Theory and verification of moiréfringes for x-ray three-phase grating interferometer

Dual-phase and three-phase grating x-ray interference is a promising new technique for grating-based x-ray differential phase contrast imaging.Dual-phase grating interferometers have been relatively completely studied and discussed.In this paper,the corresponding imaging fringe formula of the three-phase grating interferometer is provided.At the same time,the similarities and differences between the three-phase grating interferometer and the dual-phase grating interferometer are investigated and verified,and that the three-phase grating interferometer can produce large-period moiréfringes without using the analyzing grating is demonstrated experimentally.Finally,a simple method of designing three-phase grating and multi-grating imaging systems from geometric optics based on the thin-lens theory of gratings is presented.These theoretical formulas and experimental results provide optimization tools for designing three-phase grating interferometer systems.

Design of advanced porous silver powder with high-sintering activity to improve silicon solar cells

Silver(Ag)paste is widely used in semiconductor metallization,especially in silicon solar cells.Ag powder is the material with the highest proportion in Ag paste.The morphology and structure of Ag powder are crucial which determine its characteristics,especially for the sintering activity.In this work,a simple method was developed to synthesize a type of microcrystalline spherical Ag particles(SP-A)with internal pores and the structural changes and sintering behavior were thoroughly studied by combining ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),in-situ heating X-ray diffraction(XRD),focused ion beam(FIB),and thermal analysis measurement.Due to the unique internal pores,the grain size of SP-A is smaller,and the coefficient of thermal expansion(CTE)is higher than that of traditional solid Ag particles.As a result,the sintering activity of SP-A is excellent,which can form a denser sintered body and form silver nanoparticles at the Ag–Si interface to improve silver silicon contact.Polycrystalline silicon solar cell built with SP-A obtained a low series resistance(Rs)and a high photoelectric conversion efficiency(PCE)of 19.26%.These fill a gap in Ag particle structure research,which is significant for the development of high-performance electronic Ag particles and efficient semiconductor devices.

Transverse mode-coupling instability with longitudinal impedance

Transverse mode-coupling instability(TMCI)is a dangerous transverse single-bunch instability that can lead to severe par-ticle loss.The mechanism of TMCI can be explained by the coupling of transverse coherent oscillation modes owing to the transverse short-range wakefield(i.e.,the transverse broadband impedance).Recent studies on future circular colliders,e.g.,FCC-ee,showed that the threshold of TMCI decreased significantly when both longitudinal and transverse impedances were included.We performed computations for the circular electron-positron collider(CEPC)and observed a similar phenom-enon.Systematic studies on the influence of longitudinal impedance on the TMCI threshold were conducted.We concluded that the imaginary part of the longitudinal impedance,which caused a reduction in the incoherent synchrotron tune,was the primary reason for the reduction in the TMCI threshold.Additionally,the real part of the longitudinal impedance assists in increasing the TMCI threshold.

Multidisciplinary and multiscale nanoscience research roadmap based on large scientific facilities

With the advancement of modern science and technology, large scientific facilities are increasingly oriented toward demand and application, and can be used for basic research as well as serving multiple disciplines. Developing large scientific facilities and related analytical technologies enhances understanding of large scientific facilities and popularizes their application in research across multiple disciplines. The combination of light or neutron sources from large scientific facilities and advanced analytical technologies can be achieved for materials structure information, dynamics study of chemical reactions, high dissociation of biomolecules, 3D visualization of energy materials or biological samples, etc. We first introduce the progress of domestic large scientific facilities of synchrotron radiation(SR) and free electron lasers(FELs) with different wavelengths and neutron sources.We further discuss the comparison between Chinese and typical foreign facilities in X-ray radiation from X-ray tubes, synchrotrons, X-ray FELs, and neutron sources based on physical parameters of light and neutron sources. In addition, we focus on the technological progress and perspectives combined with advanced X-ray radiation and neutron sources of large scientific facilities in China, especially in the nanoscience fields of energy catalysis and biological science. We hope that this roadmap will provide references on technology and methods to experimental users, as well as prospects for future development of technologies based on large research infrastructure facilities. Comprehensive studies and guidelines for basic research to practical application in various disciplines can be made with the assistance of large scientific facilities.

The role of proton dynamics on the catalyst-electrolyte interface in the oxygen evolution reaction

The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have been employed as active OER catalysts,however,the underlying mechanism that occurs at the catalyst‐electrolyte interface is still not well understood,prohibiting the design and preparation of advanced OER catalysts.Here,we report a systematic investigation into the effect of proton dynamics on the catalyst‐electrolyte interfaces of four perovskite catalysts:La_(0.5)Sr_(0.5)CoO_(3‐δ)(LSCO),LaCoO_(3),LaFeO_(3),and LaNiO_(3).The pH‐dependent OER activities,H/D kinetic isotope effect,and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate‐limiting steps of the OER.For oxides with small charge‐transfer energies,such as LSCO and LaNiO_(3),non‐concerted proton‐coupled electron transfer steps are involved in the OER,and the activity is strongly controlled by the proton dynamics on the catalyst surface.The results demonstrate the important role of interfacial proton transfer in the OER mechanism,and suggest that proton dynamics at the interface should carefully be considered in the design of future high‐performance catalysts.

X-ray diffraction performance of thermally distorted crystals

The development of high-brightness X-ray free electron lasers(XFELs),such as hard X-ray self-seeding free electron lasers and XFEL oscillators(XFELOs),brings a severe challenge to the crystal monochromator due to a strong nonuniform thermal load.The distortion caused by spatial temperature gradients can severely affect the optical performance of crystals.Therefore,this paper presents a model to estimate the performance of non-uniform thermally distorted crystals.The model not only takes into account thermal strain,slope error and incident angle deviation,but also considers temperature-dependent factors such as the Debye-Waller factor and electric susceptibility.Our investigation indicates that the Debye-Waller factor reduces the height and bandwidth of rocking curves,and the impact of the electric susceptibility is tiny.The proposed model can describe the distortion of the reflectivity and transmissivity curves of nonuniform thermally loaded crystals and can be applied in the design of crystal monochromators,crystal splitters,crystal compressors and XFELOs.

STCF conceptual design report (Volume 1): Physics & detector

The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.

Online single-shot characterization of ultrafast pulses from high-gain free-electron lasers

X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of FEL pulses is the central issue for its applications.Here we proposed and demonstrated a novel method to determine the FEL temporal profiles online.This robust method,designed for ultrafast FELs,allows researchers to acquire real-time longitudinal profiles of FEL pulses as well as their arrive times with respect to the external optical laser with a resolution better than 6 fs.Based on this method,we can also directly measure various properties of FEL pulses and correlations between them online.This helps us to further understand the FEL lasing processes and realize the generation of stable,nearly fully coherent soft X-ray laser pulses at the Shanghai Soft X-ray FEL facility.This method will enhance the experimental opportunities for ultrafast science in various areas.

Boosting reversible anionic redox reaction with Li/Cu dual honeycomb centers

The anionic redox reaction(ARR)is a promising charge contributor to improve the reversible capacity of layeredoxide cathodes for Na-ion batteries;however,some practical bottlenecks still need to be eliminated,including a low capacity retention,large voltage hysteresis,and low rate capability.Herein,we proposed a high-Na content honeycomb-ordered cathode,P2–Na_(5/6)[Li_(1/6)Cu_(1/6)Mn_(2/3)]O_(2)(P2-NLCMO),with combined cationic/anionic redox.Neutron powder diffraction and X-ray diffraction of P2-NLCMO suggested P2-type stacking with rarely found P6322 symmetry.In addition,advanced spectroscopy techniques and density functional theory calculations confirmed the synergistic stabilizing relationship between the Li/Cu dual honeycomb centers,achieving fully active Cu^(3+)/Cu^(2+) redox and stabilized ARR with interactively suppressed local distortion.With a meticulously regulated charge/discharge protocol,both the cycling and rate capability of P2-NLCMO were significantly.

Simulation study of coupled particle cascade and finite element analysis for beam dump of DALS

Purpose Charged particle cascade simulations,in conjunction with finite element thermal and mechanical calculations,are essential for addressing engineering challenges associated with the design of accelerator beam dumps.This study aims to investigate the integration of the FLUKA Monte Carlo program and the COMSOL finite element program as indispensable tools in the development of advanced models for spatial energy deposition distributions,temperature assessments,and stress analysis within the DALS beam dump.Methods The paper delves into aspects of model development,data transfer,and practical applications,focusing on the successful coupling of FLUKA Monte Carlo simulations with COMSOL finite element analyses.Tens of millions of elements were created and utilized to estimate spatial energy deposition distributions,assess temperatures,and analyze stresses within the critical absorber of the DALS beam dump.The study comprehensively analyzes the process from the impact of high-energy electron beam on the beam dump to the spatial distribution of energy deposition,providing input for subsequent thermal and structural analyses.Results The successful coupling of FLUKA and COMSOL enabled the calculation of spatial temperature distributions and structural analyses of the absorber within the DALS beam dump.The utilization of tens of millions of defined bins ensured seamless data transfer from the particle cascade simulation to finite element analysis,guaranteeing high resolution and accuracy in the calculations.The results provide valuable insights into the thermal and mechanical behavior of the beam dump absorber,a critical safety component in accelerator systems.Conclusions The study demonstrates that the integration of FLUKA Monte Carlo simulations with COMSOL finite element analyses is a dependable and efficient tool for addressing real-world engineering challenges,particularly those related to the design of beam dumps in accelerator systems with charged particle beams.The advanced analytical approach provides crucial information for the optimal design and safety assessment of accelerator components.

Coherent optical vortex generation with multiple topological charges based on a seeded free electron laser

To generate optical vortex with multiple topological charges,a simple scheme based on the phase mask shaping technique is proposed and applied in a seeded free electron laser.With a tailored phase mask,an extreme-ultraviolet(EUV)vortex with multiple topological charges can be produced.To prove the feasibility of this method,an eight-step phase mask is designed to shape the seed laser.The simulation results demonstrate that 100-MW,fully coherent EUV vortex pulses with topological charge 2 can be generated based on the proposed technique.We have also demonstrated the possibility of generating higher topological charges by using a phase mask with more steps.

Induced radioactivity at particle accelerators:a short review

Purpose The induced radioactivity in accelerator components and decay characteristics of radioactive nuclei contained therein is critical for radiation safety of occupational workers as well as for the maintenance,repair,and decommissioning activities.The topic of induced radioactivity is widely reported and extensively explored in the literature by many researchers up to now.This mini-review would demonstrate the current state of the knowledge on induced radioactivity at particle accelerators.Methods In this article,the concepts of activation-related studies and radionuclide generation in accelerator environments are reviewed.In addition,some studies on accelerator-induced radioactivity by Monte Carlo and experimental measurement methods are briefly described.Results and conclusions The possible radiation protection problems caused by particle accelerator-induced radioactivity are briefly reviewed and analyzed.The produced radionuclides depend on the beam parameters such as particle type,energy,irradiation period,cooling time,and irradiated material.The Monte Carlo simulation method offers comparable advantages over empirical analysis method.A review of major studies in the field of induced radioactivity of particle accelerators confirmed that the extremely strong induced radioactivity generated at hot spots of accelerators means new challenges to radiation safety and deserves further investigation and discussion.