Design and performance of graded multilayers as focusing elements for x-ray optics

Abstract

We have developed a design method to produce laterally graded multilayer x-ray mirrors based on sputter deposition techniques. The optimization of all relevant parameters yields an ab initio estimation of any layer gradient suitable to achieve precise x-ray focusing devices. The performance and the accuracy of this method are demonstrated. A graded W/B4C multilayer was deposited on a flat substrate that was bent to a parabola. The obtained nonlinear lateral gradient differed from the theoretical calculations by less than 1%. Focusing experiments performed at an x-ray energy of 8 keV on the ESRF optics beamline revealed an excellent performance with a focal spot size of about 7 μm.