4.48 nm正入射软X射线激光用Cr/C多层膜高反射镜的研制

针对4.48nm类镍钽软X射线激光及其应用实验,设计制备了工作于这一波长的近正入射多层膜高反射镜。选择Cr/C为制备4.48nm高反射多层膜的材料对,通过优化设计,确定了多层膜的周期、周期数以及两种材料的厚度比。模拟了多层膜非理想界面对高反射多层膜性能的影响。采用直流磁控溅射方法在超光滑硅基片上实现了200周期Cr/C多层膜高反射镜的制备。利用X射线衍射仪测量了多层膜结构,在德国BessyⅡ同步辐射上测量了在工作波长处多层膜反射率,测量的峰值反射率达7.5%。对衍射仪测量的掠入射反射曲线和同步辐射测量的反射率曲线分别进行拟合,得到的粗糙度和厚度比的结果相近。测试结果表明,所制备的Cr/C多层膜样品结构良好,在指定工作波长处有较高的反射峰,达到了设计要求。

Fabrication of Normal Incident Cr/C High-Reflecting Mirror for 4.48 nm Soft X-Ray Laser

Near normal incident high-reflecting multilayered mirrors at 4.48 nm wavelength are designed and fabricated for Ni-like Ta soft X-ray laser and its applied experiments. Materials Cr and C are chosen to make up the high-reflecting mirror. The periodic thickness, thickness ratio of two materials and periodic number are calculated and optimized. The influence of the imperfect interface on the reflectivity of the multilayer is simulated. The Cr/C multilayer of 200 periods is deposited on the super smooth silicon substrate by the direct current magnetron sputtering technique. The periodic thickness and structure of the multilayer are measured by X-ray diffractometer (XRD). The reflectivity of the multilayer is measured at Bessy Ⅱ synchrotron radiation (SR), and the peak reflectivity is measured to be 7.5%. The grazing incident reflection index curve measured by XRD and reflection index curve by SR are fitted. The fitted thickness ratio and interface roughness of the two curves are close to each other. The measurements show the Cr/C multilayer has a good structure and a reflective peak on the demanded wavelength, which meet the design requirement.