Design and performance of graded multilayers

Hard x-ray focusing devices based on laterally graded multilayers are key elements to fully exploit the advantages of third generation synchrotron sources. We have developed a design method to produce laterally graded multilayers using sputter deposition techniques. The multilayers are adapted to the given application by the proper choice of layer materials, d spacing, and the partition of the two constituent materials. The optimization of all relevant parameters yields an ab initio estimation of the desired layer thickness gradient. The performance and the accuracy of this method are demonstrated. The experimental lateral thickness errors could be reduced below 0.5% RMS over a total length of 300 mm, Reflectivity measurements at different energies are in good agreement with theoretical simulations. During focusing experiments at 13 keV a spot size of 1 mu m and a gain in flux of 1000 were achieved.