Worbs Lena, Roth Nils, Lübke Jannik, Estillore Armando D, Xavier P Lourdu, Samanta Amit K, Küpper Jochen
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
J Appl Crystallogr. 2021 Nov 16;54(Pt 6):1730-1737. doi: 10.1107/S1600576721009973. eCollection 2021 Dec 1.
Single-particle X-ray diffractive imaging (SPI) of small (bio-)nanoparticles (NPs) requires optimized injectors to collect sufficient diffraction patterns to allow for the reconstruction of the NP structure with high resolution. Typically, aerodynamic lens-stack injectors are used for NP injection. However, current injectors were developed for larger NPs (>100 nm), and their ability to generate high-density NP beams suffers with decreasing NP size. Here, an aerodynamic lens-stack injector with variable geometry and a geometry-optimization procedure are presented. The optimization for 50 nm gold-NP (AuNP) injection using a numerical-simulation infrastructure capable of calculating the carrier-gas flow and the particle trajectories through the injector is also introduced. The simulations were experimentally validated using spherical AuNPs and sucrose NPs. In addition, the optimized injector was compared with the standard-installation 'Uppsala injector' for AuNPs. Results for these heavy particles showed a shift in the particle-beam focus position rather than a change in beam size, which results in a lower gas background for the optimized injector. Optimized aerodynamic lens-stack injectors will allow one to increase NP beam density, reduce the gas background, discover the limits of current injectors and contribute to structure determination of small NPs using SPI.
对小（生物）纳米颗粒（NP）进行单粒子X射线衍射成像（SPI）需要优化的注入器，以收集足够的衍射图案，从而能够高分辨率重建NP结构。通常，气动透镜堆叠式注入器用于NP注入。然而，当前的注入器是为较大的NP（>100 nm）开发的，随着NP尺寸减小，其产生高密度NP束的能力会受到影响。在此，提出了一种具有可变几何形状的气动透镜堆叠式注入器和一种几何形状优化程序。还介绍了使用能够计算载气流和通过注入器的粒子轨迹的数值模拟基础设施对50 nm金纳米颗粒（AuNP）注入进行的优化。使用球形AuNP和蔗糖NP对模拟进行了实验验证。此外，将优化后的注入器与用于AuNP的标准安装“乌普萨拉注入器”进行了比较。这些重粒子的结果显示粒子束焦点位置发生了偏移，而不是束尺寸发生了变化，这导致优化后的注入器的气体背景更低。优化后的气动透镜堆叠式注入器将使人们能够提高NP束密度、降低气体背景、发现当前注入器的局限性，并有助于使用SPI确定小NP的结构。
