Abstract: Fourth-generation synchrotron light sources like the APS Upgrade (APS-U) present several novel capabilities for materials characterization when coupled with new inversion methods. In this talk I will present new prospects in lens-less and lens-based imaging of crystalline materials, that will exploit the bulk penetrative capabilities of high-brilliance coherent x-rays of the APS-U. In particular: 

(i) a new high-fidelity, multi-reflection Bragg coherent diffraction imaging (BCDI) algorithm tailored to crystals/polycrystal grains with significantly more dislocation content than current phase retrieval capabilities permit to reconstruct. The new differentiable forward model uses Fourier-based methods to explicitly maintain fidelity to high-frequency features like lattice discontinuities in modeling the eventual measured signal. I will demonstrate the vast improvement in reconstruction quality over present-day concurrent reconstruction methods. 

(ii) the potential to observe irreversible processes in structural materials with coherence-enhanced dark-field x-ray microscopy (DFXM), through evolving signatures of structural defects in out-of-focus measurements of an x-ray lens. I will show with simulations how this modality could reveal structural features in crystalline bulks that may not be evident in a conventional lens-generated image, without the need for image reconstruction. This capability stands to fill a critical gap in the size of crystals that can currently be spatially resolved with synchrotron imaging methods.