Preparation and measurement of an x-ray Laue-type monochromator based on a WSi2/Si multilayer.

The Laue-type multilayer monochromator (LMM) is a promising optical element with a small size and high efficiency in a synchrotron radiation facility. By the dynamical diffraction theory, using DC magnetron sputtering technology, an LMM with a total thickness of 47 µm and a periodic thickness of 4.7 nm W S i 2/S i multilayer at 26 keV is designed and fabricated. During the preparation, the total number of layers is up to 20000, and every 300th layer of Si is replaced by WSi2 as the marker, so the multilayer is divided into 67 areas. The cross section of the multilayer is measured by a scanning electron microscope (SEM), and the marker region thickness error is 0.28% (RMS). The diffraction test experiment of the LMM is carried out at the Shanghai synchrotron radiation facility (SSRF). The 1st-order peak angle is 5.05 mrad, and the efficiency is 75.0%, which is close to the theoretical calculation result of 5.1 mrad and 79.1%. The Darwin width of the LMM is 0.17 mrad which is equal to the theoretical calculation. Based on the Bragg's diffraction equation, the energy resolution (Δ E/E) is 3.3%.

Preparation and testing of laterally graded multilayer with a double genetic algorithm and root mean square error optimization in differential deposition.

Lateral graded multilayer can realize reflection, collimation and focusing of hard X-ray, and are currently the research frontier and hotspot of synchrotron radiation and high-performance X-ray sources. To reduce the d-spacing error of graded multilayers, a root mean square error optimization method based on double genetic algorithm (DGA-RMSE) is proposed. The theoretical d-spacing distribution is obtained by optical design, and the range is 1.9 ∼ 3.1 nm. The optimized d-spacing distribution is obtained by convolution of particle beam function and continuous monotonic rate distribution line (RDL) which is constructed in the form of a polynomial. The GA is applied to optimize variables from the polynomial twice, and the RMSE of thickness error is optimized and converged to 0.0065 nm. The final thickness error which is measured by the grazing incidence X-ray reflectivity (GIXRR) is consistent with the theoretical calculation. The results show that DGA-RMSE can precisely select polynomial function of RDL, reducing the error in high-precision magnetron sputtering and mask technology.

Novel figuring method for a multilayer Laue lens.

A new, to the best of our knowledge, figuring method for a multilayer Laue lens (MLL) in the hard X-ray region is proposed in this paper. Theoretical simulation at 20 keV shows that the figuring method can compensate for the structure error. The phase errors of the first-order diffracted wave decrease from 0.85π to 0.26π after figuring. The spatial resolution changes from 45 nm to 26 nm after figuring, which is almost the same as that of the ideal MLL with a spatial resolution of 24 nm. The figured MLL can achieve 36% of the ideal MLL's first-order diffraction efficiency. Such method may reduce the requirements for the fabrication of the MLLs, and may make it possible to manufacture the larger numerical aperture MLL with the longer working distance in the future.

Refurbishment of W/B4C multilayers on Si substrate by etching a chromium buffer layer.

In synchrotron facilities, optics with multilayer coatings are used for beam monochromatization, focusing, and collimation. These coatings might be damaged by high heat load, poor film adhesion, high internal stress, or poor vacuum. Optical substrates always need high quality, which is expensive and has a long processing cycle. Therefore, it is desired to make the substrate reusable and the refurbished coating as good as a brand-new one. In this study, a W/B4C multilayer coating with a 2 nm Cr buffer layer was prepared on a Si substrate. The coating was successfully stripped from the Si substrate by dissolving the Cr buffer layer using an etchant. The roughness and morphology after the different etching times were investigated by measuring the GIXRR and 3D surface profiler. It is shown that the time required to etch the W/B4C multilayer coating with a Cr buffer layer, is quite different compared with etching a single Cr film. A layer of silicon dioxide was introduced during the fitting. After the new etching process, the roughness of the sample is as good as the one on a brand-new substrate. The W/B4C multilayer coatings with a Cr buffer layer were recoated on the etched samples, and the interface roughness was not damaged by the etching process.

Single-order focus multilayer Laue lens.

A novel sinusoidal multilayer Laue lens (MLL) in the hard X-ray region is proposed, to the best of our knowledge. The theoretical design shows that the structure function of the MLL is a sine function of the radius such as that of a sinusoidal transmission zone plate. A numerical simulation at the energy of 12 and 24 keV reveals that the MLL can suppress higher-order diffractions effectively, the characteristic of single-order diffraction with spatial resolution is the same as that of the corresponding classical MLL, and the MLL can achieve the first-order diffraction efficiency of 6.8% at 12 and 8.7% at 24 keV. The sinusoidal MLL can also work for single-order focusing at other energies.

In situ transient Laue x-ray diffraction during high strain-rate tension.

In situ transient synchrotron Laue x-ray diffraction based on high-energy and broadband x rays under high strain-rate tensile loading was developed at a superconducting wiggler beamline at the Beijing Synchrotron Radiation Facility. A split-Hopkinson tensile bar is utilized to realize this dynamic loading condition, while the transient Laue x-ray diffraction captures the transient internal structure of monocrystalline materials. Plastic deformation of a monocrystalline nickel specimen was investigated to prove the ability of this instrumentation in the characterization of a dynamic response of monocrystalline materials during a high strain-rate impact process with 5 µs time resolution.