Graded multilayers for focusing hard X rays below 50nm

摘要

Laterally graded W/B_4C multilayers were conceived for the focusing of hard X rays at 3rd generation synchrotron sources. They were deposited using a differential sputter coating technique. The multilayer mirror was bent to the correct shape on a dynamical bending device applying automated alignment routines. During experiments on the ESRF beamline ID19 the undulator source was focused vertically to a 41 nm (FWHM) wide line using a photon energy of 24 keV. The measured line width can be attributed to the finite source size, to diffraction effects, and to slope errors of the mirror. The potential impact of beam penetration into the multilayer will be discussed.