First Lasing of the Elbe Mid-ir Fel

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 is currently under transition from commissioning to regular user operation. Presently the electron linac produces an up to 18 MeV, 1 mA (cw) electron beam which is alotted 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 (15 to 22 μm). 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 . . . 0.8). The distance between the two parts is variable and the gaps can be adjusted and tapered independently. At 19.6 μm an optical power of 3 W was outcoupled in a macro pulse of 0.6 ms duration using an electron beam energy of 16.1 MeV and an energy spread of less than 100 keV. The micropulse charge was 50 pC and its width slightly above 1 ps. With the installation of a second acceleration module for additional 20 MeV shorter wavelengths will become available in the near future.