Application of Ni/C Goebel mirrors

Collimating X-ray optics can be realized by parabolically bent multilayer mirrors consisting of laterally graded layer stacks [1], [2]. Reduced influences of sample misalignment and surface topography on reflex positions are remarkable advantages when replacing the BRAGG-BRENTANO arrangement by a parallel beam geometry. Ni/C Goebel Mirrors used in our experimental arrangement were synthesized by PLD (pulsed laser deposition). A beam divergence as low as Df < 0.035° and the suppression of Cu Kb radiation (intensity ratio ICu Ka / ICu Kb > 500) are outstanding features of the parallel X-ray beam produced by these Ni/C X-ray mirrors [3]. Peak shape and angular resolution in reflectometry and diffractometry are mainly influenced by the optical properties of the beam conditioners at the primary and the diffracted beam side [4]. Medium and high resolution are achieved by using channel cuts, crystals or soller collimators, but at the expense of beam intensity. Conservation of much higher intensities (up to 109cps) combined with medium resolution can be observed by using a second Ni/C-Goebel Mirror at the diffracted beam side. Some selected measurements (diffractometer D5005/BRUKER AXS, FL Cu 4KE) show the brilliant Cu Kb suppression, the high intensity combined with low beam divergence and suppression of sample fluorescence thus demonstrating the specific features of Goebel Mirrors of the Ni/C type.