Ground-based x-ray calibration of the Astro-H soft x-ray telescopes
Ground-based x-ray calibration of the Astro-H soft x-ray telescopes
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Astro-H 软 X 射线望远镜的地面 X 射线校准
DOI：
10.1117/12.2054626
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
R. et al.
中科院分区：
文献类型：
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作者：
Iizuka;R. et al.
计划于2015年发射的X射线天文学卫星Astro-H将配备若干仪器，覆盖从几百eV到600 keV的宽能带。有四个X射线望远镜，其中两个是软X射线望远镜（SXT），覆盖范围约为15 keV。一种是用于X射线微量热检测器（SXS），另一种是用于X射线CCD检测器（SXI）。SXT的设计是Wolter Type-I光学器件的圆锥形近似，2005年发射的上一次使命Suzaku的望远镜也采用了该光学器件。它由203个薄箔反射器组成，这些反射器在铝基底（101.6 mm长）上涂有单层金（2000 μ m），厚度为0.15 mm、0.23 mm和0.31 mm。这些反射器在58 mm至225 mm的半径内共焦嵌套。SXT的焦距为5.6 m。我们介绍了两台SXT-1和SXT-2的校准活动的现状。两个SXT的开发是由NASA的戈达德太空飞行中心（GSFC）完成的。在GSFC 100 m光束线处用发散光束进行的第一次X射线测量发现，SXT-1和SXT-2在8.0 keV处的角分辨率分别为1.1和1.0弧分（HPD）。X射线性能的全面表征目前已在日本宇宙航空研究开发机构空间和宇航科学研究所的30米X射线光束线设施上得到不断校准。我们采用了发散角约为15 "的窄X射线笔形束的光栅扫描方法。2013年5月和12月分别测量了这两个SXT的X射线特征。在SXT-1的情况下，在1.5、4.5、8.0、9.4、11.1和12.9 keV的能量下，轴上有效面积分别约为580、445、370、270、185和90 cm 2。与X射线能量无关，SXT-2的有效面积比SXT-1大2%。在1.5 - 13 keV波段，SXT-1的轴上角分辨率被评估为1.3 - 1.5弧分（HPD）。在较高能量下，分辨率略微变差~0：3弧分。另外，SXT-2的分辨率为1.2弧分，几乎与X射线能量无关。视场（FOV）在1.5 keV时约为16弧分，随着X射线能量的增加而减小，在13 keV时约为8弧分。SXT-1和SXT-2的X射线性能满足系统要求。由于SXT-2望远镜的各项性能指标均略优于SXT-1望远镜，因此，我们采用SXT-2望远镜作为窄视场的Astro-H一次仪器的SXS探测器。
The X-ray astronomy satellite Astro-H, planned to be launched in 2015, will have several instruments for covering a wide energy band from a few hundreds eV to 600 keV. There are four X-ray telescopes, and two of them are soft X-ray telescopes (SXTs) covering up to about 15 keV. One is for an X-ray micro-calorimeter detector (SXS) and the other is for an X-ray CCD detector (SXI). The design of the SXTs is a conical approximation of the Wolter Type-I optics, which is also adopted for the telescopes on the previous mission Suzaku launched in 2005. It consists 203 thin-foil reflectors coated with gold monolayer (2000 Å) on the aluminum substrate (101.6 mm length) with the thickness of 0.15, 0.23 and 0.31 mm. These are nested confocally within the radius of 58 to 225 mm. The focal length of SXTs is 5.6 m. The weight is as light as ~ 43 kg per telescope.We present the current status of the calibration activity of two SXTs (SXT-1 and SXT-2). The developments of two SXTs were completed by NASA's Goddard Space Flight Center (GSFC). First X-ray measurements with a diverging beam at the GSFC 100m beamline found an angular resolution at 8.0 keV to be 1.1 and 1.0 arcmin (HPD) for SXT-1 and SXT-2, respectively. The full characterization of the X-ray performance has been now continuously calibrated with the 30m X-ray beamline facility at the Institute of Space and Astronautical Science (ISAS) of Japan Aerospace eXploration Agency (JAXA) in Japan. We adopted a raster scan method with a narrow X-ray pencil beam with the divergence of ~ 15". X-ray characterization of the two SXTs has been measured from May and December 2013, respectively.In the case of SXT-1, the on-axis effective area was approximately 580, 445, 370, 270, 185 and 90 cm2at energies of 1.5, 4.5, 8.0, 9.4, 11.1 and 12.9 keV respectively. The effective area of SXT-2 is 2% larger than that of SXT-1 irrespective to X-ray energy. The on-axis angular resolution of SXT-1 was evaluated as 1.3 - 1.5 arcmin (HPD) in the 1.5 - 13 keV band. The resolution was slightly got worse at higher energies by ~ 0:3 arcmin. Otherwise, the resolution of SXT-2 is 1.2 arcmin, almost irrespective to X-ray energy. The field of view (FOV) was ~ 16 arcmin at 1.5 keV, decreasing with increasing X-ray energy, and became ~ 8 arcmin at 13 keV. The FOV is defined here as the full-width at half-maximum (FWHM) of the vignetting curve.The X-ray performance of SXT-1 and SXT-2 meets the system requirements. Because all the parameters of the SXT-2 is slightly better that of SXT-1, we adopted the SXT-2 telescope for the SXS detector of the Astro-H primary instrument with the narrow FOV.