“Originally, the sole purpose of a synchrotron was to act a storage ring for linear accelerators and to achieve this circular orbit, bending magnets were used.  While these first generation devices created x-ray radiation that were later suitable for high energy x-ray experiments, it was found that the intensity could be increased by employing the use of a wiggler insertion device.  Wigglers work by using an array of magnets with alternating field directions to force electrons into a sinusoidal trajectory through the straight sections of a synchrotron.  This leads to a higher emitted intensity when compared to bending magnets.”

Half of the original wiggler magnet from SSRL. Length ~1.5m

Images and quotation: ssrl.slac.stanford.edu