Vol.35,

The neutron-induced total cross sections of natural lead have been measured in a wide energy range (0.3 eV - 20 MeV) on the back-streaming white neutron beamline (Back-n) at the China Spallation Neutron Source (CSNS). Neutron energy was determined by the neutron total cross-section spectrometer (NTOX) using the time-of-flight (TOF) technique. A fast multi-cell fission chamber was used as the neutron detector, and a 10 mm-thick high-purity natural lead sample was employed for the neutron transmission measurements. The on-beam background was determined using Co, In, Ag, and Cd filters. The excitation function of ^natPb(n, tot) reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program. The present results were compared with previous results, the evaluated data available in the five major evaluated nuclear data libraries (i.e., ENDF/B-VIII.0, JEFF-3.3, JENDL-5, CENDL-3.2, and BROND-3.1), and the theoretical calculation curve. Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region. This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range. This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.

883

The extended kernel ridge regression (EKRR) method with odd-even effects was adopted to improve the description of the nuclear charge radius using five commonly used nuclear models. These are: (i) the isospin dependent A^1/3 formula, (ii) relativistic continuum Hartree-Bogoliubov (RCHB) theory, (iii) Hartree-Fock-Bogoliubov (HFB) model HFB25, (iv) the Weizsäcker-Skyrme (WS) model WS^*, and (v) HFB25^* model. In the last two models, the charge radii were calculated using a five-parameter formula with the nuclear shell corrections and deformations obtained from the WS and HFB25 models, respectively. For each model, the resultant root-mean-square deviation for the 1014 nuclei with proton number Z≥8 can be significantly reduced to 0.009-0.013 fm after considering the modification with the EKRR method. The best among them was the RCHB model, with a root-mean-square deviation of 0.0092 fm. The extrapolation abilities of the KRR and EKRR methods for the neutron-rich region were examined and it was found that after considering the odd-even effects, the extrapolation power was improved compared with that of the original KRR method. The strong odd-even staggering of nuclear charge radii of Ca and Cu isotopes and the abrupt kinks across the neutron N=126 and 82 shell closures were also calculated and could be reproduced quite well by calculations using the EKRR method.

728

Ultraperipheral heavy-ion collisions (UPCs) offer unique opportunities to study processes under strong electromagnetic fields. In these collisions, highly charged fast-moving ions carry strong electromagnetic fields that can be effectively treated as photon fluxes. The exchange of photons can induce photonuclear and two-photon interactions, and excite ions. This excitation of the ions results in Coulomb dissociation with the emission of photons, neutrons, and other particles. Additionally, the electromagnetic fields generated by the ions can be sufficiently strong to enforce mutual interactions between the two colliding ions. Consequently, the two colliding ions experience an electromagnetic force that pushes them in opposite directions, causing a back-to-back correlation in the emitted neutrons. Using a Monte Carlo simulation, we qualitatively demonstrate that the above electromagnetic effect is large enough to be observed in UPCs, which would provide a clear means to study strong electromagnetic fields and their effects.

756

The GECAM series of satellites utilizes LaBr₃(Ce), LaBr₃(Ce,Sr), and NaI(Tl) crystals as sensitive materials for gamma-ray detectors (GRDs). To investigate the non-linearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship, comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons, radioactive sources, and mono-energetic X-rays. The non-linearity test results of the Compton electrons and X-rays demonstrated substantial differences, with all three crystals presenting a higher non-linearity for X/γ-rays than for Compton electrons. Despite the LaBr₃(Ce) and LaBr₃(Ce,Sr) crystals having higher absolute light yields, they exhibited a noticeable non-linear decrease in the light yield, especially at energies below 400 keV. The NaI(Tl) crystal demonstrated an "excess" light output in the 6–200 keV range, reaching a maximum "excess" of 9.2% at 30 keV in the X-ray testing and up to 15.5% at 14 keV during Compton electron testing, indicating a significant advantage in the detection of low-energy gamma rays. Furthermore, we explored the underlying causes of the observed non-linearity in these crystals. This study not only elucidates the detector responses of GECAM, but also initiates a comprehensive investigation of the non-linearity of domestically produced lanthanum bromide and sodium iodide crystals.

773

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γ ray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γ response and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4)+0.51(2)/Eγ1/2 for water and 0.0026(3)+0.446(3)/Eγ1/2 for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm× 30 cm× 30 cm and 60 cm× 60 cm× 120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

702

In this study, the effect of extreme laser fields on the α decay process of ground-state even–even nuclei was investigated. Using the deformed Gamow-like model, we found that state-of-the-art lasers can cause a slight change in the α decay penetration probability of most nuclei. In addition, we studied the correlation between the rate of change of the α decay penetration probability and angle between the directions of the laser electric field and α particle emission for different nuclei. Based on this correlation, the average effect of extreme laser fields on the half-life of many nuclei with arbitrary α particle emission angles was calculated. The calculations show that the laser suppression and promotion effects on the α decay penetration probability of the nuclei population with completely random α particle-emission directions are not completely canceled. The remainder led to a change in the average penetration probability of the nuclei. Furthermore, the possibility of achieving a higher average rate of change by altering the spatial shape of the laser is explored. We conclude that circularly polarized lasers may be helpful in future experiments to achieve a more significant average rate of change of the α decay half-life of the nuclei population.

559

A benchmark experiment on ²³⁸U slab samples was conducted using a deuterium–tritium neutron source at the China Institute of Atomic Energy. The leakage neutron spectra within energy levels of 0.8–16 MeV at 60° and 120° were measured using the time-of-flight method. The samples were prepared as rectangular slabs with a 30 cm square base and thicknesses of 3, 6, and 9 cm. The leakage neutron spectra were also calculated using the MCNP-4C program based on the latest evaluated files of ²³⁸U evaluated neutron data from CENDL-3.2, ENDF/B-VIII.0, JENDL-5.0, and JEFF-3.3. Based on the comparison, the deficiencies and improvements in ²³⁸U evaluated nuclear data were analyzed. The results showed the following. (1) The calculated results for CENDL-3.2 significantly overestimated the measurements in the energy interval of elastic scattering at 60° and 120°. (2) The calculated results of CENDL-3.2 overestimated the measurements in the energy interval of inelastic scattering at 120°. (3) The calculated results for CENDL-3.2 significantly overestimated the measurements in the 3–8.5MeV energy interval at 60° and 120°. (4) The calculated results with JENDL-5.0 were generally consistent with the measurement results.

754

The elliptic azimuthal anisotropy coefficient (v₂) of the identified particles at midrapidity (|η|<0.8) was investigated in p–Pb collisions at sNN = 5.02 TeV using a multi-phase transport model (AMPT). The calculations of differential v₂ based on the advanced flow extraction method of light flavor hadrons (pions, kaons, protons, and Λ) in small collision systems were extended to a wider transverse momentum (p_T) range of up to 8 GeV/c for the first time. The string- melting version of the AMPT model provides a good description of the measured p_T-differential v₂ of the mesons but exhibits a slight deviation from the baryon v₂. In addition, we observed the features of mass ordering at low p_T and the approximate number-of-constituent-quark (NCQ) scaling at intermediate p_T. Moreover, we demonstrate that hadronic rescattering does not have a significant impact on v₂ in p–Pb collisions for different centrality selections, whereas partonic scattering dominates in generating the elliptic anisotropy of the final particles. This study provides further insight into the origin of collective-like behavior in small collision systems and has referential value for future measurements of azimuthal anisotropy.

523

Traditional particle identification methods face time consuming, experience-dependent, and poor repeatability challenges in heavy-ion collisions at low and intermediate energies. Researchers urgently need solutions to the dilemma of traditional particle identification methods. This study explores the possibility of applying intelligent learning algorithms to the particle identification of heavy-ion collisions at low and intermediate energies. Multiple intelligence algorithms, including XgBoost and TabNet, were selected to test datasets from the neutron ion multi-detector for reaction-oriented dynamics (NIMROD–ISiS) and Geant4 simulation. Machine learning algorithms based on tree structures and deep learning algorithms e.g. TabNet show excellent performance and generalization ability. Adding additional data features besides energy deposition can improve the algorithm’s identification ability when the data distribution is nonuniform. Intelligent learning algorithms can be applied to solve the particle identification problem in heavy-ion collisions at low and intermediate energies.

632

1634

The supercritical CO₂ Brayton cycle is considered a promising energy conversion system for Generation IV reactors for its simple layout, compact structure, and high cycle efficiency. Mathematical models of four Brayton cycle layouts are developed in this study for different reactors to reduce the cost and increase the thermohydraulic performance of nuclear power generation to promote the commercialization of nuclear energy. Parametric analysis, multi-objective optimizations, and four decision-making methods are applied to obtain each Brayton scheme’s optimal thermohydraulic and economic indexes. Results show that for the same design thermal power scale of reactors, the higher the core’s exit temperature, the better the Brayton cycle’s thermo-economic performance. Among the four-cycle layouts, the recompression cycle (RC) has the best overall performance, followed by the simple recuperation cycle (SR) and the intercooling cycle (IC), and the worst is the re-heating cycle (RH). However, RH has the lowest total cost of investment (C_tot) of $1619.85 million, and IC has the lowest levelized cost of energy (LCOE) of 0.012$/(kWh). The nuclear Brayton cycle system’s overall performance has been improved due to optimization. The performance of the Molten Salt Reactor combined with the intercooling cycle (MSR-IC) scheme has the greatest improvement, with the net output power (W_net), thermal efficiency η_t, and exergy efficiency (η_e) improved by 8.58%, 8.58%, and 11.21% respectively. The performance of the Lead-cooled Fast Reactor combined with the simple recuperation cycle scheme was optimized to increase C_tot by 27.78%. In comparison, the internal rate of return (IRR) increased by only 7.8%, which is not friendly to investors with limited funds. For the nuclear Brayton cycle, the Molten Salt Reactor combined with the recompression cycle scheme should receive priority, and the Gas-cooled Fast Reactor combined with the re-heating cycle scheme should be considered carefully.

687

An in-house code, CONTHAC-3D, was developed to calculate and analyze thermal–hydraulic phenomena in containments during severe accidents. CONTHAC-3D is a three-dimensional computational fluid dynamics code that can be applied to predict gas flow, diffusion, and steam condensation in a containment during a severe hypothetical accident, as well as to obtain an estimate of the local hydrogen concentration in various zones of the containment. CONTHAC-3D was developed using multiple models to simulate the features of the proprietary systems and equipment of HPR1000 and ACP100, such as the passive cooling system (PCS), passive autocatalytic recombiners (PARs) and the passive air cooling system (PAS). To validate CONTHAC-3D, a GX6 test was performed at the Battelle Model Containment facility. The hydrogen concentration and temperature monitored by the GX6 test are accurately predicted by CONTHAC-3D. Subsequently, the hydrogen distribution in the HPR1000 containment during a severe accident was studied. The results show that the hydrogen removal rates calculated using CONTHAC-3D for different types of PARs agree well with the theoretical values, with an error of less than 1%. As the accident progresses, the hydrogen concentration in the lower compartment becomes higher than that in the large space, which implies that the lower compartment has a higher hydrogen risk than the dome and large space at a later stage of the accident. The amount of hydrogen removed by the PARs placed on the floor of the compartment is small; therefore, raising the installation height of these recombiners appropriately is recommended. However, we do not recommend installing all autocatalytic recombiners at high positions. The study findings in regards to the hydrogen distribution in the HPR1000 containment indicate that CONTHAC-3D can be applied to the study of hydrogen risk containment.

716

A nonlinear dynamic simulation model based on coordinated control of speed and flow rate for the molten salt reactor and combined cycle systems is proposed here to ensure the coordination and stability between the molten salt reactor and power system. This model considers the impact of thermal properties of fluid variation on accuracy and has been validated with Simulink. This study reveals the capability of the control system to compensate for anomalous situations and maintain shaft stability in the event of perturbations occurring in high-temperature molten salt tank outlet parameters. Meanwhile, the control system's impact on the system's dynamic characteristics under molten salt disturbance is also analyzed. The results reveal that after the disturbance occurs, the controlled system benefits from the action of the control, and the overshoot and disturbance amplitude are positively correlated while the system power and frequency eventually return to the initial values. This simulation model provides a basis for utilizing molten salt reactors for power generation and maintaining grid stability.

617

Simulating the total ionizing dose (TID) of an electrical system using transistor-level models can be difficult and expensive, particularly for digital integrated circuits (ICs). In this study, a method for modeling TID effects in complementary metal-oxide semiconductor (CMOS) digital ICs based on the input/output buffer information specification (IBIS) was proposed. The digital IC was first divided into three parts based on its internal structure: the input buffer, output buffer, and functional area. Each of these three parts was separately modeled. Using the IBIS model, the transistor V-I characteristic curves of the buffers were processed, and the physical parameters were extracted and modeled using VHDL-AMS. In the functional area, logic functions were modeled in VHDL according to the data sheet. A golden digital IC model was developed by combining the input buffer, output buffer, and functional area models. Furthermore, the golden ratio was reconstructed based on TID experimental data, enabling the assessment of TID effects on the threshold voltage, carrier mobility, and time series of the digital IC. TID experiments were conducted using a CMOS noninverting multiplexer, NC7SZ157, and the results were compared with the simulation results, which showed that the relative errors were less than 2% at each dose point. This confirms the practicality and accuracy of the proposed modeling method. The TID effect model for digital ICs developed using this modeling technique includes both the logical function of the IC and changes in electrical properties and functional degradation impacted by TID, which has potential applications in the design of radiation-hardening tolerance in digital ICs.

619

Owing to the complex lithology of unconventional reservoirs, field interpreters usually need to provide a basis for interpretation using logging simulation models. Among the various detection tools that use nuclear sources, the detector response can reflect various types of information of the medium. The Monte Carlo method is one of the primary methods used to obtain nuclear detection responses in complex environments. However, this requires a computational process with extensive random sampling, consumes considerable resources, and does not provide real-time response results. Therefore, a novel fast forward computational method (FFCM) for nuclear measurement that uses volumetric detection constraints to rapidly calculate the detector response in various complex environments is proposed. First, the data library required for the FFCM is built by collecting the detection volume, detector counts, and flux sensitivity functions (FSF) through a Monte Carlo simulation. Then, based on perturbation theory and the Rytov approximation, a model for the detector response is derived using the flux sensitivity function method and a one-group diffusion model. The environmental perturbation is constrained to optimize the model according to the tool structure and the impact of the formation and borehole within the effective detection volume. Finally, the method is applied to a neutron porosity tool for verification. In various complex simulation environments, the maximum relative error between the calculated porosity results of Monte Carlo and FFCM was 6.80%, with a root mean square error of 0.62 p.u. In field well applications, the formation porosity model obtained using FFCM was in good agreement with the model obtained by interpreters, which demonstrates the validity and accuracy of the proposed method.

535

To detect radioactive substances with low activity levels, an anticoincidence detector and a high-purity germanium (HPGe) detector are typically used simultaneously to suppress Compton scattering background, thereby resulting in an extremely low detection limit and improving the measurement accuracy. However, the complex and expensive hardware required does not facilitate the application or promotion of this method. Thus, a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector, whereby Compton scattering background is suppressed and a low minimum detectable activity (MDA) is achieved without using an expensive and complex anticoincidence detector and device. The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location, as well as the characteristics of energy-deposition distributions for full- and partial-energy deposition events. This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification. To accurately determine the relationship between the deposited energy of gamma (γ) rays in the detector and the deposition location, we extract four shape parameters from the pulse signals output by the detector. Machine learning is used to input the four shape parameters into the detector. Subsequently, the pulse signals are identified and classified to discriminate between partial- and full-energy deposition events. Some partial-energy deposition events are removed to suppress Compton scattering. The proposed method effectively decreases the MDA of an HPGe γ-energy dispersive spectrometer. Test results show that the Compton suppression factors for energy spectra obtained from measurements on ¹⁵²Eu, ¹³⁷Cs, and ⁶⁰Co radioactive sources are 1.13 (344 keV), 1.11 (662 keV), and 1.08 (1332 keV), respectively, and that the corresponding MDAs are 1.4%, 5.3%, and 21.6% lower, respectively.

665

The construction of a new beamline, BL10U1, was completed at the Shanghai Synchrotron Radiation Facility (SSRF) in 2020. This multipurpose beamline was designed to provide X-ray scattering techniques such as ultra-small-angle X-ray scattering (USAXS), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and microfocus-SAXS (μSAXS) for a broad user community. To realize fast time-resolved USAXS experiments, the beamline adopted an in-vacuum undulator with a total length of 1.6 m as the photon source. An in-house cryogenic-cooled double-multilayer monochromator (DMM) was installed to deliver a photon flux of approximately 10¹³ photons/s at a photon energy of 10 keV. The three-year successful operation of this beamline demonstrated that the monochromator operated smoothly, as expected. BL10U1 has three end stations in succession: USAXS end station, μSAXS end station, and end station for industrial applications. The minimum scattering vector q ~ 0.0042 nm^-1 at 10 keV can be achieved at the USAXS end station equipped with a 28 m-long and 1.8 m-diameter vacuum flight tube. At the μSAXS end station, a beam spot of less than 10 μm × 8 μm (FWHM) was achieved for micro-SAXS experiments. In contrast, in situ experimental instruments up to 5 m high and 8 m wide can be mounted at the industrial application end station, which offers industrial scientists the opportunity to use their large industrial equipment. BL10U1 opens up a new capability to investigate phenomena such as non-equilibrium and dynamic processes of materials with a wide length scale from angstroms to micrometers with millisecond time resolution. In this paper, we also report beamline design considerations and commissioning results.

679

The Shanghai high-repetition-rate X-ray free-electron laser and extreme light facility (SHINE) operates at a maximum repetition rate of 1 MHz. Kicker magnets are key components that distribute electron bunches into three different undulator lines in a bunch-by-bunch mode. The kicker ﬁeld width must be less than the time interval between bunches. A lumped-inductance kicker prototype was developed using a vacuum chamber with a single-turn coil. The full magnetic-field strength was 0.005 T. This paper presents the requirements, design considerations, design parameters, magnetic field calculations, and measurements of the kicker magnets. The relevant experimental results are also presented. The pulse width of the magnetic field was approximately 600 ns, and the maximum operation repetition rate was 1 MHz. The developed kicker satisfies the requirements for the SHINE project. Finally, numerous recommendations for the future optimization of kicker magnets are provided.

561