Angular resolution measurements at SPring-8 of a hard x-ray optic for the New Hard X-ray Mission
Angular resolution measurements at SPring-8 of a hard x-ray optic for the New Hard X-ray Mission
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用于新硬 X 射线任务的硬 X 射线光学器件在 SPring-8 上的角分辨率测量
DOI：
10.1117/12.894488
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发表时间：
2011
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et al
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作者：
Spiga;D;et al
要实现在硬(>；10kev)X射线波段具有成像能力的X射线望远镜，需要采用具有浅(<；0.25°)掠射角的光学元件来增强反射膜的反射率。另一方面，为了获得大的收集面积，需要大的镜面直径(<；350 mm)。这意味着应生产和测试焦距为≥10 m的反射镜。这种反射镜的全照明测试通常是利用地面X射线设备进行的，目的是测量它们的有效面积和角度分辨率；然而，它们通常受到X射线源距离有限的影响，例如失去了双重反射的有效面积。这些影响随着被测反射镜的焦距增加而增加；因此，“部分”全光照测量可能不能完全代表飞行中的性能。事实上，可以采用铅笔束测试来克服这一缺点，因为一次一个扇区暴露在X射线通量中，并且通过倾斜光学元件来实现光束发散的补偿。在这项工作中，我们介绍了在Spring-8同步辐射装置的BL20B2光束线上进行的硬X射线测试活动的结果，该活动旨在表征由镍电铸制造的多层镀膜Wolter-I镜壳的点扩展函数(PSF)。镜壳是NHXM硬X射线成像望远镜(0.3-80keV)的演示装置，预测的半能量宽度接近20角秒。我们给出了单色X射线能量为15~63keV的一些重构的PSFs，并用基于菲涅耳衍射理论的方法将它们与由运动后测量数据、自洽处理轮廓和粗糙度数据计算的PSFs进行了比较。该模型与测量的PSFs精确匹配。
The realization of X-ray telescopes with imaging capabilities in the hard (> 10 keV) X-ray band requires the adoption of optics with shallow (< 0.25 deg) grazing angles to enhance the reflectivity of reflective coatings. On the other hand, to obtain large collecting area, large mirror diameters (< 350 mm) are necessary. This implies that mirrors with focal lengths ≥10 m shall be produced and tested. Full-illumination tests of such mirrors are usually performed with onground X-ray facilities, aimed at measuring their effective area and the angular resolution; however, they in general suffer from effects of the finite distance of the X-ray source, e.g. a loss of effective area for double reflection. These effects increase with the focal length of the mirror under test; hence a "partial" full-illumination measurement might not be fully representative of the in-flight performances. Indeed, a pencil beam test can be adopted to overcome this shortcoming, because a sector at a time is exposed to the X-ray flux, and the compensation of the beam divergence is achieved by tilting the optic. In this work we present the result of a hard X-ray test campaign performed at the BL20B2 beamline of the SPring-8 synchrotron radiation facility, aimed at characterizing the Point Spread Function (PSF) of a multilayer-coated Wolter-I mirror shell manufactured by Nickel electroforming. The mirror shell is a demonstrator for the NHXM hard X-ray imaging telescope (0.3 - 80 keV), with a predicted HEW (Half Energy Width) close to 20 arcsec. We show some reconstructed PSFs at monochromatic X-ray energies of 15 to 63 keV, and compare them with the PSFs computed from post-campaign metrology data, self-consistently treating profile and roughness data by means of a method based on the Fresnel diffraction theory. The modeling matches the measured PSFs accurately.