Experimental multilayer survey in the VUV

We present an experimental survey of the performance of various multilayer systems to be used in the soft x-ray range with special emphasis on the water window. The multilayers have been designed as high reflectance normal incidence mirrors and, for polarimetry purposes, as detectors for circularly polarized synchrotron radiation, respectively. Seven different multilayer systems with spacer materials of C or the transition metals Sc, Ti, V, Cr in combination with the absorber materials Fe, W and Ni were investigated. At the 1s- and 2p absorption edges, respectively, they show a strong resonant enhancement of the reflectance due to anomalous dispersion. By tailoring the layer thickness and the thickness ratio for use at and below the resonance energy in normal incidence (θ=90°) and at θ=45°, respectively, an excellent performance with respect to reflectance, transmission and polarizance, respectively, in the water window was achieved for multilayers with period thicknesses down to 1.4 nm.