MRI: Development of an Ultrafast Electron Microscope with <1nm-ps Spatio-Temporal Resolution

伊利诺伊大学芝加哥分校（UIC）的科学家们将合作开发一种时空分辨率小于1nm-ps的超快电子显微镜（UEM）的功能原型。为了实现对当前仪器技术三个数量级的改进，将结合几种现有的最先进的技术：高功率，1-100MHz，飞秒激光系统将用于从大面积纳米图形光电阴极产生初始空间相干电子脉冲；一个短（20cm）的显微镜柱，如有必要，将结合一个射频脉冲压缩腔，将耦合到物镜，样品台，投影仪系统的JEOL JEM 100CX电子显微镜退役；生成的电子图像将使用10微米孔径的微通道板电子探测器进行检测，该探测器与25微米像素的1kx1k CCD相机光学耦合-提供原子分辨率的潜力。这种UEM的发展所提供的前所未有的时空分辨率将为分子生物学、催化、凝聚态物质和材料物理学、纳米科学和纳米技术等多种跨学科的研究领域提供重要的新研究工具。一旦研制成功，全世界的科学界将可以通过ucic的研究资源中心使用该仪器；因此，也促进了机构之间新的合作研究，为学生提供了独特的教育机会。历史上，对动态现象的直接可视化使人们对自然的基本性质和物理规律有了更深的理解。在纳米尺度（比头发直径小1000倍以上的尺寸）上，这些基本的动力学通常发生在非常短的时间尺度上；通常需要以优于皮秒的时间分辨率进行观察（皮秒是光传播一张名片厚度所花费的时间）。通过结合最先进的短脉冲激光和电子显微镜技术，以伊利诺伊大学芝加哥分校为中心的合作旨在开发一种“超快电子显微镜”，该显微镜具有前所未有的时空分辨率，可以首次研究单个纳米级系统的基本瞬态特性。未来科学家获得这种仪器将导致纳米科学和纳米技术这一重要领域的重大进展；例如，通过确定催化剂（生物和化学）的操作以提高其效率，并通过阐明缺陷（或纳米级界面）对动态应力下现代材料的性能（例如，强度）的影响。仪器开发和使用的跨学科方面也将为研究生和本科生提供重要和有价值的教育机会-国家未来的科技人力资源。

Technical AbstractA collaboration of scientists will develop a functional prototype ultrafast electron microscope (UEM) with less than 1nm-ps space-time resolution at the University of Illinois at Chicago (UIC). To achieve this improvement over current instrumentation technology by three orders of magnitude, several existing state-of-the-art technologies will be combined: a high-power, 1-100MHz, femtosecond laser system will be used to generate an initially spatially coherent electron pulse from a large-area nano-patterned photocathode; a short (20cm) microscope column, if necessary incorporating an RF pulse compression cavity, will be coupled to the objective, sample stage, and projector system of an available decommissioned JEOL JEM 100CX electron microscope; and the generated electron images will be detected using 10um-pore micro-channel plate electron detector optically-coupled to a 25um-pixel, 1kx1k, CCD camera - providing the potential of atomic resolution. The unprecedented space-time resolution afforded by the development of this UEM will clearly provide an important new research tool for a diverse and interdisciplinary set of research fields: molecular biology, catalysis, condensed matter and materials physics, and nanoscience and nanotechnology. Once developed, the world-wide scientific community will have access to the instrument through the Research Resources Center at UIC; thus, also facilitating new collaborative research between institutions and providing unique educational opportunities for students. Lay AbstractThe direct visualization of dynamic phenomena has historically led to a deeper understanding of the fundamental properties and physical laws of nature. On the nanoscale (dimensions more than 1000 times smaller than the diameter of a hair), these rudimentary dynamics often occur on very short timescales; typically requiring observation with a temporal resolution of better than a picosecond (the time taken by light to travel the thickness of a business card). By combining state-of-the-art short-pulse laser and electron microscope technologies, the collaboration centered at the University of Illinois at Chicago aims to develop an "ultrafast electron microscope" with the unprecedented space-time resolution required to study the basic transient properties of individual nanoscale systems for the first time. The future availability of such an instrument to scientists will lead to significant advances in the important area of nanoscience and nanotechnology; for example, by determining the operation of catalysts (both biological and chemical) to improve their efficiency and by elucidating the influence of defects (or nanoscale interfaces) on the properties (e.g., strength) of modern materials under dynamic stress. The interdisciplinary aspect of both in the instrument development and its use will also provide important and valuable educational opportunities for graduate and undergraduate students alike - the nation's future scientific and technological human resource.