Advanced Scanning Patterns for X-ray Ptychography at ALS COSMIC.

Recently, lensless X-ray imaging has developed to probe large volumes of material at high spatial resolution, especially with diffraction-based methods such as ptychography, removing the resolution limit imposed by the characteristics of X-ray optics. At LBNL’s Advanced Light Source (ALS), the Coherent Scattering and Microscopy (COSMIC) beamline uses soft x-ray ptychography for probing nanoscale objects, obtaining the highest-resolution x-ray microscopy achieved by imaging 5 nm structures. Ptychographic imaging at high resolution requires the data redundancy provided by overlapping x-ray probe positions and iterative reconstruction algorithms for precise reconstructions of the sample. Therefore, the scan patterns for ptychography play a critical role in the reconstructions, and the ALS uses the traditional mesh pattern which exhibits artifacts in reconstructions, worsening their quality. I have investigated ptychography scans that follow alternative scan patterns, like the Fermat spiral trajectory, and scans that account for details in the sample to more effectively sample high diffraction areas. These scan patterns show to improve the reconstructed images and reduce overhead in scanning and computation times.