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What Does a Light Source Look Like Today?

   ESRF aerial view Todays synchrotron-based light source is a large,
   roughly circular machine (usually about the size of a football field
   to much larger) that accelerates electrons to almost the speed of
   light. The accelerator components include an electron gun, one or more
   injector accelerators (usually a linear accelerator and a synchrotron
   but sometimes just a large linear accelerator) to increase the energy
   of the electrons, and a storage ring where the electrons circulate for
   many hours. In the storage ring, magnets force the electrons into
   circular paths. As the electron path bends, light is emitted
   tangentially to the curved path and streams down pipes called
   beamlines to the instruments where scientists conduct their
   experiments
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   Image 1. The largest light source facilities are campuses onto
   themselves with administrative, office, and laboratory buildings in
   addition to the light source itself. (Courtesy: European Synchrotron
   Radiation Facility) 
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   Synchrotron light is always emitted in the forward direction in a
   narrow cone, like water droplets from a spinning wet tire. As the
   electrons sweep around the curve, they generate a horizontal fan of
   light. The higher the kinetic energy (i.e. the speed) of the
   electrons, the narrower the emission cone becomes. The spectrum of the
   emitted radiation also shifts to shorter wavelengths as the energy
   increases, so that sources designed to produce x rays tend to have
   higher energy and to be larger and more expensive than those designed
   for ultraviolet. In sum, the storage ring is a stable, continuous
   source of light over a wide wavelength range. Together with additional
   features, such as controllable polarization (both linear and
   circular), laser-like collimation, and pulsed time structure, these
   characteristics make synchrotron light sources the x-ray source of
   choice for a wide range of research. Components of a synchrotron light
   source

   In the newer light sources, the storage ring is specifically designed
   to include special magnetic structures known as insertion devices
   (undulators and wigglers). Insertion devices generate specially shaped
   magnetic fields that drive electrons into an oscillating trajectory
   for linearly polarized light or sometimes a spiral trajectory for
   circularly polarized light. Each bend acts like a source radiating
   along the axis of the insertion device, hence the light is very
   intense and in some cases takes on near-laser-like brightness.
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   Image 2. Components of a synchrotron light source typically include
   (1) an electron gun, (2) a linear accelerator, (3) a booster
   synchrotron, (4) a storage ring, (5) beamlines, and (6) experiment
   stations. (Courtesy: Australian Synchrotron, Illustrator: Michael
   Payne) 
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