Abstract

Material failure begins with strain between atoms and cascades upward into macroscopic damage such as cracks. Therefore, our ability to predict (and therefore prevent) material failure is largely limited by our understanding of this process. This understanding, however, has been impeded by the difficulty of directly observing such phenomena. In this thesis, I discuss recent advances in Bragg coherent diffraction imaging (BCDI) which produce three-dimensional, mesoscopic images of interior strain in microcrystals. In particular, I present a novel algorithm, based on the concept of cyclic-constrained optimization (CCO), for the rapid, coupled reconstruction of a microcrystal from multiple Bragg diffraction patterns. Using coherent diffraction data collected from the Advanced Photon Source (APS), this algorithm achieves resolution comparable to other multipeak BCDI methods at a fraction of the computational cost. As the rate of data production at coherent X-ray sources worldwide continues to increase, such rapid algorithms will be critical to preventing a data analysis bottleneck. I also present a technique for mapping the orientations of crystal grains on a sample by analyzing the positions of Laue diffraction spots when the crystal is illuminated by a polychromatic beam. Each of these two methods constitute a significant contribution to the field of mesoscopic strain analysis.

Degree

College and Department

Computational, Mathematical, and Physical Sciences; Physics and Astronomy

Rights

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