The idea for ptychography dates back to 1969, but its realization as a practical imaging method awaited the development of iterative phase retrieval algorithms. By now, it is firmly established for nanoscale studies of materials using X rays, both in transmission mode and also using Bragg diffraction. While focusing optics greatly aid its implementation, the spatial resolution is determined not by optics but by the finest length scales from which one can measure elastic scattering. On the experimental side, the hundredfold increases in quasi-time-continuous coherent flux provided by diffraction-limited storage rings will dramatically advance what ptychography can do. On the computational side, the application of nonlinear optimization approaches has allowed one to compensate for many experimental limitations, including errors in nanopositioning as well as partial coherence, and allow one to re-think how one might acquire ptychographic data. Thus far, x-ray ptychography has been applied to millimeter-size samples in 2D, and roughly 10 micrometer size samples in 3D. How far might that go? Can one combine the advantages of X rays of high penetration power and low multiple scattering to image even larger samples? Can one carry out nanoscale imaging of cubic centimeter volumes? I outline some of the opportunities this might provide, and some of the challenges in achieving this.

Recent developments in 4th generation light sources and high-speed detectors are leading to rapid growth in data rates and data volumes, increasing the demand for automated data collection, handling/reduction/storage, and analysis processes. In combination with limited in-person access to experimental setups in times of the pandemic, portable and user-friendly tools for remote access as well as improved workflows are critical for enabling scientists from various disciplines to leverage ptychographic imaging to answer scientific questions.

With the growing popularity of ptychography, a broad range of data formats, acquisition schemes, and algorithms has been developed over the years, e.g. [1-3]. Whereas this variety has been advantageous to tackle different real-world deviations from the ideal ptychographic model such as partial incoherence [4], positioning errors [5], broad-bandwidth radiation [6], or multi-scattering [7], it also complicates the comparability and reproducibility of results. With ptychography being established as an everyday workhorse technique at many instruments around the world, it is important to find common ground and establish standards to support reliable algorithm and collaborative software development addressing the big data challenges of today and the future.

In this presentation, I will cover recent cross-facility efforts [8] to develop and promote data standards for ptychography. Furthermore, I will give an overview of ongoing software development at the Advanced Light Source in collaboration with the other DOE light sources for building data acquisition and analysis tools leveraging existing python packages with an outlook for future progress in terms of remote access and workflows.

[1] Enders B., & Thibault P., (2016). Proc Math Phys Eng Sci. 472(2196) 20160640.

[2] Wakonig K., Stadler H.-C., Odstrčil M., Tsai E. H. R., Diaz A.,Holler M.,Usov I., Raabe J., Menzel A., & Guizar-Sicairos M. (2020). Journal of Applied Crystallography, 53(2) 574-586

[3] Favre-Nicolin V., Girard G., Leake S., Carnis J., Chushkin Y., Kieffer J, Paleo P. & Richard M.-I. (2020). J. Appl. Cryst. 53, 1404-1413

[4] Thibault P. & Menzel A. (2013). Nature 494, pages 68–71

[5] Maiden A.M., Humphry M.J., Sarahan M.C., Kraus B. & Rodenburg J.M., (2012). Ultramicroscopy, 120, 64-72

[6] Enders B., Dierolf M., Cloetens P., Stockmar M., Pfeiffer F. & Thibault P., (2014). Appl. Phys. Lett. 104, 171104

[7] M Kahnt, Grote L, Brückner B., Seyrich M., Wittwer F., Koziej D. & Schroer C. G., (2021). Sci Rep 11, 1500

[8] Data Solution Task Force Pilot https://www.bnl.gov/newsroom/news.php?a=216902

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under the Data Solution Task Force Pilot.

The work was partially funded through the Center for Advanced Mathematics for Energy Research Applications (CAMERA), which is jointly funded by the Advanced Scientific Computing Research (ASCR) and Basic Energy Sciences (BES) within the Department of Energy’s Office of Science, under Contract No. DE-AC02-05CH11231.

This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02-05CH11231.

This work was supported by the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by ANL under contract No. DE-AC02-06CH11357.

This research used resources of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Cement manufacturing is responsible for ~7% of the anthropogenic CO₂ emissions and hence, decreasing the CO₂ footprint, in a sustainable, safe, and cost-effective way, is a top priority. It is also key to develop more durable binders as the estimated world concrete stock is 315 Gt which currently results in ~0.3 Gt/yr of concrete demolition waste (CDW). Moreover, models under development predict a skyrocketing increase of CDW to 20–40 Gt/yr by 2100. This amount could not be easily reprocessed as aggregates for new concretes as such volumes would be more than two times the predicted need. Furthermore, concretes have very complex hierarchical microstructures. The largest components are coarse aggregates with dimensions bigger than a few centimetres and the smallest ones are amorphous components and the calcium silicate hydrate gel with nanoparticle sizes smaller than a few nanometres. To fully understand the properties of current and new cement binders and to optimize their performances, a sound description of their spatially-resolved contents is compulsory. However, there is not a tomographic technique that can cover the spatial range of heterogeneity and features of concretes and mortars. This can only be attained within a multitechnique approach overlapping the spatial scales in order to build an accurate picture of the different microstructural features. Here, we have employed far-field and near-field synchrotron X-ray ptychographic nanotomographies to gain a deeper insight into the submicrometer microstructures of Portland cement binders. With these techniques, the available fields of view range from 40 to 300 mm with a true spatial resolution (not voxel sizes) evolving between ~50 nm to ~300 nm. It is explicitly acknowledged here that other techniques like X-ray synchrotron microtomography are necessary to develop the whole picture accessing to larger fields of view (millimetres and even centimetres) albeit with poorer spatial resolution and without the quantitativeness in the reconstructed electron densities.

After framing the problems which are being tackled, we plan to present here our recent results using X-ray ptychographic nanotomography. We will start introducing the outputs obtained using far-field ptychographic nanotomography to determine phase assemblages and mass densities of amorphous components [1,2]. Then, we will move to cover the secondary porosity induced by cement conversion with temperature [3]. Finally, we will present our ongoing work with near-field ptychographic nanotomography in Portland and Belite cements with a larger field of view, capillaries from 200 to 300 mm of diameter. Between other features, Hadley grains (hollow-shells hydrated particles) have been imaged in 3D and their properties are being statistically extracted, see Figure 1. Further details will be discussed and the comparison between far-field and near-field nanotomographies will be carried out.

[1] Cuesta, A., et al. (2017) Chemistry and Mass Density of Aluminum Hydroxide Gel in Eco-Cements by Ptychographic X‑ray Computed Tomography. J. Phys. Chem. C, 121, 3044−3054.

[2] Cuesta, A., et al. (2019) Quantitative disentanglement of nanocrystalline phases in cement pastes by synchrotron ptychographic X-ray tomography. IUCrJ, 6, 473–491.

[3] Shirani, S., et al. (2020) Calcium aluminate cement conversion analysed by ptychographic nanotomography. Cem. Con. Res. 137, 106201.

Wiring diagrams of neural circuits are of central importance in delineating mechanisms of computation in the brain (1). Hereby, the individual parts of neurons - axons, dendrites and synapses - need to be densely identified in 3-dimensional volumes of neuronal tissue. This is typically achieved by volume electron microscopy (2), which requires ultrathin physical sectioning or ablation, using high precision slicing techniques or ion beams, either before or during the image acquisition process (3-6). Here, we demonstrate that cryogenic X-ray ptychographic tomography (7-9), a coherent diffractive X-ray imaging technique, can acquire 3-dimensional images of metal-stained mouse neuronal tissue with sufficient resolution to densely resolve axon bundles, boutons, dendrites and synapses without physical sectioning. We show that the tissue volume can be subsequently imaged in 3D using high-resolution, focussed ion beam-scanning electron microscopy (FIB-SEM). This suggests that metal-stained neuronal tissue can be highly radiation-stable. Using FIB-SEM as ground truth, we could show that X-ray ptychography reliably resolves 60% of the synaptic contacts in the mouse olfactory bulb external plexiform layer with an 80% precision. Ongoing improvements in synchrotron, X-ray and detector technologies (8, 10, 11) as well as further optimization of sample preparation and staining procedures (12, 13) could lead to substantial improvements in acquisition speed. Combined with laminography (14) and nano-holotomography (15, 16) it could allow for non-destructive x-ray imaging of synapses and neural circuits in increasingly larger volumes.

Catalysts are ubiquitous materials that play a major role in many areas of economy and everyday life. The development and study of catalysts is important for progress in areas such as environment, energy, and fuels, with the main goal being to improve the performance and efficiency of catalysts, especially at the industrial scale. Therefore, a thorough analysis is crucial to understand the relation between structure and performance, the deactivation process and the reasons for the loss of efficiency over the lifetime. This analysis is challenging, because technical catalysts are complex multicomponent bodies, ranging from dozens of μm to several cm, consisting of active phases, supports and additives in shaped forms suitable for their application. One of the most important conversion processes in petroleum refineries is Fluid Catalytic Cracking (FCC) in which heavy hydrocarbon fractions of crude oil are converted into valuable products such as olefins and aromatics [1]. For this process, FCC particles of 50 - 100 µm diameter are used in an up-flow reactor, where they move up, whereas the feed flows downward. During the short contact time, catalyst and feed can react. During this reaction the catalyst is partially deactivated by coke formed during the cracking and a subsequent regeneration cycle is required [2]. Thus, the characterization of the microstructure at different length scales with a spatial resolution at the nanometer length scale and a large field of view is necessary, but also the investigation of the location and chemical state of the active metallic sites in the structure.

The imaging of a large field of view with a resolution of ~ 30 - 100 nm is possible with ptychography, even for low absorbing samples. To get spatial resolved spectral information, spectro-ptychography can be used, where the measurements are repeated at different energies, including the absorption edge of a specific element. This method has already been applied for the nanoscale chemical imaging and structural analysis of a heterogeneous catalyst [3].

We investigated a FCC catalyst containing 10 wt.% Mn₂O₃ at different lifetimes by means of spectro-ptychography. Ptychographic scans are repeated at 40 different energies around the Mn K-edge. We show here the results of the experiment carried out at the beamline ID16B at ESRF, where this method has never been used before. The absorption is weak due to the low concentration of Mn and the small thickness of the samples, and hence we work with the phase contrast images. The phase contrast can be associated with the anomalous scattering factor f’, which is energy dependent in the proximity of absorption edges. The f’ spectra can be extracted by comparing the reconstructed phase contrast images recorded at different energies. The work includes the preparation of the instrumentation, the development of the algorithms for the data preparation and the python programs for the spectral analysis. We show the methodological developments necessary for the extraction of the information from the obtained measurements, starting from the phase retrieval and normalization of the phase images, to the alignment of the images of different energies, to the extraction of the f’ spectra and the search for the Mn signature in the sample.

[1] W. Letzsch,Handbook of Petroleum Processing, Springer Int. Publishing, Cham 2015, 216-316.

[2] A. Corma, et al., Catalysis Science & Technology 2017, 7, 12.

[3] M. Hirose, et al., Angew. Chem. Int. Ed. 2017, 56, 1-6.

Three-dimensional X-ray microscopy by ptychographic tomography is usually per formed by separating the steps of acquiring two-dimensional ptychographic reconstructed projection images at different projection angles and afterwards performing the three-dimensional tomographic reconstruction. Recently it has been suggested that those two separate steps can be coupled / joined together, allowing for the sharing of information between angular views during the ptychographic reconstruction step [1, 2, 3]. We performed such a coupled X-ray ptychographic tomography reconstruction for the first time on an experimental dataset, improving the achieved resolution in the process [4]. Furthermore we validated the predicted relaxation of the overlap criterion between adjacent scan positions in the tomographic plane by successively leaving out columns of recorded diffraction patterns and achieving robust reconstructions even beyond the point of no
overlap between neighboring scan points.

References:

[1] D. Gürsoy, “Direct coupling of tomography and ptychography,” Opt. Lett., vol. 42, pp. 3169–3172, Aug 2017.
[2] T. Ramos, B. E. Grønager, M. S. Andersen, and J. W. Andreasen, “Direct three-dimensional tomographic reconstruction and phase retrieval of far-field coherent diffraction patterns,” Phys. Rev. A, vol. 99, p. 023801, Feb 2019.
[3] S. Aslan, V. Nikitin, D. J. Ching, T. Bicer, S. Leyffer, and D. Gürsoy, “Joint ptycho-tomography reconstruction through alternating direction method of multipliers,” Opt. Express, vol. 27, pp. 9128–9143, Mar 2019.
[4] M. Kahnt, J. Becher, D. Brückner, Y. Fam, T. Sheppard, T. Weissenberger, F. Wittwer, J.-D. Grunwaldt, W. Schwieger, and C. G. Schroer, “Coupled ptychography and tomography algorithm improves reconstruction of experimental data,” Optica, vol. 6, pp. 1282–1289, Oct 2019.