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The Tevatron is a circular particle accelerator in the United States, at the Fermi National Accelerator Laboratory (also known as ''Fermilab''), just east of Batavia, Illinois, and holds the title of the second highest energy particle collider in the world, after the Large Hadron Collider (LHC) near Geneva, Switzerland. The Tevatron was a synchrotron that accelerated protons and antiprotons in a 6.86 km, or 4.26 mi, ring to energies of up to 1 TeV, hence its name.〔 〕 The Tevatron was completed in 1983 at a cost of $120 million and significant upgrade investments were made in 1983–2011. The main achievement of the Tevatron was the discovery in 1995 of the top quark—the last fundamental fermion predicted by the standard model of particle physics. On July 2, 2012, scientists of the CDF and DØ collider experiment teams at Fermilab announced the findings from the analysis of around 500 trillion collisions produced from the Tevatron collider since 2001, and found that the existence of the suspected Higgs boson was highly likely with only a 1-in-550 chance that the signs were due to a statistical fluctuation. The findings were confirmed two days later as being correct with a likelihood of error less than 1 in a million by data from the LHC experiments.〔 The Tevatron ceased operations on 30 September 2011, due to budget cuts and because of the completion of the LHC, which began operations in early 2010 and was far more powerful (planned energies were two 7 TeV beams at the LHC compared to 1 TeV at the Tevatron). The main ring of the Tevatron will probably be reused in future experiments, and its components may be transferred to other particle accelerators. ==History== December 1, 1968 saw the breaking of ground for the linear accelerator (linac). The construction of the Main Accelerator Enclosure began on October 3, 1969 when the first shovel of earth was turned by Robert R. Wilson, NAL's director. This would become the 6.4 km circumference Fermilab's Main Ring.〔(【引用サイトリンク】title=Accelerator History—Main Ring )〕 The linac first 200 MeV beam started on December 1, 1970. The booster first 8 GeV beam was produced on May 20, 1971. On June 30, 1971, a proton beam was guided for the first time through the entire National Accelerator Laboratory accelerator system including the Main Ring. The beam was accelerated to only 7 Gev. Back then, the Booster Accelerator took 200 MeV protons from the Linac and "boosted" their energy to 8 billion electron volts. They were then injected into the Main Accelerator.〔 On the same year before the completion of the Main Ring, Wilson testified to the Joint Committee on Atomic Energy on March 9, 1971 that it was feasible to achieve a higher energy by using superconducting magnets. He also suggested that it could be done by using the same tunnel as the main ring and the new magnets would be installed in the same locations to be operated in parallel to the existing magnets of the Main Ring. That was the starting point of the Tevatron project.〔 The Tevatron was in research and development phase between 1973 and 1979 while the acceleration at the Main Ring continued to be enhanced.〔 A series of milestones saw acceleration rise to 20 GeV on January 22, 1972 to 53 GeV on February 4 and to 100 GeV on February 11. On March 1, 1972, the then NAL accelerator system accelerated for the first time a beam of protons to its design energy of 200 GeV. By the end of 1973, NAL's accelerator system operated routinely at 300 GeV.〔 On 14 May 1976 Fermilab took its protons all the way to 500 GeV. This achievement provided the opportunity to introduce a new energy scale, the teraelectronvolt (TeV), equal to 1000 GeV. On 17 June of that year, the European Super Proton Synchrotron accelerator (SPS) had achieved an initial circulating proton beam (with no accelerating radio-frequency power) of only 400 GeV. The conventional magnet Main Ring was shut down in 1981 for installation of superconducting magnets underneath it. The Main Ring continued to serve as an injector for the Tevatron until the Main Injector was completed west of the Main Ring in 2000.〔(【引用サイトリンク】title=Accelerator History—Main Ring transition to Energy Doubler/Saver )〕 The 'Energy Doubler', as it was known then, produced its first accelerated beam—512 GeV—on July 3, 1983. Its initial energy of 800 GeV was achieved on February 16, 1984. On October 21, 1986 acceleration at the Tevatron was pushed to 900 GeV, providing a first proton–antiproton collision at 1.8 TeV on November 30, 1986.〔(【引用サイトリンク】title=Interactive timeline )〕 The ''Main Injector'', which replaced the Main Ring,〔 was the most substantial addition, built over six years from 1993 at a cost of $290 million.〔(【引用サイトリンク】title=Main Injector and Recycler Ring History and Public Information )〕 Tevatron collider Run II begun on March 1, 2001 after successful completion of that facility upgrade. From then, the beam had been capable of delivering an energy of 980 GeV. On July 16, 2004 the Tevatron achieved a new peak luminosity, breaking the record previously held by the old European Intersecting Storage Rings (ISR) at CERN. That very Fermilab record was doubled on September 9, 2006, then a bit more than tripled on March 17, 2008 and ultimately multiplied by a factor of 4 over the previous 2004 record on April 16, 2010 (up to 4 cm−2 s−1).〔 The Tevatron ceased operations on 30 September 2011. By the end of 2011, the Large Hadron Collider (LHC) at CERN had achieved a luminosity almost ten times higher than Tevatron's (at 3.65 cm−2 s−1) and a beam energy of 3.5 TeV each (doing so since March 18, 2010), already ~3.6 times the capabilities of the Tevatron (at 0.98 TeV). 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「Tevatron」の詳細全文を読む スポンサード リンク
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