High efficiency carbon-based multilayers for LAMP at 250 eV
High efficiency carbon-based multilayers for LAMP at 250 eV
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DOI：
10.1117/12.2186275
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发表时间：
2015-09
期刊：
影响因子：
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通讯作者：
M. Wen;Qiushi Huang;R. She;Li Jiang;Zhong Zhang;Zhanshan Wang;H. Feng;D. Spiga;A. Giglia
中科院分区：
文献类型：
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作者：
M. Wen;Qiushi Huang;R. She;Li Jiang;Zhong Zhang;Zhanshan Wang;H. Feng;D. Spiga;A. Giglia
多层反射镜在布鲁斯特角附近的x射线反射可以用来探测x射线源的偏振。一些孤立的中子星和AGN/blazar等的光子发射光谱表明，它们的发射在250eV附近的低能处达到峰值，刚好低于碳k吸收边缘。轻型非对称磁探测器（LAMP）是一种用于250 eV天文x射线偏振测量的微型卫星任务，目前正处于早期研究阶段。选择并设计了能量接近250eV、掠射入射角为45°的Co/C多层膜。优化碳层厚度比可获得最高的积分反射率，从而在天体物理观测中获得更大的有效信号。采用直流磁控溅射法在D263玻璃和电铸镍上制备了多层涂层，并用8keV的掠入射x射线反射仪对涂层进行了表征。采用4%、6%和8%氮的反应溅射分别改善了Co/C多层界面。在Elettra同步加速器的BEAR光束线上测量了s偏振光和p偏振光的反射率。含氮量为6%的Co/C多层膜性能最好。
X-ray reflection near the Brewster’s angle by multilayer mirrors can be used to detect the polarization from X-ray sources. The photon emission spectra from some isolated neutron stars and AGN/blazars etc. show that their emission is peaked at low energies near 250eV, which is just below carbon K-absorption edge. The Lightweight Asymmetry and Magnetism Probe (LAMP) is proposed as a micro-satellite mission dedicated for astronomical X-ray polarimetry working at 250 eV and is currently under early phase study. Co/C multilayers are selected and designed at the energy near 250eV with a grazing incident angle of 45°. The carbon layer thickness ratio is optimized to get the highest integral reflectivity which means larger effective signals in the astrophysics observation. The multilayer coatings were manufactured by direct current magnetron sputtering on D263 glasses and electroformed nickels and characterized using Grazing incidence X-ray reflectometry at 8keV. Reactive sputtering with 4%, 6% and 8% nitrogen were used to improve the Co/C multilayer interfaces respectively. Reflectivity for s-polarization and p-polarization light was measured at BEAR beamline in Elettra synchtron facility. Co/C multilayer deposited with 6% nitrogen exhibits the best performance comparing to other multilayers with different nitrogen content.