Normal incidence monochromators (NIM) are typically used in synchrotron beamlines which are dedicated to experiments operating in an energy range of about 4 to 35 eV only. The decisive advantages of this type of monochromator design are that only small aberration errors occur and highest resolution can be easily achieved with it.

The 10m-NIM beamline (Reichardt et al. 2001) was designed for the undulator U125-2 (Bahrdt et al. 2001) and is based on the so called off-Rowland circle mounting design (Samson 1967). This implies that the grating has to be rotated and slightly translated in order to get the highest resolution and a small spot size in the experiment.

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Beamline data
Segment H03
Location (Pillar) 4.2
Source U125-2
Monochromator 10m-NIM
Energy range 6(4) - 40 eV
Energy resolution E/dE = 85000 @ d = 1200l/mm, 2nd order, 10 µm slits
Flux 1×1e12 @ 21.75 eV [photons/s/0.1A/0.1%BW]
Polarisation horizontal
Divergence horizontal 5.5 mrad
Divergence vertical 12 mrad
Focus size (hor. x vert.) 350 x 200* [v x h]
Distance Focus/last valve 1190 mm
Height Focus/floor level 1750 (1400 mm with concrete experiment platform) mm
Free photon beam available yes
Fixed end station nein
Beam available 12h/d


Reichardt, G.; Bahrdt, J.; Schmidt, J. S.; Gudat, W.; Ehresmann, A.; Muller-Albrecht, R. et al. (2001): A 10m-normal incidence monochromator at the quasi-periodic undulator U125-2 at BESSY II. In NUCL INSTRUM METH A 467, pp. 462–465.

Bahrdt, J.; Frentrup, W.; Gaupp, A.; Scheer, M.; Gudat, W.; Ingold, G.; Sasaki, S. (2001): A quasi-periodic hybrid undulator at BESSY II. In NUCL INSTRUM METH A 467-468, pp. 130–133.

Samson, James A. (1967): Techniques of Vacuum Ultraviolet Spectroscopy. New York, London, Sydney: John Wiley & Sons, Inc.