Evolution of surface morphology of glow discharge polymer processed by UV nanosecond laser: Simulation and experimental study

Glow discharge polymer (GDP) is a critical material for fabricating ablator shells in inertial confinement fusion (ICF) ignition targets, where surface smoothness directly influences fusion stability. However, conventional micromachining processes inevitably introduce surface damage and microcracks in high-toughness polymeric materials like GDP, creating a major bottleneck in target fabrication. This study systematically investigates the surface morphology evolution mechanisms of GDP under UV nanosecond laser ablation, aiming to reveal fundamental principles and evaluate the feasibility of laser polishing for achieving high-quality target surfaces. We developed a model based on Fourier heat conduction theory and fractal surface representation to analyze the dynamic topography evolution during laser processing. Single-factor experiments, which modulated pulse energy density, scanning speed, and track overlap ratio, revealed that the material removal volume increases with increasing energy density but decreases with increasing scanning speed. We identified the overlap ratio as the key control parameter for achieving continuous planar surfaces in multi-track overlapping scanning. Crucially, the competition between photochemical and photothermal pathways, a dynamically balanced process governed by parametric synergy, determines the final morphology: lower energy density and higher scanning speed promote photochemical ablation, enabling precise "cold" material removal to achieve smoother surfaces, whereas higher energy density and lower speed enhance photothermal effects, enabling efficient material removal but leading to increased surface roughness. These findings hold significant theoretical and practical implications for laser polishing applications in GDP target fabrication for ICF.