RESUMEN
The performance of metal and polymer foams used in inertial confinement fusion (ICF), inertial fusion energy (IFE), and high-energy-density (HED) experiments is currently limited by our understanding of their nanostructure and its variation in bulk material. We utilized an X-ray-free electron laser (XFEL) together with lensless X-ray imaging techniques to probe the 3D morphology of copper foams at nanoscale resolution (28 nm). The observed morphology of the thin shells is more varied than expected from previous characterizations, with a large number of them distorted, merged, or open, and a targeted mass density 14% less than calculated. This nanoscale information can be used to directly inform and improve foam modeling and fabrication methods to create a tailored material response for HED experiments.
RESUMEN
A cavity-based X-ray free-electron laser (CBXFEL) is a possible future direction in the development of fully coherent X-ray sources. CBXFELs consist of a low-emittance electron source, a magnet system with several undulators and chicanes, and an X-ray cavity. The X-ray cavity stores and circulates X-ray pulses for repeated FEL interactions with electron pulses until the FEL reaches saturation. CBXFEL cavities require low-loss wavefront-preserving optical components: near-100%-reflectivity X-ray diamond Bragg-reflecting crystals, outcoupling devices such as thin diamond membranes or X-ray gratings, and aberration-free focusing elements. In the framework of the collaborative CBXFEL research and development project of Argonne National Laboratory, SLAC National Accelerator Laboratory and SPring-8, we report here the design, manufacturing and characterization of X-ray optical components for the CBXFEL cavity, which include high-reflectivity diamond crystal mirrors, a diamond drumhead crystal with thin membranes, beryllium refractive lenses and channel-cut Si monochromators. All the designed optical components have been fully characterized at the Advanced Photon Source to demonstrate their suitability for the CBXFEL cavity application.
RESUMEN
Supercritical fluids (SCFs) can be found in a variety of environmental and industrial processes. They exhibit an anomalous thermodynamic behavior, which originates from their fluctuating heterogeneous micro-structure. Characterizing the dynamics of these fluids at high temperature and high pressure with nanometer spatial and picosecond temporal resolution has been very challenging. The advent of hard x-ray free electron lasers has enabled the development of novel multi-pulse ultrafast x-ray scattering techniques, such as x-ray photon correlation spectroscopy (XPCS) and x-ray pump x-ray probe (XPXP). These techniques offer new opportunities for resolving the ultrafast microscopic behavior in SCFs at unprecedented spatiotemporal resolution, unraveling the dynamics of their micro-structure. However, harnessing these capabilities requires a bespoke high-pressure and high-temperature sample system that is optimized to maximize signal intensity and address instrument-specific challenges, such as drift in beamline components, x-ray scattering background, and multi-x-ray-beam overlap. We present a pressure cell compatible with a wide range of SCFs with built-in optical access for XPCS and XPXP and discuss critical aspects of the pressure cell design, with a particular focus on the design optimization for XPCS.
RESUMEN
Objective@#To analyze the emotional and behavioral problems and associated factors of the only and non only child, and to provide some clues for further monitoring and intervention of psychological and behavioral development among preschool children.@*Methods@#Using a convenience sampling method, a total of 45 065 children enrolled in 153 kindergartens in 23 districts and counties of Chengdu were selected from May to June 2021 to investigate demographic characteristics and children s psycho behavioral development through online questionnaires filled out by their guardians. The Chi square tests were used to analyze whether the differences in abnormality rates of each dimension were statistically significant between the only and non only children. The emotional and behavioral problems of only children and non only children were analyzed by propensity score measurement.@*Results@#The detection rate of abnormal emotional behavior problems in children was 6.10%, including 6.34% in the only child group and 5.84 % in the non only child group. After matching, total difficulty score, and scores of emotional symptoms, conduct problems, hyperactive attention deficit, peer interaction, and social behavior differed between the only child group and the non only child group ( t =9.91, 8.97, 3.91, 15.57, -5.46, 4.08, P <0.01).@*Conclusion@#In terms of the total score of difficulties, emotional symptoms, moral problems, and hyperactivity attention defects, the non only child is better than the only child，but the opposite is true in terms of peer interaction and social behavior. Mental health conditions among the only child should be paid more attention. Whether or not the only child should be taken as an important consideration for preschool children s mental health care.