Comparative study of Pt/C periodic multilayer mirrors for x rays in the 6- to 11-keV energy region

Multilayers are important optical components in the fields of astronomical observation, synchrotron radiation, and plasma diagnostics. This paper presents the Pt/C periodic multilayer mirrors for x rays in the 6- to 11-keV energy region. The IMD software was used to optimize the coating designs, and three multilayers, namely, C/Pt30, Pt/C30, and Pt/DLC30, were prepared via the RF magnetron sputtering technique. The energy dispersive spectrometry and electron energy loss spectroscopy (EELS) images showed that the C and Pt elements exhibit a periodic distribution. The average period d of C/Pt30, Pt/C30, and Pt/DLC30 multilayers obtained from transmission electron microscopy images are 4.7, 4.7, and 4.0 nm, respectively. Then, the x-ray reflectivity tests were performed using our x-ray reflectivity test calibration device. As the grazing incidence angle increases from 1° to 1.3°, the diffraction peak moves to lower energy, and the peak reflectivity increases, which can be explained by the enlargement of the projection of sample along the optical axis. Ultimately, the C/Pt30, Pt/C30, and Pt/DLC30 multilayers achieve the responses to x rays in the 6.8–10.3 keV energy region, and the highest reflectivity can reach 30% at 6.8 keV, which is measured at a grazing incidence angle of 1.3° for the Pt/C30 multilayer. These results have guiding significance for the coating design, preparation process, and test calibration of periodic multilayer mirrors.