Michael Stevens, Explosives Science and Shock Physics Division, LANL, will present seminar. Professor Sol Gruner, host.
Seminar Title: Current Directions in Time Dependent Mesoscale Materials Science using Modern Light Sources
Abstract: The advent of new light sources, such as the synchrotron light source at the Advanced Photon Source outside Chicago, IL, and the X-ray Free Electron Laser at the Laser Coherent Light Source are providing unprecedented opportunities for materials researchers to examine the in situ response of a wide variety of materials to dynamic and extreme pressure deformation. In particular, the duty cycle and pulse structure of these facilities allows for both temporally and spatially resolved examination of the response at the mesoscale; the spatial regime where atomic regularity transitions to the continuum. The mesoscale is marked by the presence of intrinsic heterogeneities, such as grain boundaries, defects, voids, dislocation structures, and other features ranging from 10-8 to 10-4 meters in size. The capabilities at these light sources have provided revolutionary new insights to the experimentalist. At the APS, for example, experimentalists are now using several “extreme condition” platforms including gas guns, diamond anvil cells, and confinement chambers for examining the effect of high pressure and shocks on materials, while simultaneously characterizing the material response using x-ray phase contract imaging to directly observe fine scale features, or by Bragg diffraction analysis methods for determining crystal structure, orientation and strain, all as a function of time. At the LCLS, researchers are now exploiting the unique characteristics of x-ray photons associated with the XFEL for generating dynamic images of material structures with nanometer scale resolution.
Los Alamos National Laboratory researchers are actively exploiting these capabilities to develop a deeper understanding of the underlying physics mechanisms governing material response in such extreme conditions. This understanding, in turn, is not only exciting in terms of the new science discovery it allows, but is also important for the development of improved constitutive models in predictive codes used for integrated system validation. This presentation will survey a variety of preliminary materials studies conducted at these facilities to both explore these inherent possibilities and to move us from the observation of material performance to a priori control of properties.
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