Laser Cross-beam Energy Transfer Model Based on Ray Tracing Method

This paper addresses the mathematical modeling of energy transfer in direct-drive inertial confinement fusion (ICF) mediated by multi-beam stimulated Brillouin scattering (CBET). This paper proposes a ray-tracing inverse solver with a layer-by-layer propagation strategy that effectively reduces the three-dimensional problem to a two-dimensional one. This approach significantly lowers memory consumption while preserving computational accuracy, thereby enhancing the capability to evaluate CBET effects in direct-drive implosions. It reduces complexity without compromising fidelity. Our results demonstrate that laser wavelength detuning and beam crossing angle exert a strong influence on CBET, while variations in inverse bremsstrahlung absorption primarily affect the magnitude of energy transfer but not its overall trend. The model has been validated against wave-coupling calculations, confirming its reliability. This work provides an efficient and robust numerical tool for energy-coupling evaluation and asymmetry analysis in direct-drive ICF experiments.