MRI: Development Of A Next-Generation Coherent X-Ray Diffraction Microscope For 3d Imaging Of Nanosclae Systems

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Visualizing the arrangement of atoms has played a crucial role in understanding the microscopic world. There are already a few ways of imaging atomic structures, but each has its limitations. Scanning probe microscopes are limited to imaging atomic structures at the surface. Transmission electron microscopes can resolve atoms but only for samples thinner than ~ 30 nm. X-ray crystallography can reveal the globally averaged 3D atomic structures based on the diffraction phenomenon, but requires crystals. These limitations can in principle be overcome by coherent x-ray diffraction microscopy (or lensless imaging) that is based upon coherent x-ray scattering in combination with a method of direct phase recovery called oversampling. Coherent x-ray diffraction microscopy has been successfully applied to 2D and 3D imaging of nanoscale materials and biological samples, and a highest spatial resolution of 7 nm has been achieved. By using 3rd generation synchrotron radiation, we propose to develop a next-generation coherent x-ray diffraction microscope for 3D imaging and characterization of nanoscale systems. The new microscope will have the following features: i) a 4K x 4K back-illuminated CCD camera will be used to improve the resolution to the 1 nm level; (ii) data acquisition will be automated; iii) 3D images will be directly reconstructed from oversampled diffraction patterns without using lower resolution images; iv) samples will be mounted in helium ambiance which can be at room or liquid nitrogen temperatures; and v) faster and more precise phase retrieval algorithms will be developed for 3D image reconstruction. X-ray imaging has been used to probe the structure of matters for more than a century. Unlike visible light, however, x-rays are difficult to manipulate and focus. The highest resolution of x-ray images currently achievable is about 100 atomic diameters. For disordered samples x-rays cannot image at such high resolution. A promising approach, which is currently under very active development, uses x-ray and image reconstruction using a computer. This approach has been used to image materials and biological specimens with a resolution of about 14 atomic diameters . By using currently the brightest x-ray source in the nation - the Advanced Photon Source in Chicago, we propose to develop a next-generation x-ray microscope for improving the resolution to around 3 atomic diameters. The new microscope will include a larger detector and better software for quick and accurate 3D image reconstruction. We anticipate the 3D x-ray microscope will find broad applications in many areas of science and structural biology.