The ELBE Free-Electron Lasers – a user facility for the mid- to far infrared

The Radiation Source ELBE at the Forschungszentrum Dresden-Rossendorf in is centered around a superconducting Electron Linear accelerator of high Brilliance and low Emittance (ELBE), constructed to deliver a CW electron beam with up to 1 mA beam current at 40 MeV. The electron beam is used to generate various kinds of secondary radiation, mainly to drive free-electron lasers in the infrared.

First lasing of the mid-IR free-electron laser (U27) at ELBE was achieved in May, 2004. Since then, using electron beam energies from 15 to 35 MeV infrared radiation from 3 to 22 µm wavelength has been produced. At all wavelengths below 20 µm a CW optical power higher than 1 W can be produced with an electron beam of 50 pC bunch charge. The optical pulse width at its minimum was measured to 0.9 ps at 11 µm and could be increased to 4 ps by detuning the optical cavity. The optical bandwidth was in all cases close to the Fourier limit.

In August, 2006 the long-wavelength (U100) FEL was installed and lasing was achieved within a few hours from first beam injection. Equipped with a partially waveguided resonator this FEL covers a range of wavelengths from 20 µm to above 230 µm. Its output power reaches some 10 watts in CW operation.

Since 2005, the FEL is operated as a user facility, being open to users worldwide, provided their scientific proposals have been favorably evaluated by the panel responsible for distribution of beam time. Under the name "FELBE" the facility is a member of the EC funded "Integrating Activity on Synchrotron and Free Electron Laser Science (IA-SFS)", which comprises most synchrotron and FEL facilities in Europe and provides financial support to users from the EC and associated states. A unique scientific opportunity is opened with the beamline coupling the ELBE FELs to the Dresden High Magnetic Field Laboratory allowing magneto-optical experiments with IR and THz radiation under fields that will reach 100 T in the near future.