation behavior is established. FLASH simulations demonstrate that increasing surface roughness amplifies lateral nonuniformities in electron temperature and density fields, thereby accelerating the growth of Rayleigh–Taylor (RT) instability. In contrast, nanoscale-smooth surfaces exhibit ablation characteristics comparable to an ideal interface, with significantly suppressed perturbation growth. These findings establish a mechanistic link between EP-induced surface evolution and laser-driven stability, offering a framework for optimizing surface and ablation performance.