Frontiers of synchrotron research in materials science
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Introduction Since the early days (beginning in 1956), when x-rays were extracted as a byproduct in circular electron and positron accelerators,1 synchrotron radiation has developed tremendously, with brilliances (photons/s/mm2/mrad2/[0.1% bandwidth]) increasing faster than the often-cited Moore’s Law of computer-memory capacity. In so-called storage rings, electrons or positrons circulate and emit synchrotron radiation (see Figure 1). Subsequent to its parasitic use at highenergy particle-physics laboratories, rings were refurbished for the delivery of synchrotron radiation (second generation). For the third generation, dedicated facilities were optimally designed and newly built. Three third-generation high-energy storage rings for synchrotron radiation have been built and continuously refurbished since the 1990s, namely the European Synchrotron Radiation Facility (ESRF, 1994), the Advanced Photon Source (APS, 1996), and Super Photon Ring–8 GeV (SPring-8,1997) (see Figure 2), followed in the past decade by Deutsche Elektronen Synchrotron DESY’s PETRA-III (former Positron-Elektron-Tandem-Ring-Anlage) (2009). Their high-particle energies of 6 GeV, 7 GeV, 8 GeV, and 6 GeV, respectively, allow for undulator radiation into the high-energy x-ray range (100 keV) necessary for bulk studies in materials science and engineering, as well as other advantages, such as easy penetration into sample
environments, small scattering angles, and large reciprocalspace coverage.2 Numerous 3 GeV storage rings have been established all over the world, including the Diamond Light Source, Canadian Light Source, Taiwan National Synchrotron Radiation Research Center, Swiss Light Source, Australian Synchrotron, Shanghai Synchrotron Radiation Facility, Pohang Light Source, and National Synchrotron Light Source II. The flagships of such medium-energy rings have been trimmed to ultimate, diffraction-limited brightness in the soft (0.1 to 1 keV) to hard x-ray range (10 keV), delivering brilliance and a high degree of coherent light. A multitude of applications for all ranges of x-rays have evolved, including dedicated niches, such as absorption spectroscopy, inelastic scattering, surface scattering, and deep-bulk diffraction, which is beyond the scope of this article. This multitude also implies the necessity and existence of different-purpose storage rings (i.e., synchrotrons), varying in size and energy by orders of magnitude. Comprehensive information on facilities, techniques, applications, and news can be found on the LightSources. org website.3 This article discusses the underpinning concepts of diffraction, spectroscopy, and imaging, and traces the use of various x-ray energy ranges applicable to the contributions in this issue of MRS Bulletin.
Klaus-Dieter Liss, Australian Nuclear Science and Technology Organisation, Australia; and School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Australia; [email protected] Kai Chen, Center for Advancing Materials Performance from the Nanoscale, State Key Laboratory f
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