MRI: Acquisition of a field emission electron microprobe for Caltech Division of Geological and Planetary Sciences

MRI：为加州理工学院地质与行星科学部购买场发射电子探针

• 批准号: 2117942
• 负责人: Paul Asimow
• 金额: $ 100万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2117942&HistoricalAwards=false
• 关键词: MRI; Acquisition; field; emission; electron

This Major Research Instrumentation (MRI) award will enable the purchase, installation, and commissioning of a state-of-the-art instrument for chemical analysis of natural and engineered solid materials down to the nanometer (one billionth of a meter) scale. The instrument will be available to all science and engineering programs across the Caltech campus, NASA’s Jet Propulsion Laboratory, as well as to outside users. The instrument may be operated remotely and will be made available via the Remotely Accessible Instruments in Nanotechnology (RAIN) consortium for free access by student researchers and classes at minority-serving institutions nationwide ranging from community and technical colleges to high schools and even elementary schools. The electron microprobe is a basic tool of solid Earth geology and geochemistry as well as related fields such as meteoritics and planetary sample return, environmental microbiology, material science and nanotechnology. The advanced electron source included in this instrument provides a very bright, focused beam that enables imaging at high spatial resolution and excitation of characteristic X-rays from a very small analytical volume. Each chemical element emits X-rays at particular wavelengths; the count rate of X-ray photons emitted by a sample at these characteristic wavelengths is proportional to the concentration of that element in the sample. The electron probe automates the job of separating X-rays by wavelength, counting the number of X-ray photons emitted at particular wavelengths, and comparing the count rate in an unknown material to that in standard materials. This allows the electron microprobe to detect when an element is present above a low detection limit and to determine the abundance of each element in a sample with about 1% relative precision. Initial applications will include characterization of tiny mineral grains in meteorites that date back to (or even precede) the origin of the Solar system, experimental samples that reproduce conditions in the deep Earth or during collisions in the asteroid belt, and functional materials for batteries and energy generation.The key capabilities that the new instrument will bring are the field emission electron source, the Si-drift detector energy dispersive X-ray spectrometer, and the high-resolution cathodoluminescence sensor. While nanoscale imaging resolution, essential for targeting analyses and ensuring sample homogeneity, is straightforward, optimizing the spatial resolution of quantitative analysis without sacrificing accuracy or precision, requires special care. The new instrument will support a study of new approaches to unsupported thin specimen analysis as a path to high-resolution analysis. Challenges to be overcome include holding unsupported specimens in the beam path, updated software that accounts accurately for thin samples, and an extensive campaign of verification against well-characterized standards. Turning to more of the applications of the new instrument and its improved imaging and analysis capabilities, researchers will focus on several goals. These include: (1) analysis of experimental samples to probe diffusion at short length scales, fine-grained multiphase assemblages, and synthesized starting materials whose homogeneity at the nano-scale is essential information; (2) analysis of terrestrial igneous, metamorphic, and sedimentary rocks including basaltic glasses that may contain nano-inclusions, zircons for geochronology, and redox-sensitive tracers with unknown hosting phases; (3) analysis of meteorites and new nano-minerals including refractory inclusions, high-pressure shock-induced phases, non-destructive bulk analysis, and bio-synthetic single-domain magnetic crystals; and (4) analysis of microbiological specimens from the environment and culture, with single-cell resolution of the distribution of key macro- and micro-nutrient elements. This award was co-funded by the MRI program and the Instrumentation and Facilities program in the Earth Science Division.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这一重大研究仪器(MRI)奖将使人们能够购买、安装和调试最先进的仪器，用于精确到纳米(十亿分之一米)尺度的天然和工程固体材料的化学分析。该仪器将向加州理工大学园区、NASA喷气推进实验室的所有科学和工程项目以及外部用户开放。该仪器可以远程操作，并将通过远程可访问纳米技术仪器(RAIN)联盟提供，供学生研究人员和全国范围内从社区和技术学院到高中甚至小学的少数群体服务机构的课程免费使用。电子探针是固体地球地质和地球化学的基本工具，也是陨石和行星样品回收、环境微生物学、材料科学和纳米技术等相关领域的基本工具。该仪器中包含的先进电子源提供了非常明亮的聚焦光束，能够以高空间分辨率成像，并从非常小的分析体积激发出特征X射线。每种化学元素在特定波长发射X射线；样品在这些特征波长发射的X射线光子的计数速率与该元素在样品中的浓度成正比。电子探测器自动完成按波长分离X射线的工作，计算在特定波长发射的X射线光子的数量，并将未知材料和标准材料中的计数率进行比较。这允许电子探针检测元素何时存在于低检测下限之上，并以大约1%的相对精度确定样品中每种元素的丰度。最初的应用将包括表征可追溯到(或甚至早于)太阳系起源的陨石中的微小矿物颗粒，再现地球深处或小行星带碰撞期间条件的实验样品，以及用于电池和能源产生的功能材料。新仪器将带来的关键能力是场发射电子源、硅漂移探测器能量色散X射线光谱仪和高分辨率阴极发光传感器。虽然纳米级成像分辨率对于靶向分析和确保样品均一性至关重要，但在不牺牲准确度或精密度的情况下优化定量分析的空间分辨率需要特别小心。新仪器将支持对无支撑薄层样品分析的新方法的研究，作为实现高分辨率分析的途径。需要克服的挑战包括在光束路径中保持无支撑的样品，更新准确解释薄样品的软件，以及针对具有良好特征的标准开展广泛的验证活动。在谈到新仪器的更多应用及其改进的成像和分析能力时，研究人员将专注于几个目标。这些包括：(1)分析实验样品以探测短尺度的扩散、细粒多相组合和合成起始物质，其在纳米尺度上的均质性是基本信息；(2)陆地火成岩、变质岩和沉积岩的分析，包括可能含有纳米包裹体的玄武岩玻璃、锆石和具有未知赋存相的氧化还原敏感示踪剂；(3)陨石和新的纳米矿物的分析，包括耐火包裹体、高压冲击波诱导相、非破坏性块体分析和生物合成的单域磁性晶体；以及(4)从环境和培养中分析微生物标本，用单细胞分辨关键的宏微营养元素的分布。该奖项由核磁共振计划和地球科学部的仪器和设施计划共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。