Fermi National Laboratory


Accelerator Update


About the Fermilab Accelerators

In 1983 Fermilab commissioned the very first superconducting-magnet synchrotron. With this new accelerator, the lab broke the record for man-made beam energies with an energy of 512 GeV. (A synchrotron refers to a circular accelerator. GeV stands for a billion electron volts and represents how much energy a particle carries.)

The problem with a circular accelerator is keeping the particles on a constant radius while, at the same time, increasing their energies. If the magnetic field strength doesn't increase as the particle's energy increases, the particles fly out of the accelerator. As the particles reach higher and higher energy this becomes a tricky business. The conventional materials used to construct magnets, which generate the magnetic field, won't allow the field strength to increase much due to the material's resistance to electrical current. The resistance causes a certain amount of heat. As the temperature increases, the resistance of most metallic conductors also increases. However, cooling a conductor decreases its resistivity.

The history of superconductivity

In 1911 a Dutch scientist by the name of Kammerlingh Onnes discovered that some metals show an absence of electrical resistance at temperatures near absolute zero. He was the first person to liquefy helium. These particular materials are called superconductors. Onnes received the 1913 Nobel Prize in Physics for his work.

The Tevatron magnets are made from a superconducting wire of Niobium-Titanium. Liquid helium keeps the wire at a temperature of approximately 4 degrees Kelvin (absolute zero is 0 degrees Kelvin. Room temperature is 300 degrees Kelvin). The Tevatron can accelerate particles to an energy of 980 GeV.

last modified 10/17/2001   email Fermilab

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