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Advances in X-Ray Microscopy and Imaging
By Dr. Barry Lai
X-Ray Science Division, Argonne National Laboratory
Tuesday, March 16, 2010
7:30 PM Lecture
Synchrotron radiation has revolutionized the field of x-ray microscopy and imaging. It is now possible to achieve 30-nm resolution in both scanning and full field imaging mode. Together with the high brightness, high energy, and timing structure offered by third and fourth generation synchrotron sources, these unique capabilities had enabled many new and novel applications in both life and physical sciences.
In scanning mode, unique contrast can be obtained from x-ray fluorescence (XRF), x-ray diffraction (XRD), and x-ray absorption spectroscopy (XAS). XRF provides very high sensitivity for trace elements, at the level of attogram (10-18 gram), and has opened up new avenues in subcellular imaging of biological specimens. On the other hand, XRD allows high resolution structural information to be obtained, and as such has been utilized in studies of micro/nano-electronic devices and condensed matter physics. Finally XAS reveals local chemical information and oxidation state, and has become an indispensible tool for environmental studies.
In full field imaging mode, high resolution transmission microscopes have been developed to allow 2D and 3D imaging at 30 nm resolution. In particular the development of phase contrast, which can deliver much higher contrast at reduced dose compared to conventional absorption contrast, has enabled in situ observations of dynamical processes. Together with the brunch structure offered by electron storage rings, time-resolved studies down to 100-ps are now possible. These and other recent advances in x-ray microscopy and imaging will be presented.
Barry Lai is a physicist at the X-ray Science Division of Argonne National Laboratory. He had been involved in synchrotron radiation and x-ray optics since 1985 as part of his thesis research at the University of Wisconsin-Madison. Afterwards he moved to Argonne for his postdoctoral study, and witnessed the construction of the Advanced Photon Source (APS), a high-brightness third generation hard x-ray facility. Since then, he had led the design, construction, and operation of Beamline 2-ID-D which was dedicated for scanning microscopy.
Dr. Lai won an R&D 100 Award in 2000 for his contribution to the Hard X-ray Scanning Microprobe. Recently he was involved with the design of an x-ray nanoprobe, which he hold a patent in its optomechanical structure. His current interest lies in developing biomedical applications for x-ray microscopy, and as such will be tackling the issue of cryogenic sample handling capabilities in the next few years.
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