SPring-8/SACLA Research Report

　Corneal blindness is a leading cause of vision loss worldwide. Corneal curvature and transparency depend on the cornea’s unique collagen fibril architecture and, while much progress has been made in mapping collagen structure in cadaveric corneas, there is currently no way of imaging collagen fibril organization in the living eye. Our ultimate goal is to develop new artificial intelligence (AI)-assisted bioimaging technology to map collagen structure in live patient corneas. Here we present results from SPring-8 beamline BL40B2 in the form of wide-angle X-ray scattering (WAXS) maps of corneal structure from ex-vivo porcine eyes, which were previously scanned via optical coherence tomography (OCT), and will be used as a platform to train machine learning algorithms to “read” the equivalent in-vivo data from OCT images obtained from human patients.

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　The temperature rise due to high current/power operations and stress caused by the expansion or contraction of electrodes by lithium (de)-intercalation is known to be a degradation factor in lithium-ion batteries (LIBs). Therefore, in this study, a new technique is proposed to simultaneously measure the internal temperature and stress in the 18650-type LIB during its operation. The operando measurement involved retaining a constant gage volume using rotating spiral slits, obtaining X-ray diffraction images using a highly sensitive two-dimensional detector, and employing the sin²ψ method to separate the stress and change in temperature. During the charging process, at the 1C current rate, the anode expansion, owing to the lithium intercalation, induced the radial compressive stress in the Cu anode collector. The radial stress changes of the Cu anode collector were -31 MPa (compression) and 44 MPa (tensile) during the 1C charge and discharge processes, respectively. Moreover, the internal temperature, which was higher than the surface temperature, was calculated by considering the radial stress change during the battery operation. During the 4C cycle, the surface and internal temperatures rose by 26 °C and 42 °C, respectively. The results indicate that the internal temperature and stress in the 18650-LIB were successfully measured during battery operation.

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　The goal of the experiment was to image the field induced charge dynamics in Magnesium Oxide (MgO) poly-crystals in the regime of non-perturbative high-order harmonic generation using femtosecond X-ray powder diffraction. We employ asymmetric optical fields obtained from two-color fields at appropriate phase delays to pump the sample. We expect this approach to lead to an increase in the measurable time-integrated drift currents and allow us to better measure the effective changes in the X-ray diffraction intensities in several diffraction peaks. The ability to control the charge transfer process in our samples has implications for ultrafast optical switching of currents.

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