Synchrotron radiation is emitted by electrons or positrons travelling at near light speed in a circular storage ring. In recent years synchrotron facilities have become widely used as preferred sources for x-ray diffraction measurements. (The energy E of a x-ray photon and its wavelength is related by the equation E = hc/ l, where h is Planck's constant and c the speed of light) (check out this neat animated lecture on x-ray production) Common targets used in x-ray tubes include Cu and Mo, which emit 8 keV and 14 keV x-rays with corresponding wavelengths of 1.54 Å and 0.8 Å, respectively. When a free electron fills the shell, a x-ray photon with energy characteristic of the target material is emitted. The high energy electrons also eject inner shell electrons in atoms through the ionization process. As electrons collide with atoms in the target and slow down, a continuous spectrum of x-rays are emitted, which are termed Bremsstrahlung radiation. In a x-ray tube, which is the primary x-ray source used in laboratory x-ray instruments, x-rays are generated when a focused electron beam accelerated across a high voltage field bombards a stationary or rotating solid target. X-rays are produced generally by either x-ray tubes or synchrotron radiation. The energetic x-rays can penetrate deep into the materials and provide information about the bulk structure. Because the wavelength of x-rays is comparable to the size of atoms, they are ideally suited for probing the structural arrangement of atoms and molecules in a wide range of materials. For diffraction applications, only short wavelength x-rays (hard x-rays) in the range of a few angstroms to 0.1 angstrom (1 keV - 120 keV) are used. X-rays are electromagnetic radiation with typical photon energies in the range of 100 eV - 100 keV. Principles of Protein X-ray Crystallography, by Jan Drenth, Springer, 1994 (Crystallography).Brumberger, Editor, Kluwer Academic Publishers, 1993 (SAXS techniques) Modern Aspects of Small-Angle Scattering, by H.Tanner, Taylor & Francis, Ltd., 1998 (Semiconductors and thin film analysis) High Resolution X-ray Diffractometry and Topography, by D.Cullity, Addison-Wesley, 1978 (Covers most techniques used in traditional material characterization) Elements of X-ray Diffraction,2nd Ed., by B.D.Warren, General Publishing Company, 1969, 1990 (Classic x-ray physics book) Elements of Modern X-ray Physics, by Jens Als-Nielsen and Des McMorrow, John Wiley & Sons, Ltd., 2001 (Modern x-ray physics & new developments). Extensive and authoritative discussions can be found in the numerous books and journal articles on this subject. It is designed for people who are novices in this field but are interested in using the techniques in their research. This is intended as a (very) brief introduction to some of the common x-ray diffraction techniques used in materials characterization. Mitsubishi Chemical - Center for Advanced Materials.IRG 3: Resilient Multiphase Soft Materials.IRG-1: Magnetic Intermetallic Mesostructures.
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