High-energy characterization of multilayers for hard x-ray astronomy

We report the results obtained during the second phase of a program which consists of comparing the performance of different multilayer material combinations. These coatings will be used to extend the bandpass of current hard X-ray optics toward 100 keV, an order of magnitude higher than present technology. The materials studied here are W/Si, Pt/C, and W/C. A comparison of the performance of depth graded multilayers of these different materials at energies 30-80 keV was undertaken. Specular reflectivity data were acquired at 30-80 keV using the X17B1 beamline of the National Synchrotron Light Source. Reflectivity versus energy plots showed a high enough reflectivity for the bandpass of interest at grazing angles typical for hard x-ray telescope mirror shells. The next phase of our pro-ram will continue with similar high-energy pencil beam measurements on multilayer coated telescope prototype shells.