eXTP望远镜用W/Si多层膜

针对增强型X射线时变与偏振探测卫星(eXTP)项目中嵌套式聚焦成像望远镜对柱面镜片上W/Si多层膜的要求,在掠入射角为0.5°,工作波段为1~30keV条件下,设计了非周期W/Si多层膜并优化了薄膜制备工艺。首先,利用分隔板和掩模板对溅射粒子进行准直,同时优化了本底真空度和溅射工作气压,提升了薄膜的成膜质量;然后,通过调整分隔板间距和公转速率提升了在柱面基底上薄膜的沉积均匀性;最后,利用幂指数算法设计了非周期多层膜,并在北京同步辐射光源上进行了多能点反射率测试,得到了与理论设计基本吻合的测试结果。基于优化的制备工艺制备了周期数为80,周期为3.8nm和W膜层厚度占比为0.47的W/Si周期多层膜,其界面粗糙度仅为0.29nm,柱面镜薄膜厚度误差可控制在3%以内,基本满足了eXTP项目中嵌套式掠入射望远镜镜片用多层膜对于成膜质量、沉积厚度均匀性和能谱响应宽度的需求。

DW/Si multilayer for eXTP mission

For the requirements of an embedded focused imaging telescope in eXTP (enhanced X-ray Timing and Polarization satellite ) for W/Si multilayers on a cylindrical mirror ,W/Si multilayers were fabricated at a grazing incident angle of 0 .5 ° and working range of 1—30 keV , and multilayer fabrication technologies were optimized . Firstly , separator plates and masks were mounted to collimate the sputtering particles to optimize different background pressures and working gas pressures in the deposition process and to improve the quality of periodic multilayers .T hen ,a novel kind of revolution speed curve was designed for controlling the thickness to make the layer thickness be uniform at the mirror axes .The separator plates were mounted on the mounting plate on both sides of the mirror to make the different axis thicknesses be equal .Finally ,the depth-graded structure was designed by using the power law expression , a sample was prepared and measured in Beijing Synchrotron Radiation Facility (BSRF ) and the measured results are identical with that of design theory .By optimized multilayer fabrication technologies ,a multilayer with a d-spacing of 3 .8 nm , thickness ratio of tungsten of 0 .47 and the total number of bilayers of 80 was fabricated .The results show that the interfacial roughness of the multilayer is only 0 .29 nm and the layer thickness variation on the cylindrical mirror has been controlled less than 3% . T he measurement indicates that depth-graded multilayer can meet the requirements of the embedded focused imaging telescope in eXTP mission for layer quality ,layer thickness uniform and energy spectral response .