Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session S6: X-ray Synchrotron Instrumentation |
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Sponsoring Units: GIMS Chair: Tim Graber, University of Chicago Room: Colorado Convention Center 207 |
Wednesday, March 7, 2007 2:30PM - 3:06PM |
S6.00001: Multilayer Laue Lenses -- A Path Towards Nanofocusing of X-rays. Invited Speaker: The possibility of imaging at near-atomic resolution using short-wavelength x-rays has been a dream ever since the nature of x-rays was first understood nearly 100 years ago. Although hard x-rays can in principle be focused to spot sizes on the order of their wavelength (0.1 nm), this limit has never been approached because of the difficulty in fabricating the optics -- indeed, it has not even been clear what type of optics will work. We have developed a new approach towards manufacture of hard x-ray optics, the ``Multilayer Laue Lens'' (MLL) [1]. MLL's are fabricated by coating a flat substrate with alternating layers of nanometer thickness, with d-spacing varying to form the zones of a linear zone plate. Thin cross sections of the multilayer are then made. These allow focusing of x-rays when illuminated in transmission (Laue) diffraction geometry. Crossing two such linear zone plate sections will allow 2-dimensional focusing. We have shown that a resolution of 5 nm should be achievable using the non-optimized geometry we are currently fabricating, and that a resolution of 1 nm is feasible using an optimized geometry. We have experimentally demonstrated a line focus with a width of below 20 nm at photon energies of 20 keV and 30 keV, with diffraction efficiencies of 30{\%} and above 15{\%}, respectively. \newline \newline [1] H.C. Kang, J. Maser, G.B. Stephenson, C. Liu, R. Conley, A.T. Macrander, S. Vogt, Phys. Rev. Lett. \textbf{96}, March, 127401-1-127401-4 (2006). [Preview Abstract] |
Wednesday, March 7, 2007 3:06PM - 3:42PM |
S6.00002: Bright Field X-ray Topography with Sub-100-nm Spatial Resolution Invited Speaker: X-ray topography is an extreme useful technique for visualizing crystalline defects. However, its application has been restricted to investigating strain fields above the micron scale due to the limited spatial resolution of the topographic imaging methods. Consequently, x-ray diffraction investigations requiring submicron spatial resolution are carried out exclusively using a scanning method such as synchrotron x-ray microdiffraction. We have developed a new x-ray topography method to visualize the lattice distortion with a spatial resolution below 100 nm. This new method is similar to ``bright-field imaging'' in transmission electron microscopy (TEM), in that a set of x-ray optics is used to image the x-rays transmitted through the crystalline specimen in order to obtain high-resolution diffraction contrast images. In the bright field topography, both diffraction contrast and absorption contrast (i.e., inhomogeneity in density) are imaged, making it extremely useful for correlating the lattice distortion with the microscopic defects in the specimen. Our presentation will focus on the instrumentation details and the quantitative data analysis methods for our new technique, and will discuss potential applications. This research has been carried out in collaboration with Dr. Yuncheng Zhonga and Hanfei Yan in X-ray Science Division of Argonne National Laboratory and Dr. Jae Mok. Yi and Jung Ho Je in X-ray Imaging Center of POSTECH, Korea. [Preview Abstract] |
Wednesday, March 7, 2007 3:42PM - 4:18PM |
S6.00003: The 4$^{th}$ Generation Light Source at Jefferson Lab. Invited Speaker: Over the last 40 years the peak brightness of new synchrotron radiation sources has increased on average by an order of magnitude every 24 months!! By comparison, Moore's Law states that the number of transistors on an integrated circuit ``only'' doubles every 24 months. This talk will report on the physics and enabling technology of the latest round of brightness improvements, which have been achieved in the IR and THz range at Jefferson Lab but whose principles are extendable to light sources at shorter (uv to x-ray) wavelengths. Examples of scientific applications will also be given. The JLab facility is based on an Energy Recovered Linac (ERL),$^{1}$ rather than a storage ring. The power is then enhanced by multiparticle coherent effects,$^{2}$ while the source size is smaller because the horizontal emittance is approximately equal to the vertical emittance (round beams). In addition the bunch lengths are in the 100's of femtosecond range, allowing ultrafast phenomena to be studied. Finally, unlike conventional linac-based machines an ERL can operate continuously. $^{1}$G.R. Neil et al, Phys. Rev. Let. 84, 662 (2000). $^{2}$C. J. Hirschmugl, et al, Physical Review A44, 1316, (1991). [Preview Abstract] |
Wednesday, March 7, 2007 4:18PM - 4:54PM |
S6.00004: Nanofocusing of hard x-rays with profile coated elliptical mirrors Invited Speaker: The ability to focus hard x-rays by means of mirrors has progressed recently to the achievement of focus sizes well below 100 nm.[1] At the Advanced Photon Source at Argonne National Laboratory elliptical mirrors have been made by means of profile coating. [2] In this technology a highly precise elliptically shaped surface is achieved by magnetron sputtering of Au onto a flat silicon substrate. Results will be presented to detail the rapid progress being made in this technology. Also, results for wave optical simulations will be summarized. [3]. X-ray mirrors are achromatic focusing optics, and a nanofocused beam is expected to have many uses for experiments in condensed matter physics. [1] W. Liu, G. Ice, J. Tischler, A. Khounsary, C. Liu, L. Assoufid, A. Macrander, Rev. Sci. Instrum. 76, 113701(2005). [2] C. Liu, L. Assoufid, R. Conley, A. Macrander, G. Ice, J. Tischler, Opt. Eng. 42, 3622 (2003). [3] C. Kewish, L. Assoufid, A. Macrander, j. Qian, Appl. Opt. , in press . [Preview Abstract] |
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