In order to achieve the effective splitting of X-ray, the perfect crystal whose the space of lattice plane comparable to the X-ray wavelength can be used as beam splitter. This beam splitter utilizes the diffraction effect of Laue crystal to accurately manipulate X-ray beam. A stress-free crystal with thin thickness is crucial for high-quality X-ray splitting. The working area of crystal was thinned by acid etching. Additionally, the base of crystal was cut from a floating-zone silicon single-crystal ingot, which prevented the spread of stress to the working area of crystal in fabrication and experiment. The experiment of Laue diffraction was conducted at the synchrotron radiation facility. In order to obtain the inherent rocking curve and consistent imaging field of view, a non-dispersion configuration was employed to match the energy bandwidth of the incident beam with the Laue diffraction crystal. Then diffraction splitting within the energy bandwidth of the Laue crystal was achieved by utilizing a collimator to reduce the divergence of the incident beam. The fine structure of the diffraction curve was measured experimentally, and the slope error of linear fitting between the high-angle and low-angle positions of peaks is less than 0.4%, which satisfies the requirement of stress-free diffraction splitting. The design and characterization of this Laue diffraction crystal provide technical support for various applications, such as X-ray ghost imaging, X-ray multi-projection imaging, and beamline measurement at wavelength.

Achieving diffraction-limited performance in fourth-generation synchrotron radiation sources demands monochromator crystals that can preserve the wavefront across an unprecedented extensive range. There is an urgent need for techniques of absolute crystal diffraction wavefront measurement. At the Beijing Synchrotron Radiation Facility (BSRF), a novel edge scan wavefront metrology technique has been developed. This technique employs a double-edge tracking method, making diffraction-limited level absolute crystal diffraction wavefront measurement a reality. The results demonstrate an equivalent diffraction surface slope error below 70 nrad (corresponding to a wavefront phase error of 4.57% λ) r.m.s. within a nearly 6 mm range for a flat crystal in the crystal surface coordinate. The double-edge structure contributes to exceptional measurement precision for slope error reproducibility, achieving levels below 15 nrad (phase error reproducibility < λ/100) even at a first-generation synchrotron radiation source. Currently, the measurement termed double-edge scan (DES) has already been regarded as a critical feedback mechanism in the fabrication of next-generation crystals.

X-ray Raman scattering (XRS) spectroscopy is an emerging inelastic scattering technique used to measure local electronic structure and chemical bonding around low- Z atoms with hard X-rays. This technique is useful in environments where traditional soft X-ray techniques are not applicable. However, the small cross section of XRS requires that the spectrometer must simultaneously achieve large solid angles and good energy resolution. A large XRS spectrometer named `Qian Kun' is currently under construction at the High Energy Photon Source (HEPS) in China, which can hold up to 100 analyzers with an energy resolution in the range 0.4–1.0 eV. Here, the batch production and performance evaluation of the spherically bent crystal analyzers fabricated for this spectrometer are reported. The stress-relief effect of various dicing patterns and their impact on the reflectivity properties of crystal analyzers to achieve good energy resolution when studying the near-edge features of carbon and oxygen K edges were investigated. It was discovered that radially dicing the thin silicon wafers is more effective in relieving stress than conventional strip cuts in the case that the total number of divided blocks is roughly the same.

Energy sustainability is critical for social activities in the human world. The quaternary compound Cu2ZnSnSe4 (CZTSe), as a promising candidate for thin-film solar cell absorption with medium-level thermoelectric performance, is of interest for the purpose of utilizing solar energy. The defect chemistry and atomic ordering in this particular compound also triggers interests in understanding its crystallographic structure as well as defects. Hereby, high energy resolution X-ray absorption spectroscopy is employed to investigate the electronic and geometric structural complexity in pristine and cobalt-doped Cu2ZnSnSe4. The occupational atomic sites of Cu are found to be mixed with the Zn atoms, forming CuZn anti-defects, which serve as a knob to tune local electronic structures. With proper doping, the band structure can be manipulated to improve the optical and thermoelectric properties of the CZTSe compounds.

Crystal monochromators are indispensable optical components for the majority of beamlines at synchrotron radiation facilities. Channel-cut monochromators are sometimes chosen to filter monochromatic X-ray beams by virtue of their ultrahigh angular stability. Nevertheless, high-accuracy polishing on the inner diffracting surfaces remains challenging, thus hampering their performance in preserving the coherence or wavefront of the photon beam. Herein, a magnetically controlled chemical–mechanical polishing (MC-CMP) approach has been successfully developed for fine polishing of the inner surfaces of channel-cut crystals. This MC-CMP process relieves the constraints of narrow working space dictated by small offset requirements and achieves near-perfect polishing on the surface of the crystals. Using this method, a high-quality surface with roughness of 0.614 nm (root mean square, r.m.s.) is obtained in a channel-cut crystal with 7 mm gap designed for beamlines at the High Energy Photon Source, a fourth-generation synchrotron radiation source under construction. On-line X-ray topography and rocking-curve measurements indicate that the stress residual layer on the crystal surface was removed. Firstly, the measured rocking-curve width is in good agreement with the theoretical value. Secondly, the peak reflectivity is very close to theoretical values. Thirdly, topographic images of the optics after polishing were uniform without any speckle or scratches. Only a nearly 2.5 nm-thick SiO2 layer was observed on the perfect crystalline matrix from high-resolution transmission electron microscopy photographs, indicating that the structure of the bulk material is defect- and dislocation-free. Future development of MC-CMP is promising for fabricating wavefront-preserving and ultra-stable channel-cut monochromators, which are crucial to exploit the merits of fourth-generation synchrotron radiation sources or hard X-ray free-electron lasers.

A high time-resolved front-end readout chip has been developed for avalanche-photodiode (APD) array detectors in nuclear resonant scattering (NRS) experiments. The chip has eight channels. Each channel consists of a preamplifier, a voltage discriminator, an open-drain output driver, and a local digital-to-analog converter (LDAC). The application-specific integrated circuit (ASIC) chip has been designed and fabricated in a 0.13- $\mu \text{m}$ CMOS technology with a chip size of 1.1 mm $\times2.3$ mm. The electrical characterizations of all eight channels demonstrate good time resolution (TR) (rms) on the output pulse leading edge, with the measurement result better than 25 ps for high input signal charges (>30 fC) and better than 98 ps for low input signal charges (8–30 fC), for an APD sensor capacitance as large as 15 pF. The equivalent noise charge (ENC) received from the measurement can be represented as ENC = 592.4 e − + 50.7 e − /pF. The power consumption is 17.6 mW per channel: 2.7 mW for the preamplifier–discriminator stage and 14.9 mW for the output low-voltage differential signaling (LVDS) driver.

Thermoelectric materials are promising for energy harvesting using waste heat. The thermal management of the thermoelectric materials attract scientific and technological interests. The narrow bandgap semiconductor BiAgSe2 is a good candidate for thermoelectric materials due to its ultralow thermal conductivity. The mother compound BiAgSe2 crystallizes in hexagonal symmetry at room temperature, but experiences structural transitions to cubic phase at high temperature. By contrast, the daughter compound BiAgSeTe exhibits long range ordering and crystallizes into cubic phase at room temperature. Nevertheless, the local structural disorderings due to the Bi3+ and Ag+ anti-site defects, as well as local structural distortions, are ubiquitous in both parent BiAgSe2 and BiAgSeTe. BiAgSeTe exhibits distinct transport properties owing to the disordering-induced drastic changes in the electronic band structure, as well as the scattering dictated by the point defects. It is suggested that BiAgSe2 and BiAgSeTe could be good candidates for phonon glass and crystal glass (PGEC)-type thermoelectrics.

X-ray double-crystal monochromators face a shift of the exit beam when the Bragg angle and thus the transmitted photon energy changes. This can be compensated for by moving one or both crystals accordingly. In the case of monolithic channel-cut crystals, which exhibit utmost stability, the shift of the monochromated beam is inevitable. Here we report performance tests of novel, asymmetrically cut, channel-cut crystals which reduce the beam movements by more than a factor of 20 relative to the symmetric case over the typical energy range of an EXAFS spectrum at the Cu K-edge. In addition, the presented formulas for the beam offset including the asymmetry angle directly indicate the importance of this value, which has been commonly neglected so far in the operation of double-crystal monochromators.

We report improvement of the Self-referenced lattice comparator using a wide brush beam with size of 16 mm x 0.3 mm and a pair of one-dimensional position sensitive X-ray counters instead of using a pencil beam with size of 1 mm x 0.3 mm and a pair of PIN photodiode detector in the former system. The experimental time is accelerated by a factor of more than ten times. Since we use a brush beam for the measurement, the wavelength alone the horizontal beam width positions are different, it is necessary to establish a data correction procedure for the lattice comparator. We reported our first data after the system improved, the spatial resolution of mapping measurement reached to 0.5 mm x 0.3 mm, that is higher than the previous system.