Experimental Technique

Combining the low divergence of the 4th light source, twin EPUs, chopper modulation and lock-in amplification, high-sensitivity XMCD measurements are achieved. Using ultra-small beam spot down to 3 micrometers with KB mirrors and ferromagnetic resonance technology, XFMR measurements with a phase time resolution of 5 ps are realized. Utilizing a dual-layer cooling system (liquid nitrogen coil shield + thermo-insulation shield + liquid helium), PEEM measurements are performed in a liquid helium temperature (20 K) with a spatial resolution of ~20 nm.

Beamline optics

Superconducting Magnet Endstation

Overview

The beamline is sourced by twin elliptically polarizing undulators (EPU43.5). The twin EPUs can operates in parallel and collinear modes. A plane mirror M1 deflects the beam by 2° to reduce the heat load and cut off the high energy X-rays. The monochromator is a variable-line-spacing plane grating monochromator type, consisting a plane mirror and two different gratings. Monochromatized X-ray beam is switchable into two branches by the ellipsoidal cylindrical mirror M3. The parallel beams is reflected to the exist slit by M3. Then they are reflected by M6 and further focused by KB mirror set (M7&8) to the Superconducting Magnet (SCM) Endstation and Cryo-PEEM Endstation. A chopper is place behind the exist slit to make the parallel beams alternately illuminating the SCM Endstation. The beam sizes at the SCM Endstation and PEEM Endstation are 200×40 m and 26×53 m. When M3 removed from optical path, the collinear beams are reflected and focused by KB mirror set (M4&5) to the Vector Magnet (VM) Endstation. The beam sizes at the VM Endstation is  3×3 m.

Key Performance

Experimental End-station

A-Branch: SCM-XMCD

Key Performance

Overview

Branch A is a SCM-XMCD end-station with the X-ray beam energy ranging from 250 eV to 2000 eV. Equipped with a superconducting magnetic filed of (9T or 2T, along or perpendicular to the incoming x-ray beam ), this end-station is designed to measure untra-weak magnetism of quantum materials.  

I. Load-lock 

  Up to 3 sample holders can be loaded (up to 4 samples/holder )

II. Main chamber

   X-rays with variable polarization (LH(0), LV(90), CR,CL)

   Beam polarization switch with high speed choppers (up to 1 KHz)

   In-situ multi-field environment (electric filed, stress)

   Different signal detection mode:  TEY， FY， Transmission

A-Branch: Cryo-PEEM

Key Performance

Overview

Cryo-PEEM endstation at BL04 beamline is characterized with a LHe manipulator offering a low temperature of 20 K for the sample imaging. A SR200 energy analyzer is equipped to gain an energy resolution less than 0.1 eV at the spectroscopic real space imaging mode. This endstation is dedicated to spatially resolve the chemical, electronic, and magnetic properties of novel magnetic and quantum materials with high resolution and elemental specificity. 

I. Loadlock 

  Up to 4 sample holders can be loaded to the parking chamber.

II. Preparation chamber

  Sample can be prepared or treated with sputtering and annealing up to 1200 K as well as cleaved in vacuum;

  Sputter gun; RHEED; 2 ports available for evaporators;  gas doser as required;    

III. Analysis chamber

　2 ports for evaporator installation; 

    LHe manipulator

    e-gun and mercury light source

    LEEM/PEEM/SPEPEEM/MEM/ARPES imaging modes

B-Branch: Vector Magnet Endstation

Key performance

Overview

Branch B is a vector magnet endstation, equipped with a vectorial magnetic field up to 0.9 T, a loadlock, a X-ray ferromagnetic resonance (XFMR) manipulator and XAS/XMCD/XMLD manipulator. This vector magnet endstation is designed to measure small-size spintronic device with probing spot size of 3μm ×3μm, ultrafast GHz magnetic dynamic process and spin current/orbital current transmission.

Ⅰ. Loadlock

Up to 6 samples can be loaded  (flag-type sample plate)

Ⅱ. XFMR manipulator

Frequency range: 0.5GHz-8GHz (Integer multiple of 0.5GHz)

Field of view: 500μm aperture, LY mode and FY mode, transverse FMR, sensitive to phase of precession

Ⅲ. XAS/XMCD/XMLD manipulator

Sample positions: 2 TEY and 1 LY

Science

Scientific Scope 1：This capability enables the quantitative measurement of weak magnetic signals in spintronic materials, empowered by a system that integrates parallel twin EPUs, beamline choppers, and lock-in amplification to enhance detection sensitivity by ~100x. The core aim is to build a bridge between microscopic properties (orbital/spin magnetic moments and local atomic/electronic structure) and macroscopic magnetic behavior. These insights are critical for laying the physical groundwork for intelligent material design.

Scientific Scope 2：Leveraging the 3-μm micro-focus capability of KB mirrors and the 5-ps phase-temporal resolution of XFMR, this platform enables temporal- and spatial-resolved  investigations of spin currents and spin waves in spin-orbit torque (SOT) and other prototype devices. These advances provide a critical tool for probing underlying mechanisms, such as spin current propagation (via coherent or thermal magnons) and the boundary conditions governing spin wave quantum effects.

Scientific Scope 3：The capability sample environment at liquid-helium temperature via dual-cooling technology, coupled with 20-nm spatial resolution of PEEM, allows this endstation to conduct magnetic domain structure imaging and spectroscopic mapping on emerging materials including 2D magnetic topological materials, their heterostructures and altermagnets, thereby providing a foundation for understanding their novel magnetic properties.

People

Useful Link

Related beamlines:

XMCD beamlines:

https://www.nsrl.ustc.edu.cn/10957/list.htm

https://www.helmholtz-berlin.de/pubbin/igama_output?modus=einzel&sprache=en&gid=1969&typoid=76454

PEEM beamlines:

https://www.maxiv.lu.se/beamlines-accelerators/beamlines/maxpeem/

https://sites.google.com/lbl.gov/bl11-peem3-als/home

Experimental Technique

Beamline optics

Overview

This beamline, powered by the Linear Polarizing Undulator (LPU), supports in-situ soft X-ray spectroscopy and scattering experiments across 180-2500 eV with a resolution of 15000@244.4 eV and optimized photon flux. It features an SX700 monochromator with 400/800/1200 l/mm dual gratings and precision M1-M6 mirrors for beam splitting and focusing. The main line focuses at 63.5 m for the Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAPA) endstation, while the branch line focuses at 69.0 m for the in-situ photon-in photon-out spectroscopy (MARS) endstation, both utilizing a 1° grazing incidence design. Enhanced by water cooling and radiation protection, the system ensures high resolution, high flux, and reliable performance for both stations.

Key Performance

Experimental Endstation

A-Branch: NAPA

Key Performance

Overview

Branch A (NAPA) is a Near Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) endstation optimized for in-situ investigations of solid-gas phases under diverse atmospheric and reaction conditions. Equipped with a custom-designed four-stage differential pumping system featuring a Si3N4 window (available), it enables vacumm transition between the KB chamber and the analysis chamber. This endstation aims to expand the application range of APXPS through the design of rapidly switchable small chambers, and covers a broad X-ray energy range from 180 eV to 2500 eV—facilitating comprehensive surface characterization.

I. Preparation chamber

  -6 samples can be loaded (flag-type sample plate)

  -sample can be treated between 150 K to 1300 K;

  -Argon sputtering;

  -evaporator positions and ports for user equipment available;

II. Switchable chamber

  -small volume and rapidly switchable, customized according to users

 -Integrated laser heating and resistance heating sample holder, with a temperature range of 300 K to 1300 K

- 6 gas lines equipped with individual mass flow controllers (MFCs) 

III. UHV chamber

　Traditional surface science analysis in high vacuum under 150~1300 K.

B-Branch: MARS

Key Performance

Overview

Branch B is an in-situ photon-in photon-out spectroscopy endstation (MARS), designed to collect X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), and resonant inelastic X-ray scattering (RIXS) pectroscopy . This suite of techniques probes both unoccupied and occupied electronic structures, as well as elementary excitations—including crystal field splitting, charge transfer, and excitations related to spin, charge, orbital, and lattice degrees of freedom. The endstation operates over a broad X-ray beam energy range from 180 eV to 1800 eV and is equipped with in-situ capabilities, enabling detailed investigation of electronic structure and dynamics in complex materials.

I. Loadlock 

   Up to 20 samples can be loaded (flag-type sample plate);

II. Prepare chamber

   sample can be heated up to 1200 K;

   4 evaporator positions available once requested;

III. Main chamber

　 In-situ atmosphere up to 1 bar maximum;

IV. Spectrometer

      30 meV energy resolution and 3 um spatial resolution。

Science

Scientific Scope 1： Utilizing Resonant Inelastic X-ray Scattering (RIXS) for in-situ/operando investigations of alkali-ion battery systems enables comprehensive probing of electronic structure evolution during charge-discharge processes. This capability is crucial for tracking dynamic changes in redox-active transition metal centers and oxygen states, providing insights into charge compensation mechanisms and structural stability. Furthermore, it allows for the identification of intermediate phases and the quantification of electronic structure modifications at different states of charge, offering a deeper understanding of degradation pathways. Finally, RIXS is indispensable for resolving the interplay between electronic and structural dynamics in working battery materials, bridging the gap between theoretical predictions and experimental observations of energy storage mechanisms.

Scientific Scope 2： Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) enables in-situ investigation of reaction gas adsorption mechanisms on model catalyst surfaces under varying pressure conditions. This technique provides atomic-level insights into the dynamic interplay between surface adsorbates and catalytic active sites, revealing pressure-dependent adsorption configurations and reaction intermediates. By monitoring changes in chemical states and binding energies of surface species, NAP-XPS elucidates the influence of pressure on adsorption kinetics and surface coverage. Furthermore, it allows for the identification of critical pressure thresholds that govern catalytic activity and selectivity, offering a comprehensive understanding of the structure-activity relationship in reaction gas adsorption process under realistic operating conditions.

Scientific Scope 3： NAP-XPS employs tunable energies and micro-beams to study material composition and electronic structure across regions and depths, enabling spatial resolution and subsurface insights under near-ambient conditions.

Scientific Scope 4： In-situ RIXS probes photoelectrocatalytic reactions, revealing dynamic electronic changes, reaction intermediates, and charge-lattice interactions, while identifying efficiency and stability factors.

People

Useful Link

Related beamlines:

RIXS beamlines:

http://e-ssrf.sari.ac.cn/beamlines_2024/sr_72267/beamline_maps/bl09u/xzjs/

https://www.diamond.ac.uk/Instruments/Techniques/Scattering/RIXS.html

https://www.maxiv.lu.se/beamlines-accelerators/beamlines/veritas/

NAP-XPS beamlines:

https://www.maxiv.lu.se/beamlines-accelerators/beamlines/hippie/

https://www.helmholtz-berlin.de/pubbin/igama_output?modus=einzel&gid=1671&sprache=en

https://www.specs-group.com/specs/products/detail/nap-xps-system-with-spm-and-irras/

https://www.cells.es/en/instruments/beamlines/bl15-3sbar

Experimental Technique

Ptychographic Coherent Diffraction Imaging (Ptychography)

Scanning transmission x-ray microscopy (STXM)

Low-energy x-ray fluorescence (LE-XRF)

Spectro-microscopy 

TEM-compatible imaging

Beamline optics

Overview

The beamline is sourced by an elliptically polarizing undulator (EPU46). A plane mirror (M1) collects the diverging beam from the undulator and deflects it by 2° to reduce heat load and filter out high energy X-rays. The monochromator is a Plane Grating Monochromator (PGM), consisting a plane mirror (M2) and three different variable-line-spacing (VLS) gratings optimized for varied energy ranges, revolving powers and photon fluxes. The monochromator energy-disperses the X-ray, which is then focused vertically by the VLS gratings. The monochromatized X-ray beam is horizontal focused the ellipsoidal mirror (M3) to the exist slit. At the endstation, the X-ray beam is refocused using a zone plate (ZP) to some specific size (such as 25, 45, 70, 100 nm) for the experiments.

Key Performance

Experimental Endstation

Key Performance

Overview

An endstation designed for soft X-ray spectro-nanoscopy, integrates multiple techniques and operational modes, incorporating piezoelectric stages and a laser interferometer. 

Techniques: Ptychography, STXM, LE-XRF

Operation modes: 2D/3D imaging; TEM compatible 3D cryogenic imaging

Detectors: sCMOS, PD/APD, 4 channel-SDD, channeltron

Science

To investigate the inhomogeneous distribution of chemical elements with different valence states, and to reveal non-uniform orientations of electron bonds and spins. 

Scope1：

To capture static and dynamic images of ion transfer and valence evolution in energy and catalysis processes, such as the dynamic evolution of the electrode-electrolyte interface layer in all-solid-state batteries during fabrication and operation.

Scope2：

To perform tomography on composite materials composed by light elements using spectral imaging with element-, valence- or polarization-dependent X-ray resonant scattering. Examples include analyzing the morphology of semiconductor hetero-junctions in organic photovoltaic, artificial skin, etc.

Scope3：

To enable high-contrast and high-resolution imaging of frozen biological cells within the soft X-ray water window. Multimodal imaging combined with SEM, TEM and  Super-Resolution Fluorescence Imaging.

People

Useful Link

Related beamlines:

https://sm.lightsource.ca/

https://als.lbl.gov/beamlines/7-0-1-2/

https://www.maxiv.lu.se/beamlines-accelerators/beamlines/softimax/

https://www.helmholtz-berlin.de/pubbin/igama_output?modus=einzel&sprache=en&gid=1884

https://www.elettra.eu/elettra-beamlines/twinmic.html

https://www.diamond.ac.uk/Instruments/Imaging-and-Microscopy/I08.html

Experimental Technique

High flux tender in-situ/operando X-ray spectroscopy beamline specializes in (ambient pressure) X-ray photoelectron spectroscopy (XPS/APXPS) and X-ray absorption/Emission spectroscopy (XAS/XES). Specifically designed with a tender X-ray energy range and a milli- to the micro-scale beam spot, this beamline focuses on in-situ/operando characterization of dynamic interfaces under real working conditions in batteries, catalysis, chips, and other devices.

Experimental Technique

Beamline optics

The beamline is sourced by a planar hybrid in-vacuum undulator (IVU20.7) with an incident photon energy range of 770-10000 eV. A cylindrical mirror (M1) collects and focuses the divergent beam from the undulator. Considering the broad energy range, two types of monochromators are employed: a plane grating monochromator (PGM) and a double-crystal monochromator (DCM). The PGM consists of a plane mirror (M2) and a variable line spacing (VLS) grating, while the DCM is equipped with Si(111) and Si(220) crystals. The monochromatized X-ray beam is then focused onto the exit slit by a toroidal mirror (M3). The X-ray beam is subsequently refocused to a sub-micrometer spot size by a set of Kirkpatrick–Baez (KB) mirrors to meet the small-spot requirements of the HOPE endstation. Alternatively, the beam can be shaped into a millimeter-scale spot for the HOPE endstation using toroidal mirrors (M3/M4) in combination with a cylindrical mirror (HFM). In addition, the X-rays are also focused by M3 and M4 onto the TEA and IDEA experimental stations, respectively.

Experimental Endstation

The BL08 beamline has three experimental endstations—HOPE, TEA, and IDEA—capable of performing X-ray spectroscopies including HAXPES, APXPS, XAS, and XES. On this basis, a variety of in situ/operando characterizations can also be carried out, meeting the research needs across multiple fields.

Science

A mm-scale large beam spot combined with XPS enables rapid quality screening of non-uniform samples, meeting the characterization needs of the semiconductor field. In addition, for research systems such as quantum materials, it allows probing of electronic hybridization behaviors across surface-subsurface-bulk regions.

Non-metallic elements like P, S, Cl, and K: Life substance, macromolecule, geochemical cycle

Na, Mg, Al, Si, Ca: Optoelectronic devices, minerals, and ceramic metallurgy

Transition metals like Ti, Cu, Ni, Ru, Rh, and Pd: Catalytic materials, energy storage materials. 

Rare earth elements, La series and Ac series: Magnetic materials, high entropy materials

Radioactive elements like U, Th, and Ra: Important materials in military and national defense.

Tender APXPS enables the probing of solid–gas, solid–liquid, and solid–liquid–gas three phase interfaces. For solid–gas systems, the TEA endstation allows in situ measurements under high-pressure conditions up to 100 mbar and even 1 bar. For complex solid–liquid interfaces in electrochemical systems, the TEA supports in situ/operando studies of solid–liquid and solid–liquid–gas interfaces under applied electric fields, effectively filling a critical gap in the field of electrochemical research.

People

Useful Link

Related beamlines:

Beamlines:

http://e-ssrf.sari.ac.cn/beamlines_2024/sr_72267/beamline_maps/bl09u/xzjs/

https://photon-science.desy.de/facilities/petra_iii/beamlines/p04_xuv_beamline/index_eng.html

XPS beamlines:

https://als.lbl.gov/beamlines/9-3-1/

https://als.lbl.gov/beamlines/11-0-1-1/

https://als.lbl.gov/beamlines/9-3-2/#SoftX-rayAPXPS

https://www.diamond.ac.uk/Instruments/Structures-and-Surfaces/B07.html

http://e-ssrf.sari.ac.cn/beamlines_2024/sr_72267/beamline_maps/bl02b/xzjs/

https://www.synchrotron-soleil.fr/en/beamlines

Experimental Technique

The Tender X-ray  Microscopic Spectral Imaging beamline is optimized for the tender X-ray energy range and features both ptychographic and full-field transmission imaging modes. It provides a powerful detection and imaging tool for addressing challenging and critically needed scientific issues in areas such as semiconductor chips, biology, and energy sciences.

Beamline optics

Key Performance

Overview

After the beam is exit from the sawtooth wall, a white light slit is set to limit the divergence angle of the beam incident on the monochromator. It is then collimated by a front-end mirror, with a source divergence angle of 30-40 μrad. A liquid-nitrogen-cooled double-crystal monochromator is placed 43 m away from the source point, where the full width at half maximum (FWHM) beam size at the monochromator position is approximately 1.5 mm. The double-crystal monochromator uses Si(111) crystals to meet the requirements for the energy range and energy resolution. To cover the K-absorption edge of phosphorus, the energy range is selected from 2.1 to 10.0 keV. An offset of 20 mm is chosen. Finally, two vertically and horizontally arranged cylindrical mirrors focus the beam at the exit slit2 to generate a secondary source point. The focused beam exhibits nearly equal divergence in the horizontal and vertical directions, forming a defined illumination spot at the entrance of the optical components in the experimental endstation. 

Experimental Endstation

Key Performance

Overview

The Tender X-ray  Microscopic Spectral Imaging beamline has two imaging systems, ptychography and full-field TXM system, which can carry out three-dimensional nanostructure imaging and spectroscopic imaging.

I. Sample Loader and Gripper

Up to 4 samples can be loaded at a time and maintained in a cryogenic state

II. Ptychography System

Hybrid photon counting X-ray detectors;

High-resolution lensless scanning imaging

III. Full-field Transmission X-ray Microscopy System

Scintillator optically coupled to a dedicated sCMOS;

3D nanostructure imaging and spectroscopic imaging base on X-ray optics such as zone plate

Science

Scientific Scope 1：Ptychography has been applied to the research and detection of chip structures. This technology can reconstruct the internal structure based on the diffracted data of the chip structure without damage, which can be used to find deviations between chip manufacturing and design and discover possible hardware backdoors in the chip.

Scientific Scope 2： The energy range of BL09 spans 2.1–10 keV, encompassing the K-absorption edges of elements such as phosphorus, sulfur, chlorine, calcium, titanium, and manganese—elements closely related to environmental pollution, energy catalysis, agricultural ecology, and life sciences. Spectroscopic microimaging techniques can reveal three-dimensional structural changes in samples, along with the spatial distribution and valence state evolution of these elements.

Scientific Scope 3：The high-brightness characteristics of the fourth-generation diffraction-limited ring light source can significantly enhance imaging temporal resolution, enabling in-situ/operando microspectroscopic imaging of batteries and research into nanomaterial growth.

Scientific Scope 4：Cellular fibrosis is a core mechanism of aging and related diseases , involving dysregulation of various fundamental life activities. Therefore, deciphering the mechanisms of cellular fibrosis will contribute to revealing the fundamental principles of life activities.

Imaging technology of BL09 enables cross-scale (10 nm - 10 µm), in situ, and three-dimensional non-destructive cellular imaging. It allows multi-scale (molecular-subcellular structure-cellular) observation, deciphering the intricate interaction networks among biomacromolecules, metabolites, subcellular structures, and other multi-scale, multi-system components.

People

Useful Link

Related beamlines:

Ptychography beamlines:

https://www.psi.ch/en/sls/csaxs

https://www.aps.anl.gov/Microscopy/Beamlines/2-ID-D

https://www.maxiv.lu.se/beamlines-accelerators/beamlines/nanomax/

Full-field transmitted tender X-ray imaging beamlines:

https://www.bnl.gov/nsls2/beamlines/beamline.php?r=18-ID

https://www-ssrl.slac.stanford.edu/content/experimental-stations/bl6-2c

http://e-ssrf.sari.ac.cn/beamlines_2024/sr_72267/beamline_maps/bl18b/xzjs/

https://english.ihep.cas.cn/heps/fa/bl/202112/t20211222_295082.html

Experimental Technique

Wavefront sensing, Reflectivity, Ptychography, High energy resolution measurement (Mach-Zehnder interferometer), SR thermal power measurement, visible light measurement for mirror under thermal condition

The TEST beamline is dedicated to the in-house research for soft X-ray optics and SR instrumentation. It can also support detector calibration and early-stage tests for advanced experimental techniques. Currently, one of the beamline endstations supports a new experimental technique using ptychography for quantum materials research.

Beamline optics

Overview

The beamline is sourced by a linear polarization undulator (LPU38). It has two branches, namely, the mono beam branch and the white/pink beam branch. The mono beam branch uses the cPGM layout, has two gratings with energy resolving power of 100k @400 eV and 5k @ 867 eV. Endstation 3 at the end of the mono branch holds the Mach-Zehnder interferometer used to measure the ultra high-energy resolving power from the monochromator. It also supports the ptychographic characterization of quantum materials. The white/pink beam branch holds two endstations. One is for thermal management research on SR instrumentation, the other is for soft X-ray optics research. The beam directly from the source incident on the endstation for thermal management research. It then goes through a heat load chopper and two harmonic rejection mirrors before it reaches the endstation for X-ray optics research. The beam (ranging from 250 eV to 1000 eV) with the intrinsic bandwidth is used for this endstation. 

Endstation for thermal management research

Overview

The endstation for thermal management research aims to support the thermal management for the in-houses development of SR instrumentation. It provides various sensors and detectors to probe the behaviour of the optical element (mainly mirror) with the shine of white beam. Visible light interferometer is placed outside the chamber to detector the change of the surface topography, infrared camera is used to monitor the temperature on the optical surface. An in-house developed thermal power meter is also installed to measure the direct and reflected thermal power from the source.  

Key Equipment

Endstation for X-ray optics research

Overview

The endstation for X-ray optics research receives the attenuated and filtered fundamental-energy beam for in-house soft X-ray optics research. The beam is attenuated by a heat load chopper. The harmonic rejection mirrors absorb the higher harmonic beam as well as attenuate the incident beam. The endstation works on the fundamental energy ranging from 250 eV to 1000 eV. The bandwidth is the intrinsic value (~1%) from the LPU38. 

Key Parameters

Mach-Zehnder interferometer

Overview

The Mach-Zehnder interferometer is placed after the slit (~64 m) for the mono beam. Its main task is to measure the high energy resolving power from the grating monochromator. 

Key Parameters

Science

Scientific Scope 1： The TEST beamline aims to support the in-house development of SR instrumentation. The endstation for thermal management research is built to investigate the cooling schemes for the optical elements. It can help to tackle the ever-increasing thermal problem when the storage ring goes to diffraction-limited. The endstation for X-ray optics research provides an experimental chamber to test the in-house developed instrument, such as the bending mirror. By combining the various wavefront sensing techniques, we can obtain the online and at-wavelength feedback for the test of the instrumentation. 

Scientific Scope 2： The other focus for the TEST beamline is to support the research on soft X-ray optics. The endstation for X-ray optics research is dedicated to this. It provides an experimental chamber to develop the various wavefront sensing techniques. By using these techniques helps to devise all kinds of schemes for wavefront correction. The novel optics designed for advanced experimental methods can also be tested in this beamline.

People

Useful Link

Related beamlines:

TEST beamlines:

https://ssrf.sari.ac.cn/dkxzz/tbfs/gsxz_gb/xzdl_tbfs/bl09b/xzjs/

https://english.ihep.cas.cn/heps/fa/bl/202112/t20211222_295080.html