Design and fabrication of depth-graded X-ray multilayers

We present first experimental results on the fabrication and characterization of depth-graded X-ray multilayers providing a broad and well-defined reflectivity profile. Following a theoretical approach including analytical and numerical techniques we have designed and deposited multilayer structures with a practically constant reflectivity of about 20% around the first Bragg-reflection and a bandwidth of about 20% in both incident angle and photon energy. A precise characterization using numerical simulations allows the determination of residual errors in the structure, which can appear during or after the coating process. The discussion includes practical issues and technical limitations of the deposition process as well as novel applications in modern X-ray optics.