MRI:Development of a femtosecond high brightness electron beam source for time-resolved electron diffraction and imaging

一种新型的高通量射频飞秒电子衍射显微镜将被开发，以允许前所未有的分辨率和灵敏度研究与纳米级复杂材料和大分子相关的潜在物理和化学过程。 这些努力依赖于对与高亮度束相关联的空间电荷加宽问题的创新解决方案，该问题导致时间分辨率和束质量的劣化，并且克服了光枪设计中的限制以提供高亮度相干电子源。我们提出的新技术包括：采用射频腔来重新压缩因空间电荷展宽而退化的电子脉冲;通过设计和实现激光脉冲整形器来控制光电发射，从而优化相干电子源;以及采用实时电子束成像仪来提供反馈控制。科学和技术的进步将由一个独特的专家团队在加速器和束物理，射频腔的设计和实施，飞秒激光和超快电子衍射技术，和理论建模的发展，这一独特的飞秒电子束系统。 我们的最终目标是能够通过超快衍射来视频记录单粒子和单站点事件，与当前最先进的超快电子衍射系统相比，其束亮度提高了2-3个数量级。达到纳米探测极限将开辟新的研究领域，包括科学院最近的一份报告所确定的领域，如：“单点”多相催化、与光化学相关的量子点中的电荷动力学、通过与信息处理和传感相关的纳米结构进行的能量转移、强相关材料和异质结构中电子相关的出现以及纳米级的能量转换。这种桌面级飞秒电子束系统的实现将使密歇根州立大学和更广泛的社区的各种大学实验室具有前所未有的材料研究能力。 将制作一部纳米科学电影，为K-12学生提供纳米科学的引人入胜的观点，以及研究生推动构建前沿用户设施以了解纳米科学和纳米技术的方法。分子和纳米颗粒在飞秒（fs）时间尺度（1 fs=1/1000，000，000，000秒）下“活动”。 通过解决与高密度电子脉冲相关的空间电荷效应，使先进能力的突破成为可能，该空间电荷效应导致高分辨率成像的光束质量下降。 我们提出的新技术包括利用射频压缩器将高密度电子束压缩到飞秒时间尺度的加速器技术、结合飞秒激光脉冲整形的创新光电子源设计，以及提供即时反馈控制的先进高速电子束表征。 科学和技术的进步将由一个独特的专家团队在加速器和束物理，射频压缩机的设计和实施，飞秒激光技术，和理论建模的发展，这一独特的飞秒电子成像系统。 我们的最终目标是能够用纳米尺度的探针以高保真度和飞秒速度记录分子事件。 这一目标的实现将带来一个全新的层面来揭示纳米技术和纳米科学前沿的材料特性和化学反应，包括最近科学院报告确定的那些，如生化反应和催化，太阳能收集，复杂的材料功能和纳米尺度上的信息处理。 这种桌面级飞秒电子束系统的实现将使密歇根州立大学和更广泛的社区的各种大学实验室具有前所未有的材料研究能力。 将制作一部纳米科学电影，为K-12学生提供纳米科学的引人入胜的观点，以及研究生推动构建前沿用户设施以了解纳米科学和纳米技术的过程的方式。

Technical abstractA novel high flux rf enabled femtosecond electron diffraction microscope will be developed to allow unprecedented resolution and sensitivity for studying underlying physical and chemical processes associated with nanoscale complex materials and macromolecules. These efforts rest upon innovative solutions to the space-charge broadening issues associated with high-brightness beams that lead to degradation of the temporal resolution and beam quality, and overcoming the limitation in the photo-gun design to provide a high-brightness coherent electron source. Our proposed new technologies include incorporating an rf cavity to recompress electron pulses that are degraded by space-charge broadening; optimization of the coherent electron source through design and implementation of a laser pulse shaper to control photoemission; and a real-time electron bunch imager to provide feedback control. Scientific and technological progress will be enabled by a unique team of experts in accelerator and beam physics, rf cavity design and implementation, femtosecond laser and ultrafast electron diffraction technologies, and theoretical modeling for the development of this unique fs electron beam system. Our ultimate goal is to be able to videograph single-particle and single-site events by ultrafast diffraction with 2-3 orders of magnitude enhancement in the beam brightness compared with the current state-of-the art ultrafast electron diffraction systems. Reaching a nano-probe limit will open up new research areas including those identified by a recent Academy of Sciences report, such as: "single-site" heterogeneous catalysis, charge dynamics in nanocrystal quantum dots relevant for photovoltaics, energy transfer through nanostructures relevant for information processing and sensing, the emergence of electron correlation in strongly correlated materials and heterostructures, and energy transduction at the nanoscale. The realization of this table-top scale fs electron beam system will enable unprecedented material research capabilities at a wide variety of University laboratories both at Michigan State University and in the broader community. A nanoscience movie will be produced that provides K-12 students with an engaging view of nanoscience and the way in which graduate students drive the process of constructing a forefront user facility to understand nanoscience and nanotechnology.Nontechnical abstractAn innovative ultrafast electron beam system will be developed to allow unprecedented resolution and sensitivity for imaging atoms, molecules and nanoparticles "in the act" at the femtosecond (fs) timescale (1 fs=1/1000,000,000,000,000 second). The breakthrough in the advanced capabilities is made possible by solving the space-charge effects associated with high-density electron pulses causing degradation of the beam quality for high-resolution imaging. Our proposed new technologies include accelerator technology to compress high-density electron beam to the fs timescale with a radio-frequency compressor, innovative photoelectron source design incorporating fs laser pulse shaping, and advanced high-speed electron beam characterization to provide instant feedback control. Scientific and technological progress will be enabled by a unique team of experts in accelerator and beam physics, radio-frequency compressor design and implementation, fs laser technologies, and theoretical modeling for the development of this unique fs electron imaging system. Our ultimate goal is to be able to videograph the molecular events with high fidelity and fs speed with a nanometer scale probe. Realization of this goal will bring a completely new dimension to unveil material properties and chemical reactions underlying the forefront of nanotechnology and nanoscience including those identified by a recent Academy of Sciences report, such as biochemical reactions and catalysis, solar energy harvesting, complex material functions, and information processing on the nanometer scale. The realization of this table-top scale fs electron beam system will enable unprecedented material research capabilities at a wide variety of University laboratories both at Michigan State University and in the broader community. A nanoscience movie will be produced that provides K-12 students with an engaging view of nanoscience and the way in which graduate students drive the process of constructing a forefront user facility to understand nanoscience and nanotechnology.