Tevatron
41°49′55″N 88°15′06″W / 41.831904°N 88.251715°W
Tevatron is a circular particle accelerator at the Fermi National Accelerator Laboratory in Batavia, Illinois and remains the highest energy particle collider in the world until collisions begin at the Large Hadron Collider. The Tevatron is a synchrotron that accelerates protons and antiprotons in a 6.28 km (3.90 miles) ring to energies of up to 1 TeV, hence the name.[1] The Tevatron was completed in 1983 at a cost of $120 million and has been regularly upgraded since then. The Main Injector was the most substantial addition, built over five years from 1994 at a cost of $290 million.
The Tevatron is expected to cease operations in 2010 as it is obsoleted by the LHC.[2] The main ring will probably be reused in future experiments, and other components may be reused by other particle accelerators.[3]
Mechanics
The acceleration occurs in a number of stages. The first stage is the 750 keV Cockcroft-Walton pre-accelerator, which ionizes hydrogen gas and accelerates the negative ions created using a positive voltage. The ions then pass into the 150 meter long linear accelerator (linac) which uses oscillating electrical fields to accelerate the ions to 400 MeV. The ions then pass through a carbon foil, to remove the electrons, and the charged protons then move into the Booster.
The Booster is a small circular magnetic accelerator, around which the protons pass up to 20,000 times to attain an energy of around 8 GeV. From the Booster the particles pass into the Main Injector, which was completed in 1999 to perform a number of tasks. It can accelerate protons up to 150 GeV; it can produce 120 GeV protons for antiproton creation; it can increase antiproton energy to 120 GeV and it can inject protons or antiprotons into the Tevatron. The antiprotons are created by the Antiproton Source. 120 GeV protons are collided with a nickel target producing a range of particles including antiprotons which can be collected and stored in the accumulator ring. The ring can then pass the antiprotons to the Main Injector.
The Tevatron can accelerate the particles from the Main Injector up to 980 GeV. The protons and antiprotons are accelerated in opposite directions, crossing paths in the CDF and DØ detectors to collide at 1.96 TeV. To hold the particles on track the Tevatron uses superconducting dipole magnets cooled in liquid helium producing 4.2 teslas.
On September 27 1993 the cryogenic cooling system of the Tevatron Accelerator was named an International Historic Landmark by the American Society of Mechanical Engineers. The system, which provides cryogenic liquid helium to the Tevatron's superconducting magnets, was the largest low-temperature system in existence upon its completion in 1978. It keeps the coils of the magnets, which bend and focus the particle beam, in a superconducting state so that they consume only 1/3 of the power they would require at normal temperatures[citation needed].
Discoveries
In 1995, the CDF and DØ collaborations announced the discovery of the top quark, and by 2007 they measured its mass to a precision of nearly 1%. In 2006, they made the first measurement and observation of Bs oscillations, and observed two types of sigma baryon.[4]
In 2007, the D0 experiment reported the observance of the "Cascade B" (
Ξ−
b) Xi baryon.[4]
In September 2008, the DØ experiment reported the detection of the
Ω
b, a "double strange" Omega baryon.[5]
[6]
References
- ^ Wilson, R.R. (1978), The Tevatron, Batavia, Illinois: Fermilab, FERMILAB-TM-0763
- ^ http://www.sciam.com/article.cfm?id=future-of-top-us-particle
- ^ http://www.sciam.com/article.cfm?id=what-happens-to-particle-accelerators&page=2
- ^ a b http://www.sciencedaily.com/releases/2008/09/080903172201.htm
- ^ "Fermilab physicists discover "doubly strange" particle". Fermilab. September 3, 2008. Retrieved 2008-09-04.
- ^ "Observation of the doubly strange b baryon Omega_b-, Fermilab-Pub-08/335-E". Fermilab. Retrieved 2008-09-05.