View source for Tevatron

{{short description|Defunct American particle accelerator at Fermilab in Illinois (1983–2011)}}

{{Infobox particle accelerator
| name           = Tevatron
| image          = Fermilab.jpg
| caption        = The Tevatron (background) and ''Main Injector'' rings
| type           = [[synchrotron]]
| beam           = [[proton]], [[antiproton]]
| target         = [[collider]]
| energy         = 1 TeV
| current        = 
| brightness     =
| luminosity     = {{val|4e32|up=cm<sup>2</sup>⋅s}}
| length         =
| radius         =
| circumference  = {{convert|6.28|km|m}}
| location       = [[Batavia, Illinois]]
| coordinates    = <!-- {{coord|LAT|LON|type:landmark|display=inline,title}} -->
| institution    = [[Fermi National Accelerator Laboratory|Fermilab]]
| dates          = 1983–2011
| preceded       =
| succeeded      = 
}}

{{Beyond the Standard Model|expanded=Experiments}}
The '''Tevatron''' was a circular [[particle accelerator]] (active until 2011) in the [[United States]], at the [[Fermilab|Fermi National Accelerator Laboratory]] (called ''Fermilab''), east of [[Batavia, Illinois]], and was the highest energy particle collider until the [[Large Hadron Collider]] (LHC) of the [[CERN|European Organization for Nuclear Research]] (CERN) was built near [[Geneva, Switzerland]]. The Tevatron was a [[synchrotron]] that accelerated [[proton]]s and [[antiproton]]s in a {{convert|6.28|km|mi|abbr=on}} circumference ring to energies of up to 1 [[TeV]], hence its name.<ref name="Fermilab History">{{cite web|url=http://history.fnal.gov/main_ring.html#start|title=Accelerator History—Main Ring|access-date=7 October 2012|publisher=Fermilab History and Archives Project|archive-date=9 May 2012|archive-url=https://web.archive.org/web/20120509085138/http://history.fnal.gov/main_ring.html#start|url-status=dead}}</ref><ref name="TheTev">
{{Cite journal
| author=R. R. Wilson
| author-link = Robert R. Wilson
| year = 1978
| title = The Tevatron
| url = http://lss.fnal.gov/archive/test-tm/0000/fermilab-tm-0763.shtml
| publisher = [[Fermilab]]
| id = FERMILAB-TM-0763
}}</ref> The Tevatron was completed in 1983 at a cost of $120 million and significant upgrade investments were made during its active years of 1983–2011.

The main achievement of the Tevatron was the discovery in 1995 of the [[top quark]]—the last [[Elementary particle#Fundamental fermions|fundamental fermion]] predicted by the [[Standard Model]] of particle physics. On July 2, 2012, scientists of the [[Collider Detector at Fermilab|CDF]] and [[D0 experiment|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 a confidence of 99.8%,<ref name="FNAL Higgs boson results"/> later improved to over 99.9%.<ref>
{{cite web
  |title       = Tevatron experiments observe evidence for Higgs-like particle
  |url         = https://cerncourier.com/a/tevatron-experiments-observe-evidence-for-higgs-like-particle/
  |date        = 23 August 2012
  |publisher   = CERN
  |access-date = 21 April 2021
}}</ref>

The Tevatron ceased operations on 30 September 2011, due to budget cuts<ref name=sciam2011>{{cite news|url=http://www.sciam.com/article.cfm?id=future-of-top-us-particle|title=Future of Top U.S. Particle Physics Lab in Jeopardy|date=29 September 2011|access-date=7 October 2012|work=Scientific American|author=Mark Alpert}}</ref> and because of the completion of the LHC,  which began operations in early 2010 and is 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.<ref>
{{cite magazine|url= https://www.symmetrymagazine.org/article/february-2012/the-tevatrons-proud-legacy
  |title=The Tevatron's proud legacy
  |date=2012-02-01
  |first=Rhianna|last=Wisniewski
  |magazine=Symmetry Magazine
  |publisher=Fermilab/SLAC
}}</ref>

==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 6.3&nbsp;km circumference Fermilab's Main Ring.<ref name="Fermilab History"/>

The linac first 200&nbsp;MeV beam started on December 1, 1970. The booster first 8&nbsp;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&nbsp;GeV. Back then, the Booster Accelerator took 200&nbsp;MeV protons from the Linac and "boosted" their energy to 8&nbsp;billion electron volts. They were then injected into the Main Accelerator.<ref name="Fermilab History"/>

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 magnet]]s. 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.<ref name="Fermilab Transition"/> The Tevatron was in research and development phase between 1973 and 1979 while the acceleration at the Main Ring continued to be enhanced.<ref name="TevCryo"/>

A series of milestones saw acceleration rise to 20&nbsp;GeV on January 22, 1972, to 53&nbsp;GeV on February 4 and to 100&nbsp;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&nbsp;GeV. By the end of 1973, NAL's accelerator system operated routinely at 300&nbsp;GeV.<ref name="Fermilab History"/>

On 14 May 1976 Fermilab took its protons all the way to 500&nbsp;GeV. This achievement provided the opportunity to introduce a new energy scale, the teraelectronvolt (TeV), equal to 1000&nbsp;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.<ref>{{cite news|url=http://cerncourier.com/cws/article/cern/28470|title=Super Proton Synchrotron marks its 25th birthday|work=CERN courier|date=2 July 2011|access-date=7 October 2012}}</ref>

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.<ref name="Fermilab Transition">{{cite web|url=http://history.fnal.gov/transition.html|title=Accelerator History—Main Ring transition to Energy Doubler/Saver|access-date=7 October 2012|publisher=Fermilab History and Archives Project|archive-date=18 December 2012|archive-url=https://web.archive.org/web/20121218092249/http://history.fnal.gov/transition.html|url-status=dead}}</ref> The 'Energy Doubler', as it was known then, produced its first accelerated beam—512 GeV—on July 3, 1983.<ref>{{cite journal|url=http://www.fnal.gov/pub/ferminews/ferminews03-11-01/p4.html|journal=Fermi News|title=1983—The Year the Tevatron Came to Life|volume=26|year=2003|issue=15}}</ref>

Its initial energy of 800&nbsp;GeV was achieved on February 16, 1984. On October 21, 1986, acceleration at the Tevatron was pushed to 900&nbsp;GeV, providing a first proton–antiproton collision at 1.8&nbsp;TeV on November 30, 1986.<ref name=timeline>{{cite web|url=http://www.fnal.gov/pub/tevatron/milestones/interactive-timeline.html|title=Interactive timeline|access-date=7 October 2012|publisher=Fermilab}}</ref>

The ''Main Injector'', which replaced the Main Ring,<ref name=cern2001/> was the most substantial addition, built over six years from 1993 at a cost of $290 million.<ref name="Fermilab Main injector">{{cite web|url=http://www-fmi.fnal.gov/History/history.html|title=Main Injector and Recycler Ring History and Public Information|access-date=7 October 2012|publisher=Fermilab Main Injector department|url-status=dead|archive-url=https://web.archive.org/web/20111015015038/http://www-fmi.fnal.gov/History/history.html|archive-date=15 October 2011}}</ref> 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&nbsp;GeV.<ref name=cern2001>{{cite news|url=http://cerncourier.com/cws/article/cern/28420|title=Run II begins at the Tevatron|work=CERN courier|date=30 April 2001|access-date=7 October 2012}}</ref>

On July 16, 2004, the Tevatron achieved a new peak [[Luminosity_(scattering_theory)|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{{e|32}}&nbsp;cm<sup>−2</sup> s<sup>−1</sup>).<ref name=timeline/>

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{{e|33}}&nbsp;cm<sup>−2</sup> s<sup>−1</sup>) and a beam energy of 3.5&nbsp;TeV each (doing so since March 18, 2010), already ~3.6 times the capabilities of the Tevatron (at 0.98&nbsp;TeV).

==Mechanics==

The acceleration occurred in a number of stages. The first stage was the 750 [[keV]] ''[[Cockcroft–Walton generator|Cockcroft–Walton]]'' pre-accelerator, which [[ionize]]d [[hydrogen]] gas and accelerated the negative ions created using a positive [[voltage]]. The ions then passed into the 150 [[meter]] long [[linear accelerator]] (linac) which used oscillating electrical fields to accelerate the ions to 400 [[MeV]]. The ions then passed through a carbon foil, to remove the [[electron]]s, and the charged [[proton]]s then moved into the ''Booster''.<ref>
{{cite web
| title       = Accelerators—Fermilab's Chain of Accelerators
| url         = http://www.fnal.gov/pub/inquiring/physics/accelerators/chainaccel.html
| date        = 15 January 2002
| publisher   = [[Fermilab]]
| access-date  = 2 December 2009
}}</ref>

The Booster was a small circular synchrotron, around which the protons passed up to 20,000 times to attain an energy of around 8 [[GeV]]. From the Booster the particles were fed into the Main Injector, which had been completed in 1999 to perform a number of tasks. It could accelerate protons up to 150 GeV;  produce 120 GeV protons for antiproton creation; increase antiproton energy to 150 GeV; and inject protons or antiprotons into the Tevatron. The antiprotons were created by the ''Antiproton Source''.  120 GeV protons were collided with a nickel target producing a range of particles including antiprotons which could be collected and stored in the accumulator ring. The ring could then pass the antiprotons to the Main Injector.

The Tevatron could accelerate the particles from the Main Injector up to 980 GeV. The protons and antiprotons were accelerated in opposite directions, crossing paths in the [[Collider Detector at Fermilab|CDF]] and [[D0 Experiment|DØ]] detectors to collide at 1.96 TeV. To hold the particles on track the Tevatron used 774 [[niobium–titanium]] [[superconductor|superconducting]] [[Dipole magnet|dipole]] [[magnet]]s cooled in liquid [[helium]] producing the field strength of 4.2 [[tesla (unit)|tesla]]. The field ramped over about 20 seconds as the particles accelerated. Another 240 [[Niobium–titanium|NbTi]] [[quadrupole]] magnets were used to focus the beam.<ref name="TheTev"/>

The initial design [[Luminosity_(scattering_theory)|luminosity]] of the Tevatron was 10<sup>30</sup> cm<sup>−2</sup> s<sup>−1</sup>, however, following upgrades, the accelerator had been able to deliver luminosities up to 4{{e|32}}&nbsp;cm<sup>−2</sup> s<sup>−1</sup>.<ref>[http://www-ppd.fnal.gov/EPPOffice-W/colloq/Abstracts/Peoples_3_10_10.htm The TeVatron Collider: A Thirty-Year Campaign] {{webarchive|url=https://web.archive.org/web/20100527092615/http://www-ppd.fnal.gov/EPPOffice-W/colloq/Abstracts/Peoples_3_10_10.htm |date=2010-05-27 }}</ref>

On September 27, 1993, the [[cryogenic]] cooling system of the Tevatron Accelerator was named an [[List of Historic Mechanical Engineering Landmarks|International Historic Landmark]] by the [[American Society of Mechanical Engineers]]. The system, which provided cryogenic liquid helium to the Tevatron's superconducting magnets, was the largest low-temperature system in existence upon its completion in 1978. It kept the coils of the magnets, which bent and focused the particle beam, in a superconducting state, so that they consumed only ⅓ of the power they would have required at normal temperatures.<ref name="TevCryo">
{{Cite journal

| title = The Fermilab Tevatron Cryogenic Cooling System
| url = http://www.asme.org/getmedia/54536aae-9831-4a29-aabc-55b93beba1a4/169-Cryogenic-Cooling-System-Fermilab-Tevatron.aspx
| year = 1993
| publisher = [[ASME]]
| access-date=2015-08-12
}}</ref>

==Discoveries==
The Tevatron confirmed the existence of several [[subatomic particle]]s that were predicted by [[particle physics#Theory|theoretical particle physics]], or gave suggestions to their existence. In 1995, the [[Collider Detector at Fermilab|CDF experiment]] and [[D0 experiment|DØ experiment]] collaborations announced the discovery of the [[top quark]], and by 2007 they measured its mass (172 GeV) to a precision of nearly 1%. 
In 2006, the CDF collaboration reported the first measurement of [[B-Bbar oscillation|B<sub>s</sub> oscillations]], and observation of two types of [[sigma baryon]]s.<ref>{{cite web 
|title=Experimenters at Fermilab discover exotic relatives of protons and neutrons
|url=http://www.fnal.gov/pub/presspass/press_releases/sigma-b-baryon.html
|publisher=Fermilab
|date=2006-10-23
|access-date=2006-10-23}}</ref>
In 2007, the DØ and CDF collaborations reported direct observation of the "Cascade B" ({{SubatomicParticle|Bottom Xi-}}) [[Xi baryon]].<ref>{{cite web 
|title=Back-to-Back b Baryons in Batavia
|url=http://www.fnal.gov/pub/presspass/press_releases/backtobackBaryons.html
|publisher=Fermilab
|date=2007-07-25
|access-date=2007-07-25}}</ref>

In September 2008, the DØ collaboration reported detection of the {{SubatomicParticle|Bottom Omega-}}, a "double [[strangeness|strange]]" [[Omega baryon]]  with the measured mass significantly higher than the quark model prediction.<ref>{{cite web
|title=Fermilab physicists discover "doubly strange" particle
|url=http://www.fnal.gov/pub/presspass/press_releases/Dzero_Omega-sub-b.html
|publisher=Fermilab
|date=September 3, 2008
|access-date=2008-09-04}}</ref><ref>{{cite journal
|author=V. M. Abazov ''et al.'' ([[DØ experiment|DØ collaboration]])
|year=2008
|title=Observation of the doubly strange b baryon {{SubatomicParticle|Bottom Omega-}}
|volume=101 |issue=23 |pages=231002
|journal=[[Physical Review Letters]]
|arxiv=0808.4142
|doi=10.1103/PhysRevLett.101.232002
|pmid=19113541
|bibcode = 2008PhRvL.101w2002A |s2cid=30481085
}}</ref> In May 2009 the CDF collaboration made public their results on search for  {{SubatomicParticle|Bottom Omega-}} based on analysis of data sample roughly four times larger than the one used by DØ experiment.<ref>
{{cite journal
 |author=T. Aaltonen ''et al.'' ([[CDF experiment|CDF Collaboration]])
 |year=2009
 |title=Observation of the {{SubatomicParticle|Bottom Omega-}} and Measurement of the Properties of the {{SubatomicParticle|Bottom Xi-}} and {{SubatomicParticle|Bottom Omega-}}
 |journal=[[Physical Review D]]
 |volume=80 |issue=7
 |pages=072003
 |doi=10.1103/PhysRevD.80.072003
 |arxiv=0905.3123
|bibcode = 2009PhRvD..80g2003A |s2cid=54189461
 }}</ref> The mass measurements from the CDF experiment were {{val|6054.4|6.8|u=MeV/c2}} and in excellent agreement with Standard Model predictions, and no signal has been observed at the previously reported value from the DØ experiment. The two inconsistent results from DØ and CDF differ by {{val|111|18|u=MeV/c2}} or by 6.2 standard deviations. Due to excellent agreement between the mass measured by CDF and the theoretical expectation, it is a strong indication that the particle discovered by CDF is indeed the {{SubatomicParticle|Bottom Omega-}}. It is anticipated that new data from [[Large Hadron Collider|LHC]]  experiments will clarify the situation in the near future.

On July 2, 2012, two days before a scheduled announcement at the [[Large Hadron Collider]] (LHC), scientists at the Tevatron collider from the CDF and DØ collaborations announced their findings from the analysis of around 500 trillion collisions produced since 2001: They found that the existence of the Higgs boson was likely with a mass in the region of 115 to 135 GeV.<ref>{{cite web | url=http://tevnphwg.fnal.gov/results/SM_Higgs_Summer_12/index.html | title=Updated Combination of CDF and DØ's Searches for Standard Model Higgs Boson Production with up to 10.0 fb-1 of Data | publisher=Tevatron New Phenomena & Higgs Working Group | date=June 2012 | access-date=August 2, 2012}}</ref><ref>{{cite journal | url=http://tevnphwg.fnal.gov/results/Higgs_bb_Summer_12/index.html | title=Evidence for a particle produced in association with weak bosons and decaying to a bottom-antibottom quark pair in Higgs boson searches at the Tevatron | journal=Physical Review Letters | volume=109 | issue=7 | pages=071804 | date=July 2012 | access-date=August 2, 2012| bibcode=2012PhRvL.109g1804A | last1=Aaltonen | first1=T. | last2=Abazov | first2=V. M. | last3=Abbott | first3=B. | last4=Acharya | first4=B. S. | last5=Adams | first5=M. | last6=Adams | first6=T. | last7=Alexeev | first7=G. D. | last8=Alkhazov | first8=G. | last9=Alton | first9=A. | last10=Álvarez González | first10=B. | last11=Alverson | first11=G. | last12=Amerio | first12=S. | last13=Amidei | first13=D. | last14=Anastassov | first14=A. | last15=Annovi | first15=A. | last16=Antos | first16=J. | last17=Apollinari | first17=G. | last18=Appel | first18=J. A. | last19=Arisawa | first19=T. | last20=Artikov | first20=A. | last21=Asaadi | first21=J. | last22=Ashmanskas | first22=W. | last23=Askew | first23=A. | last24=Atkins | first24=S. | last25=Auerbach | first25=B. | last26=Augsten | first26=K. | last27=Aurisano | first27=A. | last28=Avila | first28=C. | last29=Azfar | first29=F. | last30=Badaud | first30=F. | display-authors=1 |collaboration=CDF, D0 | arxiv=1207.6436 | doi=10.1103/PhysRevLett.109.071804 | pmid=23006359 | s2cid=20050195 }}</ref> The statistical significance of the observed signs was 2.9 sigma, which meant that there is only a 1-in-550 chance that a signal of that magnitude would have occurred if no particle in fact existed with those properties. The final analysis of data from the Tevatron did however not settle the question of whether the Higgs particle exists.<ref name="FNAL Higgs boson results">{{cite web | url=http://www.fnal.gov/pub/presspass/press_releases/2012/Higgs-Tevatron-20120702.html | title=Tevatron scientists announce their final results on the Higgs particle | publisher=Fermi National Accelerator Laboratory | date=July 2, 2012 | access-date=July 7, 2012}}</ref><ref>{{cite magazine | url=http://www.popsci.com/technology/article/2012-07/us-scientists-almost-found-higgs-boson-time-ran-out | title=Tantalizing Signs of Higgs Boson Found By U.S. Tevatron Collider | magazine=Popular Science | date=July 2, 2012 | access-date=July 7, 2012 | author=Rebecca Boyle}}</ref> Only when the scientists from the Large Hadron Collider announced the more precise LHC results on July 4, 2012, with a mass of 125.3 ± 0.4 GeV ([[Compact Muon Solenoid|CMS]])<ref name=cms0731>{{Cite journal|author=CMS collaboration|title=Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC|journal=Physics Letters B|volume=716|issue=2012|pages=30–61|arxiv=1207.7235|date=31 July 2012|doi=10.1016/j.physletb.2012.08.021|bibcode=2012PhLB..716...30C}}</ref> or 126 ± 0.4 GeV ([[ATLAS experiment|ATLAS]])<ref name=atlas0731>{{Cite journal|author=ATLAS collaboration|title=Observation of a New Particle in the Search for the Standard Model Higgs Boson with the ATLAS Detector at the LHC|journal=Physics Letters B|volume=716|issue=2012|pages=1–29|arxiv=1207.7214|date=31 July 2012|doi=10.1016/j.physletb.2012.08.020|bibcode=2012PhLB..716....1A|s2cid=119169617 }}</ref> respectively, was there strong evidence through consistent measurements by the LHC and the Tevatron for the existence of a Higgs particle at that mass range.

==Disruptions due to earthquakes==
Even from thousands of miles away, earthquakes caused strong enough movements in the magnets to negatively affect the quality of particle beams and even disrupt them. Therefore, tiltmeters were installed on Tevatron's magnets to monitor minute movements and to help identify the cause of problems quickly. The first known earthquake to disrupt the beam was the [[2002 Denali earthquake]], with another collider shutdown caused by a moderate local quake on June 28, 2004.<ref>[http://www.symmetrymagazine.org/cms/?pid=1000767#5 Was that a quake? Ask the Tevatron]</ref> Since then, the minute seismic vibrations emanating from over 20 earthquakes were detected at the Tevatron without a shutdown including the [[2004 Indian Ocean earthquake and tsunami|2004 Indian Ocean earthquake]], the [[2005 Nias–Simeulue earthquake]], New Zealand's [[2007 Gisborne earthquake]], the [[2010 Haiti earthquake]] and the [[2010 Chile earthquake]].<ref>[http://news.discovery.com/space/tevatron-sees-haiti-earthquake.html Tevatron Sees Haiti Earthquake]</ref>

==See also==
*[[Bevatron]]
*[[Large Hadron Collider]]
*[[Superconducting Super Collider]]
*[[Ultra-high-energy cosmic ray]]
*[[Relativistic Heavy Ion Collider]]

== References ==
{{Reflist|36em}}

==Further reading==
* {{cite book|editor1-last=Valery Lebedev, Vladimir Shiltsev|title=Accelerator Physics at the Tevatron Collider|publisher=Springer|year=2014|isbn=978-1-4939-0884-4|doi=10.1007/978-1-4939-0885-1|series=Particle Acceleration and Detection|bibcode=2014aptc.book.....L |url=https://cds.cern.ch/record/1707550}}

==External links==
*{{Commons category inline}}
* [http://www-bd.fnal.gov/notifyservlet/www?project=outside Live Tevatron status]
* [http://www.fnal.gov/pub/tevatron/tevatron-accelerator.html FermiLab page for Tevatron] – with labelled components
* [http://apps3.aps.org/aps/meetings/april10/roser.pdf The Hunt for the Higgs at Tevatron]
* [https://web.archive.org/web/20100528045751/http://www-bdnew.fnal.gov/operations/rookie_books/Concepts_v3.6.pdf Technical details of the accelerators]

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{{Hadron colliders}}
{{Standard model of physics}}

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