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

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 人们对发展对受冲击固体行为的预见性理解非常感兴趣。为了实现这一理解，直接在现场和实时地探测控制现象是绝对关键的。在这项提议中考虑到的一个非常感兴趣的领域是，在高度多孔的固体中，由冲击引起的空穴结构的坍塌。纳米多孔固体被认为是高能量密度物理实验的关键，也是国家点火设施中激光聚变的目标。表征低密度材料在这些极端条件下的性能，为目标设计师和制造商提供关于现有模型可靠性的重要反馈，并为开发具有最佳性能的材料提供洞察。最近，我们成功地开发了使用单个x射线脉冲测量小角x射线散射的能力，使得使用泵浦-探测实验来测量冲击过程中的结构变化成为可能。在拟议的工作中，我们首次将这些方法应用于纳米泡沫，并期望回答一个必须解决的主要问题：现有的理论模型用于描述泡沫的压缩有多可靠？我们建议在高应变率或冲击条件下表征纳米多孔固体的形态，并利用这些结果来验证这些材料中的空穴演化模型。目前对纳米泡沫的形态在冲击条件下如何响应的了解很少，在这项工作中，我们计划用最先进的时间分辨小角X射线散射(TRSAXS)来量化动态结构变化。最终，我们希望获得这些材料在极端条件下的预测能力，作为初始结构和压缩动力学的函数。拟议中的实验将为了解孔隙坍塌过程的细节提供新的见解。

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.