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.

这项主要的研究仪器（MRI）奖将使购买，安装和调试最先进的仪器，用于对天然和工程固体材料进行化学分析，直至纳米级（十亿分之一）。该乐器将用于加州理工学院校园的所有科学和工程计划，NASA的喷气推进实验室以及外部用户。该仪器可以远程操作，并将通过纳米技术（RAIN）消费者的远程访问仪器提供，可供全国各地的少数族裔服务机构的学生研究人员和班级免费访问，从社区和技术学院到高中，甚至是小学。电子微探测是固体地质地质和地球化学以及相关领域的基本工具，例如气象和行星样品回报，环境微生物学，材料科学和纳米技术。该仪器中包含的高级电子源提供了非常明亮的聚焦光束，该光束可以在高空间分辨率和特征性X射线的兴奋下进行成像，从很小的分析体积开始。每个化学元件在特定波长处发射X射线；样品在这些特征波长下发射的X射线照片的计数速率与样品中该元素的浓度成正比。电子探测器可以自动通过波长将X射线分离，计算在特定波长处发射的X射线照片的数量，并将未知材料中的计数速率与标准材料中的计数速率进行比较。这允许电子微探针检测何时将元素显示在低检测极限以上，并确定样品中每个元素的抽象，其相对精度约为1％。最初的应用将包括在陨石中的微小矿物颗粒的表征，这些矿物颗粒可以追溯到（甚至是之前）太阳系的起源，在深层地球或小行星带碰撞期间重现条件的实验样品以及电池的功能材料以及能量和能量生成的功能。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匀性至关重要，但至关重要，但在不牺牲准确性或精确度的情况下优化了定量分析的空间分辨率，需要特殊护理。新仪器将支持对不支持薄标本分析的新方法的研究，以作为进行高分辨率分析的途径。要克服的挑战包括在梁路径中持有不支持的标本，更新的软件，可准确说明薄样品，以及针对特征良好的标准进行广泛的验证活动。研究人员将介绍新工具的更多应用及其改进的成像和分析功能，研究人员将专注于几个目标。其中包括：（1）分析实验样品以在短长度尺度上探测扩散，细颗粒的多相组合以及合成的起始材料，其同质性在纳米级是必不可少的信息； （2）分析陆生火成岩，变质和沉积岩，包括可能包含纳米嵌入的基本玻璃，用于地年代学的锆石以及具有未知宿主阶段的氧化还原敏感的示踪剂； （3）分析陨石和新的纳米矿物，包括难治性包含，高压冲击诱导的相，非破坏性体积分析和生物合成单一磁盘磁性晶体； （4）分析来自环境和培养的微生物标本，并通过关键宏观和微营养元素的分布分辨率分辨率。该奖项是由MRI计划和地球科学部的仪器和设施计划共同资助的。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，认为通过评估被认为是宝贵的支持。