Optics

 
Figure 5: Optical scheme of the SIM beamline showing the optical elements and their locations (click for an enlarged picture).

 

Optics:	Plane grating monochromator
Photon energy resolution (hn/Dhn):	> 5'000
Grating:	300 / mm, 1'200 / mm
Cooling:	Internal or side cooling (H2O)
Spotsize on sample:	100 x 30 mm2 (H x V)

The optical layout is based on a plane grating monochromator (SX-700 type) operating in collimated light. This design combines high energy resolution with high efficiency using a small number of optical elements. At the same time it gives the user the freedom to optimize the higher harmonic rejection or the energy resolution depending on the experiment. We use a commercial monochromator developed in collaboration between BESSY and JENOPTIK. To allow for switching of the photon helicity, the twin undulators can be used as separate sources with different helicities.

 
Figure 6: Spectrum of the UE56/I undulator as measured with a photodiode after the refocus mirror (click for an enlarged picture).