Hard X-ray imaging and tomography at the Biomedical Imaging and Therapy beamlines of Canadian Light Source.

The Biomedical Imaging and Therapy facility of the Canadian Light Source comprises two beamlines, which together cover a wide X-ray energy range from 13 keV up to 140 keV. The beamlines were designed with a focus on synchrotron applications in preclinical imaging and veterinary science as well as microbeam radiation therapy. While these remain a major part of the activities of both beamlines, a number of recent upgrades have enhanced the versatility and performance of the beamlines, particularly for high-resolution microtomography experiments. As a result, the user community has been quickly expanding to include researchers in advanced materials, batteries, fuel cells, agriculture, and environmental studies. This article summarizes the beam properties, describes the endstations together with the detector pool, and presents several application cases of the various X-ray imaging techniques available to users.

Temperature-Dependent Chemical and Physical Microstructure of Li Metal Anodes Revealed through Synchrotron-Based Imaging Techniques.

The Li metal anode has been long sought-after for application in Li metal batteries due to its high specific capacity (3860 mAh g-1 ) and low electrochemical potential (-3.04 V vs the standard hydrogen electrode). Nevertheless, the behavior of Li metal in different environments has been scarcely reported. Herein, the temperature-dependent behavior of Li metal anodes in carbonate electrolyte from the micro- to macroscales are explored with advanced synchrotron-based characterization techniques such as X-ray computed tomography and energy-dependent X-ray fluorescence mapping. The importance of testing methodology is exemplified, and the electrochemical behavior and failure modes of Li anodes cycled at different temperatures are discussed. Moreover, the origin of cycling performance at different temperatures is identified through analysis of Coulombic efficiencies, surface morphology, and the chemical composition of the solid electrolyte interphase in quasi-3D space with energy-dependent X-ray fluorescence mappings coupled with micro-X-ray absorption near edge structure. This work provides new characterization methods for Li metal anodes and serves as an important basis toward the understanding of their electrochemical behavior in carbonate electrolytes at different temperatures.

Showcasing the application of synchrotron-based X-ray computed tomography in host-pathogen interactions: The role of wheat rachilla and rachis nodes in Type-II resistance to Fusarium graminearum.

Fusarium head blight, caused primarily by Fusarium graminearum (Fg), is one of the most devastating diseases of wheat. Host resistance in wheat is classified into five types (Type-I to Type-V), and a majority of moderately resistant genotypes carry Type-II resistance (resistance to pathogen spread in the rachis) alleles, mainly from the Chinese cultivar Sumai 3. Histopathological studies in the past failed to identify the key tissue in the spike conferring resistance to pathogen spread, and most of the studies used destructive techniques, potentially damaging the tissue(s) under study. In the present study, nondestructive synchrotron-based phase contrast X-ray imaging and computed tomography techniques were used to confirm the part of the wheat spike conferring Type-II resistance to Fg spread, thus showcasing the application of synchrotron-based techniques to image host-pathogen interactions. Seven wheat genotypes of moderate resistance to Fusarium head blight were studied for changes in the void space volume fraction and grayscale/voxel intensity following Fg inoculation. Cell-wall biopolymeric compounds were quantified using Fourier-transform midinfrared spectroscopy for all genotype-treatment combinations. The study revealed that the rachilla and rachis nodes together are structurally important in conferring Type-II resistance. The structural reinforcement was not necessarily observed from lignin deposition but rather from an unknown mechanism.

Spectroscopic and photophysical properties of ZnTPP in a room temperature ionic liquid.

The steady-state absorption and emission spectra and the time-resolved Soret- and Q-band excited fluorescence profiles of the model metalloporphyrin, ZnTPP, have been measured in a highly purified sample of the common room temperature ionic liquid, [bmim][PF6]. S2-S0 emission resulting from Soret-band excitation behaves in a manner completely consistent with that of molecular solvents of the same polarizability. The ionic nature of the solvent and its slow solvation relaxation times have no significant effect on the nature of the radiationless decay of the S2 state, which decays quantitatively to S1 at a population decay rate that is consistent with the weak coupling case of radiationless transition theory (energy gap law). The ratio of the intensities of the Qα:Qß (0-0:1-0) bands is consistent with the solvatochromic shift correlation data obtained for molecular solvents. The temporal S1 fluorescence decay profiles measured at a single emission wavelength are biexponential; the longer-lived major component is similar to that observed for ZnTPP in molecular solvents, and the minor shorter-lived component is attributed to solvent relaxation processes on a nanosecond time scale.