Cyclotron is a machine that accelerates electrically charged atomic particles to high energies. It is a type of particle accelerator that makes the particles travel in a circle. Cyclotrons accelerate particles ranging in mass from protons to heavy nuclei. Most reach energies of from 10 million to 50 million electronvolts. A few attain even higher energies. (One electronvolt is the amount of energy needed to move an electron through an electrical potential difference of 1 volt.)
In a cyclotron, the particles travel in a vacuum chamber located between the poles of a powerful electromagnet. The electromagnet creates a magnetic field that forces the particles to follow a circular path. The vacuum chamber also contains two D-shaped electrodes, called dees, that have a gap between them. An alternating electric field is applied across this gap. It acts on the electric charge of the particles and gives them a slight “push” each time they cross the gap. As a result, the particles gradually speed up. The diameter of their path grows in proportion to their speed, and so they spiral outward. When the particles approach the edge of the magnetic field, they are traveling at their maximum speed. They are then directed to a target, or they are extracted from the machine as a particle beam.
The cyclotron was invented in 1930 by the American physicist Ernest O. Lawrence. Lawrence received the 1939 Nobel Prize for physics for his achievement. The cyclotron was originally developed for use in studying nuclear structure, but today it has many functions. Some cyclotrons can accelerate the atomic nuclei of any of the elements that occur naturally in or on the earth.
