What is a Synchrotron?

Black and white photograph of a large circular structure, with computer monitors surrounding it.
High angle view of a synchrotron in a laboratory, California Institute of Technology, Pasadena, CA. SuperStock/Getty Images

A synchrotron is a  design of a cyclical particle accelerator, in which a beam of charged particles passes repeatedly through a magnetic field to gain energy on each pass. As the beam gains energy, the field adjusts to maintain control over the path of the beam as it moves around the circular ring. The principle was developed by Vladimir Veksler in 1944, with the first electron synchrotron built in 1945 and the first proton synchrotron built in 1952.

How a Synchrotron Works

The synchrotron is an improvement on the cyclotron, which was designed in the 1930s. In cyclotrons, the beam of charged particles moves through a constant magnetic field that guides the beam in a spiral path, and then passes through a constant electromagnetic field that provides an increase in energy on each pass through the field. This bump in kinetic energy means the beam moves through a slightly wider circle on the pass through the magnetic field, getting another bump, and so on until it reaches the desired energy levels.

The improvement that leads to the synchrotron is that instead of using constant fields, the synchrotron applies a field that changes in time. As the beam gains energy, the field adjusts accordingly to hold the beam in the center of the tube that contains the beam. This allows for greater degrees of control over the beam, and the device can be built to provide more increases in energy throughout a cycle.

 

One specific type of synchrotron design is called a storage ring, which is a synchrotron that is designed for the sole purpose of maintaining a constant energy level in a beam. Many particle accelerators use the main accelerator structure to accelerate the beam up to the desired energy level, then transfer it into the storage ring to be maintained until it can be collided with another beam moving in the opposite direction.

This effectively doubles the energy of the collision without having to build two full accelerators to get two different beams up to full energy level.

Major Synchrotrons

The Cosmotron was a proton synchrotron built at Brookhaven National Laboratory. It was commissioned in 1948 and reached full strength in 1953. At the time, it was the most powerful device built, about to reach energies of about 3.3 GeV, and it remained in operation until 1968.

Construction on the Bevatron at Lawrence Berkeley National Laboratory began in 1950 and it was completed in 1954. In 1955, the Bevatron was used to discover the antiproton, an achievement that earned the 1959 Nobel Prize in Physics. (Interesting historical note: It was called the Bevatraon because it achieved energies of approximately 6.4 BeV, for "billions of electronvolts." With the adoption of SI units, however, the prefix giga- was adopted for this scale, so the notation changed to GeV.)

The Tevatron particle accelerator at Fermilab was a synchrotron. Able to accelerate protons and antiprotons to kinetic energy levels slightly less than 1 TeV, it was the most powerful particle accelerator in the world until 2008, when it was surpassed by the Large Hadron Collider.

The 27-kilometer main accelerator at the Large Hadron Collider is also a synchrotron and is current able to achieve acceleration energies of approximately 7 TeV per beam, resulting in 14 TeV collisions.

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Jones, Andrew Zimmerman. "What is a Synchrotron?" ThoughtCo, Oct. 3, 2017, thoughtco.com/what-is-synchrotron-2699062. Jones, Andrew Zimmerman. (2017, October 3). What is a Synchrotron? Retrieved from https://www.thoughtco.com/what-is-synchrotron-2699062 Jones, Andrew Zimmerman. "What is a Synchrotron?" ThoughtCo. https://www.thoughtco.com/what-is-synchrotron-2699062 (accessed November 21, 2017).