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

点击翻译按钮获取中文摘要

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.