New design concept of supermirror for hard X-ray telescope

We studied about new design of supermirror and inerfacial roughness for the X-ray telescope above 40 keV. We have developed hard X-ray telescope above 10 keV using platinum-carbon multilayer supermirror. In our balloon borne experiment, named "InFOCmuS" launched in this June, the supermirror expand the upper-limit of energy band of X-ray telescope up to 40 keV. We are trying to improve supermirror design to have energy band up to 70 keV. In previous design, the absorption of upper layers and lower-limit of layer thickness prevent us to extend the energy band. In this paper, we optimize design parameters of supermirror and use second Bragg peak, and we obtained high reflectivity up to 70 keV. We studied about interfacial roughness of platinum-carbon multilayer to design the supermirror, because the interfacial roughness is very serious problem such high energy region. In many cases, simple Debye-Waller factor can't represent measured reflectivity. We introduced two different roughness for Pt/C and C/Pt interfaces. This model well fit the data and make us possible to design the supermirrors.