UC Berkeley

X-ray imaging traces its roots back to the discovery of x-rays by Ro ̈ntgen in 1901, in the form of simple projection imaging. Several decades later, fabrication of x-ray optics enabled image formation at higher resolutions, leading to microscopy. Nevertheless, microscopy at resolutions on the order of the x-ray wavelength has only become possible in recent years, after a host of enabling technologies, including high-brightness coherent sources, advanced detectors, high-performance computers and algorithms, and precision instrumentation were brought together by multidisciplinary teams of scientists to form one coherent imaging sys- tem. Today, x-ray ptychography microscopes operating at modern synchrotrons can image thick samples at unprecedented resolutions, and yield chemical information about the sam- ple, enabling novel material science studies. The field is rapidly developing, and the advent of new Diffraction Limited Storage Ring (DLSR) sources around the world promises to provide new opportunities with increased coherent brightness.

This dissertation presents new advances in instrumentation and analysis at the Advanced Light Source at Lawrence Berkeley National Lab. A new x-ray ptychography microscope is described, compact in size and ultrastable in both vibrations and drift, enabling better than 3nm spatial resolution, and integrating a TEM-compatible in-situ sample holder to enable multimodal, operando, and cryogenic experiments. A new approach to the analysis of spectro-microscopic data is presented, combining low-resolution STXM and high-resolution ptychography images to produce chemical maps at high resolution without a priori reference spectra. This is achieved by collecting STXM data at fine x-ray energy increments, from which spectra are extracted by PCA and clustering. The ptychography data, collected at only a few energies, is then fitted to these extracted spectra. Finally, new ideas are explored to speed up scanning in ptychography, leading to a reduction in scan overhead, dose, and data collection times. This is done in two ways: firstly, a simple, yet effective, scanning algorithm is introduced to adjust feedback parameters for the piezo stage scanning the zone plate, reducing the scan overhead time. Secondly, lower density scan patterns and their effects on quality and resolution of reconstructions are investigated; based on these, ideas are proposed to intelligently reduce the total number of diffraction patterns collected, while only minimally affecting results. Combined with the promise of increased coherent flux with upcoming DLSRs, leading to much shorter exposure times, these speedups will enable much faster ptychography scans, greatly facilitating tomography or in-situ experiments, currently taking many hours or days.