At a synchrotron facility, bunches of electrons, several GeV in energy, move in a large, carefully steered, closed electron beam loop containing bending elements and linear segments, collectively called the storage ring. In each section, magnetic devices are inserted - bending magnets in the curved sections, insertion devices called wigglers and undulators in the straight sections - to bend, wiggle or undulate the path of the electrons while they pass around the ring.