Effective area is one of the most important parameters of x-ray telescopes. It can be increased by enlarging the entrance aperture or maximizing the reflectivity through the proper designing and optimization of the reflecting coating. A method to increase the reflectivity of grazing incidence x-ray mirrors in the 0.5- to 8-keV energy region is analyzed. The idea consists in the use of a trilayer reflecting coating instead of single-layer one (e.g., C/Ni/Pt mirror instead of Pt one). Deposition of low-absorbing medium-Z and low-Z layers onto the top of strongly absorbing high-Z material results in essential increase in the reflectivity while keeping the same width of the reflectivity plateau. In particular, C/Ni/Pt trilayer mirror demonstrates enhancement of the double reflection coefficient by a factor achieving 1.5 to 3.5 compared to that of Pt-coated mirror. The effective area of a telescope is also considerably increased. The experimental results are in a very good agreement with the theoretical predictions. In addition, the C/Ni/Pt trilayer mirror exhibits a reasonable thermal stability and a relatively low compressive stress of about −550 MPa.

中文翻译：

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在0.5至8keV能量范围内具有增强的X射线反射率的单层，双层和三层反射镜的比较研究

有效面积是X射线望远镜最重要的参数之一。可以通过适当设计和优化反射涂层来扩大入射孔或最大化反射率来增加反射率。分析了一种在0.5至8keV能量范围内提高掠入射X射线镜反射率的方法。该想法在于使用三层反射涂层代替单层涂层（例如，用C / Ni / Pt镜代替Pt涂层）。将低吸收性中Z和低Z层沉积到强吸收性高Z材料的顶部会导致反射率的本质增加，同时保持相同的反射率平稳宽度。尤其是，C / Ni / Pt三层反射镜展示了两倍反射系数提高了1.5到3的倍数。与Pt镀膜反射镜相比，该数值为5。望远镜的有效面积也大大增加。实验结果与理论预测非常吻合。另外，C / Ni / Pt三层镜具有合理的热稳定性和相对较低的约-550 MPa的压缩应力。