<unk>  is electromagnetic radiation, similar to cyclotron radiation, but generated by the acceleration of ultrarelativistic  (i.e., moving near the speed of light) charged particles through magnetic fields. This may be achieved artificially by storage rings in a<unk> , or naturally by fast moving electrons moving through magnetic fields in space. The radiation typically includes radio waves, infrared light, visible light, ultraviolet light, and x-rays.
The radiation was named after its discovery in a General Electric<unk>  accelerator built in 1946 and announced in May 1947 by Frank  Elder, Anatole Gurewitsch, Robert Langmuir, and Herb Pollock in a letter entitled "Radiation from Electrons in a<unk> ". Pollock recounts:
Synchrotron radiation
Gamma ray
Electron
Particle radiation
Idose
Radionuclide
Collimated light
Cryogenics