Jefferson Lab in the News
Putting Free-Electron Lasers to Work
A Free-electron laser oscillator uses a beam of relativistic electrons passing through the periodic field (green arrows) of an array of wiggler magnets in the presence of a copropagating laser light beam stored between the mirrors of a resonator. The bottom panels, each having the width of one optical wavelength, show the phase-space evolution of bunching in the electron beam as it traverses the wiggler. The vertical axis designates the electron energy and the horizontal axis gives the phase of the copropagating light at the electron's position. A beam electron sees one optical wavelength passing over it as it traverses each wiggler period. The brown end of the evolving phase-space path gives the electron's status at that point. The beam bunches up, and thus begins radiating coherently with the laser light, as electrons continue to gain or lose energy, depending on the optical phase.