Contact
Prof. Dr. Kristina Kvashnina
Head of Department "Molecular Structures"
Responsible for the BM20 (ROBL) beamline at ESRF
Phone: +33 476 88 2367
Beamline Optics
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- The X-ray optics provide both a high flux at high angular resolution for diffraction and a high flux over a wide energy range with high energy resolution for spectroscopy.
- Mirror 1: a vertically collimating mirror with Rh, Pt and Si sections
- DCM: a double crystal monochromator with LN2-cooled Si(111), Si(111)30, and Si(311) crystal pairs
- DMM: a double multilayer monochromator for higher flux at lower energy resolution
- Mirror 2: a bendable double toroid mirror with Pt and Rh coating for vertical and horizontal focusing, with a non-toroid flat Si section
| Schematic view of the beamline optics, showing the bending magnetic at the right, the first white-beam mirror, the DCM, and the second monochromatic-beam mirror. Shown are also typical beam profiles and photon fluxes for the unfocussed beam at the XAFS station, and for the focussed beam at the XRD-1 station. |
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A unique monochromator, which combines both a double crystal pair (in fact three pairs: Si(111), Si(111)30º, Si(311)) for high energy resolution, and a double multilayer monochromator for high flux with medium energy resolution (∼100 eV). |
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The Optics contain two long mirrors; the first, with Rh, Si and Pt surfaces, is water-cooled and collimates the beam into the monochromator to improve the energy resolution; the second after the monochromator has two torroidal-shaped sections coated with Rh and Pt to focus the monochromatic beam vertically and horizontally, in addition to a flat Si section. Both mirrors serve also for the rejection of higher harmonics. The figure above shows the reflectivity of the different mirror surfaces at a grazing angle of 2.5 mrad. |
