High Resaolution X-ray Microscopy And Its Application

Due to the availability of synchrotron radiation source and the development of nano-fabrication technique, Fresnel zone-plates (FZPs) based X-ray microscopy has developed rapidly over the past decade, which offers spatial resolution in the 15-50 nm range. It complements other imaging techniques, such as optical and electron microscopy, by offering a unique set of capabilities including large penetration depth, high exposure efficiency, elemental and chemical specificity, magnetization sensitivity, as well as in-situ imaging with applied fields, overcoatings, and wet environments. The outstanding feature of this technique highlights its potential in a broad variety of fields, including life sciences, environmental science, materials science and industry. National Synchrotron Radiation Laboratory (NSRL) has successfully constructed a high resolution full-field, transmission x-ray microscope (TXM) beamline and endstation with a resolution of 50 nm. The main work and innovations are described as the following:1. Construction and test of high resolution x-ray microscope beamline and system, and theory of image formationThis section introduces the optical design of the high-resolution x-ray microscope beamline and system. After the successful construction of beamline and system, we get the key parameters such as the energy resolution, photon flux and spatial resolution through a series of tests. The test results show that the performance of high-resolution x-ray microscope beamline and system achieves the design targets. The theory of image formation of the high-resolution x-ray imaging system is also presented in this section. The optical propagation equation is described here, which simplifys the computer simulation. Based on both theoretical and experimental studies, we study the relationship between spatial resolution and optics, illumination, noise, CCD detector. The results would provide fundamental principles for developing new imaging method.2. High-resolution x-ray Zernike phase-contrast imagingContrast and resolution are two important parameters of the X-ray miscroscopy. It has an extremely important significance to improve the contrast, especially for biological samples or samples consisting of light elements. X-ray absorption-contrast imaging can not provide sufficient contrast, because the imaginary part of refractive index of light elements is too small. However, the real part of refractive index of light elements is three or four orders magnitude than the imaginary part. Thus phase contrast imaging would provide much higher contrast than absorption imaging for light elements. We study the Zernike phase-contrast imaging mechanism, which were also achieved on the high-resolution X-ray microscope. The halo effect was also investigated.3. High-resolution x-ray tomography and large field of view (FOV) tomographyCombining computerized tomography (CT), we have developed high-resolution x-ray tomography, which enable us to observe the three-dimensional structure of sample at nanometer level. While increasing the the resolution of microscope, we sacrifice the field of view. However, the sizes of most samples with characteristics nano-structures beyond the field of view (15μm). Here we develop a large field of view (FOV) tomography, which can get the 3D structure of large enough volume with the same resolution. The reconstruction was performed using both the iterative algorithms and standard filtered-back-projection algorithm. The experimental results show that the method achieves the expected demand.4. Quantitative analysis of tomographic dataAccording to Beer's Law, the x-ray absorption effect of the object is linear after it passes through objects. The intensity distribution of projection is the integration of absorption coefficient along the x-ray propagation direction. The three-dimensional distribution of absorption coefficient of the sample can be solved if a complete tomographic data is taken. Quantitative analysis can be performed on the tomographic data after procedures such as histogram, setting threshold and statistical calculation.5. X-ray tomography of the nanomaterialsDesign, modeling, and characterization technologies together are intimate components of the design cycle in technology development. Design and modeling are closely intertwined, ultimately guiding fabrication. Characterization technologies, imaging and measurement, provide the data that validate or drive revision of both designs and models. Characterization technologies are crucial. We get unique 3D information of nanomaterials and nano-enabled devices such as concaved cuboctahedron copper sulfide crystal and solid oxide fuel cell.6. X-ray tomography of the yeast cellsNew imaging methods have greatly advanced our understanding of cell structure and function. However, each of these imaging methods has its pros and cons. No single imaging method proves to be the perfect solution. Combining simple chemical treatment with absorption contrast imaging at 5.4 keV, the ultrastructural details of S. pombe were well delineated. Combining high resolution X-ray tomography with X-ray fluorescent probe, the shape and 3D distribution of elemental selenium nano particles were detected in selenium enriched yeast.7. X-ray tomo graphy of the trabecula boneThree-dimensional structure and mineralization of bone are two important parameters, which are closely related to its mechanical parameters and symptoms such as osteoporosis. However, most of the current detection methods are limited to micron-level 3D structure. Here high-resolution x-ray microscopy has been used to characterize the nano 3D structure of trabecular bone. The 3D distribution of lacuna and canaliculi system in trabecular bone has been gotten. The mineralization degree of trabecular bone has also been gotten through quantitative analysis. It would be a powerful tool for studying the physical properties of bone and symptoms such as osteoporosis.