Total Reflection Mirrors

Special optics have been developed at the GKSS research centre  for several years for applications in the XUV range up to 200 eV and for FEL (free electron lasers). The research is motivated by the unpredictable peak pulse intensity from the FEL at the TESLA Test Facility at Desy in Hamburg.

50 cm synchrotron optic: uncoated and coated Si-Substrate

In order to avoid radiation damage, coatings of low atomic number Z elements with lowest possible absorption and high reflectivity have been investigated. The graph shows the high performance of the total reflection mirrors comprising of carbon layers. The mirrors are prepared at GKSS using magnetron sputtering. Si substrates are coated with a single carbon layer which is 35 nm thick. In the whole range of applicational interest between 50 and 250 eV the layer shows a good reflectivity of more than 95%. This is similar to the optimal reflectivity of a simulated diamond layer. Mirrors can be produced in lengths of up to 150 cm.

Reflectivity of a 35 nm thick carbon total reflection mirror vs. energy. In comparison the red curve shows a simulated ideal diamond layer with ρ=3.5 g/cm³.

 

Coatings up to 150 cm long
 Plot of  thickness deviation of a 44.2 nm thick C-film on 150 cm substrate: peak-to valley < 1 nm, homogeneity better 2%
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