Synchrotron light
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This article is mostly concerned with applications of synchrotron radiation produced by cyclic paticle accelerators. For details of the particle accelerator so named see synchrotron.
Synchrotron_radiation.jpg
A synchrotron is a toroidial particle accelerator that boosts the velocity of electrons, protons or ionized atoms (ions) to near the speed of light.
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Operation
When a charged particle is accelerated, either along a straight path or laterally along a curved path, it radiates electromagnetic energy. In a synchrotron this energy may be used for a number of experimental purposes.
A synchrotron can produce a wide range of well-controlled electromagnetic radiation, and they are quite often constructed so that the predominant emission consists of x-rays.
Beamlines
At a synchrotron facility, the electrons are usually accelerated by a synchrotron, and then injected into a storage ring, in which they circulate, producing synchrotron radiation, but without gaining further energy. The radiation is projected at a tangent to the electron storage ring and captured by beamlines. These beamlines may originate at bending magnets, which mark the corners of the storage ring; or insertion devices, which are located in the straight sections of the storage ring. The spectrum and energy of X-rays differ between the two types. The beamline includes X-ray optical devices which control the bandwidth, photon flux, beam dimensions, focus, and collimation of the rays. The optical devices include slits, attenuators, crystal monochromators, and mirrors. The mirrors may be bent into curves or toroidal shapes to focus the beam. A high photon flux in a small area is the most common requirement of a beamline. The design of the beamline will vary with the application. At the end of the beamline is the experimental end station, where samples are placed in the line of the radiation, and detectors are positioned to measure the resulting diffraction, scattering or secondary radiation.
Economics
Synchrotrons which are useful for cutting edge research are large machines, costing tens of millions of dollars (hundreds of millions for the largest) to construct, and each beamline (there may be 20 or more at a large synchrotron) costs another two or three million dollars. These installations are mostly built by the governments of rich countries, or by collaborations between several countries in a region, and operated as infrastructure facilities available to universities and research organisations.
Uses
Synchrotron light is an ideal tool for many types of research and also has industrial applications. Some practical uses include:
- Lithography for computer chips.
- Absorption / Scattering.
- High pressure
- Protein crystallography.
- Spectroscopy.
Some of the advantages of synchrotron light that allow for these practical uses are:
- Short wavelength photons which can penetrate matter and interact with atoms.
- High concentration, tunability and polarization thus ensuring focusing accuracy for even the smallest of targets.
List of Synchrotrons
Synchrotrons of the World (http://www-als.lbl.gov/als/synchrotron_sources.html)