Publications
Practical considerations for high-speed X-ray pixel array detectors and X-ray sensing materials
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.
Fixed-Target serial oscillation crystallography at room temperature
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.
Intermittent plasticity in individual grains: A study using high energy x-ray diffraction
Long-standing evidence suggests that plasticity in metals may proceed in an intermittent fashion. While the documentation of intermittency in plastically deforming materials has been achieved in several experimental settings, efforts to draw connections from dislocation motion and structure development to stress relaxation have been limited, especially in the bulk of deforming polycrystals.
Development of a Fast-Framing X-Ray Camera with Wide Dynamic Range for High-Energy Imaging
With upgrades planned at several x-ray light sources, including improvements to beam quality and brilliance at high energies (> 20 keV), corresponding advances in area detector technology are needed. Pixel array detectors (PADs) are one class of detectors that can meet these needs. PADs feature highly customizable CMOS circuitry for signal processing and data streaming, which facilitates high frame rates and the exploration of various dynamic range extension techniques.
Solving protein structure from sparse serial microcrystal diffraction data at a storage-ring synchrotron source
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.
The consequences of cavity creation on the folding landscape of a repeat protein depend upon context
The effect of introducing internal cavities on protein native structure and global stability has been well documented, but the consequences of these packing defects on folding free-energy landscapes have received less attention. We investigated the effects of cavity creation on the folding landscape of the leucine-rich repeat protein pp32 by high-pressure (HP) and urea-dependent NMR and high-pressure small-angle X-ray scattering (HPSAXS).
Electron ptychography of 2D materials to deep sub-ångström resolution
Aberration-corrected optics have made electron microscopy at atomic resolution a widespread and often essential tool for characterizing nanoscale structures. Image resolution has traditionally been improved by increasing the numerical aperture of the lens (α) and the beam energy, with the state-of-the-art at 300 kiloelectronvolts just entering the deep sub-ångström (that is, less than 0.5 ångström) regime. Two-dimensional (2D) materials are imaged at lower beam energies to avoid displacement damage from large momenta transfers, limiting spatial resolution to about 1 ångström.
Strain Mapping of Two-Dimensional Heterostructures with Subpicometer Precision
Next-generation, atomically thin devices require in-plane, one-dimensional heterojunctions to electrically connect different two-dimensional (2D) materials. However, the lattice mismatch between most 2D materials leads to unavoidable strain, dislocations, or ripples, which can strongly affect their mechanical, optical, and electronic properties. We have developed an approach to map 2D heterojunction lattice and strain profiles with subpicometer precision and the ability to identify dislocations and out-of-plane ripples.
In Situ Time-Resolved Measurements of Extension Twinning During Dynamic Compression of Polycrystalline Magnesium
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.
Mechanisms of oxide growth during the combustion of Al:Zr nanolaminate foils
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.