Nuclear Science and Techniques最新文献

We present a theoretical study of the medium modifications of the (p_textrm{T}) balance ((x_textrm{J})) of dijets in Xe+Xe collisions at (sqrt{s_textrm{NN}}=5.44) TeV. The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription, which matches the next-to-leading-order (NLO) QCD matrix elements with the parton shower (PS) effect. The SHELL model described the in-medium evolution of nucleus–nucleus collisions using a transport approach. The theoretical results of the dijet (x_textrm{J}) in the Xe+Xe collisions exhibit more imbalanced distributions than those in the p+p collisions, consistent with recently reported ATLAS data. By utilizing the Interleaved Flavor Neutralisation, an infrared-and-collinear-safe jet flavor algorithm, to identify the flavor of the reconstructed jets, we classify dijets processes into three categories: gluon–gluon (gg), quark–gluon (qg), and quark–quark (qq), and investigated the respective medium modification patterns and fraction changes of the gg, qg, and qq components of the dijet sample in Xe+Xe collisions. It is shown that the increased fraction of qg component at a small (x_textrm{J}) contributes to the imbalance of the dijet; in particular, the (q_1g_2) (quark-jet-leading) dijets experience more significant asymmetric energy loss than the (g_1q_2) (gluon-jet-leading) dijets traversing the QGP. By comparing the (Delta langle x_textrm{J}rangle = langle x_textrm{J} rangle _textrm{pp} - langle x_textrm{J} rangle _textrm{AA}) of inclusive, (cbar{c}) and (bbar{b}) dijets in Xe+Xe collisions, we observe (Delta langle x_textrm{J} rangle _mathrm{incl.}>Delta langle x_textrm{J} rangle _mathrm{cbar{c}}>Delta langle x_textrm{J} rangle _mathrm{bbar{b}}). Moreover, (rho _textrm{Xe, Pb}), the ratios of the nuclear modification factors of dijets in Xe+Xe to those in Pb+Pb, were calculated, which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe owing to the larger radius of the lead nucleus.

The advantages of a flat-panel X-ray source (FPXS) make it a promising candidate for imaging applications. Accurate imaging-system modeling and projection simulation are critical for analyzing imaging performance and resolving overlapping projection issues in FPXS. The conventional analytical ray-tracing approach is limited by the number of patterns and is not applicable to FPXS-projection calculations. However, the computation time of Monte Carlo (MC) simulation is independent of the size of the patterned arrays in FPXS. This study proposes two high-efficiency MC projection simulators for FPXS: a graphics processing unit (GPU)-based phase-space sampling MC (gPSMC) simulator and GPU-based fluence sampling MC (gFSMC) simulator. The two simulators comprise three components: imaging-system modeling, photon initialization, and physical-interaction simulations in the phantom. Imaging-system modeling was performed by modeling the FPXS, imaging geometry, and detector. The gPSMC simulator samples the initial photons from the phase space, whereas the gFSMC simulator performs photon initialization from the calculated energy spectrum and fluence map. The entire process of photon interaction with the geometry and arrival at the detector was simulated in parallel using multiple GPU kernels, and projections based on the two simulators were calculated. The accuracies of the two simulators were evaluated by comparing them with the conventional analytical ray-tracing approach and acquired projections, and the efficiencies were evaluated by comparing the computation time. The results of simulated and realistic experiments illustrate the accuracy and efficiency of the proposed gPSMC and gFSMC simulators in the projection calculation of various phantoms.

The Shanghai Laser Electron Gamma Source (SLEGS, located in BL03SSID) beamline at the Shanghai Synchrotron Radiation Facility (SSRF) is a Laser Compton Scattering (LCS) gamma source used for the investigation of nuclear structure, which is in extensive demand in fields such as nuclear astrophysics, nuclear cluster structure, polarization physics, and nuclear energy. The beamline is based on the inverse Compton scattering of 10640 nm photons on 3.5 GeV electrons and a gamma source with variable energy by changing the scattering angle from 20(^circ) to 160(^circ). (gamma) rays of 0.25(-)21.1 MeV can be extracted by the scheme consisting of the interaction chamber, coarse collimator, fine collimator, and attenuator. The maximum photon flux for 180(^circ) is approximately (10^{7}) photons/s at the target at 21.7 MeV, with a 3-mm-diameter beam. The beamline was equipped with four types of spectrometers for experiments in ((gamma),(gamma)’), ((gamma),n), ((gamma),p), and ((gamma,!alpha)). At present, Nuclear Resonance Fluorescence (NRF) spectrometry, Flat-Efficiency neutron Detector (FED) spectrometry, neutron Time-Of-Flight (TOF) spectrometry, and Light-Charged Particle (LCP) spectrometry methods have been developed.

This study presents a new method for characterizing the thermal lattice deformation of a monochromator with high precision under service conditions and first reports the operando measurements of nanoscale thermal lattice deformation on a double-crystal monochromator at different incident powers. The nanoscale thermal lattice deformation of the monochromator first crystal was obtained by analyzing the intensity of the distorted DuMond diagrams. DuMond diagrams of the 333 diffraction index, sensitive to lattice deformation, were obtained directly using a 2D detector and an analyzer crystal orthogonal to the monochromator. With increasing incident power and power density, the maximum height of the lattice deformation increased from 3.2 to 18.5 nm, and the deformation coefficient of the maximum height increased from 1.1 to 3.2 nm/W. The maximum relative standard deviation was 4.2(%), and the maximum standard deviation was 0.1 nm. Based on the measured thermal deformations, the flux saturation phenomenon and critical point for the linear operation of the monochromator were predicted with increasing incident power. This study provides a simple solution to the problem of the lower precision of synchrotron radiation monochromator characterizations compared to simulations.

Relativistic isobar (left( {_{{44}}^{{96}} {text{Ru}} +, _{{44}}^{{96}} {{text{Ru}, text{and} }},_{{40}}^{{96}} {text{Zr}} +, _{{40}}^{{96}} {text{Zr}}} right)) collisions have revealed intricate differences in their nuclear size and shape, inspiring unconventional studies of nuclear structure using relativistic heavy ion collisions. In this study, we investigate the relative differences in the mean multiplicity (left(R_{langle N_{{textrm{ch}}}rangle }right)) and the second- (left(R_{epsilon _{2}}right)) and third-order eccentricity (left(R_{epsilon _{3}}right)) between isobar collisions using initial state Glauber models. It is found that initial fluctuations and nuclear deformations have negligible effects on (R_{langle N_{{textrm{ch}}}rangle }) in most central collisions, while both are important for the (R_{epsilon _{2}}) and (R_{epsilon _{3}}), the degree of which is sensitive to the underlying nucleonic or sub-nucleonic degree of freedom. These features, compared to real data, may probe the particle production mechanism and the physics underlying nuclear structure.

Carbon-based nanomaterials have important research significance in various disciplines, such as composite materials, nanoelectronic devices, biosensors, biological imaging, and drug delivery. Recently, the human and ecological risks associated with carbon-based nanomaterials have received increasing attention. However, the biological safety of carbon based nanomaterials has not been systematically studied. In this study, we used different types of carbon materials, namely, graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and multiwalled carbon nanotubes (MWCNTs), as models to observe their distribution and oxidative damage in vivo. The results of Histopathological and ultrastructural examinations indicated that the liver and lungs were the main accumulation targets of these nanomaterials. SR-(upmu)-XRF analysis revealed that SWCNTs and MWCNTs might be present in the brain. This shows that the three types of carbon-based nanomaterials could cross the gas–blood barrier and eventually reach the liver tissue. In addition, SWCNTs and MWCNTs could cross the blood–brain barrier and accumulate in the cerebral cortex. The increase in ROS and MDA levels and the decrease in GSH, SOD, and CAT levels indicated that the three types of nanomaterials might cause oxidative stress in the liver. This suggests that direct instillation of these carbon-based nanomaterials into rats could induce ROS generation. In addition, iron (Fe) contaminants in these nanomaterials were a definite source of free radicals. However, these nanomaterials did not cause obvious damage to the rat brain tissue. The deposition of selenoprotein in the rat brain was found to be related to oxidative stress and Fe deficiency. This information may support the development of secure and reasonable applications of the studied carbon-based nanomaterials.

The recently discovered, extremely proton-rich nuclide (^{18})Mg exhibits ground-state decay via two sequential two-proton (2p) emissions through the intermediate nucleus, (^{16})Ne. This study investigates the structure and the initial 2p decay mechanism of (^{18}textrm{Mg}) by examining the density and correlations of the valence protons using a three-body Gamow coupled-channel method. The results show that the ground state of (^{18}textrm{Mg}) is significantly influenced by the continuum, resulting in a significant s-wave component. However, based on the current framework, this does not lead to a significant deviation in mirror symmetry in either the structure or spectroscopy of the (^{18}textrm{Mg})–(^{18}textrm{C}) pair. Additionally, the time evolution analysis of the (^{18}textrm{Mg}) ground state suggests a simultaneous 2p emission during the first step of decay. The observed nucleon–nucleon correlations align with those of the light-mass 2p emitters, indicating a consistent decay behavior within this nuclear region.

The ultrahard X-ray multifunctional application beamline (BL12SW) is a phase-II beamline project at the Shanghai Synchrotron Radiation Facility. The primary X-ray techniques used at the beamline are high-energy X-ray diffraction and imaging using white and monochromatic light. The main scientific objectives of ultrahard X-ray beamlines are focused on two research areas. One is the study of the structural properties of Earth’s interior and new materials under extreme high-temperature and high-pressure conditions, and the other is the characterization of materials and processes in near-real service environments. The beamline utilizes a superconducting wiggler as the light source, with two diamond windows and SiC discs to filter out low-energy light (primarily below 30 keV) and a Cu filter assembly to control the thermal load entering the subsequent optical components. The beamline is equipped with dual monochromators. The first was a meridional bending Laue monochromator cooled by liquid nitrogen, achieving a full-energy coverage of 30–162 keV. The second was a sagittal bending Laue monochromator installed in an external building, providing a focused beam in the horizontal direction with an energy range of 60–120 keV. There were four experimental hutches: two large-volume press experimental hutches (LVP1 and LVP2) and two engineering material experimental hutches (ENG1 and ENG2). Each hutch was equipped with various near-real service conditions to satisfy different requirements. For example, LVP1 and LVP2 were equipped with a 200-ton DDIA press and a 2000-ton dual-mode (DDIA and Kawai) press, respectively. ENG1 and ENG2 provide in situ tensile, creep, and fatigue tests as well as high-temperature conditions. Since June 2023, the BL12SW has been in trial operation. It is expected to officially open to users by early 2024.

The layout and characteristics of the hard X-ray spectroscopy beamline (BL11B) at the Shanghai synchrotron radiation facility are described herein. BL11B is a bending-magnet beamline dedicated to conventional and millisecond-scale quick-scanning X-ray absorption fine structures. It is equipped with a cylindrical collimating mirror, a double-crystal monochromator comprising Si(111) and Si(311), a channel-cut quick-scanning Si(111) monochromator, a toroidal focusing mirror, and a high harmonics rejection mirror. It can provide 5–30 keV of X-rays with a photon flux of ~ 5 × 10¹¹ photons/s and an energy resolution of ~ 1.31 × 10^–4 at 10 keV. The performance of the beamline can satisfy the demands of users in the fields of catalysis, materials, and environmental science. This paper presents an overview of the beamline design and a detailed description of its performance and capabilities.

The heavy water-moderated molten salt reactor (HWMSR) is a newly proposed reactor concept, in which heavy water is adopted as the moderator and molten salt dissolved with fissile and fertile elements is used as the fuel. Issues arising from graphite in traditional molten salt reactors, including the positive temperature coefficient and management of highly radioactive spent graphite waste, can be addressed using the HWMSR. Until now, research on the HWMSR has been centered on the core design and nuclear fuel cycle to explore the viability of the HWMSR and its advantages in fuel utilization. However, the core safety of the HWMSR has not been extensively studied. Therefore, we evaluate typical accidents in a small modular HWMSR, including fuel salt inlet temperature overcooling and overheating accidents, fuel salt inlet flow rate decrease, heavy water inlet temperature overcooling accidents, and heavy water inlet mass flow rate decrease accidents, based on a neutronics and thermal–hydraulics coupled code. The results demonstrated that the core maintained safety during the investigated accidents.