FTIR Transfer Line

From the ring to the spectrometer

The synchrotron emission is collected on BM21. The transfer line, which links the ring to the spectrometer is a complex succession of 12 mirrors, whose function is to collect, collimate, transfer, direct the beam and finally provide a parallel source. The optical concept aims at reaching the best matching of the IR beam divergence with the microscope Schwarzschild lens aperture.

 The IR extraction mirror

The extraction mirror was one of the most critical technical challenges. A new dipole chamber with enlarged vertical opening had to be installed in the cell 22. Edge geometry, i.e. the edge radiation emitted from the short straight section (focusing electron lenses) upstream of the bending magnet, was preferred. The extraction mirror located at 3.2m from the dipole entrance is a flat un-cooled aluminium mirror, with a horizontal slot. This 5mm slotted-aperture lets the energetic part of the synchrotron light go through for absorption 2.5m further down. The mirror assembly is vertically movable, and by the use of thermo-probes, located on its backside and separated by 2.5mm, the slot is kept vertically centered on the heart of the X-ray beam in a slow feed-back loop. The edge radiation from up- and down-stream dipoles as well as constant field radiation are all collected and transferred to the spectrometer and microscope via a series of 12 mirrors.

The optical pathway