IN-SITU, TIME RESOLVED SCATTERING MEASUREMENTS OF SHOCK DRIVEN NANOPOROUS FILMS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. There is significant interest in developing a predictive understanding the behavior of shocked solids. In order to achieve this understanding, it is absolutely crucial to directly probe the controlling phenomena, in-situ and in real time. One area of keen interest, considered in this proposal, are the shock-induced collapse of the void structure in highly porous solids. Nanoporous solids are considered essential for high energy density physics experiments as well as targets for laser fusion at the National Ignition Facility. Characterizing the performance of low density materials under these extreme conditions provides crucial feedback to target designers and fabricators on the reliability of existing models and insight in developing materials with optimal properties. Recently, we have successfully developed the capability of measuring small angle x-ray scattering using a single x-ray pulse, enabling the use of pump-probe experiments to measure structural changes in-situ during a shock. In the proposed work we are applying these methods to nanofoams for the first time, and expect to answer a major question that must be resolved: How reliable are the existing theoretical models used to describe the compression of foams? We propose to characterize the morphology of nanoporous solids under high strain rate or shocked conditions, and to use these results to validate models of void evolution in these materials. Very little is currently understood about how the morphology of nanofoams responds under shock conditions and in this work we plan to quantify dynamic structural changes with a state of the art time resolved small angle x-ray scattering (TRSAXS). Ultimately, we hope to obtain a predictive capability for these materials under extreme conditions as a function of initial structure and compression dynamics. The proposed experiments would provide new insight into the details of the pore collapse process.