Optical beam transport from the FELs to the user laboratories

The beamline has been designed to transport infrared light with a wavelength between 3 and 150 μm. Accepting losses up to 60% the wavelength can be extended to 300 μm. The average radiation power is limited to 300W. The beamline conserves the linear polarization.

The laser light is guided from the outcoupling holes in one of the FEL resonators (right side of the figure below) to a diagnostic station and then distributed to various user laboratories including the magnetic high-field laboratory (HLD).

Fig.1: Schematic view of the beam transport system from the FEL resonators U27 and U100 (right hand side, room 114) to the optical tables in the user laboratories 113a/b-g.

The beam is transported in 10 cm pipes.  to avoid light absorption by air components (e.g. water vapour). Taking into account the broad tuning range and the short pulse duration (0.5 - 10 ps rms) broadband metal mirrors are used to refocus the beam. In dependence on the location of the user laboratory the beam has to be transported over distances of up to 50 m.

First the beams are guided to a diagnostic station. Here it is analyzed (wavelength, intensity, pulse duration). Moreover it can be attenuated, the polarization can be rotated and the repetition rate can be reduced up to 1 Hz.

Behind the diagnostic table (DT) the beam is distributed into the various laboratories using a common beampipe. One branch guides the beam into the neighboring magnetic high-field laboratory (HLD) via a tunnel


beamline to HLD (top view)

beamline to HLD (side view)

Fig.2: Design of the beamline from the ELBE building to the Magnetic High-Field Laboratory (HLD).
Upper figure: Top view. Lower figure: Side view.

The arrangement of mirrors generates a narrow beam profile with a waist on each optical table independently of the wavelength.

The beamsize calculated along the beamline is shown here.