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中国物理学会期刊

多层嵌套掠入射光学系统研制及在轨性能评价

CSTR: 32037.14.aps.69.20191446

Development and in-orbit performance evaluation of multi-layered nested grazing incidence optics

CSTR: 32037.14.aps.69.20191446
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  • X射线掠入射光学系统是我国首颗脉冲星导航试验卫星主载荷聚焦型脉冲星探测器的核心部件, 在增大探测面积、提高探测器灵敏度方面发挥着重要作用, 实现了国内首次在轨验证. 针对脉冲星导航探测X射线光子到达时间的特点, 开展了基于单次抛物面镜反射的掠入射聚焦光学系统设计, 通过理论计算与推导, 获得了可制造的光学系统反射镜设计参数, 光学系统理论有效面积为15.6 cm2@1 keV, 对设计的光学系统进行了聚焦性能仿真, 全视场范围内均满足探测器聚焦要求, 开展电铸镍复制工艺研究, 完成了芯轴的超精密控形加工, 在此基础上制造了4层金属反射镜, 利用北京同步辐射4B7B光束线测试了各层反射镜的反射率, 基于实测反射率的光学系统有效面积为13.2 cm2@1 keV. 最后基于在轨观测数据, 评价得到光学系统的有效面积为4.22 cm2@1 keV, 分析了地面标定有效面积与在轨评价有效面积存在差别的原因, 验证了设计、仿真与制造方法的正确性, 为大面积掠入射光学系统的研制奠定了基础.

     

    On November 10, 2016, China launched an X-ray pulsar navigation test satellite (XPNAV-1) to investigate the X-ray pulsar navigation technology, and a lot of scientific observation data have been obtained. The X-ray grazing incidence optics is a critical component of the focusing pulsar telescope. It plays an important role in increasing the effective area and enhancing the sensitivity of the telescope. It is also the first grazing incidence optics verified in orbit in China. According to the characteristic that the times of arrival (TOA) of X-ray photons are measured in pulsar navigation, the grazing incidence focusing optics based on single-reflection paraboloid mirror is designed, and manufacturable mirror design parameters are obtained through theoretical calculation and derivation. The theoretical effective area of the designed optics is 15.6 cm2 at 1 keV. The designed optics is then simulated to evaluate its focusing performance. It meets the focusing requirement in the full field of view. The electroforming nickel replication process used for manufacturing the mirrors for XMM-Newton and eRosita missions is investigated. A super-smooth mandrel is firstly fabricated and used for follow-up replication. An about-100 nm-thick gold layer is deposited on the mandrel, and serves as the reflection and release layer of the mirror. The nickel substrate of the mirror is electroformed on the gold layer. The mirror is finally obtained by releasing the nickel and gold layer from the mandrel. The patterns and roughness of the mandrel are then replicated onto the inner surface of the mirror. The 4-layered mirror is fabricated for the optics. The reflectivity for each layer of the 4-layered mirror is then measured with a dedicated facility on 4B7B beamline of BSRF. The effective area of the optics based on the above-measured reflectivity is 13.2 cm2 at 1 keV. Finally, according to the in-orbit observation data, the effective area of the optical system is evaluated to be a typical value of 4.22 cm2 at 1 keV, which is less than the ground-tested value. The reason for this is analyzed and it turns out to be due to the thermal deformation of mechanical structure and contamination of the mirrors. Therefore, in our future work, we will strictly control the environmental factors and implement space environmental adaptability design, while increasing the accuracy of the optics.

     

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