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The Relativistic Heavy Ion Collider (RHIC ) is one of only two operating heavy-ion colliders, and the only spin-polarized proton collider ever built. Located at Brookhaven National Laboratory (BNL) in Upton, New York, and used by an international team of researchers, it is the only operating particle collider in the US.〔 〕〔 〕〔 〕 By using RHIC to collide ions traveling at relativistic speeds, physicists study the primordial form of matter that existed in the universe shortly after the Big Bang.〔 〕〔 ((Listen ))〕 By colliding spin-polarized protons, the spin structure of the proton is explored. RHIC is now the second-highest-energy heavy-ion collider in the world. As of November 7, 2010, the LHC has collided heavy ions of lead at higher energies than RHIC.〔 〕 The LHC operating time for ions is limited to about one month per year. In 2010, RHIC physicists published results of temperature measurements from earlier experiments which concluded that temperatures in excess of 345 MeV (4 terakelvins or 7 trillion degrees Fahrenheit) had been achieved in gold ion collisions, and that these collision temperatures resulted in the breakdown of "normal matter" and the creation of a liquid-like quark–gluon plasma.〔 〕 ==The accelerator== RHIC is an intersecting storage ring particle accelerator. Two independent rings (arbitrarily denoted as "Blue" and "Yellow" rings) circulate heavy ions and/or protons in opposite directions and allow a virtually free choice of colliding positively charged particles (the eRHIC upgrade will allow collisions between positively and negatively charged particles). The RHIC double storage ring is itself hexagonally shaped and long in circumference, with curved edges in which stored particles are deflected and focused by 1,740 superconducting magnets using niobium-titanium conductors. The dipole magnets operate at .〔 〕 The six interaction points (between the particles circulating in the two rings) are at the middle of the six relatively straight sections, where the two rings cross, allowing the particles to collide. The interaction points are enumerated by clock positions, with the injection near 6 o'clock. Two large experiments, STAR and PHENIX, are located at 6 and 8 o'clock respectively.〔See (【引用サイトリンク】url=http://www.bnl.gov/RHIC/complex.asp )〕 A particle passes through several stages of boosters before it reaches the RHIC storage ring. The first stage for ions is the electron beam ion source (EBIS), while for protons, the linear accelerator (Linac) is used. As an example, gold nuclei leaving the EBIS have a kinetic energy of per nucleon and have an electric charge ''Q'' = +32 (32 of 79 electrons stripped from the gold atom). The particles are then accelerated by the Booster Synchrotron to per nucleon, which injects the projectile now with ''Q'' = +77 into the Alternating Gradient Synchrotron (AGS), before they finally reach per nucleon and are injected in a ''Q'' = +79 state (no electrons left) into the RHIC storage ring over the AGS-to-RHIC Transfer Line (AtR). To date the types of particle combinations explored at RHIC are , , , , , , , and . The projectiles typically travel at a speed of 99.995% of the speed of light. For collisions, the center-of-mass energy is typically per nucleon-pair, and was as low as per nucleon-pair. An average luminosity of was targeted during the planning. The current average luminosity of the collider is , 25 times the design value.〔(【引用サイトリンク】url=http://www.agsrhichome.bnl.gov/RHIC/Runs/ )〕 The heavy ion luminosity is substantially increased through stochastic cooling.〔 〕 One unique characteristic of RHIC is its capability to collide polarized protons. RHIC holds the record of highest energy polarized protons. Polarized protons are injected into RHIC and preserve this state throughout the energy ramp. This is a difficult task that can only be accomplished with the aid of Siberian snakes (in RHIC a chain 4 helical dipole magnets).〔 〕 Run-9 achieved center-of-mass energy of on 12 February 2009.〔 (【引用サイトリンク】url=http://www.agsrhichome.bnl.gov/AP/Spin2009/ )〕 In Run-13 the average luminosity of the collider reached , with a time and intensity averaged polarization of 52%.〔 AC dipoles have been used in non-linear machine diagnostics for the first time in RHIC.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Relativistic Heavy Ion Collider」の詳細全文を読む スポンサード リンク
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