Relativistic Heavy Ion Collider

The Relativistic Heavy Ion Collider (RHIC /ˈrɪk/) is the first and 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. By colliding spin-polarized protons, the spin structure of the proton is explored.The 25 kW Helium refrigeration system that cools the superconducting magnets down to the operating temperature of 4.5KAn arc dipole magnet. Electrical bus slots (top and bottom) and beam tube (middle) at the top section of the vacuum shellCurvature of beam tube seen through the ends of an arc dipole magnetTwo main accelerator rings inside the RHIC tunnelSTAR detectorA Forward Silicon Vertex Detector (FVTX) sensor of PHENIX detector on a microscope The Relativistic Heavy Ion Collider (RHIC /ˈrɪk/) is the first and 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. 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 Large Hadron Collider (LHC) has collided heavy ions of lead at higher energies than RHIC. The LHC operating time for ions (lead-lead and lead-proton collisions) 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. RHIC is an intersecting storage ring particle accelerator. Two independent rings (arbitrarily denoted as 'Blue' and 'Yellow') circulate heavy ions and/or polarized 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 hexagonally shaped and has a circumference of 3834 m, 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 3.45 T. The six interaction points (between the particles circulating in the two rings) are in 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. The PHENIX experiment is presently undergoing a major upgrade to become sPHENIX. 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 200 MeV linear accelerator (Linac) is used. As an example, gold nuclei leaving the EBIS have a kinetic energy of 2 MeV 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 100 MeV per nucleon, which injects the projectile now with Q = +77 into the Alternating Gradient Synchrotron (AGS), before they finally reach 8.86 GeV 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 p + p, p + Al, p + Au, d + Au, h + Au, Cu + Cu, Cu + Au, Zr + Zr, Ru + Ru, Au + Au and U + U. The projectiles typically travel at a speed of 99.995% of the speed of light. For Au + Au collisions, the center-of-mass energy is typically 200 GeV per nucleon-pair, and was as low as 7.7 GeV per nucleon-pair. An average luminosity of 2×1026 cm−2s−1 was targeted during the planning. The current average Au + Au luminosity of the collider has reached 87×1026 cm−2s−1, 44 times the design value. 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 proton beams. Polarized protons are injected into RHIC and preserve this state throughout the energy ramp. This is a difficult task that is accomplished with the aid of corkscrew magnetics called 'Siberian snakes' (in RHIC a chain 4 helical dipole magnets). The corkscrew induces the magnetic field to spiral along the direction of the beam Run-9 achieved center-of-mass energy of 500 GeV on 12 February 2009. In Run-13 the average p + p luminosity of the collider reached 160×1030 cm−2s−1, 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. There are two detectors continuing to operate at RHIC: STAR (6 o'clock, and near the AGS-to-RHIC Transfer Line) and PHENIX (8 o'clock). PHOBOS (10 o'clock) completed its operation in 2005, and BRAHMS (2 o'clock) in 2006.