Athena, a future high-energy mission, is expected to consist of a large aperture x-ray mirror with a focal length of 12 m. The mirror surface is to be coated with iridium and a low Z overcoat. To define the effective area of the x-ray telescope, the atomic scattering factors of iridium with an energy resolution less than that (2.5 eV) of the x-ray integral field unit are needed. We measured the reflectance of the silicon pore optics mirror plate coated with iridium in the energy range of 9 to 15 keV and that near the iridium L-edges in steps of 10 and 1.5 eV, respectively, at the synchrotron beamline SPring-8. The L3, L2, and L1 edges were clearly detected around 11,215, 12,824, and 13,428 eV, respectively. The measured scattering factors were ∼3 % smaller than the corresponding values reported by Henke et al., likely due to the presence of an overlayer on the iridium coating, and were consistent with those measured by Graessle et al. The angular dependence of the reflectivity measured indicates that the iridium surface was extremely smooth, with a surface roughness of 0.3 nm.

中文翻译：

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测量Athena硅孔隙光学反射器在铱L边缘附近的原子散射因子

雅典娜是一项未来的高能飞行任务，预计将包括一个焦距为12 m的大口径X射线反射镜。镜面要涂铱和低Z涂层。为了定义X射线望远镜的有效面积，需要具有能量分辨率小于X射线积分场单元的能量分辨率（2.5 eV）的铱的原子散射因子。我们在同步加速器光束线SPring-8上分别以10至1.5 eV的步长测量了能量在9至15 keV范围内的涂有铱的硅孔隙光学镜板的反射率，以及在铱L边缘附近的反射率。分别在11,215、12,824和13,428 eV附近清楚地检测到L3，L2和L1边缘。测得的散射因子比Henke等人报道的相应值小约3％，可能是由于铱涂层上存在覆盖层，与Graessle等人的测量结果一致。测得的反射率的角度依赖性表明铱表面非常光滑，表面粗糙度为0.3 nm。