Putting free-electron lasers to work

The generation of intense coherent light with wavelengths tunable from centimeters to angstroms by free-electron lasers (FEL) is demonstrated. The FEL uses a beam of relativistic electrons passing through a periodic transverse magnetostatic field to amplify the laser light beam propagating along the axis of the electron beam. The laser light is stored between the resonator mirrors as fresh electrons from the accelerator enter the wiggler and the spent electron beam exits the wiggler without leaving any waste heat.