Synchrotron radiation is electromagnetic radiation emitted from electrons or positrons which are moved with relativistic velocities along closed paths with small radius of curvature. The theoretical study of the phenomenon of emission of electromagnetic radiation from accelerated electrons started around 1945. The first observation of emission of synchrotron radiation took place in 1946 in the General Electric labs in a 70 MeV device whereas after 20 years Tantalus was set in operation in the University of Wisconsin-Madison. Tantalus was the first electron storage ring with energy of 240 MeV and it was a second generation source which means that is was used for the generation of synchrotron radiation dedicated to the users. In such second generation sources, the beam of relativistic electrons accelerated in a synchrotron source, are circulating for many hours in a storage ring. An important innovation which introduced in mid-90s wasthe deleopment of insertion devices (undulators and wigglers) which improve the characteristics of the radiation beam. The use of such devices resulted in the third generation sources. Nowadays, synchrotron radiation facilities exist all over the world.
The main characteristics of synchrotron radiation are:
* It has a continuum spectrum that covers a broad energy region from IR to the hard X-rays.
* High brilliance
* Highly collimated
* Linearly polarization on the horizontal plane and circular polarization above and below the horizontal plane. The use of circularly polarized light allows for the study of magnetic materials.
* Pulsed character
The unique characteristics of synchrotron radiation allow for the application of various techniques which are useful tools for the study of properties of matter and are used from physicists, chemists, biologists, geologists, doctors, archaeologists as well as from polymer, metal, microelectronics, cosmetics industry. These techniques are based on various ways of interaction of radiation with matter:
* X-ray absorption (XAFS), fluorescence (XRF), photoelectron emission (XPS) spctroscopies
* Small/wide angle X-ray Scattering (SAXS, WAXS) and X-ray diffraction (XRD)
* UV and X-ray reflectivity
* Imaging techniques (tomography, topography, X-ray microscopy, fluorescence mapping)
* X-ray lihtography
Many of these techniques can be applied for the study of the alterations in properties of materials with time (catalysis, melting, phase transitions) or under pressures and /or temperatures beyond the normal ones.