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Any charge particle undergoing acceleration will emit electromagnetic radiation. For a relativistic electron beamthis radiation will have very unique properties that will make it very suitable as a radiation. The radiation will be highlycollimated in the orbital plane of acceleration; it has a continuous spectral distribution from the infrared to hard x-rays,it is polarized, and has unprecedented brightness. It was termed synchrotron radiation since it was first observedin synchrotron accelerators. Presently storage rings are used as the preferred radiation source due to its higherstability. In the 1960's it was realized that synchrotron radiation (SR) would be a superb light source for a varietyof investigations. The first utilization was in a parasitic mode on high-energy physics machines, later coined firstgeneration SR sources. These first sources provided about six orders of magnitude increase in spectral brightnessover conventional x-ray tubes. This led to the construction storage rings in the 1980's dedicated to the use of SR forstudies in physics, chemistry and biology (second generation SR sources). In the 1980's it was also realized that thebrightness could be further increased many orders of magnitude by manipulating the electron beam through magneticinsertion devices, so-called wigglers and undulators. All modern SR sources (third generation SR sources) are basedon this technology.. Presently there are about 50 facilities in operation worldwide serving a user community of morethan 20000 scientists. The spectacular development of the SR sources and the engagement of a large user communityhave been accompanied by major advancements in instrumentation.
SR is being used to determine the electronic and structural properties of matter with impact on a broad range ofdisciplines. High-resolution band mapping and core-level spectroscopies are used extensively to probe the electronicstructure, also being extended to spin-resolved studies of magnetic properties. The latter also studies with dichroismin the 2p absorption edges. One of the most successful techniques for structural studies is EXAFS (Extended X-RayAbsorption Spectroscopy) that can be applied to crystalline as well as non-crystalline materials in all its forms.. X-rayscattering (S/WAXS = small/wide angle x-ray scattering) provides a wealth of information on a broad range of materialsof technological relevance. SR is widely used for protein crystallography and the technique is highly developed withautomation and robotics. Of the 60000 protein structures in the protein data bank about 85% have been determinedwith SR. X-Ray microscopy with lateral resolutions down to 20-30 nm and tomography are recent and fast developingfields. SR is inherently an incoherent source but with slits/apertures coherent radiation can be extracted and is nowbeing used extensively for coherent imaging.
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