1 m long multilayer-coated deformable piezoelectric bimorph mirror for adjustable focusing of high-energy X-rays.

The Diamond Light Source (DLS) beamline 115-1 measures atomic pair distribution functions (PDF) using scattering of 40-80 keV X-rays. A unique focusing element was needed to condense these X-rays from an initial large cross section (11.0 mm H x 4.2 mm V) into a required spot size of FWHM approximate to 680 mu m (H) x 20 mu m (V) at a Variable position between the sample and the detector. The large numerical aperture is achieved by coating a silicon substrate over 1 in long with three multilayer stripes of Bragg angle 4.2 mrad. One stripe selects X-rays of each energy 40.0; 65.4; and 76.6 keV. Sixteen piezoelectric bimorph actuators attached to the sides of the mirror substrate adjusted the reflecting surface's shape. Focal spots of Vertical width < 15 mu m were obtained at three positions over a 0.92 in range, with fast, easy switching from one focal position to another. Minimized root mean square slope errors were close to 0.5 mu rad after subtraction of a uniform curvature. Reflectivity curves taken along each stripe showed consistent high peaks with generally small angular variation of peak positions. This is the first application of a 1 m long multilayer-coated bimorph mirror at a synchrotron beamline. Data collected with its help on a slice of a lithium ion battery's cathode are presented. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement