Microscale Investigation into Selenium Distribution and Speciation in Se-Rich Soils from Enshi, China.

In this study, we investigated the distribution and chemical speciation of Se in Se-rich soil by using micro-focused X-ray absorption near-edge structure (µ-XANES) spectroscopy coupling with X-ray fluorescence (µ-XRF) mapping. The microscale distribution showed that Se is heterogeneously distributed in the soil from seleniferous areas in Enshi, China. Se K-edge µ-XANES analysis suggested that Se is mainly present as Se(IV), organic Se(-II) or Se(0) species in Se-rich agricultural soil. The findings from this study would help improve the understanding of the fate, mobility, bioavailability, and biogeochemical cycling of Se in the seleniferous soil environment.

A 1-m non-resonant inelastic x-ray scattering spectrometer at BL15U, Shanghai Synchrotron Radiation Facility.

We report the design, construction, and commissioning of a spectrometer for non-resonant inelastic x-ray scattering study installed at BL15U, Shanghai Synchrotron Radiation Facility. It features a 1-m vertical scattering arm. An energy resolution of 1.3 eV is achieved based on the 1 m Rowland circle and the diced Si(555) crystal analyzer with a fixed Bragg angle of about 88.8°. The inelastic squared form factors of 21S + 21P of helium with respect to the momentum transfer were measured and compared with the accurate and reliable theoretical calculations in order to verify the spectrometer. Furthermore, the spectrometer is designed to work in the momentum transfer region of 0 Å-1 < q < 8.68 Å-1 and to initially focus on the non-resonant inelastic x-ray scattering studies on gaseous samples.

[High accuracy sample positioning system for hard X-ray microprobe].

A novel sample offline positioning system was developed for hard X-ray micro-focus beamline (BL15U1) at Shanghai Synchrotron Radiation Facility (SSRF). The positioning system is composed of three parts: off-line sample microscope system, on-line sample experiment system, and high-precision positioning sample holder. It makes a potent combination of the on-line X-ray fluorescence imaging and the off-line microscopic examination in three steps: compiling of control program, positioning of sample holder, and conversion of the two coordinates. It's the first time in the domestic synchrotron radiation facilities to achieve sample offline positioning in micron scale. The system helps the researchers find the object of study in micro zone quickly and accurately, when they study the micro characteristics of materials using synchrotron radiation micro X-ray beam. The gold mesh was used as an object of study. By comparing the differences of coordinates of gold mesh nodes between pictures from offline microscope and pictures from X-ray fluorescence mapping, the accuracy of the offline positioning system was verified. The results showed that the average errors of X-axis and Z-axis were 1.3 and 2.5 microm respectively, using the positioning method. It was demonstrated that the sample offline positioning system not only is suitable for these applications with high efficiency, but also supply hard X-ray micro-focus beamline with the technical preparations of sample automatic focusing method.