Sagittally focusing diffractive-refractive x-ray lens with a large acceptance and a long focusing distance

The high resolution, high asymmetric diffractive-refractive x-ray lens was tested at BM5 beamline in ESRF. The lens consists of two Si (111) channel-cut crystals in dispersive arrangement with the angle of asymmetry of 12.7°. The channels have a circular profile with the diameter of 22 mm. The test was performed for the energy of 7.8 - 8.1 keV and the focusing distance of 19 - 20 m. At the place of the focus the beam was squeezed horizontally from 8.8 mm (unfocused beam) to 0.4 mm, i.e. more than 20 times. To get a good reflectivity in such a highly asymmetric diffraction, the cylindrical surface had to be mechanically-chemically polished.