Multiphysics Modeling of Material Response to High-Intensity X-ray and Laser Pulses: Heating, Ablation, and Plasma Expansion

This dissertation presents a computational framework to investigate material response under high-intensity X-ray fluxes produced by an exo-atmospheric nuclear detonation and laser-material irradiations, with a focus on heating, ablation, and plasma expansion phenomena relevant to satellite vulnerability and high-energy-density environments. A hybrid Monte Carlo and Two-Temperature Model (MC-TTM) was developed to simulate X-ray and laser energy deposition and thermal relaxation in metals and semiconductors across a range of X-ray and laser pulse durations from femtoseconds to nanoseconds. Results demonstrate distinct thermal behavior between materials, with ablation thresholds and phase transitions captured in good agreement with experimental data. In parallel, a multiphase Computational Fluid Dynamics (CFD) model was implemented to study the hydrodynamic expansion of femtosecond laser-induced plasma plumes. The CFD model accounts for interfacial momentum exchange, viscous effects, and ambient gas composition. This enables a detailed analysis of plume morphology and shockwave dynamics. Simulations highlight the sensitivity of plasma evolution to thermophysical properties, crater geometry, and turbulence. A comparative analysis also shows how optical laser parameters can be tuned to mimic X-ray-induced ablation, offering practical insights for experimental design. Collectively, the tools and results developed in this work enhance the understanding of radiation–matter interactions in extreme environments. They also provide a predictive foundation for evaluating the resilience of relevant systems.