Synchrotron Emission or Radiation: Electromagnetic radiation that is emitted by charged particles moving at relativistic speeds in circular orbits in a magnetic field. The rate of emission is inversely proportional to the product of the radius of curvature of the orbit and the fourth power of the mass of the particles. For this reason, synchrotron radiation is not a problem in the design of proton synchrotrons, but it is significant in electron synchrotrons. The synchrotron emission from a relativistic proton or electron is directly proportional to the square of its energy.