Fast X-ray imaging beamline at SSRF

The fast X-ray imaging beamline(BL16U2)at Shanghai Synchrotron Radiation Facility(SSRF)is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales,spanning from 100 ps toμs and ms.This beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena,such as the deformation and failure of materials subjected to intense dynamic loads.In addition,it enables the study of high-pressure and high-speed fuel spray processes in automotive engines.The light source of this beamline is a cryogenic permanent magnet undulator(CPMU)that is cooled by liquid nitrogen.This CPMU can generate X-ray photons within an energy range of 8.7-30 keV.The beamline offers two modes of operation:monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator(DCM)and pink beam mode with the first crystal of the DCM out of the beam path.Four X-ray imaging methods were implemented in BL16U2:single-pulse ultrafast X-ray imaging,microsecond-resolved X-ray dynamic imaging,millisecond-resolved X-ray dynamic micro-CT,and high-resolution quantitative micro-CT.Furthermore,BL16U2 is equipped with various in situ impact loading systems,such as a split Hopkinson bar system,light gas gun,and fuel spray chamber.Following the completion of the final commissioning in 2021 and subsequent trial operations in 2022,the beamline has been officially available to users from 2023.

Intensity correlation properties of x-ray beams split with Laue diffraction

Beam splitting is one of the main approaches to achieving x-ray ghost imaging, and the intensity correlation between diffraction beam and transmission beam will directly affect the imaging quality. In this paper, we investigate the intensity correlation between the split x-ray beams by Laue diffraction of stress-free crystal. The analysis based on the dynamical theory of x-ray diffraction indicates that the spatial resolution of diffraction image and transmission image are reduced due to the position shift of the exit beam. In the experimental setup, a stress-free crystal with a thickness of hundredmicrometers-level is used for beam splitting. The crystal is in a non-dispersive configuration equipped with a double-crystal monochromator to ensure that the dimension of the diffraction beam and transmission beam are consistent. A correlation coefficient of 0.92 is achieved experimentally and the high signal-to-noise ratio of the x-ray ghost imaging is anticipated.Results of this paper demonstrate that the developed beam splitter of Laue crystal has the potential in the efficient data acquisition of x-ray ghost imaging.

Determination of Water Diffusion Coefficients and Dynamics in Adhesive/Carbon Fiber Reinforced Epoxy Resin Composite Joints

To determinate the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis（EDX） is used to establish the content change of oxy- gen in the adhesive in adhesive/carbon fther reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analy-sis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of beth energy dispersive X-ray spectroscopy and elemental analysis. The de- termined results with EDX analysis are almost the same as those determined with elemental analysis and the results al- so show that the durability of the adhesive/carbon fther reinforced epoxy resin composite joints subjected to silane cou- pling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treat- ment.

Radiation characteristics and implosion dynamics of tungsten wire array Z-pinches on the YANG accelerator

We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ～ 90 ns.The arrays are made up of（8-32）×5 μm wires 6/10 mm in diameter and 15 mm in height.The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ～ 13 kJ and the energy conversion efficiency ～ 9%（24×5 μm wires,6 mm in diameter）.Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV,peaked at 250 and 375 eV.The dominant wavelengths of the wire ablation and the magneto-Rayleigh-Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images.Through analyzing the implosion trajectories obtained by an optical streak camera,the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about（1.3-2.1）×10 7 cm/s.

Solvation Structure and Dynamics of Mg(TFSI)_(2) Aqueous Electrolyte

Using ab initio molecular dynamics(AIMD)simulations,classical molecular dynamics(CMD)simulations,small-angle X-ray scattering(SAXS),and pulsed-field gradient nuclear magnetic resonance(PFG-NMR),the solvation structure and ion dynamics of magnesium bis(trifluoromethanesulfonyl)imide(Mg(TFSI)_(2))aqueous electrolyte at 1,2,and 3 m concentrations are investigated.From AIMD and CMD simulations,the first solvation shell of an Mg;ion is found to be composed of six water molecules in an octahedral configuration and the solvation shell is rather rigid.The TFSI^(-)ions prefer to stay in the second solvation shell and beyond.Meanwhile,the comparable diffusion coefficients of positive and negative ions in Mg(TFSI)_(2)aqueous electrolytes have been observed,which is mainly due to the formation of the stable[Mg(H_(2)O_(6))_(2)]^(+)complex,and,as a result,the increased effective Mg ion size.Finally,the calculated correlated transference numbers are lower than the uncorrelated ones even at the low concentration of 2 and 3 m,suggesting the enhanced correlations between ions in the multivalent electrolytes.This work provides a molecular-level understanding of how the solvation structure and multivalency of the ion affect the dynamics and transport properties of the multivalent electrolyte,providing insight for rational designs of electrolytes for improved ion transport properties.

Dislocation characteristics and dynamic recrystallization in hot deformed AM30 and AZ31 alloys

Zn addition to Mg alloys activates non-basal slip or twinning with solute softening effects.On the other hand,the effects of the Zn solute on the macroscopic dislocation behavior and dynamic recrystallization are not completely understood.Moreover,it is unclear ifslip can be affected by changes in the c/a ratio of solute atoms.This study was conducted to understand the solute strengthening of Zn addition and its effects on the dislocation characteristics and dynamic recrystallization.A hot torsion test was performed on both AM30 and AZ31 alloys up to a high strain to investigate the Zn solute effect on the dislocation characteristics and dynamic recrystallization.The dislocation components of the hot torsioned alloys were evaluated by X-ray line profile analysis and electron backscatter diffraction.The results showed that the Zn solutes slightly accelerate strain accumulation at the initial stages of hot deformation,which accelerated recrystallization at high strain.The dislocation characteristics were changed dynamically by Zn addition:fortified-type slip,dislocation arrangement and strain anisotropy parameters.The most important point was that the dislocation characteristics were changed dramatically at the critical strain for recrystallization and high strain regions.The addition of Zn also acted greatly in these strain areas.This indicates that the rapid formation of-type slip at the serrated grain boundaries occurs at the initiation of dynamic recrystallization and the increase in the grain triple junction because grain refinement has a great influence on the dislocation characteristics at high strain.

Dynamic scaling behavior of iron nitride thin films prepared by magnetron sputtering and ion implantation

Under far from equilibrium conditions, the formation mechanism of solid can be studied in terms of the dynamic scaling theory. The roughness and dynamic scaling behavior of the Fe-N thin films were studied by atomic force microscopy and grazing incidence X-ray scattering. The results indicate that the roughness of the surface increases with increasing sputtering time during the course of magnetron sputtering, and the surface exhibits a fractal characteristic. While the Fe-N films prepared by compound technology—combining magnetron sputtering with plasma based ion implantation are not in agreement with the fractal theory.

Calculation of the coefficient and dynamics of water diffusion in graphite joints

The coefficient and dynamics of water diffusion in adhesive-graphite joints were calculated in-situ with energy dispersive X-ray (EDX) analysis, a method that is significantly simpler than elemental analysis. Water diffusion coefficient and dynamics of adhesive-graphite joints treated by different surface treatment methods were also investigated. Calculation results indicated that the water diffusion rate in adhesive-graphite joints treated by sandpaper was higher than that treated by chemical oxidation or by silane couple agent. Also the durability of graphite joints treated by coupling agent is superior to that treated by chemical oxidation or sandpaper burnishing.

Protein dynamics via computational microscope

The purpose of this overview is to provide a concise introduction to the methodology and current advances in molecular dynamics(MD) simulations. MD simulations emerged as a powerful and popular tool to study dynamic behavior of proteins and macromolecule complexes at the atomic resolution. This approach can extend static structural data, such as X-ray crystallography, into dynamic domains with realistic timescales(up to millisecond) and high precision, therefore becoming a veritable computational microscope. This perspective covers current advances and methodology in the simulation of protein folding and drug design as illustrated by several important published examples Overall, recent progress in the simulation field points to the direction that MD will have significant impact on molecular biology and pharmaceutical science.

The new X-ray imaging and biomedical application beamline BL13HB at SSRF

A new X-ray imaging and biomedical application beamline(BL13HB)has been implemented at the Shanghai Radiation Synchrotron Facility(SSRF)as an upgrade to the old X-ray imaging and biomedical application beamline(BL13W1).This is part of the Phase II construction project of the SSRF.The BL13HB is dedicated to 2D and 3D static and dynamic X-ray imaging,with a field of view of up to 48.5 mm×5.2 mm and spatial resolution as high as 0.8μm.A super-bending magnet is used as the X-ray source in BL13HB,which has a maximum magnetic field of 2.293 T.The energy range of monochromatic X-ray photons from a double-multiplayer monochromator was 8–40 keV,and the white beam mode was provided on the beamline for dynamic X-ray imaging and dynamic X-ray micro-CT.While maintaining the previous experimental setup of BL13W1,new equipment was added to the beamline experimental station.The beamline is equipped with different sets of X-ray imaging detectors for several experimental methods such as micro-CT,dynamic micro-CT,and pair distribution function.The experimental station of BL13HB is designed specifically for various in situ dynamic experiments,and BL13HB has been open to users since June 2021.

Low-fat microwaved peanut snacks production:Effect of defatting treatment on structural characteristics,texture,color,and nutrition

This study develops low-fat microwaved peanut snacks(LMPS)using partially defatted peanuts(PDP)with different defatting ratios,catering to people’s pursuit of healthy,low-fat cuisine.The effects of defatting treatment on the structural characteristics,texture,color,and nutrient composition of LMPS were comprehensively explored.The structural characteristics of LMPS were characterized using X-ray micro-computed tomography(Micro-CT)and scanning electron microscope(SEM).The results demonstrated that the porosity,pore number,pore volume,brightness,brittleness,protein content,and total sugar content of LMPS all significantly increased(P<0.05)with the increase in the defatting ratio.At the micro level,porous structure,cell wall rupture,and loss of intracellular material could be observed in LMPS after defatting treatments.LMPS made from PDP with a defatting ratio of 64.44%had the highest internal pore structural parameters(porosity 59%,pore number 85.3×10^(5),pore volume 68.23 mm3),the brightest color(L^(*) 78.39±0.39),the best brittleness(3.64±0.21)mm^(–1)),and the best nutrition(high protein content,(34.02±0.38)%;high total sugar content,(17.45±0.59)%;low-fat content,(27.58±0.85)%).The study provides a theoretical basis for the quality improvement of LMPS.

Operando measurement of lattice deformation profiles of synchrotron radiation monochromator

This study presents a new method for characterizing the thermal lattice deformation of a monochromator with high precision under service conditions and first reports the operando measurements of nanoscale thermal lattice deformation on a double-crystal monochromator at different incident powers.The nanoscale thermal lattice deformation of the monochromator first crystal was obtained by analyzing the intensity of the distorted DuMond diagrams.DuMond diagrams of the 333 diffraction index,sensitive to lattice deformation,were obtained directly using a 2D detector and an analyzer crystal orthogonal to the monochromator.With increasing incident power and power density,the maximum height of the lattice deformation increased from 3.2 to 18.5 nm,and the deformation coefficient of the maximum height increased from 1.1 to 3.2 nm/W.The maximum relative standard deviation was 4.2%,and the maximum standard deviation was 0.1 nm.Based on the measured thermal deformations,the flux saturation phenomenon and critical point for the linear operation of the monochromator were predicted with increasing incident power.This study provides a simple solution to the problem of the lower precision of synchrotron radiation monochromator characterizations compared to simulations.

Methodology development and application of X-ray imaging beamline at SSRF

This paper introduces some latest developments regarding the X-ray imaging methodology and applications of the X-ray imaging and biomedical application beamline(BL13W1)at Shanghai Synchrotron Radiation Facility in the past 5 years.The photon energy range of the beamline is 8–72.5 keV.Several sets of X-ray imaging detectors with different pixel sizes(0.19–24 lm)are used to realize X-ray microcomputed tomography(X-ray micro-CT)and X-ray in-line phase-contrast imaging.To satisfy the requirements of user experiments,new X-ray imaging methods and image processing techniques are developed.In vivo dynamic micro-CT experiments with living insects are performed in 0.5 s(sampling rate of 2 Hz,2 tomograms/s)with a monochromatic beam from a wiggler source and in 40 ms(sampling rate of 25 Hz,25 tomograms/s)with a white beam from a bending magnet source.A new X-ray imaging method known as move contrast X-ray imaging is proposed,with which blood flow and moving tissues in raw images can be distinguished according to their moving frequencies in the time domain.Furthermore,X-ray speckle-tracking imaging with twice exposures to eliminate the edge enhancement effect is developed.A high-precision quantification method is realized to measure complex three-dimensional blood vessels obtained via X-ray micro-CT.X-ray imaging methods such as three-dimensional X-ray diffraction microscopy,small-angle X-ray scattering CT,and X-ray fluorescence CT are developed,in which the X-ray micro-CT imaging method is combined with other contrast mechanisms such as diffraction,scattering,and fluorescence contrasts respectively.Moreover,an X-ray nano-CT experiment is performed with a 100 nm spatial resolution.Typical user experimental results from the fields of material science,biomedicine,paleontology,physics,chemistry,and environmental science obtained on the beamline are provided.

State of the Art of Micro-CT Applications in Dental Research

This review highlights the recent advances in X-ray microcomputed tomography （Micro-CT） applied in dental research. It summarizes Micro-CT applications in mea- surement of enamel thickness, root canal morphology, evaluation of root canal preparation, craniofacial skeletalstructure, micro finite element modeling, dental tissue engineering, mineral density of dental hard tissues and about dental implants. Details of studies in each of these areas are highlighted along with the advantages of Micro-CT, and finally a summary of the future applications of Micro-CT in dental research is given.

Effects of dry-wet cycles on three-dimensional pore structure and permeability characteristics of granite residual soil using X-ray micro computed tomography

Due to seasonal climate alterations,the microstructure and permeability of granite residual soil are easily affected by multiple dry-wet cycles.The X-ray micro computed tomography(micro-CT)acted as a nondestructive tool for characterizing the microstructure of soil samples exposed to a range of damage levels induced by dry-wet cycles.Subsequently,the variations of pore distribution and permeability due to drywet cycling effects were revealed based on three-dimensional(3D)pore distribution analysis and seepage simulations.According to the results,granite residual soils could be separated into four different components,namely,pores,clay,quartz,and hematite,from micro-CT images.The reconstructed 3D pore models dynamically demonstrated the expanding and connecting patterns of pore structures during drywet cycles.The values of porosity and connectivity are positively correlated with the number of dry-wet cycles,which were expressed by exponential and linear functions,respectively.The pore volume probability distribution curves of granite residual soil coincide with the χ^(2)distribution curve,which verifies the effectiveness of the assumption of χ^(2)distribution probability.The pore volume distribution curves suggest that the pores in soils were divided into four types based on their volumes,i.e.micropores,mesopores,macropores,and cracks.From a quantitative and visual perspective,considerable small pores are gradually transformed into cracks with a large volume and a high connectivity.Under the action of dry-wet cycles,the number of seepage flow streamlines which contribute to water permeation in seepage simulation increases distinctly,as well as the permeability and hydraulic conductivity.The calculated hydraulic conductivity is comparable with measured ones with an acceptable error margin in general,verifying the accuracy of seepage simulations based on micro-CT results.

Oscillator strength study of the excitations of valence-shell of C2H2 by high-resolution inelastic x-ray scattering

The oscillator strengths of the valence-shell excitations of C_(2)H_(2) are extremely important for testing theoretical models and studying interstellar gases.In this study,the high-resolution inelastic x-ray scattering(IXS)method is adopted to determine the generalized oscillator strengths(GOSs)of the valence-shell excitations of C_(2)H_(2) at a photon energy of10 ke V.The GOSs are extrapolated to their zero limit to obtain the corresponding optical oscillator strengths(OOSs).Through taking a completely different experimental method of the IXS,the present results offer the high energy limit for electron collision to satisfy the first Born approximation(FBA)and cross-check the previous experimental and theoretical results independently.The comparisons indicate that an electron collision energy of 1500 e V is not enough for C_(2)H_(2) to satisfy the FBA for the large squared momentum transfer,and the line saturation effect limits the accuracy of the OOSs measured by the photoabsorption method.

Synchrotron X-ray micro-computed tomography imaging of solid bridges between potash particles near contact points

Chemical fertilizers,such as potash,have a strong tendency to cake when exposed to humidity.In this work,a novel synchrotron-based X-ray tomography 3D-imaging technique was for the first time employed to investigate the solid bridge formation from 2D and 3D perspectives.Image processing and a theoretical model were presented to demonstrate recrystallization near contact points between potash particles during a conventional drying process.The effect of initial moisture content on the water activity of surface surrounding the contact points was investigated.The results showed that by increasing the moisture content of particles(3%–5%),the dissolution of sylvite increased and the solid bridge length between potash particles was enlarged from 28μm to 44μm due to supersaturation conditions.In addition,the external porosity of potash particles at the end of drying process decreased from 25.3%to 19.5%for 3%and 5%moisture content,respectively.

One-pot synthesis of a giant twisted double-layer chiral macrocycle via [4+8] imine condensation and its X-ray structure

Trifluoroacetic acid(TFA)catalyzed condensation reaction between tetraaminooxacalix[4]arene and N-alkylcarbazole-3,6-dicarbaldehyde in CH_(2)Cl2afforded a single product in 87%–89%yield.Well-defined yet undissolvable1H NMR spectra suggested formation of robust and discrete structures in solution.X-ray single crystal analysis further revealed a giant twisted double-layer chiral macrocycle in the solid state,which was formed from[4+8]condensation of the two reactants via 16 imine bonds.DFT calculations discovered that only the[4+8]twisted product is thermodynamically favorable,which accounts for its highly selective and efficient formation out of a library of many other combinations.

An experimental investigation of failure mechanical behavior in cylindrical granite specimens containing two non-coplanar open fissures under different confining pressures

Fissures play a significant role in predicting the unstable failure of rock mass engineering.For deep rock underground engineering,rock mass containing pre-existing fissures is usually located in triaxial stress state.Therefore,not only pre-existing fissure but also confining pressure affects the failure mechanical behavior of rock material.In this research,the granite specimens containing two non-coplanar open fissures were investigated by a series of conventional triaxial compression tests.First,the effect of bridge angle and confining pressure on strength and deformation characteristics of granite specimens was evaluated.Results show that the triaxial compressive strength,failure axial strain,and crack damage threshold increased nonlinearly with confining pressure.Under high confining pressures,elastic modulus was insensitive to bridge angle.Then,an X-ray micro-CT scanning technique was used to analyze the internal fracture characteristics of granite specimens with respect to various bridge angles and confining pressures.Five typical crack coalescence modes were identified,namely,indirect coalescence,shear coalescence and three types of tensile coalescence.The reconstructed 3-D CT images indicated that under uniaxial or low confining pressures,the bridge angle had a significant effect on crack evolution behavior,while under high confining pressures,shear-dominated failures occurred with the development of anti-wing cracks.

Dynamic shrinkage of metal-oxygen bonds in atomic Co-doped nanoporous RuO_(2) for acidic oxygen evolution

The design of highly active and stable catalysts for the oxygen evolution reaction(OER) in acidic media has become an attractive research area for the development of energy conversion and storage technologies. However, progress in this area has been limited by the poor understanding of the dynamic active structure of catalysts under realistic OER conditions. Here, an atomic Co-doped nanoporous Ru O_(2)electrocatalyst, which exhibited excellent OER activity and stability in acidic conditions, was synthesized through annealing and etching of a nanoporous Co-Ru alloy. Operando X-ray absorption spectroscopy results confirmed that the etching strategy produced abundant oxygen vacancies around the metal centers in the atomic Co-doped nanoporous Ru O_(2)electrocatalyst. These vacancies created contracted metaloxygen ligand bonds under realistic OER conditions. The dynamic structural evolution of the synthesized electrocatalyst allowed them to experience lower kinetic barriers during OER catalysis, resulting in enhanced catalytic activity and stability.This study also provided atomic details on the active structure of the electrocatalyst and the influence of their structural evolution on OER activity.