The Radiation Source at Dresden-Rossendorf - a New FEL User Facility for the Infrared

First lasing of the mid-infrared free-electron laser at ELBE was achieved on May 7, 2004. The Radiation Source ELBE at the Forschungszentrum Rossendorf in Dresden, Germany is currently under transition from commissioning to regular user operation. Presently the electron linac produces an up to 35 MeV, 1 mA (cw) electron beam which is allotted to generate various kinds of secondary radiation. After the successful commissioning of the bremsstrahlung and channeling-X-ray facilities during 2003 stable lasing has now been observed in the IR range. The oscillator FEL is equipped with two planar undulator units, both consisting of 34 hybrid permanent magnets with a period of 27.3 mm (Krms = 0.3 . . . 0.7). The distance between the two parts is variable and the gaps can be adjusted and tapered independently. This devise provides continuously tunable radiation in the spectral range of 450 - 2500 cm-1 (4 to 22 µm), at peak energies of several hundred nJ in a ps pulse train at 13 MHz repetition rate. To ensure the continuous variation of the wavelength up to 150 microns we want to complement the U27 undulator by a permanent magnet undulator with a period of 100 mm (U100) in 2006.
Starting 2005, the FEL operates 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 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 EC and associated states. Instructions for beam time applications is available on the FELBE website (www.fz-rossendof.de/FELBE) .
The relevant user facilities at FELBE comprise 6 laboratories. Some of these are also used by in-house groups, mainly in the areas of semiconductor physics, biophysics, and radiochemistry and experiments there will require a certain level of collaboration with the in-house researchers. In particular noteworthy is the fact that a number of other optical sources from the visible to the THz frequency range are available, e.g. for two-color pump-probe experiments. These sources (Ti:sapphire laser and amplifer, OPO, OPA, broad-band THz generator) are all based on Ti:sapphire oscillators which are synchronized with the FEL with an accuracy better than one ps. Two laboratories are intended to provide users with utmost flexibility for their own experiments, also in scientific areas not covered by in-house groups (e.g., surface physics, molecular physics).
For the ELBE team.