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In this talk, we will review recent progress in characterizing the ultrafast excitation and the transformations of materials using Ultrafast Electron Diffraction (UED) at mega-electron volts energies. These experiments resolve material dynamics at ultra-fast temporal (1 ps) and atomic spatial (1 Å) resolutions. Initially motivated by the need to understand the material responses to the harsh environments produced by fusion plasmas, that emit intense radiation by X-rays, neutrons, and charged particles, we successfully visualized heterogeneous and homogeneous melting transition in warm dense gold and captured the incipient plasticity in dynamically compressed aluminum. Importantly, our time-resolved diffraction data quantified the dependencies on nucleation seeds in ultrafast melting and have determined dislocation nucleation and transport that constitute the underlying defect kinetics of incipient plasticity. Comparisons with modeling that include two-temperature Molecular Dynamics (MD) simulations reveal the crucial role of the choice of the inter-atomic potentials to describe the material state in extreme conditions. The successes of these studies have motivated us to expand this research area at SLAC; the combination of structural data of ultrafast laser-excited materials from UED with accelerator-based THz and free electron laser measurements is now providing new insight into questions ranging from electrical and thermal conductivity to the microphysics of radiation-damaged materials.
Work in collaboration with: Mianzhen Mo Z. Chen, M. Dunning, B. B. L. Witte, J. K. Baldwin, L. B. Fletcher, J. B. Kim, A. Ng, R. Redmer, A. H. Reid, P. Shekhar, M. Shen, K. Sokolowski-Tinten, Y. Y. Tsui, J. R. Peterson, X. Shen, J. K. Baldwin, M. Frost, M. Kozina, A. Reid, Y. Wang, Juncheng E, A. Descamps, B. K. Ofori-Okai, R. Li, M. Tang, P. Fossati, S. Murphy, S.-N. Luo, and Xijie Wang
We acknowledge support for sample synthesis and characterization from the Center for Integrated Nanotechnologies (CINT), an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. This work was supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515 and the DOE Fusion Energy Sciences under FWP #100182. The experimental part of this research was performed at SLAC MeV-UED, which is supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (DOE BES) SUF Division Accelerator & Detector R&D program, the LCLS facility, and SLAC under contract nos. DE-AC02-05-CH11231 and DE-AC02-76SF00515. This work was per- formed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is managed by Triad National Security, LLC for the U.S. Department of Energy’s NNSA, under contract 89233218CNA000001. M.Z.M. acknowledges the support from Department of Energy, Laboratory Directed Research and Development program at SLAC, under contract DE- AC02-76SF00515. M.X.T. and S.-N.L. acknowledge the support from National Natural Science Foundation of China under Grant No. 11627901. S.M. acknowledges funding from EPSRC under the grant codes EP/R006288/1 and EP/R0029431.
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Sakura Pascarelli / Gabriella Mulá-Mathews