Fritz-Haber-Institut der Max-Planck-Gesellschaft
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The FHI FEL
The FHI free-electron laser (FEL) facility
Ever since the first demonstration of a free-electron laser in 1976 at Stanford University, it has been realized that this type of laser can potentially deliver high-power tuneable radiation over a large spectral range. A layout of the FHI FEL is shown in the figure:
Electrons are emitted from the electron gun. After acceleration to an energy of up to 50 MeV (mega-electronvolt) by two linear accelerators (LINACs), the electron beam is bent and injected into the resonator, consisting of two high-reflectivity mirrors at each end of the undulator. The magnetic field in the undulator is perpendicular to the direction of the electron beam and periodically changes polarity a large number of times along its length. This causes a periodic deflection, a `wiggling' motion, of the electrons while traversing the undulator. This wiggling causes the emission of light and its wavelength is determined by the electron energy as well as by the undulator parameters. The initial weak radiation is captured in the resonator and amplified by interaction with successive electron bunches. A small hole in one of the two resonator mirrors couples out some light, which is sent to user experiments.
The following research groups and companies have contributed:
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