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Precision and accuracy of quantitative scanning transmission electron microscopy (STEM) methods such as ptychography, and the mapping of electric, magnetic, and strain fields depend on the dose. Reasonable acquisition time requires high beam current and the ability to quantitatively detect both large and minute changes in signal. A new hybrid pixel array detector (PAD), the second-generation Electron Microscope Pixel Array Detector (EMPAD-G2), addresses this challenge by advancing the technology of a previous generation PAD, the EMPAD. The EMPAD-G2 images continuously at a frame-rates up to 10 kHz with a dynamic range that spans from low-noise detection of single electrons to electron beam currents exceeding 180 pA per pixel, even at electron energies of 300 keV. The EMPAD-G2 enables rapid collection of high-quality STEM data that simultaneously contain full diffraction information from unsaturated bright-field disks to usable Kikuchi bands and higher-order Laue zones. Test results from 80 to 300 keV are presented, as are first experimental results demonstrating ptychographic reconstructions, strain and polarization maps. We introduce a new information metric, the maximum usable imaging speed (MUIS), to identify when a detector becomes electron-starved, saturated or its pixel count is mismatched with the beam current.

Advances in synchrotron light sources are creating new opportunities for scientific discovery by producing intense, low-emittance pulses of X-ray illumination. Detectors play a critical link in the experimental process because they are the tools of observation, charged with providing quantitative records of events that are the product of experiments. The capabilities of X-ray imaging detectors often limit the experimental possibilities, and dedicated development is needed to meet source capabilities. Currently, challenging demands on imaging detectors include hard X-ray imaging (e.g., > 25 keV), high-speed imaging (e.g. matching X-ray pulse rates), and high dynamic range imaging. Pixel Array Detector (PAD) development efforts at Cornell aiming to meet these demands are described, including high atomic number (high-Z) sensor materials, single bunch imaging, high-speed continuous acquisition, and high dynamic range imaging. This paper discusses detector design considerations and development efforts at Cornell.

IUCrJ 6(3), 1-9 (2019). doi:10.1107/S2052252519002781, The routine atomic resolution structure determination of single particles is expected to have profound implications for probing structure–function relationships in systems ranging from energy-storage materials to biological molecules. Extremely bright ultrashort-pulse X-ray sources – X-ray free-electron lasers (XFELs) – provide X-rays that can be used to probe ensembles of nearly identical nanoscale particles. When combined with coherent diffractive imaging, these objects can be imaged; however, as the resolution of the images approaches the atomic scale, the measured data are increasingly difficult to obtain and, during an X-ray pulse, the number of photons incident on the 2D detector is much smaller than the number of pixels. This latter concern, the signal `sparsity', materially impedes the application of the method. An experimental analog using a conventional X-ray source is demonstrated and yields signal levels comparable with those expected from single biomolecules illuminated by focused XFEL pulses. The analog experiment provides an invaluable cross check on the fidelity of the reconstructed data that is not available during XFEL experiments. Using these experimental data, it is established that a sparsity of order 1.3 × 10−3 photons per pixel per frame can be overcome, lending vital insight to the solution of the atomic resolution XFEL single-particle imaging problem by experimentally demonstrating 3D coherent diffractive imaging from photon-sparse random projections., Published by Chester

The combination of oscillation data collection with fixed-target microchips for regular crystal dispersion is an efficient method for collecting serial crystallography data at synchrotrons. Background scatter from noncrystal substrates is especially minimized., A fixed-target approach to high-throughput room-temperature serial synchrotron crystallography with oscillation is described. Patterned silicon chips with microwells provide high crystal-loading density with an extremely high hit rate. The microfocus, undulator-fed beamline at CHESS, which has compound refractive optics and a fast-framing detector, was built and optimized for this experiment. The high-throughput oscillation method described here collects 1–5° of data per crystal at room temperature with fast (10° s−1) oscillation rates and translation times, giving a crystal-data collection rate of 2.5 Hz. Partial datasets collected by the oscillation method at a storage-ring source provide more complete data per crystal than still images, dramatically lowering the total number of crystals needed for a complete dataset suitable for structure solution and refinement – up to two orders of magnitude fewer being required. Thus, this method is particularly well suited to instances where crystal quantities are low. It is demonstrated, through comparison of first and last oscillation images of two systems, that dose and the effects of radiation damage can be minimized through fast rotation and low angular sweeps for each crystal.

Superconducting quantum metamaterials are expected to exhibit a variety of novel properties, but have been a major challenge to prepare as a result of the lack of appropriate synthetic routes to high-quality materials. Here, the discovery of synthesis routes to block copolymer (BCP) self-assembly-directed niobium nitrides and carbonitrides is described. The resulting materials exhibit unusual structure retention even at temperatures as high as 1000 °C and resulting critical temperature, Tc , values comparable to their bulk analogues. Applying the concepts of soft matter self-assembly, it is demonstrated that a series of four different BCP-directed mesostructured superconductors are accessible from a single triblock terpolymer. Resulting materials display a mesostructure-dependent Tc without substantial variation of the XRD-measured lattice parameters. Finally, field-dependent magnetization measurements of a sample with double-gyroid morphology show abrupt jumps comparable in overall behavior to flux avalanches. Results suggest a fruitful convergence of soft and hard condensed matter science.

We have fabricated 128×128 pixel readout ASICs for the MM-PAD-2.1, a wide-dynamic-range photon-integrating detector intended for high-energy x-ray imaging (>20 keV). Design specifications include a signal-to-noise ratio of 10 for measurement of a single 20-keV photon, a maximum measureable signal of 108 20-keV photons/pixel/frame, and the ability to accurately measure sustained photon rates of ≥ 109 20-keV photons/pixel/s. The pixel pitch is 150 µm, resulting in an active area of 19.2 mm × 19.2 mm per single-chip module. ASICs have been bonded to both Si and CdTe sensors. Detector control firmware has been designed that allows for selective readout of a 128×128 pixel area at 9 kHz, or readout of the full array at 1.5 kHz. First results from characterization of the full-scale chip are reported.

Pressure is a fundamental thermodynamic parameter controlling the behavior of biological macromolecules. Pressure affects protein denaturation, kinetic parameters of enzymes, ligand binding, membrane permeability, ion transduction, expression of genetic information, viral infectivity, protein association and aggregation, and chemical processes. In many cases pressure alters the molecular shape. Small-angle X-ray scattering (SAXS) is a primary method to determine the shape and size of macromolecules. However, relatively few SAXS cells described in the literature are suitable for use at high pressures and with biological materials. Described here is a novel high-pressure SAXS sample cell that is suitable for general facility use by prioritization of ease of sample loading, temperature control, mechanical stability and X-ray background minimization. Cell operation at 14 keV is described, providing a q range of 0.01 < q < 0.7 Å−1, pressures of 0–400 MPa and an achievable temperature range of 0–80°C. The high-pressure SAXS cell has recently been commissioned on the ID7A beamline at the Cornell High Energy Synchrotron Source and is available to users on a peer-reviewed proposal basis.

A hard x-ray, high-speed, high dynamic range scientific x-ray imager is described. The imager is based on the mixed-mode pixel array detector (MM-PAD) readout chip coupled to a 750 micron thick cadmium telluride (CdTe) sensor. The full imager is a 2 x 3 tiled array of MM-PAD sensor/readout chip hybrids. CdTe improves detection for high energy x-rays as compared to silicon sensors, enabling efficient x-ray imaging to extend to >100 keV. The detector is capable of 1 kHz imaging and in-pixel circuitry has been designed to allow for well depths of greater than 4 x 10^{6} 80 keV x-rays. A charge integrating front-end allows for quantitative measurement of high flux x-ray images beyond the capabilities of photon counting detectors. Detector performance is summarized and experimental measurements are presented.

In recent years, the success of serial femtosecond crystallography and the paucity of beamtime at X-ray free-electron lasers have motivated the development of serial microcrystallography experiments at storage-ring synchrotron sources. However, especially at storage-ring sources, if a crystal is too small it will have suffered significant radiation damage before diffracting a sufficient number of X-rays into Bragg peaks for peak-indexing software to determine the crystal orientation. As a consequence, the data frames of small crystals often cannot be indexed and are discarded. Introduced here is a method based on the expand–maximize–compress (EMC) algorithm to solve protein structures, specifically from data frames for which indexing methods fail because too few X-rays are diffracted into Bragg peaks. The method is demonstrated on a real serial microcrystallography data set whose signals are too weak to be indexed by conventional methods. In spite of the daunting background scatter from the sample-delivery medium, it was still possible to solve the protein structure at 2.1 Å resolution. The ability of the EMC algorithm to analyze weak data frames will help to reduce sample consumption. It will also allow serial microcrystallography to be performed with crystals that are otherwise too small to be feasibly analyzed at storage-ring sources.

Reactive metal nanolaminates, most notably aluminum/zirconium composites, have been developed as fuels to aid combustion in explosive formulations. Thus far, however, their energy density is limited by incomplete oxidation. An in situ x-ray diffraction (XRD) study was performed on a 40 µm thick Al:Zr (atomic ratio 1:1) multilayer foil to track the growth of reaction products during ignition, combustion, and cooling (over approximately 5 s) to determine the mechanisms that prevent complete combustion from occurring. Simultaneous pyrometry provides the ability to relate the observed phase progression to the foil temperature throughout the reaction, and post-reaction cross-sectional electron microprobe and transmission electron microscopy (TEM) of the combusted foils identify the location, composition, and microstructure of each product phase. We have used the combined results to develop an understanding of the growth mechanisms at play during the rapid reactions. The most significant finding is that the primary combustion product, orthorhombic ZrO2, grows linearly throughout the first 1.3 s of the reaction, indicating interface-limited growth, but then switches to slower diffusion-controlled growth. The transition in growth rate coincides with the abrupt end of a temperature plateau that is associated with self-sustained combustion. A thick (≈8 µm) Al2Zr layer is observed beneath the oxidized exterior in cross-sections of the reacted foil and is likely responsible for the reaction “turning off” before complete combustion is achieved. This underlying Al-rich intermetallic layer prevents the diffusion of aluminum away from the oxide interface, causing an increasing proportion of aluminum to oxidize. The resulting alumina creates a barrier to oxygen diffusion and is responsible for the incomplete combustion in air.

We report in situ time-resolved measurements of the dynamic evolution of the volume fraction of extension twins in polycrystalline pure magnesium and in the AZ31B magnesium alloy, using synchrotron x-ray diffraction during compressive loading at high strain rates. The dynamic evolution of the twinning volume fraction leads to a dynamic evolution of the texture. Although both the pure metal and the alloy had similar initial textures, we observe that the evolution of texture is slower in the alloy. We also measured the evolution of the lattice strains in each material during deformation which, together with the twin volume fractions, allows us to place some constraints on the relative contributions of dislocation-based slip and deformation twinning to the overall plastic deformation during the dynamic deformations.

Finite element simulations are carried out to follow the evolution of residual stresses in Ti-7Al ( α -hcp) alloy, as developed under an applied stress gradient. A model built upon phenomenological mesoscopic field dislocation mechanics is employed to simulate the deformation behavior. Model predictions are validated with results generated from high energy X-ray diffraction experiments using synchrotron radiation. These experiments provide for important simulation input, viz. grain positions and orientations, and strain rate sensitivities of the prismatic and basal slip systems of Ti-7Al. X-ray diffraction data obtained from individual grains enabled calculation of strain rate sensitivities of the prismatic and basal slip systems and the values are estimated as ∼ 0.04 and ∼ 0.02 respectively. Residual stresses at the length scale of individual grains and subgrains are successfully predicted and validated against experimental data. A key achievement of the present work is the measurement and simulation of residual stress gradients within individual grains. Conclusions from this work are that grains deform mainly via prismatic slip, and accurate characterization of rate-sensitivity is needed to model the development of grain-level residual stresses.

Ordered mesoporous transition metal nitrides are interesting as high-surface-area catalyst supports, as materials for energy conversion and storage devices, and as a platform for investigating mesostructured superconductors. The Pluronics/poloxamer family of ABA triblock copolymers has been widely used to produce crystalline ordered mesoporous transition metal oxides, but is considered to pose a major challenge in the synthesis of the corresponding nitrides and other classes of inorganic materials. We report a synthesis of hexagonally-ordered mesoporous niobium nitrides based on commercially available ABA triblock copolymers of the poloxamer/Pluronics family. Employing in situ small- and wide-angle synchrotron x-ray scattering (SAXS/WAXS), we demonstrate that successful thermal processing conditions are confined to a narrow parameter window, which explains previous challenges to access such nitrides. These studies further suggest synthesis of high quality nitrides via e.g. rapid thermal processing. We ant...

To simulate the signal level of serial microcrystallography experiments at storage ring sources, data frames were collected from a large lysozyme crystal rotated about two orthogonal axes and illuminated by a dim X-ray source. Using the EMC algorithm, this study shows that three-dimensional intensity reconstruction is still feasible even without the knowledge of the crystal orientation in each data frame., Recently, there has been a growing interest in adapting serial microcrystallography (SMX) experiments to existing storage ring (SR) sources. For very small crystals, however, radiation damage occurs before sufficient numbers of photons are diffracted to determine the orientation of the crystal. The challenge is to merge data from a large number of such ‘sparse’ frames in order to measure the full reciprocal space intensity. To simulate sparse frames, a dataset was collected from a large lysozyme crystal illuminated by a dim X-ray source. The crystal was continuously rotated about two orthogonal axes to sample a subset of the rotation space. With the EMC algorithm [expand–maximize–compress; Loh & Elser (2009). Phys. Rev. E, 80, 026705], it is shown that the diffracted intensity of the crystal can still be reconstructed even without knowledge of the orientation of the crystal in any sparse frame. Moreover, parallel computation implementations were designed to considerably improve the time and memory scaling of the algorithm. The results show that EMC-based SMX experiments should be feasible at SR sources.

Optimization of an area detector involves compromises between various parameters like frame rate, read noise, dynamic range and pixel size. We have implemented and tested a novel front-end binning design in a photon-integrating hybrid pixel array detector using the MM-PAD-2.0 pixel architecture. In this architecture, the pixels can be optionally binned in a 2$\times$2 pixel configuration using a network of switches to selectively direct the output of 4 sensor pixels to a single amplifier input. Doing this allows a trade-off between frame rate and spatial resolution. Tests show that the binned pixels perform well, but with some degradation on performance as compared to an un-binned pixel. The increased parasitic input capacitance does reduce the signal collected per x-ray as well as increases the noise of the pixel. The increase in noise is, however, less than the factor of 2 increase one would observe for binning in post-processing. Spatial scans across the binned pixels show that no measured signal intensity is lost at the inner binning unit boundaries. In the high flux regime, at a 2$\times$2 pixel wide beam spot (FWHM) size, binned mode responds linearly up to a photon flux of ~10$^{7}$ x-rays/s, and performs comparably with un-binned mode up to a photon flux of ~10$^{8}$ x-rays/s. While this study demonstrates a proof of concept for front-end binning in integrating detectors, we also identify changes to this early-stage prototype which can further improve the performance of binning pixel structures., Comment: Revised manuscript reflecting minor proofreading changes

We present first characterization results, with a focus on high-flux measurements, of a fast-framing, wide-dynamic-range x-ray camera intended for high-energy imaging. The MM-PAD-2.1 uses an integrating pixel front-end with a charge removal architecture and in-pixel counter to extend the pixel well depth while maintaining low read noise across the full dynamic range. The charge-removal mechanism is dead-time-less (i.e., incoming signal continues to be integrated by the front-end while charge removal is taking place). The purpose of the high-flux characterization was to determine the maximum sustained incident flux that could be measured while still exhibiting linear behavior. To this end, a 16 × 16 pixel prototype was tested at the Advanced Photon Source at Argonne National Laboratory using 10 keV photons generated by an undulator source. The intensity of the incident beam was varied over 3 orders of magnitude using a series of attenuators, and the signal integrated by the MM-PAD-2.1 prototype was compared to that measured by a He-filled ion chamber directly upstream. Initial results indicate linear performance up to ca. 1010 ph/s in a spot spanning approximately 2 × 1.5 pixels (FWHM). The onset of transient radiation damage was observed during these measurements, characterized primarily by failure of digital readout from the detector ASIC. These effects were observed to reverse after annealing at 30° C for several hours, with full recovery of the detector readout.

This article describes a highly parallel event driven interface between a Pixel Array Detector (PAD) and its processing electronics. The method used was originally developed for the Field Programmable Gate Array (FPGA) X-ray Pixel Array detector to allow for real-time processing of X-ray image data on its processing FPGA. This interface potentially allows for entirely asynchronous data transfer off the detector at rates exceeding 110Gbps and operates without the need for a constantly running clock. It thus presents a potential a low-power, low-noise interface option for 10-bit data transfer from photon-counting detectors at frame rates greater than 1MHz with no input dead time. This interface has been successfully tested on 64 independent 16-pixel channels at a transfer frequency of 294MHz achieving maximum data transfer rates of 16.7 Gbps.

Objectives Analysis of fresh capillary blood using darkfield microscopy involves measuring red blood cell (RBC) diameter to assess for microcytosis or macrocytosis. The reference range for normal RBC diameter currently used in fresh capillary blood analysis by darkfield microscopy (FCB-DM) is the same as that used in haematology, i.e. 6.2–8.2μm. However, the haematology reference range for RBC diameter refers to stained and dried blood specimens. Evidence from early research suggests that fresh RBCs are larger than stained and dried RBCs. The following article presents methodology and findings for the objective measurement of RBC diameter using the FCB-DM technique. Methods FCB-DM screenings of 14 consenting participants were photographed to permit a quantitative analysis of RBC size and morphology. Participants also provided a venous blood sample for pathology testing, which included markers for RBC size. The researcher was blinded to the pathology results until all FCB-DM data analysis was complete. Results All participants had a normal reference range for all pathology markers tested. The mean RBC diameter, determined by FCB-DM, was 8.51μm ( s =0.161, s 2 =0.026, range=±0.656) and the mode was 8.55μm. Conclusion These findings support evidence from early studies of RBC diameter, that fresh blood cells observed with darkfield microscopy are approximately 1.3μm larger than dried and stained RBCs. Further research using a larger sample size is recommended.

Recent reports from UN International Resource Panel call for double decoupling – decoupling of material use and related environmental impacts from economic growth. The construction and use of buildings constitute a significant portion of energy use, GHG emissions and extraction of materials in Europe. One of the central strategies addressing double decoupling in the construction industry is reuse and recycling of building materials and components that would limit raw material extraction and embodied emissions related to new products. A recent IPCC report states the urgency of limiting GHG emissions already by 2030 to remain below the 1.5-degree target. Given this timeframe, reducing emissions in the early stages of a buildings lifetime appears worth considering, meaning prioritizing embodied over operational emissions. The case study used for this article is an ongoing building project “Selbukassa” (“the Selbu box”) situated in Svartlamon – an experimental neighbourhood for urban ecology in Trondheim, Norway. It is a bottom-up, self-build project with a strong focus on reuse of materials. The 300 m2 building will house 4 families and is built reusing an old log house, as well as CLT-elements from a former pavilion used for exhibiting an art piece by the local artist Killi Olsen. Other salvaged materials and components include windows, doors, roof slate and most of the internal and external finishes. Due to the experimental status of the area and to allow for reuse of building components with lower energy performance, the fulfilment of energy requirements in the building code TEK 17 was not required by the local building authorities. The article examines the embodied and operational emissions of Selbukassa, and compares it with a reference building with no reused components and complying with energy requirements in the building code TEK17. Simien v.6.009 is used for energy simulations of the two cases, and LCA tool One Click LCA Norge for NS 3720:2018 with data sourced from Norwegian and other European EPDs is used for estimating embodied emissions. The article investigates the possible savings in emissions linked to reuse of materials, as well as the trade-offs between reused components with worse energy performance and the consequential higher energy demand. The article contributes to the discussion about the various implications of reuse of materials and more generally on how the built environment could respond more optimally to a combined emission and resource use reduction challenge.