Characterization of a multilayer Laue lens with imperfections

We present a simulation result of the focusing performance of a multilayer Laue lens (MLL) with imperfections. Imperfections we have studied correspond to deviations of sequence of layers in the fabricated structure from the zone plate law. The actual sequence of layers of the MLL is measured by scanning electron microscope (SEM), and fitted by second order polynomials. X-ray characterization of the MLL structures is performed using coherent X-rays at the Advanced Photon Source. We observe very good agreement between experiment and simulation. This demonstrates that our simulation method can serve as an efficient tool to characterize the focusing performance of MLLs with imperfections, and thereby allows us to provide feedback following deposition and fabrication of the MLL structures and optimization of focusing structures prior to X-ray characterization.