A synchrotron is a machine that accelerates charged particles such as electrons to extremely high energies – creating an electron beam that travels at almost the speed of light. This is done by creating strong magnetic and electric fields and simultaneously increasing (synchronously ramping) the strength of the fields. Powerful electromagnets are used to focus and steer the beam inside a ring-shaped vacuum chamber, which minimises collisions with air molecules and allows storage of the beam at high energy levels for many hours.
Originally, synchrotrons were used exclusively in the field of particle physics, allowing scientists to study collisions between subatomic particles with higher and higher energies. However, when high-energy electrons are forced to travel in a circular orbit, they release extremely intense radiation – or synchrotron light’. Synchrotron light has many useful properties and can be filtered and directed down ‘beamlines’ for use in a wide range of non-destructive, high-resolution, rapid, in-situ, real-time imaging and analysis techniques. Due to the usefulness of synchrotron light, many accelerators today now exist solely to generate light for scientific experiments. Facilities dedicated to the production and use of synchrotron radiation are known as synchrotron light sources or synchrotron radiation facilities, commonly abbreviated to ‘synchrotrons’ by users.
First-generation synchrotron light sources were basically beamlines built onto existing facilities designed for particle physics studies. Second-generation synchrotron light sources were dedicated to the production of synchrotron radiation and employed electron storage rings to harness the synchrotron light. Current (third-generation) synchrotron light sources optimise the intensity of the light by incorporating long straight sections into the storage ring for ‘insertion devices’ such as undulator and wiggler magnets. Wigglers create a broad but intense beam of incoherent light. Undulators create a narrower and significantly more intense beam of coherent light, with selected wavelengths, or ‘harmonics’, which can be ‘tuned’ by manipulating the magnetic field in the device. Laboratories around the world are now working to overcome the technical challenges associated with the development of fourth-generation light sources, which are likely to utilise hard x-ray free-electron lasers (FEL).
Information about light sources around the world: www.lightsources.org
Evolution of synchrotrons: http://xdb.lbl.gov/Section2/Sec_2-2.html
Electron gun and linac details: http://ados.web.psi.ch/slsdesc/linac/
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