English: Working of the undulator. An undulator is a device from high-energy physics and usually part of a larger installation, a synchrotron. It consists of a periodic dipole magnet structure (1: magnets). The static magnetic field is alternating along the length of the undulator with a wavelength ${\displaystyle \lambda _{u}}$. Electron beam (2) traversing the periodic magnet structure are forced to undergo oscillations and radiate (3: radiation).