The reaction dynamics of weakly-bound nuclear systems at near-barrier energies is a compelling topic in nuclear physics. This review summarizes decades of experimental work by the Nuclear Reaction Group at the China Institute of Atomic Energy. Using transfer reactions with the distorted wave born approximation and asymptotic normalization coefficient analyses, we confirm the first excited neutron halo (13C) on the β-stability line and identified new halo states in 12B. Total reaction cross-section measurements revealed proton halo nuclei P27 and S29, with core enlargement observed in P27 and P28. We established conditions for halo formation and delineated the proton halo existence region. In two-proton emission studies, we observed He2 cluster emission from highly excited Ne17,18 and S28,29, with S29 being the second such case internationally. In β-delayed decay, we discovered β2p emission in Si22 and determined its mass, observing isospin-symmetry breaking in Mg20, Si22, and S27. Decay schemes for S27 and P26 addressed the Al26 abundance problem. For nuclear interactions, we investigated the He6 optical potential, finding the dispersion relation inapplicable for He6 + Bi209, and developed notch and Bayesian methods to constrain uncertainties. For unstable nuclei, the proton drip-line systems 8B and 17F have been intensively studied via complete kinematics measurements of the 8B + 120Sn and 17F + 58Ni reactions, respectively. The results show that elastic breakup dominates for proton-halo B8, while inelastic breakup prevails for F17, with proton-rich nuclei exhibiting lower breakup probabilities than neutron-halo nuclei due to Coulomb effects. Fusion studies revealed sub-barrier enhancement in F17 + Ni58 from continuum couplings. We propose direct fusion–evaporation measurements with deflection systems integrated with breakup detection to disentangle complete and incomplete fusion channels.

The astrophysical S*(E) factor for the 12C+12C reaction within the Gamow window plays a pivotal role in modeling stellar carbon burning and explosive nucleosynthesis scenarios. However, direct measurements or even simple extrapolations at these energies are severely hindered by Coulomb suppression and the possible presence of narrow resonances. To address this challenge, we performed an indirect measurement of the 12C(16O,ap)23Na reaction at the HI-13 Tandem Accelerator, employing 16O=(12C+a) as the Trojan Horse nucleus. A key innovation of this Trojan Horse Method (THM) study is the implementation of a copper beam-stopper foil, which enabled the detection of spectator particles near 0, the angular region where their yield is maximized under quasi-free kinematics. The S*(E) factor for the 12C(12C,p)23Na reaction in the astrophysically relevant energy range was extracted using the THM formalism based on the DWBA. Our results confirm the presence of resonant structures within the Gamow window around 1.5 MeV in both the p0 and p1 proton channels. No evidence of a hindrance effect is observed in the measured energy range. Without considering the resonance details, the overall trend of our results is qualitatively in reasonable agreement with the THM-Tumino2018 and TTIK2025 data, but differs significantly from the trend of the Modified-THM-Muk2019 data.

Present and future rare isotope accelerator facilities provide new opportunities to explore the structure of unstable nuclei. We report the measurements of the elastic scattering angular distributions of 21Na and 22Na on the doubly magic 40Ca above the Coulomb barrier energies, using high-purity post-accelerated ISOL beams from Beijing Radioactive Ion Beam Facility (BRIF). Angular distributions were measured with a silicon detector telescope array, and relative cross sections were determined with a CaF2 target on Au backing. The data were well reproduced by optical model calculations with Woods–Saxon and USNP potentials, the latter giving better agreement. These results confirm the stable operation and performance of the BRIF ISOL production and post-acceleration system, demonstrate its capability to provide radioactive beams of useful intensity and purity for future investigations of reaction dynamics and astrophysically relevant processes involving proton-rich nuclei, and simultaneously extend proton-rich elastic scattering studies to heavier systems.

The optical potential is a key tool for describing interactions in nuclear collisions and is widely used in studies of nuclear reaction mechanisms. The optical potential is highly sensitive to nuclear structure, thereby leading to distinct characteristics between weakly bound and tightly bound nuclear systems. For weakly bound nuclei such as 6Li, 9Be and 6He, the behavior of the optical potential remains controversial due to insufficient experimental data at near-barrier and deep-barrier energies. In this work, elastic scattering angular distributions for the 6Li+208Pb system are measured at near-barrier and deep-barrier energies. Optical model fitting is employed to extract the optical potential parameters. The results indicate that there is an anomalous threshold anomaly for the optical potential of this system, so the dispersion relation is not applicable. Furthermore, the reaction threshold for the 6Li+208Pb system is determined to be approximately 0.73VB based on deep-barrier data. A systematic analysis is also performed on the reaction thresholds and breakup thresholds of different nuclear systems. In this work the optical potential of the 6Li+208Pb system is measured at near-barrier and deep sub-barrier energies, providing data support for further investigation of the anomalous threshold anomaly. The datasets presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00218.

We present a preliminary design of the Advanced Multi-neutron Detection Array (AMDA). A prototype array was constructed using BC408 plastic scintillators and SiPMs, and its performance was evaluated through cosmic-ray and proton-beam tests. The time resolution of the prototype reached 150 ps. We also developed a neural network-based algorithm for multi-neutron identification, which improved the four-neutron detection efficiency by more than tenfold compared to conventional methods.

The 12C(12C, alpha)20Ne reaction at astrophysical energies is crucial for understanding the carbon burning process in massive star and explosive astrophysical scenarios like Type Ia supernovae and X-ray bursts. However, directly measuring or simply extrapolating its S*(E) factor is extremely challenging due to Coulomb suppression and potential complex resonance structures near the Gamow window (EG = 1.5 +/- 0.3 MeV). The Trojan horse method (THM) can circumvent the Coulomb barrier, providing data within the Gamow window without extrapolation. Strong resonances near 1.5 MeV were previously reported by Tumino et al. (2018) using THM with 14N = (12C (R) d), a result that generated significant interest and debate, underscoring the need for further experimental verification. In this work, we selected 16O = (12C (R) alpha) as the Trojan-horse nucleus due to its lower binding energy, which favors quasi-free reactions. We performed an indirect measurement of 12C(16O, alpha alpha)20Ne at the HI-13 Tandem Accelerator at CIAE. Employing a copper beam-stopper foil, we measured, for the first time in a THM experiment, the spectator alpha-particle within a small angular range around 0 degrees, where the quasi-free mechanism predicts its highest concentration. The S*(E) factor of 12C(12C, alpha)20Ne in the astrophysical energy region was extracted from the measured three-body reaction using THM based on the distorted-wave Born approximation (DWBA). Our results confirm the existence of resonances within the Gamow window around 1.5 MeV in both the alpha 0 and alpha 1 channels. Without considering the details of the resonance structures, the overall trend of our results is qualitatively in reasonable agreement with the THM-Tumino2018 and TTIK2025 data, but differs significantly from the trend of the Modified-THM-Muk2019 data. We observe no evidence for hindrance effect in our results.

The Beijing Radioactive Ion-beam Facility (BRIF), based on the Isotope Separation On-Line (ISOL) technique, consists of a 100 MeV proton cyclotron as the driving accelerator, a two-stage ISOL system for ion separation, a 13-MV tandem accelerator for post-acceleration, a superconducting linac for further boosting beam energies. It is capable of providing ISOL beams in the energy range from 60 to 300 keV, and post-accelerated beams in the energy range from 3 to 10 MeV/u for nuclei with mass numbers of A < 80. For nuclei with A up to 170, energies are still able to reach 3 MeV/u. This facility offers opportunities to address key questions of current interest in nuclear astrophysics, nuclear structure and reactions of unstable nuclei. In this review we present a comprehensive introduction to the BRIF and the typical experimental instruments installed on it, and then summarize current experimental results on unstable Na and Rb isotopes and future plan for development of the BRIF to improve its performance.

A new detector array with a large solid angle coverage for the coincidence measurement of charged fragments was developed to study the breakup reaction mechanisms of weakly bound nuclear systems at energies around the Coulomb barrier. The array has been used to explore the breakup reaction mechanisms of ^6,7 Li + ^209 Bi systems at E_beam = 30, 40, 47 MeV, showing good performance in particle identification and complete kinematic measurements. Based on this, different breakup modes and breakup components were clearly distinguished, and some new breakup modes were discovered, such as ^7 Li → α + t breakup mode in ^6 Li + ^209 Bi system and ^7 Li → ^6 He + p breakup mode in ^7 Li + ^209 Bi system. This array can also be used to explore other breakup reaction mechanisms induced by weakly bound nuclei.

The nuclear potential is a cornerstone in the study of nuclear structures and reactions.Research on the real part of nuclear potential has been well described using various models;however,that on the imaginary part of nuclear potential remains insufficient.This study proposes a novel method to extract the imaginary nuclear potential from the high-precision excitation function of backward quasi-elastic scattering.The typical systems 16O+152,154Sm,184,186W with deformed target nuclei were analyzed.Nuclear imaginary potentials were obtained successfully by fitting the excitation functions within the single-channel and coupled-channel frameworks,respect-ively.A good reproduction at the energy range between sub-and above-barrier energy regions was achieved.Res-ults show long-range imaginary-part potential at a wide energy region covering the Coulomb barrier,consistent with the strong absorption for well-deformed systems.This work is a preliminary attempt to bridge the gap between fu-sion and scattering and extract the deformation parameters in the whole energy range.The subsequent systematic analysis needs to be further improved.

A heavy-ion time-of-flight spectrometer called HiToF, with magnet focusing accomplished by a quadrupole triplet lens, was constructed at the Beijing Tandem Accelerator National Laboratory, mainly for studies of multi-nucleon transfer reactions at energies near the Coulomb barrier. The spectrometer was equipped with a rotating chamber with a diameter of 40 cm and could be rotated over a large angular range from -40^∘ to 160^∘ . The length from the target to the focal plane is 2.7 m, enabling high-precision time-of-flight measurements using two microchannel plate detectors with a 1.9 m apart and a typical time resolution of 120 ps. A multisampling position-sensitive ionization chamber for ΔE-E measurement is placed on the focal plane, which offers a ΔZ/Z resolution of 1/50 . The setup provided a maximum solid angle ΔΩ = 20 msr. An experiment on ^32 S + ^90,94 Zr at a beam energy of 135 MeV was performed to test the performance. The projectile-like ions were identified with a mass resolution of σ = 0.2 amu. The results showed that the HiToF spectrometer is a powerful setup for studying heavy-ion reaction mechanisms at low energies.

In the past three decades, the structural properties and reaction mechanisms of weakly bound nuclei have been one of the hot topics in nuclear physics research. Experimental data on neutron-rich weakly bound nuclei near the barrier energy region, such as He-6 and Be-11, have shown significant Coulomb suppression effects, and the total fusion cross sections have exhibited certain systematic regularities consistent with the trend of universal fusion functions. However, there is a lack of experimental data on proton-rich weakly bound nuclei near the barrier energy region, leading to inconsistent experimental conclusions. For example, the B-8+Si-28 system shows an enhanced trend at the barrier, while the B-8+Ni-58 system exhibits a suppression trend at the barrier, and the F-17+Pb-208 system shows a normal trend, demonstrating different reaction characteristics. This review focuses on the proton drip-line nucleus Be-7, and summarizes the experimental results of the Be-7+Li-7, Be-9, C-12, Al-27, Ni-58, and Pb-208 systems from the perspective of elastic scattering. Currently, there are no abnormal threshold anomalies in the optical potential of Be-7, and no strong Coulomb suppression effects have been observed. In terms of fusion reactions, comparing different systems using universal fusion functions shows good consistency at the barrier, but there is a trend of enhanced cross sections in the near-barrier and sub-barrier energy regions, indicating that the enhancement mechanism in the near-barrier and sub-barrier regions may be related to the Be-7 projectile nucleus, rather than the target nucleus. For breakup reactions, there is a lack of relevant experimental data, and existing measurements show few correlated events and low breakup cross sections, with direct alpha transfer considered as the main mechanism leading to the observed He-3 yield. Currently, there is still a lack of reaction data for Be-7 with medium-heavy target nuclei, where both Coulomb interaction and nuclear interaction play important roles, allowing for the study of coherent effects between the two. We conducted experiments with two sets of large solid-angle silicon detector arrays at the RIBLL1 facility of the Institute of Modern Physics, Chinese Academy of Sciences, studying the interactions of Be-7 projectile nuclei with Sn-120 and Bi-209 target nuclei. The experimental results showed that the Coulomb suppression effects in the angular distributions of quasi-elastic scattering for both systems were not significant, and the coupling of Be-7 breakup continuum states had little impact on quasi-elastic scattering. The continuum discretized coupled-channels (CDCC) method could effectively describe the experimental data, validating the effectiveness of the He-4+He-3 structure. These experimental results provide a comprehensive dataset for the reactions of Be-7 with medium-heavy target nuclei.

The 4H-silicon carbide (SiC) detector has been widely used for detecting charged particles in a strong radiation environment due to its resistance to radiation. The Delta E-E measurement is an important method for particle identification, especially for identifying the atomic number of heavy-ions. However, the existing epitaxial SiC detector has a thick substrate, typically larger than 100 mu m. This dead layer limits the application of SiC in the Delta E-E telescope. In this work, the 4H-SiC substrate was completely removed using the picosecond laser etching process. Benefiting from the stepwise power modulation strategy, the thin films can be free-standing to complete the subsequent processes. Two substrate-free detectors with thicknesses of similar to 17 and 90 mu m were assembled into a Delta E-E telescope. It exhibits a good detection performance. The energy resolution is about 2.1% for Am-241-Pu-239-Cm-244 alpha source. Besides, it has been successfully used in a proton scattering experiment performed at the China Institute of Atomic Energy (CIAE). This work provides a route to fabricate substrate-free 4H-SiC telescopes for detecting low-energy charged-particles.

Fusion excitation functions have been measured for the 16,18O + 50Cr systems at energies near and below the Coulomb barrier, in order to study the positive Q-value two-neutron stripping channel in 18O + 50Cr, wherein 16O + 50Cr was selected as a reference system. The coupling effect of the inelastic excitation states in heavy-ion fusion reactions was conducted through a comparative analysis of the two systems and based on the CCFULL calculations. The subtle under-estimation of the calculated cross sections, by coupled-channels calculations including the 2+ vibrational state of the target nucleus and the 2+ vibrational state of 18O projectile, leaves limited room for the widely accepted positive Q-value 2n-transfer effect at the measured energy-region. Analogous systems of neutron-rich 18O-induced fusion in the literatures show a systematic behavior that positive Q-value two-neutron stripping channel has no remarkable influence on enhancing sub-barrier fusion cross sections.

Nuclear physics has been expanding rapidly to the limits of nuclear stability due to the increase of available rare isotopes[1].The nuclear binding energies of light loosely bound nuclei near the drip-lines are lower than those of stable isotopes located in the β-stability valley.Light loosely bound nuclei could exhibit exo-tic properties,such as neutron halo,neutron skin and two-proton emission.

Physics-Informed Neural Networks(PINNs)have emerged as a powerful tool for solving high-dimen-sional partial differential equations and have demonstrated promising results across various fields of physics and en-gineering.In this paper,we present the first application of PINNs to quantum tunneling in heavy-ion fusion reac-tions.By incorporating the physical laws directly into the neural network's loss function,PINNs enable the accurate solution of the multidimensional Schrödinger equation,whose wavefunction has substantial oscillations.The calcu-lated quantum tunneling probabilities exhibit good agreement with those obtained using the finite element method at the considered near barrier energy region.Furthermore,we demonstrate a significant advantage of the PINN ap-proach to save and fine-tune pre-trained neural networks for related tunneling calculations,thereby enhancing com-putational efficiency and adaptability.

The exploration of reaction dynamics, particularly the breakup and fusion mechanisms of proton drip-line nuclei at energies around the Coulomb barrier, is crucial in the field of nuclear physics. This study reviews experimental investigations on the reactions induced by proton-rich nuclei, ^7 Be, ^8 B, and ^17 F, including elastic scattering and direct and fusion reactions at the near-barrier energies. In particular, we briefly introduce complete kinematic measurements of ^8 B+ ^120 Sn and ^17 F+ ^58 Ni at the energies of interest. Distinct reaction dynamics are observed for proton-rich nuclei compared with neutron-rich nuclei.

12 C + 12 C is the main reaction during core and shell carbon burning in massive stars, however, at temperatures higher than 10 9 K when most of the carbon is depleted and its abundance is lower than 16 O, the 12 C + 16 O fusion can also become relevant. Moreover, 12 C + 16 O reaction can ignite also in the scenario of explosive carbon burning. The astrophysical energy region of interest thus ranges from 3 to 7.2 MeV in the center-of-mass frame. There are various measurements of the cross-section available in the literature, however, they all stop around 4 MeV, making extrapolation necessary at lower energies. To try to solve this uncertainty and corroborate direct measurement the Trojan Horse Method was applied to three-body processes 16 O( 14 N, α 24 Mg) 2 H and 16 O( 14 N, p 27 Al) 2 H to study the 16 O( 12 C, α) 24 Mg and 16 O( 12 C, p) 27 Al reactions.

中国原子能科学研究院核反应团队依托国内外的大科学装置,在重离子熔合-裂变机制、垒下熔合增强机制、奇特核反应机制、奇异结构和奇异衰变方面取得了多项原创性成果.本文对其中的代表性成果进行了简要回顾.主要包括:(1)系统调查了正Q值中子转移的耦合道效应,并提出了自洽的方法评估转移耦合的贡献,发现了异常的同位素效应;(2)提出了用高精度背角准弹散射方法抽取原子核的形变参数,确证了原子核存在十六极形变;(3)提出了用轻带电粒子的替代俘获反应方法,基于此方法给出了关键的239Pu(n,2n)反应截面;(4)系统考察了 sd壳丰质子核奇异衰变谱学,发现了22Si的β缓发双质子衰变模式,并发现镜像核22Si/22O的β衰变中存在极大的同位旋不对称性,同时在26Si中发现了迄今为止最强的同位旋混合态;(5)系统研究了奇特核体系在近垒能区的反应机制,首次给出了实验证据表明经典色散关系不适用于中子晕核6He+209Bi体系,并对质子滴线核8B和17F的反应机制进行了细致考察.本文也对将来基于重离子飞行时间谱仪和北京放射性束流线可能开展的工作进行了展望.

The reaction kinetics of weakly bound nuclei in the nearbarrier energy region is currently one of the hotspots in nuclear physics research.The quasielastic scattering of the 7Be+120Sn system at 48.05 MeV was measured using a large solid angle covered silicon detector array,and its differential cross section was obtained in combination with Monte Carlo simula-tions.Based on the optical model,the angular distributions were fitted by the frequentist method and the Bayesian method,re-spectively.At the forward angles,the two methods give consistent results;at the backward angles,the results of the frequent-ist method show an obvious oscillatory structure,while the results of the Bayesian method are smooth,with an oscillatory up-ward trend near 180°.