Graded index W/Si Multilayer mirror for soft X-rays

In this report we show first results of the production of a W/Si graded index multilayer mirror using ion induced intermixing. We used electron beam evaporation in UHV to deposit ten-period multilayer mirrors with a periodicity of ≅ 4 nm. Reflectometry of CKa radiation was used to monitor real time the growth and intermixing procedure. A full period of silicon (4 nm) was deposited followed by the deposition of ≅ 1 nm tungsten. The graded index was achieved after removing the entire layer of tungsten by sputter etching using Kr ions from a Kaufman source. We used 300 eV as well as 1000 eV ions for the etch procedure. From our reflectometry measurements we learned that 1000 eV ions result in the highest reflection. From CuKa diffraction we found that the W/Si intermixed layers have indeed a graded index corresponding to modelled index profiles. (Authors)