Synchrotron Radiation Research Articles

Effect of post-weld heat treatment on the microstructure, phase composition and mechanical properties of dissimilar Al-Mg-Li/Al-Cu-Li laser welded joints

Butt joints of the V-1461 and 1424 heat treated aluminum–lithium alloys of the third generation were welded with a CO2 laser and studied in detail for the first time. In particular, spatial distributions of the formed phases and their evolution upon post-weld heat treatment (PWHT), determining the mechanical properties of the joints, were investigated. The PWHT included quenching and subsequent artificial aging. The key factors, affecting the metallurgical processes in a weld pool, were the following: 1) the alloying elements and the thermal properties of the alloys, 2) the dynamics of the local non-equilibrium melting, the convective transfer of the molten metal in the weld pool and its subsequent solidification, 3) the cooling rate, and 4) the PWHT procedure. By using synchrotron radiation and scanning electron microscopy, new θ(Al2Cu), T1(Al2CuLi) and S1(Al2MgLi) phases were found in the weld metal that were absent in both base metals. This phenomenon reduced the mechanical properties of the joints to the levels, corresponding to about 50 % of the 1424 alloy as the weakest one. Quenching contributed to the formation of the δ′(Al3Li) strengthening phase in the weld metal. As a result, the ultimate tensile strength increased up to 70 % and elongation up to 95 % of the corresponding levels of the 1424 alloy. Artificial aging made it possible to form the T1(Al2CuLi) strengthening phase, to increase the content of the δ′(Al3Li) one, as well as to improve the mechanical properties of the joint. In this case, the ultimate tensile strength was 411 MPa, the yield point was 327 MPa and elongation was 1.7 %. These values were close to those for the 1424 alloy (about 80 %, 89 % and 23 %, respectively).

Multiband Nonthermal Radiative Study of PeVatron Candidate Pulsar Wind Nebula HESS J1849-000

Pulsar wind nebula HESS J1849-000 is one of the sources that may emit PeV γ-ray photons based on the recent measurement by the Tibet Air Shower Array and the Large High Altitude Air Shower Observatory. We use a time-dependent model to investigate the nonthermal radiative properties of HESS J1849-000. Observed multiband data are produced well by relativistic leptons through synchrotron radiation and inverse Compton processes, and the particle transport and cooling processes are analyzed. Our results show that the particle adiabatic loss dominates over the synchrotron loss and inverse Compton losses, and the particle advection dominates over diffusion for the low-energy band. On the other hand, the particle synchrotron loss dominates over the adiabatic loss and inverse Compton losses, and the diffusion dominates over advection for the high-energy band. Furthermore, particle transport would be playing a significant role in the low-energy band, whereas the particle cooling processes may play a more important role in the high-energy band. The current diffusion coefficient 3.4 × 1026 cm2 s−1 at an electron energy of 1 TeV is derived, which implies a slow diffusion mechanism may occur within the nebula. More importantly, our model suggests that the particle's maximum energy is 3.6 PeV, which makes HESS J1849-000 a PeVatron candidate.

Thermodynamic stability and vibrational properties of multi-alkali antimonides

Abstract Modern advances in generating ultrabright electron beams have unlocked unprecedented experimental advances based on synchrotron radiation. Current challenges lie in improving the quality of electron sources with novel photocathode materials such as alkali-based semiconductors. To unleash their potential, a detailed characterization and prediction of their fundamental properties is essential. In this work, we employ density functional theory combined with machine learning techniques integrated into the hiphive package to probe the thermodynamic stability of various alkali antimonide crystals, emphasizing the role of the approximations taken for the exchange-correlation potential. Our results reveal that the SCAN functional offers an optimal trade-off between accuracy and computational costs to describe the vibrational properties of these materials. Furthermore, it is found that systems with a higher concentration of Cs atoms exhibit enhanced anharmonicities, which are accurately predicted and characterized with the employed methodology.

Dynamics and emission properties of flux ropes from two-temperature GRMHD simulations with multiple magnetic loops

Flux ropes erupting in the vicinity of a black hole are thought to be a potential model for the flares observed in Sagittarius\,A$^*$. In this study, we examine the radiative properties of flux ropes that emerged in the vicinity of a black hole. We performed three-dimensional two-temperature general relativistic magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows with alternating multiple magnetic loops and general relativistic radiation transfer (GRRT) calculations. In the GRMHD simulations, we implemented two different sizes of initial magnetic loops. In the small loop case, magnetic dissipation leads to a weaker excitement of magneto-rotational instability inside the torus, which generates a lower accretion rate compared to the large loop case. However, the small loop case generates more flux ropes due to frequent reconnection by magnetic loops with different polarities. By calculating the thermal synchrotron emission, we found that the variability of light curves and the emitting region are tightly related. At $230\ GHz$ and higher, the emission from the flux ropes is relatively stronger compared to the background, which is responsible for the filamentary structure in the images. At lower frequencies (e.g. $43\ GHz$), emission comes from more extended regions, which have a less filamentary structure in the image. Our study shows that self-consistent electron temperature models are essential for the calculation of thermal synchrotron radiation and the morphology of the GRRT images. Flux ropes contribute considerable emission at frequencies $ GHz$.

Existence of density inhomogeneity of liquid Te associated with liquid–liquid phase transition

We performed small-angle x-ray scattering measurements of liquid Te using a synchrotron radiation facility and observed maximum scattering intensity near 620 K in the supercooled region (melting temperature 723 K). This indicates that density inhomogeneity exists in liquid Te, and the fact that this temperature coincides with the temperature at which the specific heat, sound velocity, and thermal expansion coefficient reach their maxima means that this density inhomogeneity is the cause of these thermodynamic anomalies. The thermodynamic anomalies in liquid Te had already been shown in the 1980s to be comprehensively explained by the inhomogeneity associated with the continuous liquid–liquid phase transition (LLT), but direct experimental evidence for the existence of the inhomogeneity had not been obtained. The present results, together with those already obtained for mixture systems (Te–Se, Te–Ge), indicate the existence of inhomogeneity associated with LLT in liquid Te systems, and strongly support the model. Recently, similar maximum scattering intensity has also been observed in supercooled liquid water, which exhibits thermodynamic anomalies similar to those of Te, indicating the universality of the inhomogeneous model or LLT scenario to explain the thermodynamics of such ‘anomalous liquids’. Further development of the LLT scenario is expected in near future.

Off-energy operation for the Extremely Brilliant Source at the European Synchrotron Radiation Facility

The European Synchrotron Radiation Facility Extremely Brilliant Source (ESRF-EBS) is the first fourth generation 6 GeV storage ring (SR) light source making use of the hybrid multibend achromat lattice, reaching a natural horizontal emittance of 140 pm rad. Further, reducing the horizontal emittance would provide a more brilliant and a higher quality photon source for the EBS users. One way of achieving this is to operate the SR off-energy. The first approach reduces the electron beam energy by −1%, which gives a 121 pm rad natural horizontal emittance. To fulfill operation requirements, the full ring had to be rematched, including both the quadrupoles and the sextupoles in the linear optics correction. The off-energy settings are then tested in the SR in terms of lifetime, injection efficiency, and operability. Published by the American Physical Society 2024

Fabrication of 3D Polycaprolactone Macrostructures by 3D Electrospinning.

Building 3D electrospun macrostructures and monitoring the biological activities inside them are challenging. In this study, 3D fibrous polycaprolactone (PCL) macrostructures were successfully fabricated using in-house 3D electrospinning. The main factors supporting the 3D self-assembled nanofiber fabrication are the H3PO4 additives, flow rate, and initial distance. The effects of solution concentration, solvent, H3PO4 concentration, flow rate, initial distance, voltage, and nozzle speed on the 3D macrostructures were examined. The optimal conditions of 4 mL/h flow rate, 4 cm initial nozzle-collector distance, 14 kV voltage, and 1 mm/s nozzle speed provided a rapid buildup of cylinder macrostructures with 6 cm of diameter, reaching a final height of 16.18 ± 2.58 mm and a wall thickness of 3.98 ± 1.01 mm on one perimeter with uniform diameter across different sections (1.40 ± 1.10 μm average). Oxygen plasma treatment with 30-50 W for 5 min significantly improved the hydrophilicity of the PCL macrostructures, proving a suitable scaffold for in vitro cell cultures. Additionally, 3D images obtained by synchrotron radiation X-ray tomographic microscopy (SRXTM) presented cell penetration and cell growth within the scaffolds. This breakthrough in 3D electrospinning surpasses current scaffold fabrication limitations, opening new possibilities in various fields.

Revisiting High-energy Polarization from Leptonic and Hadronic Blazar Scenarios

X-ray and MeV polarization can be powerful diagnostics for leptonic and hadronic blazar models. Previous predictions are mostly based on a one-zone framework. However, recent IXPE observations of Mrk 421 and 501 strongly favor a multizone framework. Thus, the leptonic and hadronic polarization predictions need to be revisited. Here we identify two generic radiation transfer effects, namely, double depolarization and energy stratification, that can have an impact on the leptonic and hadronic polarization. We show how they are generalized from previously known multizone effects of the primary electron synchrotron radiation. Under our generic multizone model, the leptonic polarization degree is expected to be much lower than the one-zone prediction, unlikely detectable in most cases. The hadronic polarization degree can reach a value as high as the primary electron synchrotron polarization during simultaneous multiwavelength flares, consistent with the one-zone prediction. Therefore, IXPE and future X-ray and MeV polarimeters such as eXTP, COSI, and AMEGO-X, have good chances to detect hadronic polarization during flares. However, the hadronic polarization cannot be well constrained during the quiescent state. Nonetheless, if some blazar jets possess relatively stable large-scale magnetic structures, as suggested by radio observations, a nontrivial polarization degree may show up for the hadronic model after a very long exposure time (≳1 yr).

Structure heterogeneity in polycrystalline and single-crystal high-nickel cathode materials by synchrotron radiation XAS

Structure heterogeneity in polycrystalline and single-crystal high-nickel cathode materials by synchrotron radiation XAS

Ion beam figuring for X-ray mirrors: history, state-of-the-art and future prospects.

Synchrotron light sources require X-ray optics with extremely demanding accuracy for the surface profile, with less than 100 nrad slope errors and sub-nanometre height errors. Such errors are challenging to achieve for aspheres using traditional polishing methods. However, post-polishing error correction can be performed using techniques such as ion beam figuring (IBF) to improve optics to the desired quality. This work presents a brief overview of the history of IBF, introduces some of the challenges for obtaining such demanding figure errors, and highlights the work done at several in-house IBF facilities at synchrotron light sources worldwide to obtain state-of-the-art optical quality.

Teaching about the birth of synchrotron light: the role of Frascati and a missed opportunity.

The users of synchrotron light are now tens of thousands throughout the world. Paradoxically, many of them do not know much about the early history of their domain. This is regrettable, since education about the initial developments makes it easier to fully understand synchrotron radiation and effectively use its amazing features. Scarcely known, in particular, is the key role of scientists working in Frascati, Italy. Partly based on his personal experiences, the author reports here relevant aspects of this story, including a pioneering French-Italian experiment that started in the early 1960s, and the Frascati contributions in the 1970s and 1980s to the birth of synchrotron light research. Finally, the unwise strategic decisions that prevented Italy from achieving absolute leadership in this domain - in spite of its unique initial advantages - are analyzed.

Confirming the theoretical foundation of steady-state microbunching

Steady-State Microbunching (SSMB) has been proposed as a concept to generate coherent synchrotron radiation at an electron storage ring. SSMB promises to supply kilowatt level average power radiation in the extreme ultraviolet regime, meeting the power level demands for lithography applications that presently cannot be fulfilled by established accelerator technologies. SSMB is under theoretical and experimental study, building on a proof-of-principle (PoP) experiment at the Metrology Light Source which previously showed the viability of the idea. Here we report experimental findings from systematic studies in the ongoing SSMB PoP experiment, where microbunching is generated from an energy modulation imposed by a laser of wavelength 1064 nm. The results confirm the expected dependence of the microbunching process on modulation amplitude and show that the influence of transverse-longitudinal coupling dynamics is as predicted. This confirmation of key parts of the SSMB theory establishes a solid footing for continuing the proof-of-principle efforts towards the goal of constructing a prototype SSMB light source facility.

Inflammation subsequent to mild iron excess differentially alters regional brain iron metabolism, oxidation and neuroinflammation status in mice

Iron dyshomeostasis and neuroinflammation, characteristic features of the aged brain, and exacerbated in neurodegenerative disease, may induce oxidative stress-mediated neurodegeneration. In this study, the effects of potential priming with mild systemic iron injections on subsequent lipopolysaccharide (LPS)-induced inflammation in adult C57Bl/6J mice were examined. After cognitive testing, regional brain tissues were dissected for iron (metal) measurements by total reflection X-ray fluorescence and synchrotron radiation X-Ray fluorescence-based elemental mapping; and iron regulatory, ferroptosis-related, and glia-specific protein analysis, and lipid peroxidation by western blotting. Microglial morphology and astrogliosis were assessed by immunohistochemistry. Iron only treatment enhanced cognitive performance on the novel object location task compared with iron priming and subsequent LPS-induced inflammation. LPS-induced inflammation, with or without iron treatment, attenuated hippocampal heme oxygenase-1 and augmented 4-hydroxynonenal levels. Conversely, in the cortex, elevated ferritin light chain and xCT (light chain of System Xc−) were observed in response to LPS-induced inflammation, without and with iron-priming. Increased microglial branch/process lengths and astrocyte immunoreactivity were also increased by combined iron and LPS in both the hippocampus and cortex. Here, we demonstrate iron priming and subsequent LPS-induced inflammation led to iron dyshomeostasis, compromised antioxidant function, increased lipid peroxidation and altered neuroinflammatory state in a brain region-dependent manner.

In Operando study of Microsupercapacitors with Gel Electrolytes using nano‐beam synchrotron X‐ray diffraction.

Synchrotron radiation X‐ray diffraction (XRD) with nanoscale beam size was used here for in situ and in operando study of micro‐supercapacitors (MSC) with gel electrolyte and MXene Ti3C2Tx electrodes. The electrode structure was characterized as a function of applied voltage and distance from the gap separating electrodes using microscopic cells with cylindrical shape designed for transmission mode XRD. The devices with gel electrolytes based on H2SO4 (with H2O/PVA and DMSO/PVA) showed stable performance with no changes in MXene structure under voltage swaps between positive and negative values. Experiments with KI‐based electrolytes demonstrated changes of MXene structure correlated with decrease of energy storage parameters under conditions of increased operation voltage starting from 0.8V. The best performance of MSC was observed when no changes in MXene structure occur after switch of applied voltage polarity. The changes of inter‐layer distance of Mxene upon swap of applied voltage correlate with decrease of device performance and are undesirable for stable operation of MSC’s. We also tested feasibility of X‐ray fluorescence (XRF) for characterization of electrolyte ion migration in MSCs using 2D element mapping. Irreversible sorption of iodine by MXene was found using XRF mapping of charged electrodes using standard in‐plane MSC device and KI electrolyte.

Runaway electron plateau current profile reconstruction from synchrotron imaging and Ar-II line polarization angle measurements in DIII-D

Abstract Current profile reconstructions are obtained for high current (Ip = 550 kA) post-disruption runaway electron (RE) plateau plasmas in DIII-D. Two novel methods of measuring the RE current profile in high-current RE plateaus are introduced and compared: localization of the q = 2 rational surface using visible synchrotron emission (SE) imaging and the measurement of the polarization angle of line-integrated Ar-II line emission. The two methods are found to be consistent with each other within the data uncertainties. Different simulations of the RE current profile are compared with the measurements: the toroidal fluid RE model is found to best fit the data, within the measurement uncertainties. In addition to introducing two novel methods to measure the RE current profile and validating present simulation capabilities, this work demonstrates that instabilities can grow at q = 2 and q = 1 surfaces without necessarily causing a RE final loss instability. Numerical simulations are also presented to elucidate the role of these instabilities on synchrotron emission.

Synchrotron Phase-Contrast Imaging and Cochlear Otosclerosis A case-report.

Otosclerosis is a bone disorder affecting the labyrinthine capsule that leads to conductive and occasionally sensorineural hearing loss. The etiology of otosclerosis remains unknown; factors such as infection, hormones, inflammation, genetics, and autoimmunity have been discussed. Treatment consists primarily of surgical stapes replacement and cochlear implantation. High-resolution computed tomography (HRCT) is routinely used to visualize bone pathology. In the present study, we used synchrotron radiation phase-contrast imaging (SR-PCI) to examine otosclerosis plaques in a temporal bone for the first time. The primary aim was to study their three-dimensional (3D) outline, vascular interrelationships and connections to the middle ear. A donated ear from a patient with otosclerosis who had undergone partial stapedectomy with insertion of a stapes wire prosthesis was investigated using SR-PCI and compared with a control ear. Otosclerotic lesions were 3D rendered using the composite with shading technique. Scalar opacity and color mapping were adjusted to display volume properties with the removal of bones to enhance surfaces. Vascular bone channels were segmented, and the communications between lesions and the middle ear were established. Fenestral, cochlear, meatal and vestibular lesions were outlined three-dimensionally. Vascular bone channels were found to be frequently connected to the middle ear mucosa, perilabyrinthine air spaces, and facial nerve vessels. Round window lesions partly embedded the cochlear aqueduct which was pathologically narrowed, while the inferior cochlear vein was significantly dilated in its proximal part. Otosclerotic/otospongiotic lesions were imaged for the first time using SR-PCI and 3D rendering. The presence of shunts and abnormal vascular connections to the labyrinth appeared to result in hyper-vascularization, overloading the venous system, and leading to sensorineural hearing loss. We speculate about possible local treatments to alleviate the impact of such critical lesions on the labyrinthine micro-circulation.

In situ investigation on the evolution mechanism of heterogeneous micro-scale structure in potassium-niobate microwave flash sintering

Heterogeneity in the final product of flash sintering is a significant limitation for massive development. Synchrotron radiation computed tomography (SR-CT) was initially used to investigate the in-situ experiment of potassium-niobate (KNbO3) prepared by microwave flash sintering, revealing the temporal evolution of KNbO3 microstructure. The study has revealed the critical role of spatial arrangement between incompact particles and sintered agglomerates in achieving homogeneity in flash-sintered samples. Particles located the angle formed by the sintered agglomerate are more likely to experience electric field concentration, resulting in densification, and the densification rate decreases as the increases of angle size formed by the dense sintered agglomerates. This letter highlights that the presence of particles between sintered agglomerates is a significant factor contributing to heterogeneous sintering. The phenomenon is explained through a combination of experiments and simulation, which holds promise for enhancing the homogeneity of the sintering process.

Enhancement of mineral density and mechanical properties in root caries treated with silver diammine fluoride and glass ionomer cement, with emphasis on silver ion distribution

ObjectivesThis study aimed to measure the distribution of silver ion (Ag+), mineral recovery, and nanohardness in carious lesions and comprehensively evaluate the degree of dentin restoration. MethodsSixty human teeth with root caries were randomly assigned to the control, silver diammine fluoride (SDF) [Safo], and SDF+Glass ionomer cement (GIC) treatment [Safo+Fuji] groups. Micro-computed tomography (CT) was performed at five time points for each sample before/after treatment to evaluate mineral density within and around carious lesions. Three months following treatment, 12 samples were selected for synchrotron radiation X-ray fluorescence analysis to evaluate Ag+ distribution, while 15 samples were selected for nanoindentation. Data were analyzed using Dunnett's T3 test for micro-CT and Wilcoxon rank sum test with Bonferroni correction (p = 0.017) for nanoindentation. The correlation between hardness and mineral change was analyzed using the Spearman rank correlation coefficient. ResultsThe Safo and Safo+Fuji groups showed significantly higher mineral recovery rates than did the control group (p<0.001). In the Safo group, Ag+ accumulated in the deeper layers rather than the superficial layer of caries. In the Safo+Fuji group, Ag+ was found evenly distributed throughout caries, with only a few Ag+ detected in the GIC layer. Hardness in the Safo+Fuji group was significantly higher compared with the Safo group at depths in the range of 10–50 µm. ConclusionIn the presence of GICs, SDF exhibited high remineralization capacity when diffusing throughout carious lesions over time. Combined treatment with SDF and GIC could strengthen root dentin even in the presence of caries. Clinical significanceWe found that combination treatment with SDF and GIC could increase mineral density in caries and improve the hardness of the tooth structure compared with fluoride-based agents alone. These findings might pave the way for future clinical trials to determine the therapeutic potential of nanotechnology-based restorative materials.

In situ/Operando Synchrotron Radiation Analytical Techniques for CO2/CO Reduction Reaction: From Atomic Scales to Mesoscales.

Electrocatalytic carbon dioxide/carbon monoxide reduction reaction (CO(2)RR) has emerged as a prospective and appealing strategy to realize carbon neutrality for manufacturing sustainable chemical products. Developing highly active electrocatalysts and stable devices has been demonstrated as effective approach to enhance the conversion efficiency of CO(2)RR. In order to rationally design electrocatalysts and devices, a comprehensive understanding of the intrinsic structure evolution within catalysts and micro-environment change around electrode interface, particularly under operation conditions, is indispensable. Synchrotron radiation has been recognized as a versatile characterization platform, garnering widespread attention owing to its high brightness, elevated flux, excellent directivity, strong polarization and exceptional stability. This review systematically introduces the applications of synchrotron radiation technologies classified by radiation sources with varying wavelengths in CO(2)RR. By virtue of in situ/operando synchrotron radiationanalytical techniques, we also summarize relevant dynamic evolution processes from electronic structure, atomic configuration, molecular adsorption, crystal lattice and devices, spanning scales from the angstrom to the micrometer. The merits and limitations of diverse synchrotron characterization techniques are summarized, and their applicable scenarios in CO(2)RR are further presented. On the basis of the state-of-the-art fourth-generation synchrotron facilities, a perspective for further deeper understanding of the CO(2)RR process using synchrotron radiation analytical techniques is proposed.

In situ/Operando Synchrotron Radiation Analytical Techniques for CO2/CO Reduction Reaction: From Atomic Scales to Mesoscales

AbstractElectrocatalytic carbon dioxide/carbon monoxide reduction reaction (CO(2)RR) has emerged as a prospective and appealing strategy to realize carbon neutrality for manufacturing sustainable chemical products. Developing highly active electrocatalysts and stable devices has been demonstrated as effective approach to enhance the conversion efficiency of CO(2)RR. In order to rationally design electrocatalysts and devices, a comprehensive understanding of the intrinsic structure evolution within catalysts and micro‐environment change around electrode interface, particularly under operation conditions, is indispensable. Synchrotron radiation has been recognized as a versatile characterization platform, garnering widespread attention owing to its high brightness, elevated flux, excellent directivity, strong polarization and exceptional stability. This review systematically introduces the applications of synchrotron radiation technologies classified by radiation sources with varying wavelengths in CO(2)RR. By virtue of in situ/operando synchrotron radiationanalytical techniques, we also summarize relevant dynamic evolution processes from electronic structure, atomic configuration, molecular adsorption, crystal lattice and devices, spanning scales from the angstrom to the micrometer. The merits and limitations of diverse synchrotron characterization techniques are summarized, and their applicable scenarios in CO(2)RR are further presented. On the basis of the state‐of‐the‐art fourth‐generation synchrotron facilities, a perspective for further deeper understanding of the CO(2)RR process using synchrotron radiation analytical techniques is proposed.