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What is synchrotron radiation?

In light sources, we make use of the fact that when charged particles are accelerated, they emit light (radiate). If electrons are accelerated back and forth in an antenna at kilohertz or Megahertz frequencies they radiate in the radio or TV portions of the electromagnetic spectrum. If electrons that are moving with nearly teh velocity of light (v=0.9c) are constrained to move in a curved path (circles, spirals, and undulations are examples) they will be accelerating toward the inside of the curve and will also radiate what we call synchrotron light or synchrotron radiation.

Synchrotron light of this type occurs naturally in the distant reaches of outer space. For example, magnetic fields are found throughout the Milky Way, such as the striking galactic center radio arc, comprising filamentary structures whose radio-wave emission spectra suggest the filaments are produced by synchrotron radiation from relativistic electrons spiraling around a magnetic field.

Accelerator-based synchrotron light was seen for the first time at the General Electric Research Laboratory in the USA in 1947 in a type of accelerator known as a synchrotron. First considered a nuisance because it caused the particles to lose energy, it recognized in the 1960s as light with exceptional properties. The light produced at today’s light sources is very bright. In other words, the beam of x rays or other wavelengths is as thin as a hair and very intense. Just as laser light is much more intense and concentrated than the beam of light generated by a flashlight, so an x-ray beam produced by a synchrotron is a trillion times brighter than the beam produced by a hospital x-ray machine whose x-ray tubes emit light over a wide angle and with high intensity only at particular wavelengths. Synchrotron radiation is polarised and pulsed, and the frequency and duration of the pulses can be manipulated to a certain extent, see figure.

To produce synchrotron radiation in the lab, one does actually not use the synchrotron, but storage rings. While the charged particles are accelerated further in a synchrotron, in a storage ring only the energy loss is balanced out to keep the energy of the particle beam and thus the energy spectrum of the synchrotron radiation constant. A newer development is the Free-Elektronen-Laser (FEL), which also produces synchrotron radiation. Worldwide there exist about 30 laboratories for the production of synchrotron radiation. In Germany those are amongst others BESSYII at HZB in Berlin, PETRAIII and FLASH at DESY in Hamburg, European XFEL in Hamburg and Schenefeld, the electron-stretching-device in Bonn, DELTA at Dortmund University and KARA in Karlsruhe.

Sources: Wikipedia /