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Laser-wakefeld accelerators (LWFAs) are high acceleration-gradient plasma-based particle accelerators capable of producing ultra-relativistic electron beams. Within the strong focusing felds of the wakefeld, accelerated electrons undergo betatron oscillations, emitting a bright pulse of X-rays with a micrometer-scale source size that may be used for imaging applications. Non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials can provide insight into their processing, structure, and performance. To demonstrate the imaging capability of X-rays from an LWFA we have examined an irregular eutectic in the aluminum-silicon (Al-Si) system. The lamellar spacing of the Al-Si eutectic microstructure is on the order of amore » few micrometers, thus requiring high spatial resolution. We present comparisons between the sharpness and spatial resolution in phase contrast images of this eutectic alloy obtained via X-ray phase contrast imaging at the Swiss Light Source (SLS) synchrotron and X-ray projection microscopy via an LWFA source. An upper bound on the resolving power of 2.7±0.3μm of the LWFA source in this experiment was measured. These results indicate that betatron X-rays from laser wakefeld acceleration can provide an alternative to conventional synchrotron sources for high resolution imaging of eutectics and, more broadly, complex microstructures.« less

Synchrotron characterization techniques provide some of the most powerful tools for the study of film structure and chemistry. The brilliance and tunability of the Advanced Photon Source allow access to scattering and spectroscopic techniques unavailable with in-house laboratory setups and provide the opportunity to probe various atomic layer deposition (ALD) processes in situ starting at the very first deposition cycle. In this work, we present the design and implementation of a portable ALD instrument which possesses a modular reactor scheme that enables simple experimental switchover between various beamlines and characterization techniques. We present in situ results for (1) X-ray surfacemore » scattering and reflectivity measurements of epitaxial ZnO ALD on sapphire, (2) grazing-incidence small angle scattering of MnO nucleation on silicon, and (3) grazing-incidence X-ray absorption spectroscopy of nucleation-regime Er₂O₃ ALD on amorphous ALD alumina and single crystalline sapphire.« less

Novel X-ray imaging of structural domains in a ferroelectric epitaxial thin film using diffraction contrast is presented. The full-field hard X-ray microscope uses the surface scattering signal, in a reflectivity or diffraction experiment, to spatially resolve the local structure with 70 nm lateral spatial resolution and sub-nanometer height sensitivity. Sub-second X-ray exposures can be used to acquire a 14 µm × 14 µm image with an effective pixel size of 20 nm on the sample. The optical configuration and various engineering considerations that are necessary to achieve optimal imaging resolution and contrast in this type of microscopy are discussed.

Here, we present an analysis of Nb₃Sn surface layers grown on a bulk Nb coupon prepared at the same time and by the same vapor diffusion process used to make Nb₃Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveal a well developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperature's (T_c) up to 16.3K. Transmission electron microscopy (TEM) performed on cross sections of the sample's surface shows a ~ 2 microns thick Nb₃Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio ofmore » 3:1 with buried substoichiometric regions with a ratio of 5:1. Synchrotron diffraction experiments indicate a polycrystalline Nb₃Sn film and confirm the presence of Nb rich regions that occupies about a third of the coating volume. These low T_c regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb₃Sn -coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.« less