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Multilayer monochromators

Multilayer monochromators

Multilayer monochromators can be used for the monochromatisation of X-rays similar to crystals. Various wave lengths and band widths can be regulated by choosing the multilayer material, the period thickness and the thickness gradient.

Typical photon energies of laboratory X-ray sources:

Cu Ka 8041 eV Mo Ka 17444 eV
Cr Kα 5412 eV  
Co Kα 6926 eV  
Cu Kα 8040 eV  
W Lα 8392 eV  
Ga Kα 9241 eV  
Mo Kα 17444 eV  
Rh Kα 20167 eV  
Ag Kα 22103 eV  

Typical dimensions:

[Translate to English:] Foto typischer Multilayerspiegel-Abmessungen.

Multilayer monochromators can be produced in various sizes, from a few square millimeters (e.g. 6 x 4 mm² like shown in the picture) to a length of 500mm (typically synchronotron reflectors) or a diameter of 8" (wafer).

Typical parameters for multilayer monochromators:

Spectral range: 50 eV – 100 keV
Resolution: 0.25 % < ΔE/E < 2 % (periodic multilayers)
  ΔE/E > 5% on request (aperiodic multilayers)
Thickness homogeneity: Δd/d < 0.02%

Material systems optimized on maximum peak reflectivity or desired spectral band width with given wave length or on customer's request.

Applications:

Monochromators for laboratory X-ray sources and synchrotrons

Polarizers in supple X-ray range (e.g. O-K, Fe-L, Ni-L)

Integral reflectivity vs. resolution:

[Translate to English:] (courtesy of C. Morawe, ESRF, Grenoble, France)

Integral reflectivity vs. resolution for crystals and various multilayer types. High resolution (HR) multilayer connect typical multilayer (resolution ~1-3%) and crystals (<0.1%), depth graded multilayers factor total reflecting optics.

 

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