Academician ZHANG Huanqiao is an outstanding scientist cultivated by the new China in the 1950s. The impoverished and weak war environment of the old China and the hardship era of the new China have nurtured his patriotic determination to serve his motherland. He adhered to the frontline of scientific research and devoted himself wholeheartedly to it. His research fields spanned neutron physics, fission physics and heavy-ion nuclear physics, and he has achieved excellent results under difficult conditions. He committed himself to the country and measured the urgently needed nuclear data to cooperate with nuclear weapon development. He is rigorous and realistic, and repeatedly verifies the experimental results to ensure accuracy. He dares to take the lead and constantly delves into new research fields. All his actions reflect a silent loyalty and love for his motherland and science. He is an inheritor and speaker of the older generation scientists' spirit, and a microcosm of the scientist's spirit and the development of science and technology in the new China. We write this article for sharing on the occasion of academician ZHANG Huanqiao's 90th birthday.

Cluster structures can be stable in the interior of atomic nuclei. The study of α-cluster structure of atomic nuclei and its effects are important topics in nuclear physics as well as astrophysics. In the past few decades, cluster structure effects in atomic nuclei have been much studied for heavy-ion nuclear reactions. This paper summarizes the authors' studies on the α-cluster structure effects on nuclei in nuclear reactions and relativistic heavy-ion collisions. For example, the cluster structure of atomic nuclei has been studied through giant resonances of atomic nuclei. The cluster structure of the nucleus is studied through the emission and correlation of particles (including neutrons, protons, and photons) in nuclear reactions and through collective flows. We extend the cluster effect of atomic nuclei to relativistic heavy-ion collisions, e.g., to the study of collective flows and their rise and fall, the HBT (Hanbury Brown and Twiss) correlation, multiplicity correlations, the dihadron azimuthal correlation, and electromagnetic fields.

The first radioactive ion beam line, GIRAFFE, has been built at the CIAE HI-13 tandem accelerator in China. A total of eleven types of radioactive ion beam, including 6He, 7Be, and 8Li, have been generated. Several significant reactions in nuclear astrophysics have been indirectly measured via transfer reactions, and research on nuclear structure, relevant to nuclear astrophysics, has been performed using charge exchange reactions and thick-target experimental methods. A series of single nucleon or α cluster transfer reactions have been measured using a Q3D magnetic spectrometer, and the astrophysical S-factors and reaction rates for essential reactions have been obtained. The obtained results serve as a crucial experimental foundation for research involving element abundance and celestial body models.

Nuclear data, especially neutron nuclear data, forms the foundation of national defense, nuclear energy development, and the applications of nuclear technology. It also plays a critical role in fundamental nuclear physics research. The quality of nuclear data directly impacts the effectiveness, safety, reliability, and economy of related devices and products. Experimental data serves as the foundation for developing theoretical models and nuclear data libraries. Therefore, experimental research holds a paramount position in nuclear data research. The experimental research on nuclear data in China commenced in the mid-1950s and has achieved fruitful results after decades of development. In this article, we provide a brief overview of the progress made in experimental research on nuclear data in China and outline potential future advancements.

The atomic nucleus, governed by short-range nuclear force, is a quantum many-body system that plays a vital role in the visible energy-mass dynamics of the universe and significantly influences the sustenance, development of society, and the security of nations. There have been numerous discoveries in the past decades concerning exotic structures and properties of short-lived nuclei. These findings have sparked breakthroughs in our understanding of nuclear structures and have given rise to a new field called radioactive ion beam physics, which focuses on the study of unstable nuclei. For more than 30 years, the Beijing Tandem-Accelerator Nuclear-Physics National Laboratory has provided a basic research platform for low-energy nuclear physics experiments. The experimental nuclear physics team at Peking University has continuously developed a dedicated experimental apparatus, conducted a series of physics experiments at the Beijing HI-13 tandem accelerator, and achieved important results related to exotic nuclear structures. In this article, we present several notable experimental achievements of our team at the HI-13 accelerator. These include the investigation of the shape evolution of germanium isotopes (around A=70) using in-beam γ-spectroscopy, the exploration of cluster structures in light neutron-rich nuclei through direct nuclear reactions, and the development and commissioning of collinear laser spectroscopy experiments at the Beijing Radioactive Ion-beam Facility.

The HI-13 tandem accelerator, located at the Beijing Tandem Accelerator National Laboratory, has been in operation for 35 years. To ensure the continued performance of the accelerator, the operation and maintenance team has prioritized focus on various aspects. The operation team conducted research that involved developing key components, cultivating a high-quality operational team, improving the machine time efficiency, and increasing the participation of users outside the China Institute of Atomic Energy (CIAE). The primary emphasis has been on developing key components and upgrading subsystems. These efforts have successfully maintained and improved the accelerator's performance, ensuring its safe and stable operation. Finally, the paper alse discusses the challenges faced by tandem accelerators and presents future development plans.

Through the use of the accelerator facilities at home and abroad, the nuclear reaction group of the China Institute of Atomic Energy has made many remarkable achievements in the study of fusion-fission dynamics, fusion-enhancement mechanisms at sub-barrier energies, reaction dynamics induced by exotic nuclei, and the related exotic nuclear structure and proton decay. In this study, some representative achievements are reviewed briefly. (1) The fusion mechanisms at near-barrier energies were investigated systematically, and a self-consistent method to evaluate the coupled-channel effects was proposed. (2) Nuclear deformation parameters were extracted from backward quasi-elastic scattering, which offered evidence for hexadecapole shapes. (3) A surrogate capture method was developed, based on which the first 239Pu(n,2n) excitation function developed in China was derived. (4) Systematic studies of exotic decay spectroscopies for proton-rich nuclei in the sd-shell were performed, following which a β2p decay of 22Si and a large isospin-asymmetry decay were discovered, and a strongly isospin-mixed doublet in 26Si was revealed. (5) Systematic studies of reaction mechanisms induced by exotic nuclei at energies close to the Coulomb barrier were performed, providing evidence for the failure of the dispersion relation in the optical potential of 6He+209Bi, and the reaction dynamics of proton drip-line nuclei of 8B and 17F were investigated. Future research based on the new HiTOF and BRIF facilities is discussed as well.

Aerospace integrated circuits represent core components of space electronic systems, and anti-radiation hardening is a key technology to ensure the reliable operation of aerospace integrated circuits in the space domain. As the feature sizes of integrated circuits shrink to the nanometer scale, the single-event effect gradually becomes the most critical factor limiting the radiation-hardened performance level of aerospace integrated circuits. In this study, radiation hardened by design is utilized as a method to develop radiation-hardened performance. Based on single-event radiation tests on a heavy ion accelerator, new methods are proposed for the single-event test evaluation of new processes and devices. Consequently, new technique development and radiation effect law research are also undertaken. The effectiveness of the design hardening technology is evaluated, and a single-event radiation damage mechanism is discovered. The proposed technology provides key support for the production of high-reliability and long-lifetime aerospace integrated circuit products.

BackgroundThe space environment contains numerous high-energy particles, and a single high-energy particle passing through a spacecraft shell bombards the electronic devices within, triggering single-particle effects such as device logic state upset and function failures, which, in turn, affect spacecraft operation reliability and mission accomplishment.PurposeNotably, ground accelerator irradiation tests provide an important and effective means for simulating space single event effects and for predicting the risks of single event effect rates for electronic devices in space applications. Generally, electronic devices can be used in spacecraft only if their resistance radiation indicators meet astronautical application requirements.MethodsSpacecraft are typically exposed to space radiation particles, primarily heavy ions and protons; therefore, single event effect simulation testing for electronic devices relies predominantly on heavy ion and proton accelerators. To address the requirements of single event effect testing, technologies such as large-area beam expansion and homogenization, high-precision beam current diagnosis, and efficient test terminals have been developed to fulfill the requirements of various test tasks.ResultsParticular focus is placed on the CIAE's (China Institute of Atomic Energy) heavy ion single event and proton single event effect simulation test techniques and the heavy ion microbeam technique for radiation sensitive area identification for electronic devices. Subsequently, the aforementioned techniques are applied to a single event effect risk evaluation for astronautical electronic devices.ConclusionsIn the future, the demand for radiation-resistant devices is expected to continue to increase in the aerospace, nuclear industry, and other radiation application fields. It is, therefore, necessary to further exploit the irradiation potential of existing domestic single event effect simulation equipment and establish new accelerator platforms with improved capacity for single event effect simulation testing.

BackgroundMachine learning, which has been widely applied to scientific research in recent years, can be used to investigate the inherent correlations within a large number of complex data.PurposeWe evaluate the performances of two types of machine-learning algorithms for correcting nuclear mass models, reconstructing the impact parameter in heavy-ion collisions, and extracting the symmetry energy slope parameter. We also discuss the extrapolation and generalization ability of the machine-learning models.MethodFor correcting the nuclear mass models, 10 characteristic quantities are fed into the LightGBM to mimic the residual between the experimental and the theoretical binding energies. For impact parameter or symmetry energy, two types of observables constructed based on the particle information simulated by using the UrQMD transport model for setting up the different impact parameters or symmetry energy slope parameters are used as inputs to a conventional neural network and the LightGBM to extract the original information.ResultAnalysis of these nuclear physics problems reveals the potential applicability of machine-learning methods.ConclusionsMachine-learning methods can be used to investigate new physical problems, thereby promoting the development of both theory and experiment.

We reviewed the recent progress on strange particle production and hypernuclear physics both in experiments and in theories. The temporal evolutions of nucleons and resonances are described by the Skyrme energy density functional and relativistic covariant density functional theory, in which the meson-nucleon and hyperon-nucleon interactions are considered. Calculations are performed for the reactions of 12C+12C, 40Ca+40Ca, 112Sn+112Sn, and 197Au+197Au. The in-medium effects and high-density symmetry energy from the production of kaon, antikaon, and hyperon (Λ, Σ, Ξ) are investigated systematically. A quantum coalescence method is used to construct the hypernucleus, and the phase-space distribution is investigated in terms of the mass, charge, kinetic energy, rapidity distribution, collective flows, etc. Pre-equilibrium cluster emission in heavy-ion collisions is analyzed by implementing 2-, 3-, and 4-body nucleon collisions. The relativistic quantum molecular dynamics model is introduced by including ρ and δ coupling for nucleon transportation, and the collective flows are calculated for protons and neutrons.

BackgroundTo date, various nuclides up to Z = 118 have been discovered and synthesized, raising the challenge of synthesizing nuclides with Z ≥ 119. Recently, the fusion-evaporation reactions 243Am54Cr, xn119297-x and 243Am55Mn, xn120298-x have been suggested as methods for synthesizing new elements with Z = 119 and 120. As α-decay is a powerful tool for the identification of new elements or nuclides, accurate predictions of the α-decay properties of the reaction products could be a useful reference for future experiments.PurposeThis study aims to provide quantitative predictions of the α-decay, spontaneous fission, and β-decay half-lives for the α-decay chains of 293, 294119 and 294, 295120 and to demonstrate the competition between the decay modes for these nuclei.MethodsAn improved density-dependent cluster model (DDCM+) is used to calculate the α-decay half-lives, taking the anisotropy of the surface diffuseness into account. The spontaneous fission half-lives are calculated using the Karpov formula, which is related to the fissility parameter and fission barrier height of the potential energy surface. The β-decay half-lives are determined using a finite-range droplet model (FRDM).ResultsThe predictive α-decay half-lives for the α-decay chains of 293, 294119 and 294, 295120 are obtained using the DDCM+ model, and the theoretical half-lives of the spontaneous fission and β-decay for these nuclides are also presented.ConclusionsFor the α-decay chains of 293, 294119 and 294, 295120, α-decay is predicted to be the dominant decay mode for most of the nuclei, while the half-lives of spontaneous fission and β-decay are predicted to be comparable to those of the α-decay near the region of A = 261. We expect that these results will serve as a useful reference for the synthesis of new isotopes in the future.

We developed a Gamow shell model based on first principles and successfully applied it to the nuclei around driplines. Herein, we review the theoretical and technical developments of this method. Starting from the realistic nuclear forces, the model uses the Berggren basis, which contains bound, resonant, and scattering continuum states. Therefore, the Gamow shell model can handle the coupling to the continuum. In the complex-momentum plane, we used many-body perturbation theory (i.e., so-called Q^-box folded diagrams) to derive the Hamiltonian for the valence space. Subsequently, the shell-model calculations, which included the resonance and continuum effects, were performed. Therefore, such ab initio calculations can describe the weakly bound properties of nuclei near driplines and unbound resonance properties of nuclei beyond driplines. In this study, the symmetry breaking between oxygen isotopes and their mirror nuclei is discussed, and the important continuum effects on the excitation spectra of neutron-rich carbon isotopes are analyzed.

Backgroundβ-decay half-life is one of the fundamental physical properties of unstable nuclei and plays an important role in nuclear physics and astrophysics.PurposeThis study aimed to provide accurate nuclear β-decay half-life predictions and reasonable uncertainties associated with the predictions.MethodsNuclear β-decay half-lives were studied based on the Bayesian neural network (BNN) approach. Three types of neural networks with x = (Z, N), x = (Z, N, Qβ), and x = (Z, N, δ, Qβ) were constructed as inputs to explore the influence of the input on the prediction. The posterior distributions were sampled using the Markov chain Monte Carlo algorithm. The mathematical expectations and standard deviations of the neural network predictions on the posterior distributions were used as the predicted values and errors of the BNN approach.ResultsThe learning accuracy can be significantly improved by incorporating the β-decay energy and physical quantity related to the nuclear pair effect into the neural network input layer and then using the logarithm of β-decay half-life as the network output. For nuclei with half-lives of less than 1 s, the prediction accuracy is approximately 0.2 orders of magnitude, which is similar to that afforded by the BNN method by learning the differences between the logarithms of the experimental half-lives and theoretical results.ConclusionsThe Bayesian neural network can accurately predict β-decay half-lives. When extrapolated to the unknown nuclear region, the predicted β-decay half-lives agree with the results of other theoretical models within errors, especially for nuclei with Z ? 50.

With experimental facilities being developed globally, producing superheavy nuclei using heavy-ion collision has become feasible, which is essential for exploring charge and mass limits of nuclei and understanding the r-process in nuclear astrophysics. Fusion reactions are crucial for the synthesis of superheavy nuclei, yet only neutron-deficient superheavy nuclei get produced due to the limited neutron number of stable beams. Recent experiments suggest that multinucleon transfer reactions are promising for producing new neutron-rich superheavy nuclei. As a result, transport models are required for extracting physics information from these experiments and making predictions about incident energies and projectile-target combinations, to synthesize new super-heavy nuclei. In this article, we introduce the development of transport models such as the dinuclear system (DNS) model, quantum molecular dynamics (QMD) type model, Boltzmann type model, and Time-dependent Hatree-Fock (TDHF) type model, and conclude with their latest applications in the synthesis of superheavy nuclei, especially in fusion reactions and multinucleon transfer reactions. In addition, various international large-scale scientific facilities, as well as their scientific objectives, and future plans, are also summarized.

With the rapid development of radioactive-ion-beam facilities worldwide, many exotic nuclear phenomena have been observed or predicted in nuclei far from the β-stability line or close to the neutron (proton) drip lines, such as halos in atomic nuclei and shape decoupling in deformed halo nuclei. The study of exotic nuclear phenomena, including halos, is at the frontier of current nuclear physics research. The covariant density functional theory (CDFT) is one of the most successful models in nuclear physics. The CDFT has been widely used to study structures and properties of exotic nuclei. The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) has been developed and achieved a self-consistent description of deformed halo nuclei by including deformation and continuum effects, with the deformed relativistic Hartree-Bogoliubov equations solved in the Dirac Woods-Saxon basis. The DRHBc theory has been used to predict the deformed halo structure in 44Mg and the shape decoupling between the core and halo. The theory has also been used to address unresolved problems concerning the radius and configuration of valence neutrons in 22C, deformed halos in carbon and boron isotopes, particles in the classically forbidden regions in magnesium isotopes, and other similar phenomena. The rotational excitation of deformed halos has been investigated by implementing an angular momentum projection based on the DRHBc theory. This investigation has shown that the effects of deformed halos and shape decoupling are also present in the low-lying rotational excitation states of deformed halo nuclei.

The physics of radioactive nuclear beams is one of the frontiers of nuclear physics. New phenomena and physics appear in exotic nuclei far from the β-stability line. The neutron skin is an exotic phenomena in unstable nuclei and is closely correlated with the properties of the equation of state (EOS) of asymmetric nuclear matter and neutron stars. This study sought to examine previous studies on the effect of the neutron skin on nuclei-nuclei collisions to identify good observables for determining the neutron skin thickness, which could in turn be used to investigate the EOS of asymmetric nuclear matter. Various theoretical models are used to study the effect of neutron skin in nuclei-nuclei collisions. The statistical abrasion-ablation (SAA) and isospin-dependent quantum molecular dynamics (IQMD) models are used to study the neutron abrasion cross-section, neutron/proton ratio, and t/3He ratios. A nuclear structure model is used to investigate the relation between the neutron skin and α-cluster formation, α decay, nuclear surface, and nuclear temperature. Strong correlations have been found between the neutron skin thickness and neutron abrasion cross-section, neutron/proton ratio, and t/3He ratios, photo production, and other quantities. By measuring quantities that have a strong correlation with the neutron skin, the skin thickness can be obtained. The EOS of asymmetric nuclear matter and properties of neutron stars can be studied or constrained by using the obtained neutron skin data. Further investigations are necessary for determining observables that are useful for determining the neutron skin thickness from experimental measurements.

The fundamental properties of unstable nuclei are highly related to the nuclear structure and effective nucleon-nucleon interaction, and they can be used to study various exotic structures of unstable nuclei. Laser spectroscopy is a powerful tool used to study nuclear properties and structure by probing the hyperfine structure and isotope shift of the corresponding atoms or ions, from which the nuclear properties can be extracted in a nuclear model-independent manner. Multi-step laser resonance ionization spectroscopy (RIS) can be used to measure the atomic or ionic hyperfine structure. Based on this approach, various experimental techniques have been developed at radioactive ion beam (RIB) facilities worldwide to study the nuclear properties and structure of atomic nuclei. In this paper, the RIS approaches and relevant RIS experimental techniques are first introduced. Subsequently, the recently-developed collinear resonance ionization spectroscopy experimental technique, which can be used to measure the atomic or ionic hyperfine structure spectrum with a high-resolution and high sensitivity and plays an important role in the study of the nuclear properties and structure of unstable nuclei in the large mass regions of nuclear charts, is discussed in detail. Finally, the development status of RIS and its application in domestic RIB facilities are discussed.

China Jinping Underground Laboratory (CJPL) has the deepest rock overburden in the world, which considerably shields the detectors from muons. Thus, it has ultra-low radiation background level and is useful for experiments investigating rare physical events. Previously, experiments including the CDEX (China Dark matter EXperiment), PandaX (Particle and Astrophysical Xenon Experiments), JUNA (Jinping Underground Nuclear Astrophysics Experiment), and neutrino experiment have been carried out at CJPL and have given good results in dark matter detection, neutrinoless double beta decay, and more. This review introduces the construction process of CJPL, and introduces the facilities, results, and future plans of the aforementioned experiments. The CDEX used a high-purity germanium detector array for the dark matter detection and neutrinoless double-beta decay searches; whereas, for the same searches, PandaX used a dual-phase liquid xenon time projection chamber detector. A proton and helium accelerator was used by JUNA to simulate four nuclear reactions that occur in the Universe. A 103-kg prototype was constructed for feasibility verification by the neutrino experiment. The CDEX, PandaX, and JUNA collaboration groups give their latest results, all of which have approached or replaced the best results in the world. These experiments verify the extraordinary experimental conditions at CJPL. With the construction of CJPL-II, we expect an increase in the number of experiments based in Jinping and for further significant results to be achieved.

BackgroundIsoscalar pairing plays an important role in the spin-isospin excitation of nuclei. The discovery of super Gamow-Teller (GT) states in N≈Z nuclei has motivated researchers to explore the effects of isoscalar pairing on spin-isospin excitations.PurposeThis study aims to investigate the effects of the isoscalar pairing interaction on GT and spin-dipole (SD) transitions in 42Ca.MethodsBy solving the relativistic Hartree-Bogoliubov equation, we obtained the canonical single-nucleon basis and occupation amplitudes, which were used as inputs for the quasiparticle phase-random approximation (QRPA) calculation. Using the QRPA model, the GT and SD transitions in 42Ca were calculated, where the Gaussian isoscalar pairing force was adopted, with its strength being a free parameter.ResultsFor GT states, the isoscalar pairing mixed the spin-flip transition configuration into the low-lying GT state, enhancing the collectivity of the low-energy GT state and significantly increasing its transition strength. Meanwhile, the isoscalar pairing force induced a shift of the low-energy GT state toward lower energies owing to the attractive properties of the isoscalar pairing force. For SD states, the isoscalar pairing force hardly affected the strengths and energies of SD states in 42Ca.ConclusionsIsoscalar pairing force was essential for restoring the SU(4) symmetry and hence reproducing the low-energy super GT state of 42Ca in the experiment, whereas it hardly affected the SD states.

The nucleus is a quantum many-body complex system governed by the nuclear force, and it is prone to global changes such as deformation, rotation, vibration, fission, and clustering. In the past >30 a, we have witnessed the rapid expansion of the experimentally attainable nuclear chart and new discoveries and breakthroughs in studies on unstable nuclei. Examples include the halo nuclei and the associated exotic structural phenomena, the shell evolution observed using in-beam γ spectroscopy through the application of the achromatic magnetic spectrometer, the measurement of the basic properties of unstable nuclei, and the discovery of new magic numbers and rich phenomena in multi-nucleon correlations along with the formation of clusters and molecules. In the coming years, the expanded area of the nuclear chart—particularly the medium-heavy-mass neutron-rich region—will be the host of extreme exotic structures, the astrophysical r-process, and the reaction pathways to reach the superheavy island. Therefore, many new-generation radioactive ion-beam facilities are under development worldwide, and essential breakthroughs are foreseen.

Supernovae are the most gorgeous fireworks that people can observe in the universe. Their explosion can produce a maximum luminosity 10 billion times that of the Sun, helping scientists see farther. Type Ia supernovae can be used as a standard candle to facilitate measurement of the distance between galaxies in the universe. A supernova explosion will also propel a large number of heavy elements into interstellar space, which is a major driving force for the chemical evolution of galaxies. In addition, supernovae are crucial to the origin of elements in the Milky Way, the formation of the structure of the solar system, and the evolution of life on the Earth. The study of supernovae will further enrich our understanding of the universe and help us solve the mysteries of the expansion of the universe, the generation of heavy elements, and the origin of life. At present, scientists predict that the next supernova will explode at any time, and preparations are in progress for observing the coming supernova.

The year 2023 marks the 35th anniversary of the establishment of the Beijing Tandem Accelerator Nuclear Physics National Laboratory. Accelerators and nuclear reactors are the two main tools for studying nuclear science. In 1988, the Tandem Laboratory was officially founded, serving as a significant research hub for nuclear physics in our country. It has consistently played a leading role in nuclear science innovation, achieving 140 000 h of stable operation. The laboratory has undertaken research in nuclear physics research, nuclear data measurement, nuclear physics applications, and interdisciplinary studies. This has resulted in a series of internationally recognized basic and technological achievements that meet national major demands, fostering a group of outstanding talents. It has provided solid support for the continuous development of nuclear physics research and nuclear technology strategy in our country. This article provides a comprehensive overview of the 35 years of development of the Tandem Laboratory.