Recent advances in photoneutron detection: High-precision measurement of photoneutron cross section data using the LCS source

High-Precision Measurements Resolve Decades-Old Discrepancies 

The ²⁷Al(γ,n)²⁶Al reaction plays a pivotal role in nucleosynthesis within high-energy astrophysical environments, such as supernovae and star cores. However, conflicting experimental results from traditional methods bremsstrahlung and positron annihilation have hindered progress. Using SLEGS’s advanced laser Compton scattering (LCS) γ-ray beams, researchers mapped cross sections at 38 energy points with unprecedented accuracy. The new flat-efficiency detector array minimized systematic errors, enabling direct comparisons with global datasets like TENDL-2021 and resolving discrepancies of up to 50%. 

Innovative Detector Design Enhances Data Reliability 

The study introduced a ³He flat-efficiency detector (FED) with concentric neutron counters embedded in polyethylene moderators. Optimized geometry and shielding achieved uniform detection efficiency (40–42%) across neutron energies, while advanced pulse processing ensured high signal clarity. Geant4 simulations validated the setup’s performance, and calibration with ²⁵²Cf confirmed accuracy within 1.3%.

Implications for Nuclear Data and Astrophysical Models

Results showed strong agreement with TENDL-2021 below 16.3 MeV but highlighted deviations at higher energies, where prior datasets exhibited unphysical oscillations. Integral cross-section ratios revealed discrepancies of 3–28% compared to historical data, underscoring SLEGS’s reliability. These findings refine parameters for nuclear reaction models like the quasiparticle random phase approximation (QRPA), critical for simulating ²⁶Al production in cosmic events. Future work will extend measurements to the ²⁷Al(γ,2n) reaction, further bridging nuclear physics and astrophysics. 

Global Impact and Future Applications  

The SLEGS facility’s success demonstrates China’s leadership in photonuclear research. By addressing data inconsistencies, this work supports safer nuclear energy practices, precise astrophysical simulations, and improved medical isotope production. As global demand for accurate nuclear data grows, advancements in detector technology and beamline precision—such as SLEGS’s 10 keV energy-tuning capability—will drive innovation across scientific and industrial sectors. 

Regarding the data's global structure, this work's dataset highly aligns with TENDL - 2021 data, showing more uniform smoothness, while the oscillations in other datasets poorly match QRPA calculations, especially during the rise of the QRPA ²⁷Al(γ, n)²⁶Al cross section. This work thus significantly benefits nuclear data evaluation and theoretical model parameter optimization.

Dr. Pu Jiao , the author of this article, is a member of the Institute of Particle Physics and Nuclear Physics at Henan Normal University and the Institute of Nuclear Science and Technology of Henan Academy of Sciences. He is affiliated with the research team led by Professor Chunwang Ma, a Distinguished Professor of Henan Province. This team focuses on the exploration of the frontiers of nuclear science and the development of nuclear technologies. It primarily centers on research directions such as nuclear physics and large scientific installations, radiation chemistry, radiochemistry, and biological nuclear technologies, and systematically conducts fundamental, frontier, and applied research in the field of nuclear science and technology.

Data Availability: 

Open datasets are accessible via Science Data Bank at (https://doi.org/10.57760/sciencedb.j00186.00535 ). 

Funding: 

Supported by the National Key R&D Program of China, National Natural Science Foundation, and Natural Science Foundation of Henan Province.  

The complete study is accessible via DOI: 10.1007/s41365-025-01662-y