Storage ring

A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating typically for many hours. Storage of a particular particle depends upon the mass, momentum and usually the charge of the particle to be stored. Storage rings most commonly store electrons, positrons, or protons. Storage rings are most often used to store electrons that radiate synchrotron radiation. Over 50 facilities based on electron storage rings exist and are used for a variety of studies in chemistry and biology. Storage rings can also be used to produce polarized high-energy electron beams through the Sokolov-Ternov effect. The best-known application of storage rings is their use in particle accelerators and in particle colliders, where two counter-rotating beams of stored particles are brought into collision at discrete locations. The resulting subatomic interactions are then studied in a surrounding particle detector. Examples of such facilities are LHC, LEP, PEP-II, KEKB, RHIC, Tevatron and HERA. A storage ring is a type of synchrotron. While a conventional synchrotron serves to accelerate particles from a low to a high energy state with the aid of radio-frequency accelerating cavities, a storage ring keeps particles stored at a constant energy and radio-frequency cavities are only used to replace energy lost through synchrotron radiation and other processes. Gerard K. O'Neill proposed the use of storage rings as building blocks for a collider in 1956. A key benefit of storage rings in this context is that the storage ring can accumulate a high beam flux from an injection accelerator that achieves a much lower flux. A force must be applied to particles in such a way that they are constrained to move approximately in a circular path. This may be accomplished using either dipole electrostatic or dipole magnetic fields, but because most storage rings store relativistic charged particles it turns out that it is most practical to utilise magnetic fields produced by dipole magnets.