This paper presents the results of using the laboratory X-ray system to study the diamond X-ray optics: single-crystal diamond plates and diamond X-ray parabolic refractive lenses. The system is equipped with the Excillum MetalJet D2+ 70kV high-brightness X-ray source with a liquid GaIn anode. To analyze the defects of the crystal structure, the X-ray diffraction imaging (topography) technique was applied. Two-dimensional images of the diamond plate were experimentally recorded from (111) crystal plane with 12 μm and 1.5 μm resolution. The images of the X-ray semi-lens were recorded from (400) and (220) crystal planes with 20 μm resolution. These topographs displayed various defects, such as growth striations and dislocations.
The study of the applicability of a nano-polycrystalline diamond (NPD) as a lens material is presented. Two NPD plates with a diameter of 8 mm and a thickness of 0.1 and 1 mm were manufactured using the HPHT process. Coherence preservation properties of the NPD samples were checked using in-line phase-contrast imaging. Wide-Angle X-ray Scattering and Small Angle X-ray Scattering experiments were performed to examine the NPD scattering properties. Rotationally parabolic half-lens from a 100 μm thick NPD plate was manufactured using the maskless direct milling using a Zeiss CrossBeam 540 FIB-SEM system.
In the manuscript we report on characterization of single-crystalline (111) plates prepared from type Ib diamonds with nitrogen content of 100-150 ppm and (100) plates prepared from IIa diamond by means of high-resolution rocking curve imaging (RCI). Contrary to a common opinion about intrinsic poor diffraction quality of type Ib diamonds, RCI showed the presence of nearly defect-free areas of several mm2 in the central part of the (111)-oriented diamond plates. In comparison with the (100)-oriented IIa diamond plates prepared by the same HPHT setup the Ib diamonds possess better diffraction quality. The observed broadening of the rocking curves associates with the cutting and polishing processes, causing strains around the edges of the plates and rare defects. An improvement of preparation technique will thus allow to make single-crystalline diamond plates for Laue and Bragg monochromators and beam splitters from type Ib diamond with areas large enough to be used as wavefront-preserving optical elements at 4th generation synchrotron facilities. Contrary to a common opinion about intrinsically poor diffraction quality of type I diamonds, RCI showed the presence of nearly defect-free areas of several mm2 in the central part of the diamond plates. The observed broadening of the rocking curves results from the cutting and polishing processes, causing strains around the edges of the plates and rare defects. An improvement of preparation technique will thus allow to make single-crystalline diamond plates for Laue and Bragg monochromators and beam splitters from type Ib material with areas large enough to be used as optical elements at 4th generation synchrotron facilities.
The requirement for the high-quality optics for the 4th generation synchrotrons is becoming particularly urgent nowadays. We present a laboratory complex “SynchrotronLike” designed for the X-ray optics tests and development of the X-ray optical techniques before their use on the synchrotron sources. This complex consists of four main parts: 1) microfocus Xray source MetalJet D2+ 70kV, 2) detector module that contains X-ray spectrometer and three X-ray cameras with different resolution and field of view, 3) Micro-Optics Test Bench for X-ray optics tests and development of the X-ray optical techniques, 4) X-ray Single Crystal Diagnostics Endstation for the X-ray diffraction microscopy experiments. This complex was successfully used for the preliminary tests of the X-ray refractive lenses made from polymer, epoxy, and diamond. Moreover, the ultracompact X-ray transfocators, diamond monochromators, and beam-splitters for the 4th generation synchrotron sources were also tested on the “SynchrotronLike”. The unique parameters of our laboratory source, such as high brightness and high beam coherency make it possible to implement versatile experimental synchrotron techniques. Consequently, we managed to get excellent results in the X-ray reflecto-interferometry and X-ray microradian diffraction. The results of the latter technique are presented in this paper.
We demonstrate the capabilities of ion-beam lithography (IBL) for the manufacturing of the X-ray refractive micro-optics. For the first time with the help of IBL, the hardest of current materials – diamond – was milled, and microscale diamond half-lenses were produced. Lenses have a rotationally parabolic profile with radii of parabola apexes in the range from 3 to 10 μm. As has been confirmed with SEM, the surface of produced lenses was free of low- and high-frequency modulations: figure errors of fabricated lenses were < 200 nm, while the surface roughness was estimated to be 30 nm. The optical performance of the lens was successfully tested at a third-generation synchrotron, where the lenses provided diffraction-limited focusing of X-ray radiation and demonstrated intensity profiles with Gaussian distributions at every measured longitudinal position (along the optical axis) downstream of the optics.
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