ON THE FEASIBILITY OF EMPLOYING GRADIENT CRYSTALS FOR HIGH-RESOLUTIONSYNCHROTRON OPTICS

We present first experimental data on a novel type of optical element for synchrotron radiation applications in the X-ray region: namely lat erally-graded aperiodic crystals on the basis of Si1-xGex alloys. The lattice parameter of such gradient crystals containing up to some atom ic % in Si(1-x)G(x) crystal changes nearly linearly along the plane of diffraction. Thus the variation of the Bragg angle of divergent incid ent light on the crystal can be compensated for. This opens up the pos sibility to operate a crystal monochromator in nearly crystal limited resolution in the whole energy range above 2 keV at the full vertical divergence without a collimating premirror. Simultaneously the reflect ed spectral intensity can be increased considerably as compared with a conventional Si-crystal monochromator.