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功能原型超快电子显微镜(UEM)，其时空分辨率低于1 nm-ps。为了实现对当前仪器技术的三个数量级的改进，将结合几种现有的最先进技术：将使用高功率、1-100 MHz的飞秒激光系统，从大面积纳米图案光电阴极产生初始空间相干电子脉冲；一个短(20厘米)显微镜柱，如有必要，将包括射频脉冲压缩腔，将耦合到现有退役JEOL JEM 100CX电子显微镜的物镜、样品台和投影仪系统；产生的电子图像将使用10um孔微通道板式电子探测器进行检测-光学耦合到25um像素、1Kx1K的CCD相机-提供原子分辨率的潜力。UEM的发展提供了前所未有的时空分辨率，这显然将为一系列不同和跨学科的研究领域提供重要的新研究工具：分子生物学、催化、凝聚态和材料物理，以及纳米科学和纳米技术。一旦开发完成，全世界的科学界将可以通过UIC的研究资源中心获得该仪器；因此，还可以促进各机构之间的新的合作研究，并为学生提供独特的教育机会。对动态现象的直接可视化在历史上使人们对自然的基本性质和物理规律有了更深刻的理解。在纳米尺度(尺寸比头发直径小1000多倍)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(光穿过名片厚度所需的时间)的时间分辨率进行观测。通过结合最先进的短脉冲激光和电子显微镜技术，这项以芝加哥伊利诺伊大学为中心的合作旨在开发一种具有前所未有的时空分辨率的“超快电子显微镜”，首次研究单个纳米尺度系统的基本瞬变特性。这种仪器的未来可供科学家使用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，以及通过阐明缺陷(或纳米级界面)对现代材料在动态应力下的性能(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宝贵的教育机会--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.