Optical constants in the hard X-ray/Soft gamma ray range of selected materials for multilayer reflectors

Future Astrophysics missions operating in the hard X-ray/Soft Gamma ray range is slated to carry novel focusing telescopes based on the use of depth graded multilayer reflectors. Current design studies show that, at the foreseen focal lengths, it should be feasible to focus X-rays at energies as high as 300 keV.

These designs use extrapolations of theoretical and experimentally determined optical constants from below 200 keV. In this paper we report on the first experimental determination of optical constants up to and above 200 keV. We present these first results as obtained at the National Synchrotron Light Source in Brookhaven and compare these to results obtained previously up to 180 keV of some of the same materials at the European Synchrotron Radiation Facility in Grenoble.