论文和技术资料

The Dynamic Transmission Electron Microscope (DTEM) at Lawrence Livermore National Laboratory is a unique instrument able to capture images of fast-evolving microstructure with exposure times of only 15 ns. This is more than six orders of magnitude faster than conventional in situ electron microscopy and has enabled new insights into phase transformations, chemical reactions, and materials dynamics on otherwise inaccessible spatiotemporal scales.
Interpretation of DTEM experiments requires an understanding of the interaction of the laser with the sample as well as the subsequent diffusion of heat. These processes are complicated by the fact that the samples often have structure on the nanometer scale and also that the processes of interest can couple with the heat diffusion in a nonlinear way. We discuss how finite element simulations in COMSOL Multiphysics have allowed us to address these issues, producing fully three-dimensional electrodynamic models of the laser absorption while also predicting the nonlinear heat flow and its coupling to phase transformations in a two-dimensional enthalpy formalism.