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Accurate characterization of high-power laser parameters, especially the near-field and far-field distributions, is crucial for inertial confinement fusion experiments. In this paper, we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging. This method has the advantage of being able to simultaneously calculate both the near-field (intensity and wavefront/phase) and far-field (focal-spot) distributions using the reconstructed complex amplitude. More importantly, the focal-spot distributions at different focal planes can also be calculated. To verify the feasibility, the complex amplitude optical field of the high-power pulsed laser was measured after static aberrations calibration. Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement. In addition, the far-field focal spot exhibits a higher dynamic range (176 dB) than that of traditional direct imaging (62 dB).
This review article describes the co-evolution of structural biology as a discipline and the Protein Data Bank (PDB), established in 1971 as the first open-access data resource in biology by like-minded structural scientists. As the PDB archive grew in size and scope to encompass macromolecular crystallography, NMR spectroscopy, and cryo-electron microscopy, new technologies were developed to ingest, validate, curate, store, and distribute the information. Community engagement ensured that the needs of structural biologists (data depositors) and data consumers were met. Today, the archive houses more than 230,000 experimentally determined structures of proteins, nucleic acids, and macromolecular machines and their complexes with one another and small-molecule ligands. Aggregate costs of PDB data preservation are ~1% of the cost of structure determination. The enormous impact of PDB data on basic and applied research and education across the natural and medical sciences is presented and highlighted with illustrative examples. Enablement of de novo protein structure prediction (AlphaFold2, RoseTTAfold, OpenFold, etc.) is the most widely appreciated benefit of having a corpus of rigorously validated, expertly curated 3D biostructure data.
For near-future missions planed for Mars Sample Return (MSR), an international working group organized by the Committee on Space Research (COSPAR) developed the sample safety assessment framework (SSAF). For the SSAF, analytical instruments were selected by taking the practical limitations of hosting them within a facility with the highest level of biosafety precautions (biosafety level 4) and the precious nature of returned samples into account. To prepare for MSR, analytical instruments of high sensitivity need to be tested on effective Mars analogue materials. As an analogue material, we selected a rock core of basalt, a prominent rock type on the Martian surface. Two basalt samples with aqueous alteration cached in Jezero crater by the Perseverance rover are planned to be returned to Earth. Our previously published analytical procedures using destructive but spatially sensitive instruments such as nanoscale secondary ion mass spectrometry (NanoSIMS) and transmission electron microscopy coupled to energy-dispersive spectroscopy revealed microbial colonization at clay-filled fractures. With an aim to test the capability of an analytical instrument listed in SSAF, we now extend that work to conventional Fourier transform infrared (FT-IR) microscopy with a spatial resolution of 10 μm. Although Fe-rich smectite called nontronite was identified after crushing some portion of the rock core sample into powder, the application of conventional FT-IR microscopy is limited to a sample thickness of <30 μm. In order to obtain IR-based spectra without destructive preparation, a new technique called optical-photothermal infrared (O-PTIR) spectroscopy with a spatial resolution of 0.5 μm was applied to a 100 μm thick section of the rock core. By O-PTIR spectroscopic analysis of the clay-filled fracture, we obtained in-situ spectra diagnostic to microbial cells, consistent with our previously published data obtained by NanoSIMS. In addition, nontronite identification was also possible by O-PTIR spectroscopic analysis. From these results, O-PTIR spectroscopy is suggested be superior to deep ultraviolet fluorescence microscopy/μ-Raman spectroscopy, particularly for smectite identification. A simultaneous acquisition of the spatial distribution of structural motifs associated with biomolecules and smectites is critical for distinguishing biological material in samples as well as characterizing an abiotic background.
Thanks to advances in plasma science and enabling technology, mirror machines are being reconsidered for fusion power plants and as possible fusion volumetric neutron sources. However, cross-field transport and turbulence in mirrors remains relatively understudied compared with toroidal devices. Turbulence and transport in mirror configurations were studied utilizing the flexible magnetic geometry of the Large Plasma Device (LAPD). Multiple mirror ratios from $M=1$ to $M=2.68$ and three mirror-cell lengths from $L=3.51$ to $L=10.86$ m were examined. Langmuir and magnetic probes were used to measure profiles of density, temperature, potential and magnetic field. The electric field-fluctuation-driven ${\tilde {\boldsymbol{E}}} \times {\boldsymbol{B}}$ particle flux, where $\boldsymbol{B}$ is the background field, was calculated from these quantities. Two probe correlation techniques were used to infer wavenumbers and two-dimensional structure. Cross-field particle flux and density fluctuation power decreased with increased mirror ratio. Core density and temperatures remain similar with mirror ratio, but radial line-integrated density increased. The physical expansion of the plasma in the mirror cell by using a higher field in the source region may have led to reduced density fluctuation power through the increased gradient scale length. This increased scale length reduced the growth rate and saturation level of rotational interchange and drift-like instabilities. Despite the introduction of magnetic curvature, no evidence of mirror-driven instabilities – interchange, velocity space or otherwise – were observed. For curvature-induced interchange, many possible stabilization mechanisms were present, suppressing the visibility of the instability.
The betatron radiation source features a micrometer-scale source size, a femtosecond-scale pulse duration, milliradian-level divergence angles and a broad spectrum exceeding tens of keV. It is conducive to the high-contrast imaging of minute structures and for investigating interdisciplinary ultrafast processes. In this study, we present a betatron X-ray source derived from a high-charge, high-energy electron beam through a laser wakefield accelerator driven by the 1 PW/0.1 Hz laser system at the Shanghai Superintense Ultrafast Laser Facility (SULF). The critical energy of the betatron X-ray source is 22 ± 5 keV. The maximum X-ray flux reaches up to 4 × 109 photons for each shot in the spectral range of 5–30 keV. Correspondingly, the experiment demonstrates a peak brightness of 1.0 × 1023 photons·s−1·mm−2·mrad−2·0.1%BW−1, comparable to those demonstrated by third-generation synchrotron light sources. In addition, the imaging capability of the betatron X-ray source is validated. This study lays the foundation for future imaging applications.