The Cyclotron and Particle Physics

A modern cyclotron used in medical therapy. Ikiwaner, Wikimedia Commons

The history of particle physics is a story of seeking to find ever-smaller pieces of matter. As scientists delved deeply into the makeup of the atom, they needed to find a way to split it apart to see its building blocks. These are called the "elementary particles" (such as the electrons, quarks, and other sub-atomic particles). It required a great deal of energy to split them apart. It also meant that scientists had to come up with new technologies to do this work.

For that, they devised the cyclotron, a type of particle accelerator that uses a constant magnetic field to hold charged particles as they move faster and faster in a circular spiral pattern. Eventually, they hit a target, which results in secondary particles for physicists to study. Cyclotrons have been used in high-energy physics experiments for decades, and are also useful in medical treatments for cancer and other conditions.

The History of the Cyclotron

The first cyclotron was built at the University of California, Berkeley, in 1932, by Ernest Lawrence in collaboration with his student M. Stanley Livingston. They placed large electromagnets in a circle and then devised a way to shoot the particles through the cyclotron to accelerate them. This work earned Lawrence the 1939 Nobel Prize in Physics. Prior to this, the main particle accelerator in use was a linear particle accelerator, Iinac for short.

The first linac was built in 1928 at Aachen University in Germany. Linacs are still in use today, particularly in medicine and as part of larger and more complex accelerators. 

Since Lawrence's work on the cyclotron, these test units have been built around the world. The University of California at Berkeley built several of them for its Radiation Laboratory, and the first European facility was created in Leningrad in Russia at the Radium Institute.

Another was built during the early years of World War II in Heidelberg. 

The cyclotron was a great improvement over the linac. As opposed to the linac design, which required a series of magnets and magnetic fields to accelerate the charged particles in a straight line, the benefit of the circular design was that the charged particle stream would keep passing through the same magnetic field created by the magnets over and over, gaining a bit of energy each time it did so. As the particles gained energy, they would make larger and larger loops around the cyclotron's interior, continuing to gain more energy with each loop. Eventually, the loop would be so large that the beam of high-energy electrons would pass through the window, at which point they would enter the bombardment chamber for study. In essence, they collided with a plate, and that scattered particles around the chamber. 

The cyclotron was the first of the cyclical particle accelerators and it provided a much more efficient way to accelerate particles for further study. 

Cyclotrons in the Modern Age

Today, cyclotrons are still used for certain areas of medical research, and range in size from roughly table-top designs to building size and larger.

  Another type is the synchrotron accelerator, designed in the 1950s, and is more powerful. The largest cyclotrons are the TRIUMF 500 MeV Cyclotron, which is still in operation at the University of British Columbia in Vancouver, British Columbia, Canada, and the Superconducting Ring Cyclotron at Riken laboratory in Japan. It is 19 meters across. Scientists use them to study properties of particles, of something called condensed matter (where particles stick to each other.

More modern particle accelerator designs, such as those in place at the Large Hadron Collider, can far surpass this energy level.  These so-called "atom smashers" have been built to accelerate particles to very close to the speed of light, as physicists search out ever smaller pieces of matter. The search for the Higgs Boson is part of the LHC's work in Switzerland.

Other accelerators exist at Brookhaven National Laboratory in New York, at Fermilab in Illinois, the KEKB in Japan, and others. These are highly expensive and complex versions of the cyclotron, all dedicated to understanding the particles that make up the matter in the universe. 

Edited and updated by Carolyn Collins Petersen.


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Jones, Andrew Zimmerman. "The Cyclotron and Particle Physics." ThoughtCo, Nov. 27, 2017, Jones, Andrew Zimmerman. (2017, November 27). The Cyclotron and Particle Physics. Retrieved from Jones, Andrew Zimmerman. "The Cyclotron and Particle Physics." ThoughtCo. (accessed March 23, 2018).