When a particle changes direction, it also emits electromagnetic radiation known as synchrotron radiation. Scientists built the first synchrotrons in the 1940's to study subatomic particles. In those machines and in similar machines built since then, the particle beam strikes a target. The resulting impacts break particles away from the target or produce new particles. Special devices detect the particles that fly away from the points of impact.
Physicists then study the information provided by the detectors.
Synchrotron radiation plays no role in such experiments. In fact, it is unwanted because the machine must make up for the energy that is radiated away. However, synchrotron radiation has proved useful to crystallographers and other scientists who investigate the structure of matter. It has been so useful that, since the 1970's, scientists have built machines just to produce synchrotron radiation in the ultraviolet and X-ray ranges. There are now about 50 such synchrotron sources in the world.