Optimization Design of Pt/C Multilayer Supermirrors for Hard X-rays

Aperiodic multilayers have important applications in hard X-rays astronomical observations due to their broadband responses. This paper presents an optimization model of Pt/C power-law graded stack multilayers using the IMD software. The reflectivity expression of multilayers was derived from the reflection theory of X-ray multilayers and Fresnel recursion formulas. Then, the effects of maximum bi-layer thickness ([Formula: see text]), ratio of high-density material thickness to bi-layer thickness ([Formula: see text]), power-law index ([Formula: see text]), number of bi-layers ([Formula: see text]), grazing incidence angle ([Formula: see text]), interfacial roughness ([Formula: see text]), and photon energy ([Formula: see text]) on the reflectivity were analyzed. The calculation results showed that the [Formula: see text], [Formula: see text] and [Formula: see text] control the shift of response range, absorption peak and Bragg peaks, respectively. And the decrease of [Formula: see text] and increase of [Formula: see text] and [Formula: see text] can result in the reduction of reflectivity at different energies. Additionally, an optimized multilayer structure was proposed according to the extremum of merit function, which can achieve a broadband reflectivity of no less than 0.6 from 1[Formula: see text]keV up to 80[Formula: see text]keV. These results can provide important references for the response characteristic analysis and optimization design of multilayers.