Accelerators

The search for the very small requires very high energies. The discoveries necessary for the electroweak unification were near the upper end of available energies in the current generation of particle accelerators. High energy particle physics experimental research is now concentrated in a relatively small number of places.

These large accelerator facilities employ a variety of acceleration devices and have sophisticated arrays of detectors to permit analysis of the results of the high energy scattering events.

Fermilab

The Fermi National Accelerator Laboratory near Chicago has the most powerful proton-antiproton collider, designed to reach 1 TeV. It is the only current facility which seems to have the power to produce evidence for the last of the quarks, the top quark.

Protons from the Main Ring in bunches of a quadrillion are smashed into a metal target to make antiprotons. About 10 billion are made and extracted into a triangular magnet array called an accumulator. Once a sufficient "stack" of antiprotons is accumulated, they are injected into the Tevatron. Six bunches of each type of particle, each bunch 2 ft long and thinner than a pencil, are accelerated in opposite directions around the ring to collide in a "shot" in the collider detector (Trefil,Discover Dec89, p56).

The Fermilab facility houses the Main Injector, a proton synchrotron accelerator. Beneath it in the same tunnel is another synchrotron, a superconducting magnetic ring called the Tevatron which boosts the energy to 1 TeV. There is an antiproton storage ring which achieves collision energies of about 1.8 TeV.

Before entering the Main Injector, protons are accelerated to about 750 keV by a Cockroft-Walton accelerator, then to about 400 MeV by a linear accelerator. They are raised to 8 GeV by a comparatively small booster accelerator and then up to 150 GeV by the Main Injector.

Associated with the Tevatron are two large detector facilities, the Collider Detector Facility and the D0 detector facility.

Fermilab's Booster and Main Injector

As part of Fermilab's chain of accelerators, the booster and main injector increase the energy of particles before injection into the Tevatron.

After being accelerated by Cockroft-Walton and linear accelerators, protons enter the third stage, the Booster, is located about 20 feet below ground. The Booster is a circular accelerator (synchrotron) that uses magnets to bend the beam of protons in a circular path. The protons travel around the Booster about 20,000 times so that they repeatedly experience electric fields. With each revolution the protons pick up more energy, leaving the Booster with 8 billion electron volts (8 GeV).

The Main Injector, completed in 1999, accelerates particles and transfers beams. It has four functions: (1) It accelerates protons from 8 GeV to 150 GeV. (2) It produces 120 GeV protons, which are used for antiproton production. (3) It receives antiprotons from the Antiproton Source and increases their energy to 150 GeV. (4) It injects protons and antiprotons into the Tevatron. Inside the Main Injector tunnel, physicists have also installed an Antiproton Recycler (green ring). It stores antiprotons that return from a trip through the Tevatron, waiting to be re-injected. The Tevatron receives 150 GeV protons and antiprotons from the Main Injector and accelerates them to almost 1000 GeV, or one tera electron volt (1 TeV). Traveling only 200 miles per hour slower than the speed of light, the protons and antiprotons circle the Tevatron in opposite directions. The beams cross each other at the centers of the 5000-ton CDF and DZero detectors located inside the Tevatron tunnel, creating bursts of new particles. (Fermilab)

Images courtesy Fermilab

Fermilab's Tevatron

Beneath the Main Ring at Fermilab in the same tunnel is another synchrotron, a superconducting magnetic ring called the Tevatron which boosts the energy to 1 TeV. There is an antiproton storage ring which achieves collision energies of about 1.8 TeV.

The Tevatron makes use of superconducting magnets to achieve the high energies and reduce operating costs.

The Tevatron receives 150 GeV protons and antiprotons from the Main Injector and accelerates them to almost 1000 GeV, or one tera electron volt (1 TeV). Traveling only 200 miles per hour slower than the speed of light, the protons and antiprotons circle the Tevatron in opposite directions. The beams cross each other at the centers of the 5000-ton CDF and DZero detectors located inside the Tevatron tunnel, creating bursts of new particles. (Fermilab)