New results for directly searching for dark matter electromagnetic interactions have been reported by the PandaX Collaboration. The study reveals the most stringent upper limits on dark matter charge radius, millicharge, magnetic dipole moment, electric dipole moment, and anapole moment to date. These findings demonstrate that dark matter is significantly darker than previously anticipated.

High-precision vertex and energy reconstruction are crucial for large liquid scintillator detectors such as that at the Jiangmen Underground Neutrino Observatory (JUNO), especially for the determination of neutrino mass ordering by analyzing the energy spectrum of reactor neutrinos. This paper presents a data-driven method to obtain a more realistic and accurate expected PMT response of positron events in JUNO and develops a simultaneous vertex and energy reconstruction method that combines the charge and time information of PMTs. For the JUNO detector, the impact of the vertex inaccuracy on the energy resolution is approximately 0.6%.

This study utilizes large-scale shell model calculations with the extended pairing and multipole-multipole force model (EPQQM) to investigate low-lying states in the nuclei of ⁴²Ca, ⁴²Sc, and ^42-44Ti. The model space in this study includes the fp shell as well as the intruder g_9/2 orbit, which accurately reproduces the positive parity levels observed in the aforementioned nuclei and predicts high-energy states with negative parity coupled with the intruder g_9/2. The study further predicts two different configurations in ⁴³Ti at around 6 MeV, specifically πf7/22νg9/2 and πf_7/2g_9/2vf_7/2, both of which involve the intruder orbit g_9/2. The levels coupled with the intruder g_9/2 in ⁴⁴Ti are predicted to lie between 7 and 11 MeV. The inclusion of the intruder orbit g_9/2 is crucial for the exploration of high-energy states in the northeast region of the doubly magic nucleus ⁴⁰Ca.

Although seemingly disparate, high-energy nuclear physics (HENP) and machine learning (ML) have begun to merge in the last few years, yielding interesting results. It is worthy to raise the profile of utilizing this novel mindset from ML in HENP, to help interested readers see the breadth of activities around this intersection. The aim of this mini-review is to inform the community of the current status and present an overview of the application of ML to HENP. From different aspects and using examples, we examine how scientific questions involving HENP can be answered using ML.

In this work, we perform a Bayesian inference of the crust-core transition density ρ_t of neutron stars based on the neutron-star radius and neutron-skin thickness data using a thermodynamical method. Uniform and Gaussian distributions for the ρ_t prior were adopted in the Bayesian approach. It has a larger probability of having values higher than 0.1 fm^-3 for ρ_t as the uniform prior and neutron-star radius data were used. This was found to be controlled by the curvature K_sym of the nuclear symmetry energy. This phenomenon did not occur if K_sym was not extremely negative, namely, K_sym> -200 MeV. The value of ρ_t obtained was 0.075 −0.01+0.005 fm^-3 at a confidence level of 68% when both the neutron-star radius and neutron-skin thickness data were considered. Strong anti-correlations were observed between ρ_t, slope L, and curvature of the nuclear symmetry energy. The dependence of the three L-K_sym correlations predicted in the literature on crust-core density and pressure was quantitatively investigated. The most probable value of 0.08 fm^-3 for ρ_t was obtained from the L–K_sym relationship proposed by Holt et al while larger values were preferred for the other two relationships.

The main objective of this study was to investigate the impact of effective mass splitting on heavy-ion-collision observables. We first analyzed correlations between different nuclear matter parameters obtained from 119 effective Skyrme interaction sets. The values of the correlation coefficients illustrate that the magnitude of effective mass splitting is crucial for tight constraints on the symmetry energy via heavy-ion collisions. The ⁸⁶Kr + ²⁰⁸Pb system at beam energies ranging from 25A to 200A MeV was simulated within the framework of the improved quantum molecular dynamics model (ImQMD-Sky). Our calculations show that the slopes of the spectra of ln [Y(n)/Y(p)] and ln [Y(t)/Y(³He)], which are the logarithms of the neutron to proton and triton to helium-3 yield ratios, are directly related to effective mass splitting and can be used to probe the effective mass splitting.

The theoretical uncertainties of single proton transfer cross-sections of the (³He,d) and (d,³He) reactions, owing to the uncertainties of the entrance- and exit-channel optical model potentials, are examined with the ³⁰Si(³He,d)³¹P, ¹³B(d,³He)¹²Be, and ³⁴S(³He,d)³⁵Cl reactions at incident energies of 25, 46, and 25 MeV, respectively, within the framework of the distorted wave Born approximation. The differential cross-sections at the first peaks in the angular distributions of these reactions are found to have uncertainties of approximately 5%, owing to the uncertainties in the optical model potentials from 20000 calculations of randomly sampled parameters. This amount of uncertainty is found to be nearly independent of the angular momentum transfer and the target masses within the studied range of incident energies. Uncertainties in the single proton spectroscopic factors obtained by matching the theoretical and experimental cross-sections at different scattering angles are also discussed.

Directed flow (v₁) of the hypernuclei Λ3H and Λ4H have been observed in mid-central Au+Au collisions at sNN = 3 GeV 3 at RHIC. This measurement opens up a new possibility for studying hyperon-nucleon (Y-N) interaction under finite pressure. In addition, multi-strangeness hypernuclei provide a venue to probe hyperon-nucleon-nucleon (Y-N-N) and even hyperon-hyperon-nucleon (Y-Y-N) interactions. Hypernuclei are important for making connection between nuclear collisions and the equation of state which governs the inner structure of compact stars.

The nuclear fuel assembly is the core component of a nuclear reactor. In a pressurized water reactor fuel assembly, the top-connection structure connects the top nozzle to the guide thimble. Its performance reliability is essential for the stability of the nuclear fuel assembly. In this study, an assembly-oriented reliability analysis method for top-connection structures is presented by establishing an assembly-oriented top-connection structure parameter modeling method and a nonlinear contact gap and penetration correction method. A reliability model of the top-connection assembly structure, including multiple stochastic design variables, was constructed, and the overall reliability of the top-connection assembly structure was obtained via a Kriging model and Monte Carlo simulation. The acquired experimental data were consistent with real-world failure conditions, which verified the practicability and feasibility of the reliability analysis method proposed in this study.

Various sources of solid particles might exist in the coolant flow of a liquid metal cooled fast reactor (e.g., through chemical interaction between the coolant and impurities, air, or water, through corrosion of structural materials, or from damaged/molten fuel). Such particles may cause flow blockage accidents in a fuel assembly, resulting in a reduction in coolant flow, which potentially causes a local temperature rise in the fuel cladding, cladding failure, and fuel melt. To understand the blockage formation mechanism, in this study, a series of simulated experiments was conducted by releasing different solid particles from a release device into a reducer pipe using gravity. Through detailed analyses, the influence of various experimental parameters (e.g., particle diameter, capacity, shape, and static friction coefficient, and the diameter and height of the particle release nozzle) on the blockage characteristics (i.e., blockage probability and position) was examined. Under the current range of experimental conditions, the blockage was significantly influenced by the aforementioned parameters. The ratio between the particle diameter and outlet size of the reducer pipe might be one of the determining factors governing the occurrence of blockage. Specifically, increasing the ratio enhanced blockage (i.e., larger probability and higher position within the reducer pipe). Increasing the particle size, particle capacity, particle static friction coefficient, and particle release nozzle diameter led to a rise in the blockage probability; however, increasing the particle release nozzle height had a downward influence on the blockage probability. Finally, blockage was more likely to occur in non-spherical particles case than that of spherical particles. This study provides a large experimental database to promote an understanding of the flow blockage mechanism and improve the validation process of fast reactor safety analysis codes.

An investigation of the decoupled thermal–hydraulic analysis of a separated heat pipe spent fuel pool passive cooling system (SFS) is essential for practical engineering applications. Based on the principles of thermal and mass balance, this study decoupled the heat transfer processes in the SFS. In accordance with the decoupling conditions we modeled the spent fuel pool of the CAP1400 pressurized water reactor in Weihai and used computational fluid dynamics (CFD) to explore the heat dissipation capacity of the SFS under different air temperatures and wind speeds. The results show that the air-cooled separated heat pipe radiator achieved optimal performance at an air temperature of 10 °C or wind speed of 8 m/s. Fitted equations for the equivalent thermal conductivity of the separated heat pipes with the wind speed and air temperature we obtained according to the thermal resistance network model. This study is instructive for the actual operation of an SFS.

The uncertainty of nuclide libraries in the analysis of the gamma spectra of low- and intermediate-level radioactive waste (LILW) using existing methods produces unstable results. To address this problem, a novel spectral analysis method is proposed in this study. In this method, overlapping peaks are located using a continuous wavelet transform. An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks. Combined with the adaptive sensitive nonlinear iterative peak, this method can effectively subtracts the background. Finally, a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library. Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152, a segmented gamma scanning experiment for a 200 L standard drum, and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides (Sb-125, Sb-124, and Cs-134) are conducted. The results of the experiments indicate that (1) the novel method and gamma vision (GV) with an accurate nuclide library have the same spectral analysis capability, and the peak area calculation error is less than 4%; (2) compared with the GV, the analysis results of the novel method are more stable; (3) the novel method can be applied to the activity measurement of LILW, and the error of the activity reconstruction at the equivalent radius is 2.4%; and (4) The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library. This novel method can improve the accuracy and precision of LILW measurements, provide key technical support for the reasonable disposal of LILW, and ensure the safety of humans and the environment.

This paper presents the concept of a passive electrochemical hydrogen recombiner (PEHR). The reaction energy of the recombination of hydrogen and oxygen is used as a source of electrical energy according to the operating principle for hydrogen fuel cells to establish forced circulation of the hydrogen mixture as an alternative to natural circulation (as is not utilized in conventional passive autocatalytic hydrogen recombiners currently used in nuclear power plants (NPPs)). The proposed concept of applying the physical operation principles of a PEHR based on a fuel cell simultaneously increases both productivity in terms of recombined hydrogen and the concentration threshold of flameless operation (the 'ignition’ limit). Thus, it is possible to reliably ensure the hydrogen explosion safety of NPPs under all conditions, including beyond-design accidents. An experimental setup was assembled to test a laboratory sample of a membrane electrode assembly (MEA) at various hydrogen concentrations near the catalytic surfaces of the electrodes, and the corresponding current–voltage characteristics were recorded. The simplest MEA based on the Advent P1100W PBI membrane demonstrated stable performance (delivery of electrical power) over a wide range of hydrogen concentrations.

Direct collection of uranium from low-uranium systems via adsorption remains challenging. Fibrous sorbent materials with amidoxime (AO) groups are promising adsorbents for uranium extraction from seawater. However, low AO adsorption group utilization remains an issue. We herein fabricated a branched structure containing AO groups on polypropylene/polyethylene spun-laced nonwoven (PP/PE SNW) fibers using grafting polymerization induced by radiation (RIGP) to improve AO utilization. The chemical structures, thermal properties, and surface morphologies of the raw and treated PP/PE SNW fibers were studied. The results show that an adsorptive functional layer with a branching structure was successfully anchored to the fiber surface. The adsorption properties were investigated using batch adsorption experiments in simulated seawater with an initial uranium concentration of 500 μg·L^-1 (pH 4, 25 °C). The maximum adsorption capacity of the adsorbent material was 137.3 mg·g^-1 within 24 h; moreover, the uranyl removal reached 96% within 240 min. The adsorbent had an AO utilization rate of 1/3.5 and was stable over a pH range of 4–10, with good selectivity and reusability, demonstrating its potential for seawater uranium extraction.

High-energy proton microbeam facilities are powerful tools in space science, biology, and cancer therapy studies. The primary limitations of the 50 MeV proton microbeam system are the poor beam quality provided by the cyclotron and the problem of intense scattering in the slit position. Here, we present an optical design for a cyclotron-based 50 MeV high-energy proton microbeam system with a micron-sized resolution. The microbeam system, which has an Oxford triplet lens configuration, has relatively small spherical aberrations and is insensitive to changes in the beam divergence angle and momentum spread. In addition, the energy filtration included in the system can reduce the beam momentum spread from 1% to 0.02%. The effects of lens parasitic aberrations and the lens fringe field on the beam spot resolution are also discussed. In addition, owing to the severe scattering of 50 MeV protons in slit materials, a slit system model based on the Geant4 toolkit enables the quantitative analysis of scattered protons and secondary particles. For the slit system settings under a 10-micron final beam spot, very few scattered protons can enter the quadrupole lens system and affect the focusing performance of the microbeam system, but the secondary radiation of neutrons and gamma rays generated at the collimation system should be considered for the 50 MeV proton microbeam. These data demonstrate that a 50 MeV proton microbeam system with a micron-sized beam spot based on a cyclotron is feasible.

Image distortion caused by the angular misalignment of quadrupole magnets in high-energy electron radiography has been studied systematically. We propose that the distortion originates from the coupling of the electron motions in the transverse directions, based on a theoretical analysis and the transfer-matrix method. The relative angular rotation between the second and third magnetic quadrupoles was identified as the main contributor to image distortion. This was verified by both a beam-dynamics simulation and experiments. Different strategies to mitigate this image distortion are also explored, including magnets online tuning, higher beam energy and larger magnification factor. This study provides criteria for designing experiments and paves the way for achieving higher image precision.

A 3W1 superconducting wiggler (SCW) with the pole gap of 68 mm was successfully tested and installed in a BEPC II storage ring in November, 2019. The goal of zero liquid helium consumption was achieved, and the cryogenic system exhibited a 12% residual cooling capacity (approximately 0.69 W @4.2K). The 3W1-SCW was set to operate at 2.49 T and has been operating for more than seven months. Three instances of magnet quenching occurred during the normal operation. The evaporated helium gas can be recycled to the helium gas recycling system when the pressure in the helium tank is higher than the parameter value (the setpoint of the pressure value is 1.2 bara). The cryogenic system can be recovered within 4 h if sufficient liquid helium is available to inject into the cryostat.

Tomographic Gamma Scanner (TGS), an advanced γ-ray nondestructive analysis technique, can locate and analyze nuclides in radioactive nuclear waste, and TGS can be categorized into two types: e.g., transmission measurement and emission measurement). Specifically, transmission measurements provide the basis for accurate measurement of nonuniform radionuclide content in TGS scanning. The scan data were obtained using the Monte Carlo tool Geant4 simulation, and 25 voxels were divided into five lengths and five widths in a square barrel. In this study, an encoding cropping algorithm based on draped foot vector judgment was adopted to rapidly calculate the voxel trace matrix within a square bucket of nuclear waste, and the transmission images were reconstructed using ordered subset expectation maximization (OSEM). The results indicated that the cropping speed of the improved coding algorithm was significantly higher than that of the original algorithm, and the relative mean deviation (RMD) and root mean square error (RMSE) between the reconstructed attenuation coefficient and the reference standard value tended to decrease with an increase in the cropped line segments in the voxel; the Pearson correlation coefficient (PCC) tended to converge to 1.0. The image quality evaluation parameters of the high media-density materials were better than those of the low media-density materials in the above three indexes. The reconstruction effect was relatively poor for more complex filling materials. When there were more than 10 cropped line segments in the voxel, the reconstruction data generally tended to be stable. The graphical trimming algorithm can rapidly calculate the trace matrix of the scanned voxels; it exhibits the advantages of speed and efficiency and can serve as a novel method to solve the trace matrix of TGS nuclear waste transmission scans.