Sub 25 nm focusing with a long working distance using multilayer Laue lenses

We report on recent results of focusing experiments with monolithic assembled multi-layer Laue lenses (MLLs) at ESRF ID13 with a focal length of 9.5 mm at an X-ray photon energy of 12.7 keV. Using an aperture of approximately 40 mu m we have achieved a size of the focal profiles of less than 25 nm in horizontal and vertical direction with a physical working distance of approximately 2.5 mm. The current MLL mounting approach is aiming for the reduction of the physical distance of the two crossed lenses. Assuming an identical focal length of both ideally the downstream surface to downstream surface distance of the lenses should be smaller than the depth of focus. This would avoid the otherwise necessary matching of the focal lengths and significantly reduce the alignment complexity of an MLL pair.