Image: Giovani Punzi
M. Spencer Green  /  AP
Employees man the main control room that runs all the accelerators at the Fermi National Accelerator Laboratory in Batavia, Ill., including the Tevatron collider.
By Senior writer
updated 9/30/2011 5:08:01 PM ET 2011-09-30T21:08:01

One of the world's most powerful atom smashers, the Tevatron, shut down Friday, with video from the event streamed online.

The atom smasher is located at the federal Fermilab physics laboratory in Batavia, Ill. Inside the accelerator, particles were ramped up to near light speed as they zipped around a 4-mile-round (6.3-kilometer-round) ring. When two particles collided, they disintegrated into other exotic particles in a powerful outpouring of energy.

  1. Science news from
    1. NOAA
      Cosmic rays may spark Earth's lightning

      All lightning on Earth may have its roots in space, new research suggests.

    2. How our brains can track a 100 mph pitch
    3. Moth found to have ultrasonic hearing
    4. Quantum network could secure Internet

While it was once the most powerful atom smasher, the Tevatron was surpassed by the new Large Hadron Collider at Europe's CERN physics lab on the French-Swiss border. [Twisted Physics: 7 Mind-Blowing Findings]

The Tevatron's end came a little after 2:30 p.m. CT (3:30 p.m. ET), as Fermilab physicist Helen Edwards pushed two specially constructed buttons, one red and the other blue. The red button shut down the collision of protons and antiprotons in the Tevatron. The blue button shut off the electrical current to the accelerator.

That one, Edwards had to push twice.

"It didn't want to give up so easy," said Bob Mau, the head of the accelerator division operation department at Fermilab, who was leading the live-streamed shutdown. 

The 28-year-old Tevatron was most recently in the news in April when a report suggested the accelerator's CDF experiment might have detected a never-before-seen subatomic particle. However, further tests have suggested that the tantalizing signal was a fluke.

The Tevatron played a part in some major physics finds, such as the existence of the top quark and five baryons. The baryon discovery helped scientists test and refine the Standard Model of particle physics and shape our understanding of matter, energy, space and time. 

The experiments at Tevatron have also helped narrow down the search for the elusive Higgs boson, or "God particle." LHC physicists are on the hunt for the Higgs, the last fundamental particle to be predicted by the Standard Model but not found.

Officials said those involved with the two detector experiments, CDF and DZero, will continue to analyze already-collected data. Those results will be detailed in future scientific papers. The studies at the two detectors are aimed at understanding and identifying the origin of mass, extra dimensions of space and new particles.

In addition, Fermilab officials say they will continue to operate most of the 10 particle accelerators onsite to generate particle beams for experiments involving protons, neutrinos and muons.

The mood today, however, was nostalgic. 

"For many of us, CDF is more than a machine," CDF scientist Ben Kilminster said as he and his team shut down their detector. "It's a living creature that has the superhuman ability to see the microscopic quantum world. So it's going to be with heavy hearts that many of us watch it close its eyes to this world that has captivated us for so long."

© 2012 All rights reserved.

Explainer: What’s a hadron? Tour the particle zoo

  • Image: Elementary particles

    The Standard Model of particle physics is one of science's most successful theories, enabling the development of devices ranging from light bulbs, to microwave ovens and television, to quantum computing devices. The Standard Model is also one of the oddest theories, because it lays out a dizzying menagerie of hundreds of subatomic particles. At its heart are 16 types of elementary particles ... plus at least one more mysterious particle that scientists are spending billions of dollars to detect.

    Click on "Next" to get the full rundown.

  • Quarks

    Image: Quarks and gluons
    Berkeley Lab

    Six "flavors" of quarks have been detected: up and down, charm and strange, top and bottom. Quarks are almost always found in different combinations, bound together by gluons (more on those later). Particles built up from quarks and gluons are called hadrons. The Large Hadron Collider is so named because it's a large collider that smashes hadrons together.

    Three-quark combinations fit in the category of baryons. The best-known baryons are the proton (with two up quarks and one down quark) and the neutron (with two down quarks and one up quark).

    Particles that have one quark and one antiquark fit in the category of mesons. For example, the pion, or pi meson, contains an up quark and an anti-down quark.

  • Leptons

    Image: Single electrons in helium
    Brown University

    Six "flavors" of leptons have been detected: The negatively charged electron is the best-known lepton — along with its antimatter counterpart, the positron. This photo shows the path of single electrons passing through liquid helium, in an experiment devised by Brown University researchers.

    The muon is also negatively charged, but it's about 207 times as massive as the electron. ("Who ordered that?" physicist Isidor Rabi reportedly asked.) The negatively charged tau particle is even bigger — 3,477 times as massive as the electron — but it decays into other particles in less than a trillionth of a second.

    Each of those leptons has a neutrino associated with it: the electron neutrino, the muon neutrino and the tau neutrino. Neutrinos interact only weakly with other particles, and they zip through our planet virtually without a trace. Physicists only recently determined that they have mass, but there's still a great deal of mystery surrounding the ghostly particles.

  • Force carriers

    Image: Graviton

    The Standard Model sets aside a category for particles that are associated with force fields. The effect of a field can be viewed as involving an exchange of such force-carrying particles.

    Four elementary force-carrying particles have been detected. The best-known force carrier is the photon — which plays a part in the electromagnetic spectrum, including visible light. The gluon binds quarks together through the strong nuclear force. The weak nuclear force involves the exchange of W and Z bosons. The W boson can carry a positive or a negative charge, while the Z boson is neutral.

    If gravity could be incorporated into the Standard Model, the force-carrying particle would be called the graviton (shown here in an artist's depiction). However, gravitons have not yet been detected, and at least for now, such particles are not accounted for in the Standard Model.

  • Bosons vs. fermions

    Image: Bosons vs. fermions
    Rice Univ. via AIP

    All force-carrying particles are bosons, but not all bosons are force carriers. The difference has to do with a property known as particle spin. Particles with a fractional spin value (for example, electrons, protons and neutrons) are fermions. Two identical fermions cannot occupy the same quantum state. This is a property that keeps electrons from collapsing into a jumble, and thus makes chemical reactions possible.

    All particles with a whole-integer spin value are classified as bosons, and such particles can occupy the same quantum state even if they're identical. The photon is the best-known type of boson.

    Even atoms can be classified as fermions and bosons. This photo shows how atom clouds of lithium-7 (bosons) and lithium-6 (fermions) behave at low temperatures. The bosons collapse into a compact cloud, while the fermions can't squeeze that closely together.

  • The mysterious Higgs

    Image: Higgs as seen by CMS
    Ianna Osborne / CERN / CMS Collection

    The Higgs boson is the only particle predicted by the Standard Model that has not yet been detected. The Higgs is the main quarry for physicists at the Large Hadron Collider. This image is a simulation of the Higgs' signature as it might appear in one of the LHC's detectors.

    The Higgs boson, named after Scottish theorist Peter Higgs, is thought to be associated with a field that endows some particles (such as the weak nuclear force's W and Z bosons) with mass, while leaving the electromagnetic force's photons without mass.

    This Higgs field may have played a role at the very beginnings of the universe: Physicists believe that at the highest energies, the electromagnetic and weak nuclear forces were unified, but something led to "electroweak symmetry breaking" as the infant cosmos cooled. That would be why the electromagnetic force and the weak nuclear force are distinct in the current universe. The Large Hadron Collider could shed new light on this mysterious Higgs mechanism.

  • Why so complicated?

    Image: Particle zoo
    Tim Jones / McDonald Observatory / HETDEX

    Hadrons and leptons? Baryons and mesons? Fermions and bosons? Sometimes it seems as if particle physicists set up these classifications just to keep outsiders totally confused. But for researchers, these occasionally overlapping categories are useful for figuring out how different types of particles interact with each other.

    In a sense, it's as if we've been talking about the game of chess but have gotten only to the point of naming the different pieces on the board: black pieces and white ones, pawns and knights, bishops and rooks, kings and queens. The real meaning of the game comes out when you start studying how the pieces perform and interact.

    To delve into the deeper meaning of the Standard Model, you can visit The Particle Adventure at Lawrence Berkeley National Laboratory, "A Subatomic Venture" at CERN, or Particle Physics UK.

Interactive: Inside the big bang machine


Discussion comments


Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments