Researchers Proposed a Direct-Amplification Enabled Harmonic Generation Free-Electron Laser

Recently, the Free-Electron Laser (FEL) team at the Shanghai Advanced Research Institute (SARI), Chinese Academy of Sciences experimentally demonstrated their independently proposed concept of Direct-Amplification Enabled Harmonic Generation Free-Electron Laser (DEHG-FEL) for the first time, and successfully achieved its lasing and stable operation.

Recently, the Free-Electron Laser (FEL) team at the Shanghai Advanced Research Institute (SARI), Chinese Academy of Sciences experimentally demonstrated their independently proposed concept of Direct-Amplification Enabled Harmonic Generation Free-Electron Laser (DEHG-FEL) for the first time, and successfully achieved its lasing and stable operation.This marks a key milestone toward realizing X-ray FEL sources operating at megahertz (MHz) repetition rates. The results were published in Physical Review Letters and were highlighted as an Editors’ Suggestion.Soft X-ray FELs with high repetition rates hold great promise in cutting-edge research areas such as time-resolved spectroscopy, coherent diffraction imaging, and ultrafast dynamics studies of nanostructures and nanodevices. However, traditional externally seeded FEL schemes typically require ultraviolet seed lasers with peak powers up to ~100 megawatts, limiting their repetition rates to the kilohertz (kHz) range.Figure1 Amplification of seed laser via high-gain FEL process while maintaining its coherence (Image by SARI)SARI’s FEL team has long been dedicated to the development of high-repetition-rate, fully coherent FELs. In previous work, they demonstrated a self-amplification mechanism of coherent energy modulation at the Shanghai Soft X-ray FEL facility (SXFEL) (Phys. Rev. Lett. 126, 084801, 2021).In the present study, by employing a long modulator section, the team directly amplified a weak seed laser through a high-gain FEL process, achieving a powerful and stable modulation laser (Figure 1).During this process, the electron beam acquired sufficient energy modulation. After passing through a dispersive section, coherent microbunching on the scale of optical wavelengths was formed, leading to the generation of fully coherent radiation up to the 12th harmonic.By further amplifying the 7th harmonic to saturation, the team achieved a pulse energy of approximately 160 µJ with an energy stability of 5.5%. Through harmonic cascading, the team successfully generated 16th harmonic output with a spectral bandwidth approaching the Fourier transform limit, indicating excellent longitudinal coherence of the DEHG-FEL (Figure 2).Figure 2 Stable, fully coherent short-wavelength FEL output achieved via harmonic conversion (Image by SARI)DEHG technology enables effective amplification of extremely weak seed laser signals with a simplified system configuration. In principle, it can reduce the required seed laser power by two to three orders of magnitude while delivering stable, controllable, high-harmonic output—making it particularly suitable for high-repetition-rate externally seeded FELs.Moreover, it has the potential to provide solutions for achieving high repetition rates in more advanced two-stage seeding schemes, such as echo-enabled harmonic generation (EEHG). In the future, DEHG could also be integrated with high-order harmonic generation (HHG) technologies to offer new tools for ultrafast spectroscopy, imaging, and materials research in the soft X-ray region.

Shanghai Synchrotron Radiation Facility Deciphers Real-Time Morphology Evolution in All-Polymer Solar Cells During Solvent Vapor "Sauna"

All-polymer solar cells (APSCs) possess excellent material flexibility, solution processability, and thermal stability, offering great potential for lightweight and large-area printed applications in wearable and stretchable devices. A critical factor in achieving high performance is the optimization of active layer morphology, especially the regulation of crystallization and phase separation of the donor. However, the real-time morphological evolution during post-treatment processes such as solvent vapor annealing (SVA) has remained unclear.To address this challenge, a research team led by Prof. YANG Chunming at the Shanghai Advanced Research Institute, Chinese Academy of Sciences established an in situ grazing-incidence X-ray scattering platform for organic solar cells at SSRF beamlines BL16B1 and BL10U1.By combining synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS), in situ ultraviolet-visible (UV–vis) absorption spectroscopy and grazing-incidence small-angle X-ray scattering (GISAXS), they tracked in real time the dynamic morphological changes of blade-coated PM6:PY-IT all-polymer active layers during SVA treatment.This study, for the first time, revealed a three-stage mechanism (swelling-recrystallization-rearrangement), by which SVA regulates the morphology of all-polymer blended films and its correlation with device performance (Figure 1).The related results were published in Advanced Science recently.Figure 1. (a) Schematic diagram of simultaneous in situ GIWAXS and in situ UV–vis measurements during SVA of blade-coated all-polymer solar cells,(b) Illustration of microscopic morphology evolution under different solvent vapors.In situ UV–vis spectroscopy revealed that carbon disulfide (CS2) vapor—a nonpolar solvent with high saturated vapor pressure and low solubility, induced a redshift in the PY-IT absorption peak. Conversely, chloroform (CF), a polar solvent with low saturated vapor pressure and high solubility, triggered a blueshift.This indicates that polar solvents exert a more pronounced effect on the polymer acceptor (PY-IT), driving conformational changes (blueshift) that result in a denser hole transport layer and enhanced hole transport efficiency.In situ GIWAXS analysis further confirmed three characteristic stages in the SVA process includes: solvent swelling, recrystallization, and molecular rearrangement. An appropriate SVA duration helps stabilize the crystalline structure, as evidenced by reduced lattice spacing, increased charge carrier mobility, and optimized phase separation dimensions, ultimately improving the power conversion efficiency (PCE) of the device. However, prolonged SVA can lead to re-swelling during molecular rearrangement, which is detrimental to performance.Pretreatment via thermal annealing (TA) effectively suppresses this unfavorable expansion (Figure 2). GISAXS measurements further investigated nanoscale phase separation behavior. Films subjected with combined TA and SVA of CF exhibited optimal morphology, characterized by the maximum donor coherence length (ξ), the largest acceptor aggregate radius (2Rg), and the greatest acceptor coherence length (η).The TA pretreatment induced increase in PY-IT aggregate size is key to achieving balanced crystallinity and ideal phase separation, promoting efficient charge separation and transport. This work clarified a critical mechanism: SVA with polar solvents primarily optimizes molecular packing, while SVA with nonpolar solvents tends to enhance phase separation.These insights provide a clear strategy for synergistic process-material optimization—such as combining TA with polar solvent SVA—to fabricate high-performance blade-coated devices.Furthermore, the findings lay an important foundation for future exploration of multi-solvent synergistic annealing, precise control of dynamic processes, and the development of environmentally friendly green processing, thereby accelerating the industrialization of large-area flexible APSCs.Figure 2. Evolution of d-spacing and CCL evolution of (OOP)100 peak for blade coated PM6: PY-IT blend films with a) CF, b)TA+ CF, c) CS2, and d) TA+ CS2.<!--!doctype-->

Researchers Found Novel Approach to Low-loading Pt Based Catalyst for PEM Fuel Cell

A research team at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences proposed an entropy-increase assisted anti-sintering concept to fundamentally reduce the surface energy of NPs by increasing the mixing entropy, thus hindering the migration and coalescence of NPs. The research results were published in Advanced Functional Materials in May, 2025.

High-loaded Pt intermetallic compounds (IMCs) present the practical application potential in low-Pt PEM fuel cells while ordering transformation under high temperature inevitably leads to severe sintering of high-density IMC nanoparticles (NPs), thus the decayed oxygen reduction reaction (ORR) performance.Motivated by such a challenge, a research team led by Prof. YANG Hui at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences proposed an entropy-increase assisted anti-sintering concept to fundamentally reduce the surface energy of NPs by increasing the mixing entropy, thus hindering the migration and coalescence of NPs.The research results were published in Advanced Functional Materials in May, 2025.Ex/in situ electron microscopy and density functional theory (DFT) corroborate that the higher the entropy of pristine NPs, the lower the surface energy, the smaller the average size, and the more uniform distribution after annealing.The prepared Pt high-entropy IMC (Pt-HEI@Pt/C) demonstrates high metal loading (40.53 wt.%) and small particle size (≈3.15 nm). The reinforced strain regulation effect of the HEI core on the Pt shell, which optimizes the *OOH adsorption and elevates the energy barrier of Pt dissolution, thus simultaneously enhancing the intrinsic ORR activity and durability.The prepared Pt-HEI@Pt/C catalysts exhibited an excellent ORR activity with mass activity (MA@0.9V, 0.65 A mg−1 Pt) and durability over 20k potential-cycling.Membrane electrode assembly integrated with this catalyst delivers a peak power density of 0.96 W cm−2 and an exceptional stability (12.5% decline in MA) under H2-air condition at 0.1 mgPt cm−2.This study not only offers a new concept to fundamentally inhibit the NPs sintering under high temperature but also provides an ideal approach to synthesize high-loaded and small-sized Pt-IMCs/C catalysts toward the ORR, laying the foundation for the future development of low-Pt fuel cells.Electrocatalytic performance of the prepared Pt-HEI@Pt/C catalysts (Image by SARI)

Researchers Reveal Novel Thermal Conduction Crossover due to Broken Parity in Superlattice

A research team from Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a crossover of thermal conduction with a third-order-like singularity in a Fermi-Pasta-Ulam-Tsingou (FPUT) superlattice. The research results were published in Physical Review E in May 2025.

Parity represents the mirror inversion symmetry in physics. Commonly, interaction parity between atoms is broken in a crystalline solid due to the asymmetric interatomic repulsion. Symmetry breaking often involves a phase transition, however, it is still unclear if there are any comparable behaviors in a crystalline solid due to the broken interaction parity.Motivated by such a challenge, a research team led by Prof. CHEN Jige at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a crossover of thermal conduction with a third-order-like singularity in a Fermi-Pasta-Ulam-Tsingou (FPUT) superlattice.The research results were published in Physical Review E in May 2025.The superlattice is consisted of repeating periodic cells of arithmetically increased cubic nonlinearity. Researchers find that, before a critical point of interaction asymmetry, thermal conduction is cell-length-independent. After crossing the critical point, thermal conduction relies on the unit cell length.The calculation of reflection symmetry and configuration entropy of the atomic displacement reveals a third-order-like singularity at the critical point, which further determines the peculiar dynamics of energy carriers.The result indicates a high-order singularity arising from the broken interaction parity in a crystalline solid and a promising strategy in adjusting phononic superlattice materials. It enlightens our understanding of the critical role of interatomic interaction parity in lattice thermal behaviors since thermal expansion is the most common feature in a crystalline solid.Schematic of the FPUT Superlattice and its complete Hamiltonian. (Image by SARI)

Researchers Unveiled Key Role of Bridge Adsorbed Hydrogen in Efficient Acidic Hydrogen Production

A research team at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences designed a face-centered cubic-Ru nanocrystal modified with Pt atomic chains and unveiled the important role of *Hbridge intermediates adsorbed on Pt-Ru atomic pairs in determining the intrinsic activity of HER.

Proton exchange membrane water electrolysis (PEMWE) has emerged as a promising approach in green hydrogen production, owing to its broad power fluctuation adaptability, rapid dynamic response, and high energy efficiency under elevated current densities, which enable effective integration of intermittent renewable energy sources such as wind and solar power.For hydrogen evolution reaction (HER) in acid, atop and multiple adsorbed hydrogen are key intermediates on Pt-group metal. However, the role of bridge hydrogen intermediate (*Hbridge) is oftenneglectedin experiments.Motivated by this challenge, a research team led by Prof. YANG Hui at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences designed a face-centered cubic-Ru nanocrystal modified with Pt atomic chains and unveiled the important role of *Hbridge intermediates adsorbed on Pt-Ru atomic pairs in determining the intrinsic activity of HER.The research results were published in Advanced Materials.The results of in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy and density functional theory calculations, demonstrate the key role of *Hbridge in enhancing HER catalytic activity and stability. The electrons leap from Pt-Ru pair site to *Hbridge significantly accelerates the Tafel kinetics.For the HER performances evaluation, the developed Pt-Ru(fcc) achieves an ultralow overpotential of ~ 4 mV at a current density of 10 mA cm−2 under 2.0 μgPt cm-2in three-electrode configuration, and the intrinsic activity at 50 mV is 10.6 times higher than that of commercial Pt/C.The PEMWE device integrated by advanced fcc electrocatalyst with ultra-low Pt loadings of only 10 μg cm-2, which is 30 ~ 50 folds lower than that used in current industrial PEMWE systems (300~500 μg cm-2), achieves exceptional activity (1.0 A cm-2 at 1.61 V) and remarkable stability (4.0 μV h-1 degradation rate over 1000 h at 1.0 A cm-2). The PEMWE based 80 μm Gore membrane under identical operating conditions requires only 1.54 and 1.58 V to achieve 1.0 and 1.5 A cm-2. Furthermore, the device exhibits negligible decay during the 240 h fluctuating tests.The identification of the key role of *Hbridge provides mechanistic insights into the activity origin of the Pt–Ru bimetallic catalysts, and opens new avenues for designing next-generation bimetallic catalysts for clean hydrogen energy.Table of Contents (Image by SARI)In situ ATR-SEIRAS of hydrogen intermediate (Image by SARI)The performance of PEMWE (Image by SARI)<!--!doctype-->

Researchers Propose Bit-Cigma: A Zero-Error, Sparsity-Aware Matrix Multiplication Accelerator for AI

A research group from Shanghai Advanced Research Institute of Chinese Academy of Sciences has unveiled Bit-Cigma, a revolutionary generic matric multiplication accelerator hardware architecture that optimizes bit-sparsity, ensures zero-error accuracy, and remodels floating-point computations. The results were published in Feb 2025 in IEEE Transactions on Computers.

Recently, a research group led by Prof. ZHU Yongxin from Shanghai Advanced Research Institute of Chinese Academy of Sciences has unveiled Bit-Cigma, a revolutionary generic matric multiplication accelerator hardware architecture that optimizes bit-sparsity, ensures zero-error accuracy, and remodels floating-point computations.The results were published in Feb 2025 in IEEE Transactions on Computers, a top-tier journal in the field of computer architecture.Matrix multiplication underpins artificial intelligence (AI) and scientific computing, driving processes such as neural network training and complex simulations. These fields demand efficient computing power capable of both floating-point (FP) and quantized integer (QINT) operations with exceptional performance and accuracy.However, the development of efficient matrix multiplication accelerators faces two persistent challenges. First, the inherent bit-level redundancy in binary data representation wastes computational resources and limits computational efficiency. Second, the floating-point exponent matching relies on slow, resource-heavy methods that bottleneck throughput and compromise accuracy.Bit-Cigma is a scalable, bit-level sparsity-aware architecture designed to handle various datatypes while delivering superior performance, accuracy, and efficiency for matrix multiplications across diverse tasks. The researchers proposed the Compact Canonical Signed Digit (CCSD) encoding technique, a streamlined on-chip method that slashes redundant computations by maximizing bit-level sparsity, all at half the cost of traditional approaches. For large matrices, the team devised a segmented approach that splits data into manageable blocks and aligns floating-point exponents dynamically. This ensures pinpoint accuracy and boosts processing speed and throughput without taxing hardware resources.Extensive experiments demonstrate that Bit-Cigma, utilizing CCSD, achieves a performance boost of 3 to 4 times and improves efficiency by over 10 times compared to state-of-the-art FP and QINT accelerators. Additionally, Bit-Cigma achieves zero computational error, a feat not matched by other accelerators.The Bit-Cigma architecture and the CCSD technique pave the way for more efficient, high-performance solutions for generic matrix multiplication. These advancements promise to support a range of applications and set the foundation for future hardware-centric high-performance systems.