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Tevatron

Coordinates: 41°49′55″N 88°15′06″W / 41.831904°N 88.251715°W / 41.831904; -88.251715
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41°49′55″N 88°15′06″W / 41.831904°N 88.251715°W / 41.831904; -88.251715

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 is the second highest energy particle collider in the world after the Large Hadron Collider (LHC) near Geneva, Switzerland. The Tevatron is a synchrotron that accelerates protons and antiprotons in a 6.28 km (3.90 mi) ring to energies of up to 1 TeV, hence its name.[1] The Tevatron was completed in 1983 at a cost of $120 million ($367 million today[2]) and significant upgrade investments were made in 1983-2011. (The 'Energy Doubler', as it was known then, produced its first accelerated beam — 512 GeV — on July 3, 1983.[3]) The Main Injector was the most substantial addition, built over five years from 1994 at a cost of $290 million ($887 million today[2]).

Experiments done in the Tevatron collider produced results determining that the existence of the Higgs boson was highly likely. 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 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 by the results from the LHC experiments.[4]

The Tevatron ceased operations on 30 September, 2011,[5] due to budget cuts;[6] it is not as powerful as the LHC, which began operations in early 2010. The main ring of the Tevatron will probably be reused in future experiments, and its components may be transferred to other particle accelerators.[7]

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.[8]

The Booster is a small circular synchrotron, 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 774 niobium-titanium superconducting dipole magnets cooled in liquid helium producing 4.2 teslas. The field ramps over about 20 seconds as the particles are accelerated. Another 240 NbTi quadrupole magnets are used to focus the beam.[1]

The initial design luminosity of the Tevatron was 1030 cm−2 s−1, however the accelerator has following upgrades been able to deliver luminosities up to 4x1032 cm−2 s−1.[9]

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.[10]

Earthquake detection

Sensors on underground magnets in the Tevatron are capable of detecting minute seismic vibrations from earthquakes thousands of miles away. The Tevatron recorded vibration spikes emanating from the 2004 Indian Ocean earthquake, the 2005 Sumatra earthquake, New Zealand's 2007 Gisborne earthquake, the 2010 Haiti earthquake and the 2010 Chile earthquake.[11]

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, CDF made the first measurement of Bs oscillations, and observed two types of sigma baryon. [12]

In 2007, the DØ and CDF experiments reported direct observation of the "Cascade B" (
Ξ−
b) Xi baryon. [13]

In September 2008, the DØ experiment reported detection of the
Ω−
b, a "double strange" Omega baryon [14] [15] with the measured mass significantly higher than the quark model prediction. In May 2009 the CDF collaboration made public their results on search for
Ω−
b based on analysis of data sample roughly four times larger than the one used by DZero experiment.[16] CDF measured mass to be 6054.4±6.8 MeV/c2 in excellent agreement with Standard Model prediction. No signal has been observed at DZero reported value. The two results differ by 111±18 MeV/c2 or by 6.2 standard deviations and therefore are inconsistent. Excellent agreement between CDF measured mass and theoretical expectations is a strong indication that the particle discovered by CDF is indeed the
Ω−
b. It is anticipated that new data from LHC experiments will clarify the situation in the near future.

On April 7, 2011, the CDF team at Fermilab announced the discovery of a possible new particle after signs of a new particle appeared in their data.[citation needed] However, an independent analysis of data from trillions of particle collisions by the DØ team was not able to reproduce the detection of the new particle, thus suggesting that the initial observation was a statistical fluke and that, in fact, no new particle had been discovered.[citation needed]

On July 2, 2012, two days before the announcement of the Higgs boson search results from the Large Hadron Collider, scientists of the CDF and DØ collider experiments 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 Higgs boson was highly likely. 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. This meant that it was very likely that the Higgs boson had been observed. The final analysis of the data did not not settle the question of whether the Higgs particle exists, and further confirmation was expected from the announcement of the LHC results on July 4.[4][17] The results from the Tevatron experiments were confirmed 2 days later on July 4, 2012, when the results of the LHC experiments were announced.

See also

References

  1. ^ a b R. R. Wilson (1978). "The Tevatron" (Document). Fermilab. FERMILAB-TM-0763. {{cite document}}: Unknown parameter |url= ignored (help)
  2. ^ a b 1634–1699: McCusker, J. J. (1997). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States: Addenda et Corrigenda (PDF). American Antiquarian Society. 1700–1799: McCusker, J. J. (1992). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States (PDF). American Antiquarian Society. 1800–present: Federal Reserve Bank of Minneapolis. "Consumer Price Index (estimate) 1800–". Retrieved February 29, 2024.
  3. ^ FermNews - 20th anniversary issue
  4. ^ a b "Tevatron scientists announce their final results on the Higgs particle". Fermi National Accelerator Laboratory. July 02, 2012. Retrieved July 07, 2012. {{cite web}}: Check date values in: |accessdate= and |date= (help)
  5. ^ "'Nothing lasts forever at the edge of science': U.S. drops behind in race to find origins of the universe as huge particle collider is shut down". Daily Mail.
  6. ^ http://www.sciam.com/article.cfm?id=future-of-top-us-particle
  7. ^ http://www.sciam.com/article.cfm?id=what-happens-to-particle-accelerators&page=2
  8. ^ "Accelerators - Fermilab's Chain of Accelerators". Fermilab. 15 January 2002. Retrieved 2 December 2009.
  9. ^ The TeVatron Collider: A Thirty-Year Campaign
  10. ^ "The Fermilab Tevatron Cryogenic Cooling System" (Document). ASME. 1993. {{cite document}}: Unknown parameter |accessdate= ignored (help); Unknown parameter |url= ignored (help)
  11. ^ Tevatron Sees Haiti Earthquake
  12. ^ "Experimenters at Fermilab discover exotic relatives of protons and neutrons". Fermilab. 2006-10-23. Retrieved 2006-10-23.
  13. ^ "Back-to-Back b Baryons in Batavia". Fermilab. 2007-07-25. Retrieved 2007-07-25.
  14. ^ "Fermilab physicists discover "doubly strange" particle". Fermilab. September 3, 2008. Retrieved 2008-09-04.
  15. ^ V. M. Abazov et al. (DØ collaboration) (2008). "Observation of the doubly strange b baryon
    Ω−
    b    ". Physical Review Letters. 101 (23): 231002. arXiv:0808.4142. Bibcode:2008PhRvL.101w2002A. doi:10.1103/PhysRevLett.101.232002.
  16. ^ T. Aaltonen et al. (CDF Collaboration) (2009). "Observation of the
    Ω−
    b     and Measurement of the Properties of the
    Ξ−
    b     and
    Ω−
    b    ". Physical Review D. 80: 072003. arXiv:0905.3123. Bibcode:2009PhRvD..80g2003A. doi:10.1103/PhysRevD.80.072003.
  17. ^ Rebecca Boyle (July 02, 2012). "Tantalizing Signs of Higgs Boson Found By U.S. Tevatron Collider". Popular Science. Retrieved July 07, 2012. {{cite web}}: Check date values in: |accessdate= and |date= (help)

External links

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