An accelerator propels charged particles, such as protons or electrons, at high speeds, close to the speed of light. They are then smashed either onto a target or against other particles circulating in the opposite direction. By studying these collisions, physicists are able to probe the world of the infinitely small.

Protons are separated from hydrogen atoms and sped up in a particle accelerator such as a synchrotron or cyclotron. A special device — usually a gantry that can rotate 360 degrees — uses a large magnet to focus the stream of protons into a thin beam, just 5 millimeters wide.

As with electrons, there are protons in all materials, but only the nuclei of hydrogen atoms consist of single protons, so hydrogen gas is the source of particles for proton accelerators. In this case the gas is ionized—the electrons and protons are separated in an electric field—and the protons escape through a hole.

The synchrotron (as in Proton Synchrotron) is a type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed path. The magnetic field which bends the particle beam into its fixed path increases with time, and is synchronized to the increasing energy of the particles.

The Proton Synchrotron (PS) is a key component in CERN’s accelerator complex, where it usually accelerates either protons delivered by the Proton Synchrotron Booster or heavy ions from the Low Energy Ion Ring (LEIR).