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arXiv 1509.03478astro-ph.IM
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新硬X射线任务硬X射线光学器件SPring-8的角分辨率测量

Angular resolution measurements at SPring-8 of a hard X-ray optic for the New Hard X-ray Mission

D. Spiga, L. Raimondi, A. Furuzawa, S. Basso, R. Binda, G. Borghi, V. Cotroneo, G. Grisoni, H. Kunieda, F. Marioni, H. Matsumoto, H. Mori, T. Miyazawa, B. Negri… 展开作者

D. Spiga, L. Raimondi, A. Furuzawa, S. Basso, R. Binda, G. Borghi, V. Cotroneo, G. Grisoni, H. Kunieda, F. Marioni, H. Matsumoto, H. Mori, T. Miyazawa, B. Negri, A. Orlandi, G. Pareschi, B. Salmaso, G. Tagliaferri, K. Uesugi, G. Valsecchi, D. Vernani

摘要:

实现具有硬(> 10 keV)X射线波段成像能力的X射线望远镜需要采用具有浅(< 0.25度)掠射角的光学器件以增强反射涂层的反射率。另一方面,为了获得大的收集面积,需要大的反射镜直径(< 350 mm)。这意味着应生产和测试焦距>10 m的反射镜。通常使用地面X射线设施对这种反射镜进行全照明测试,目的是测量其有效面积和角分辨率;然而,它们通常受到X射线源有限距离的影响,例如双反射的有效面积损失。这些影响随着被测反射镜焦距的增加而增加;因此,“部分”全照度测量可能不能完全代表飞行中的性能。实际上,可以采用笔形射束测试来克服这个缺点,因为每次一个扇区暴露于X射线通量,并且通过倾斜光学器件来实现射束发散的补偿。在这项工作中,我们提出了一个硬X射线测试活动的结果,在BL 20 B2光束线的SPring-8同步辐射设施,旨在表征点扩散函数(PSF)的多层涂层的Wolter-I镜壳镍电铸制造。镜壳是NHXM硬X射线成像望远镜(0.3 - 80 keV)的演示器,预计HEW(半能宽)接近20弧秒。我们显示了一些重建的PSF在单色X射线能量为15至63千电子伏,并比较它们与PSF计算后的运动计量数据,自洽处理的轮廓和粗糙度数据的方法的基础上的菲涅耳衍射理论。建模准确地匹配测量的PSF。

英文摘要:

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 on- ground 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.

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