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  • Speed of sound in asymmetric quark matter

    分类: 物理学 >> 核物理学 提交时间: 2024-03-04

    摘要: The speed of sound in quark matter is an important physical quantity for studying the properties and the spacetime evolution of quark-gluon plasma (QGP). The behavior of the speed of sound with respect to temperature and density can reveal  to some extent the equation of state and the phase structure of QGP. Building upon the previous studies on the speed of sound in symmetric quark matter,  the formulae for calculating the speed of sound in asymmetric quark matter in the temperature-density space are further derived. The PNJL model is then used to calculate the dependence of the speed of sound on isospin asymmetry. Furthermore, the relationship between the magnitude of the speed of sound and the QCD phase structure is discussed, and  the regions where the acoustic equation fails  are indicated under different physical conditions.

  • The breaking of spin symmetry in the single-particle resonances in deformed nuclei

    分类: 物理学 >> 核物理学 提交时间: 2024-03-01

    摘要: The exploration of spin symmetry (SS) in nuclear physics has been instrumental in identifying
    atomic nucleus structures. In this study, we solve the Dirac equation from the relativistic mean field (RMF)
    in complex momentum representation. We investigated SS and its breaking in single-particle resonant states
    within deformed nuclei, with a focus on the illustrative nucleus 168Er. This was the initial discovery of a resonant spin doublet in a deformed nucleus, with the expectation of the SS approaching the continuum threshold.
    With increasing single-particle energy, the splitting of the resonant spin doublets widened significantly. This escalating splitting implies diminishing adherence to the SS, indicating a departure from the expected behavior as
    the energy levels increase. We also analyzed the width of the resonant states, showing that lower orbital angular
    momentum resonances possess shorter decay times and that SS is preserved within broad resonant doublets, as
    opposed to narrow resonant doublets. Comparing the radial density of the upper components for the bound-state
    and resonant-state doublets, it becomes evident that while SS is well-preserved in the bound states, it deteriorates in the resonant states. The impact of nuclear deformation (β2) on SS was examined, demonstrating that an
    increase in β2 resulted in higher energy and width splitting in the resonant spin doublets, which is attributed to
    increased component mixing. Furthermore, the sensitivity of spin doublets to various potential parameters such
    as surface diffuseness (a), radius (R), and depth (Σ0) is discussed, emphasizing the role of these parameters
    in SS. This study provides valuable insights into the behavior of spin doublets in deformed nuclei and their
    interplay with the nuclear structure, thereby advancing our understanding of SS in the resonance state.

  • Heavy ion energy influence on multiple-cell upsets in small sensitive volumes: From standard to high energies

    分类: 物理学 >> 核物理学 提交时间: 2024-02-29

    摘要: The 28nm process has a high cost-performance ratio and has gradually become the standard for the field
    of radiation-hardened devices. However, owing to the minimum physical gate length of only 35nm, the physical
    area of a standard 6T SRAM unit is approximately 0.16 μm2, resulting in a significant enhancement of
    multi-cell charge-sharing effects. Multiple-cell upsets (MCUs) have become the primary physical mechanism
    behind single-event upsets (SEUs) in advanced nanometer node devices. The range of ionization track effects
    increases with higher ion energies, and spacecraft in orbit primarily experience SEUs caused by high-energy
    ions. However, ground accelerator experiments have mainly obtained low-energy ion irradiation data. Therefore,
    the impact of ion energy on the SEU cross-section, charge collection mechanisms, and MCU patterns and
    quantities in advanced nanometer devices remains unclear. In this study, based on the experimental platform
    of the Heavy Ion Research Facility in Lanzhou (HIRFL), low- and high-energy heavy-ion beams were used
    to study the SEUs of 28nm SRAM devices. The influence of ion energy on the charge collection processes
    of small-sensitive-volume devices, MCU patterns, and upset cross-sections was obtained, and the applicable
    range of the inverse-cosine law was clarified. The findings of this study are an important guide for the accurate
    evaluation of SEUs in advanced nanometer devices and for the development of radiation-hardening techniques.

  • Theoretical analysis of double-differential cross-sections of neutron, proton, deuteron, 3He, and α for the p+6Li reaction

    分类: 物理学 >> 核物理学 分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-02-29

    摘要: Based on the unified Hauser–Feshbach and exciton model, which can describe the particle emission processes between discrete energy levels with energy, angular momentum, and parity conservations, a statistical theory of light nucleus reaction (STLN) is developed to calculate the double-differential cross-sections of the outgoing neutron and light charged particles for the proton-induced 6Li reaction. A significant difference is observed between the p + 6Li and p +7Lireactions owing to the discrepancies in the energy-level structures of the targets. The reaction channels, including sequential and simultaneous emission processes, are analyzed in detail. Taking the double-differential cross-sections of the outgoing proton as an example, the influence of contaminations (such as 1H, 7Li, 12C, and 16O) on the target is identified in terms of the kinetic energy of the first emitted particles. The optical potential parameters of the proton are obtained by fitting the elastic scattering differential cross-sections. The calculated total double-differential cross-sections of the outgoing proton and deuteron at Ep = 14MeVagree well with the experimental data for different outgoing angles. Simultaneously, the mixed double differential cross-sections of 3He and α are in good agreement with the measurements. The agreement between the measured data and calculated results indicates that the two-body and three-body breakup reactions need to be considered, and the pre-equilibrium reaction mechanism dominates the reaction processes. Based on the STLN model, a PLUNF code for the p + 6Li reaction is developed to obtain an ENDF-6-formatted file of the double-differential cross-sections of the nucleon and light composite charged particles.

  • Grain boundary engineering for enhancing intergranular damage resistance of ferritic/martensitic steel P92

    分类: 核科学技术 >> 核科学技术其他学科 分类: 物理学 >> 核物理学 提交时间: 2024-02-28

    摘要: Ferritic/martensitic (F/M) steels have been widely used as structural material for thermal and nuclear power plants. However, it is susceptible to intergranular damage in service conditions, which is expected to be critical issues. In order to improve the intergranular damage resistance of F/M steel, thermomechanical process (TMP) was employed to achieve a grain boundary engineering (GBE) microstructure in a kind of F/M steel P92 in this study. TMP, including cold rolling to 6%, 9%, and 12% thickness reduction, respectively, followed by austenization at 1323 K for 40 min plus tempering at 1053 K for 45 min, were applied on as-received (AR) P92 steel. Both prior austenite grain (PAG) size, prior austenite grain boundary character distribution (GBCD), and the connectivity of prior austenite grain boundaries (PAGBs) were investigated. Compared with AR specimen, the PAG size does not change significantly. The fraction of coincident site lattice boundaries (CSLBs, 3 ≤ Σ ≤ 29) and Σ3n boundaries along PAGBs decreases with increasing reduction ratio due to the recrystallization fraction increases with increasing reduction ratio. The PAGBs connectivity of the 6%-deformed specimen deteriorates compared with that of AR specimen slightly. Moreover, the potentiodynamic polarization studies revealed that the intergranular damage resistance of studied steel could be improved by enhancing the fraction of CSLBs along PAGBs, indicating that TMP, involving low deformation, could enhance the intergranular damage resistance.

  • 上海激光电子伽马源的建设与试运行

    分类: 物理学 >> 核物理学 提交时间: 2024-02-28

    摘要: 介绍了上海光源线站工程之一的上海激光电子伽马源 (Shanghai Laser Electron Gamma Source, SLEGS)光束线站的建设与试运行情况,在SLEGS伽马源装置上可以开展核物理、核天体物理等基础研究、开展伽马辐照,伽马成像及伽马活化等应用研究。SLEGS光束线站在2021年12月通过工艺验收,2022年10月进入到试运行阶段,2023年9月对用户开放运行。SLEGS是国际上首台采用变换碰撞角度连续改变伽马束能量,具有最好的能量扫描精度、流强密度以及高效的能量调节能力。试运行阶段SLEGS光束线站重点解决了伽马束能谱和流强的在线监测问题,主要完成了平坦效率谱仪(FED)测量光中子截面的实验方法学研究,以及开展了伽马成像、伽马活化,正电子产生等应用平台的拓展和研究。随着逆康普顿散射技术的发展和应用需求的增加,未来短脉冲、高极化、高通量以及小型化的激光康普顿散射光源将会迎来更好的发展机遇,将在核物理、天体物理、粒子物理,极化物理,以及航空航天,医学检测,能源开发等伽马源应用研究领域发挥重要的作用。

  • Construction of Gamma Activation Experimental Platform for Shanghai Laser Electron Gamma Source

    分类: 物理学 >> 核物理学 提交时间: 2024-02-28

    摘要: 上海激光电子伽马源(Shanghai Laser Electron Gamma Source,SLEGS)是通过激光与电子逆康普顿散射产生准单能、能量连续可调的兆电子伏伽马束,是目前国际上唯一一台可连续变换碰撞角度的激光康普顿散射(Laser Compton Scattering,LCS)伽马源装置。伽马活化是研究材料特性的有效手段之一,本文介
    绍了上海激光电子伽马源的伽马活化平台情况、包括在线活化过程,离线低本底测量,高纯锗(High Purity Germanium,HPGe)探测器的能量效率刻度等。目前的简易低本底屏蔽使得测量系统本底计数率降低到约 5.2cps/(60 keV-3 MeV 能区)。SLEGS 伽马源的活化平台为开展伽马活化测量研究提供了有利条件,未来在核物理、核天体物理、医学应用、材料科学和环境科学等领域的研究将会发挥重要的作用。

  • 一种高计数率的能损探测器方案研究

    分类: 物理学 >> 核物理学 分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-27

    摘要: 正在建设中的强流重离子加速器装置 HIAF 配备了一条先进的放射性束流线 HFRS,建成后将为中国 高能放射性核束物理研究提供新的机遇。HFRS 的特点是流强极高 (初级束流强度 1 × 1011 ppp),这对用于粒 子鉴别的能损探测器提出了非常高的计数率要求。传统的能损探测器对信号处理一般依次采用电荷灵敏前放、 主放、ADC 的技术路线。该方案存在电子学响应速度较慢、灵活性较差、难以处理高计数率下信号堆积严重 等问题。我们对此提出一种新的适用于高计数率的能损探测器方案:以耐辐照的多次取样电离室为能损探测 器,优化结构和读出方式提高探测器响应速度,使用快电荷灵敏前放对能损探测器信号初步放大后、直接用 波形数字化仪采集波形再进行后续数字算法处理。并利用放射源和束流对该方案进行了验证测试。利用 3 组 分 𝛼 源测试时,对采集的波形使用数字成形算法处理,能量分辨率(FWHM)可达 1.31%。在 RIBLL2 提供 300 MeV/u 的 56Fe 束流测试中,采用时间常数 𝜏f = 2 𝜇𝑠 的快电荷灵敏前放在计数率接近 1 MHz 时仍未发生明显堆积。

  • Atomistic study on the microscopic mechanism of grain boundary embrittlement induced by small dense helium bubbles in iron

    分类: 物理学 >> 核物理学 分类: 核科学技术 >> 核聚变工程技术 提交时间: 2024-02-27

    摘要: The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic (RAFM) steel, which is a candidate structural material for fusion reactors. In order to elucidate the susceptibility of different grain boundaries (GBs) to helium-induced embrittlement, the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic (bcc) iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods. The results indicate that in the absence of helium bubbles, the GBs studied here can be classified into two distinct categories: brittle GBs and ductile GBs. The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms, including the Bain/Burgers path phase transition and deformation twinning, in which the Bain path phase transition is the most dominant plastic deformation mechanism. However, the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs, resulting in a significant decrease in elongation at fractures. For bubble-decorated GBs, the ultimate tensile strength increases with the increase of the misorientation angle. Interestingly, the coherent twin boundary Ʃ3{112} was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.

  • Recent Progress on Halo Nuclei in Relativistic Density Functional Theory

    分类: 物理学 >> 核物理学 提交时间: 2024-02-26

    摘要: Since the discovery of the halo nucleus 11Li in 1985, halo phenomena in exotic nuclei have always been an important frontier in nuclear physics research. The relativistic density functional theory has achieved great success in the study of halo nuclei, e.g., the self-consistent description of halo nucleus 11Li and the microscopic prediction of deformed halo nuclei. This paper introduces some recent progresses, including the investigation of halo nucleus 37Mg and the prediction of the N = 28 shell collapse and a deformed halo in the new isotope 39Na based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), as well as the exploration of triaxially deformed halo nuclei by the newly developed triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc).

  • Studies of an Event Building algorithm of the readout system for the twin TPCs in HFR

    分类: 物理学 >> 核物理学 提交时间: 2024-02-26

    摘要: The High Energy Fragment Separator (HFRS), which is currently under construction, is a leading international radioactive beam device. Multiple sets of position-sensitive Twin Time Projection Chamber (TPC)
    detectors are distributed on HFRS for particle identification and beam monitoring. The twin TPCs’ readout
    electronics system operates in a trigger-less mode due to its high counting rate, leading to a challenge of handling large amounts of data. To address this problem, we introduced an event-building algorithm. This algorithm
    employs a hierarchical processing strategy to compress data during transmission and aggregation. In addition,
    it reconstructs twin TPCs’ events online and stores only the reconstructed particle information, which significantly reduces the burden on data transmission and storage resources. Simulation studies demonstrated that the
    algorithm accurately matches twin TPCs’ events and reduces more than 98% of the data volume at a counting
    rate of 500 kHz/channel.
     

  • HIRFL-CSR 外靶实验终端 Veto 探测器的刻度

    分类: 核科学技术 >> 核探测技术与核电子学 分类: 物理学 >> 核物理学 提交时间: 2024-02-26

    摘要: 使用宇宙射线对兰州重离子加速器冷却储存环 (HIRFL-CSR) 外靶实验终端 (ETF) 的 Veto 探测器开展了
    刻度工作,工作主要分为位置刻度与时间刻度两部分。位置刻度可给出粒子在探测器上的击中位置,时间刻
    度则能为粒子在探测器上击中时刻的探测建立统一标准。这些信息是剔除入射到中子墙探测器的带电粒子事
    件的依据,可为中子墙探测器物理目标的实现提供重要支持。在刻度过程中,得到了 Veto 探测器的位置分辨
    半高全宽 (FWHM) 为 2.53 cm,所有单元条时间归一后的时间分辨 FWHM 为 1.09 ns。

  • Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

    分类: 物理学 >> 核物理学 提交时间: 2024-02-24

    摘要: The yield ratios of neutron-proton (R(n/p)) and 3H-3He (R(3H/3He)) with reduced rapidity from 0 to 0.5 were simulated for 50 MeV/u even-even 36-56Ca + 40Ca, even-even 48-78Ni + 58Ni and 100-139Sn (every third isotopes) + 112Sn at full reduced impact parameters using the isospin-dependent quantum molecular dynamics (IQMD) model. The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model, which was used for the phase space initialization of the projectile and target in IQMD. We defined the unified neutron skin thickness as ΔRnp=2>n1/2-2>p1/2, which was negative for neutron-deficient nuclei. The unified ΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal, except for extreme neutron-rich isotopes, which is a type of scaling behavior. The yield ratios of the three isotopic chains-induced reactions, which dependent on the reduced impact parameter and the unified neutron skin thickness, were studied. The results show that both R(n/p) and R(3H/3He) decreased with a reduced impact parameter for extreme neutron-deficient isotopes; however, they increased with reduced impact parameters for extreme neutron-rich isotopes, and increased with the ΔRnp of the projectiles for all reduced impact parameters. In addition, a scaling phenomena was observed between ΔRnp and the yield ratios in peripheral collisions from different isotopic chain projectiles (except for extreme neutron-rich isotopes). Thus, R(n/p) and R(3H/3He) from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.

  • 多重物理约束下 Duflo-Zuker 核质量模型的研究

    分类: 物理学 >> 核物理学 提交时间: 2024-02-23

    摘要: 原子核质量在核物理和核天体研究中扮演着十分重要的角色。尽管当前的理论模型可较好的描述已知核素的质量,但不同模型在外推上仍然存在许多争议,尤其是丰中子区的预言。本文回顾了我们近年来在核质量模型外推研究的主要成果,即使用严格的多目标优化算法将核素质量差 𝛼 衰变能和局域质量关系作为限制条件,缓和质量模型中的过拟合问题,在一定程度上提升模型的外推能力。

  • 低能N+-He 碰撞中的态选择单电子俘获研究

    分类: 物理学 >> 核物理学 分类: 物理学 >> 原子与分子物理学 提交时间: 2024-02-22

    摘要: 利用反应显微成像谱仪,采用二重符合方法,实验测量了0.64 keV/u N+ 与He 单电子俘获产生的反冲离子He+ 三维动量,获得了电子俘获到炮弹离子不同量子态的态选择截面和角分布。实验结果表明:基态的 炮弹离子N+(1s22s22p2 3P) 俘获He 靶的一个1s 电子主要布居到2p 壳层,也可以看到布居到更高壳层的贡献; 亚稳态的炮弹离子N+(1s22s2p3 5S) 俘获He 靶的一个1s 电子主要布居到2s 壳层,几乎看不到布居到更高壳层 的贡献。利用NHe+ 准分子离子的势能曲线定性地解释了实验结果,但分子库仑过垒模型的反应窗预测与实 验存在较大差别。在亚稳态炮弹离子N+(1s22s2p3 5S) 俘获靶电子到2s 轨道的过程中,角微分截面出现了明显 的振荡结构, 这很可能来自Demkov 型跃迁。

  • POLAR2/LPD探测器的校准和校正算法

    分类: 物理学 >> 核物理学 提交时间: 2024-02-21

    摘要: 气体X射线偏振测量是指一类用于测量软X射线偏振的探测器。这些探测器的系统效应会引入残余调制,导致源的偏振检测结果出现系统偏差。本文讨论了这些系统效应及其在Polar2/低能X射线偏振探测器(LPD)的气体微通道像素探测器(GMPD)原型中的校准和校正。此外,我们提出了一种算法,该算法将参数化与蒙特卡洛模拟和贝叶斯迭代相结合,以消除残余调制。数据校正后,不同能量点的残余调制已降至1%以下,并观察到偏振度与调制度之间存在良好的线性关系。校正后调制度的改善范围为2%至15%,结果超过了5 keV以上的IXPE。

  • Sensitivity impacts owing to the variations in the type of zero-range pairing forces on the fission properties using the density functional theory

    分类: 物理学 >> 核物理学 提交时间: 2024-02-21

    摘要: By the Skyrme density functional theory (DFT), potential energy surfaces (PES) of $^{240}$Pu with constraints on the axial quadrupole and octupole deformations($q_{20}$ and $q_{30}$) are calculated.
    The volume-like, and the surface-like pairing forces, and the mixing between these two forces are used, within the Hartree-Fock-Bogoliubov (HFB) approximation. The variations of the least-energy fission path, fission barrier, paring energy, total kinetic energy, scission line, and mass distribution of fission fragments by the different forms of paring force are analyzed and discussed. The fission dynamics is studied based on the time-dependent generator coordinate method (TDGCM) plus Gaussian overlap approximation (GOA). The results show a sensitivity of the mass and charge distributions of fission fragments to the form of the pairing force. Based on the investigation of the neutron-induced fission of $^{239}$Pu, among the volume, mixed, and surface pairing forces, the mixed-type of pairing force can give a good reproduction of experimental data.

  • 中子诱发d产物的微分反应截面的测量

    分类: 物理学 >> 核物理学 提交时间: 2024-02-20

    摘要: 在中国散裂中子源反角白光终端,测量了中子能量为33.9MeV  12C(n,d)x的角微分反应截面。利用轻带电粒子探测器阵列(LPDA)ΔE-E 望远镜系统, 测量了在实验室坐标系下从24.5°到155.5° 12C(n,d)x 的角微分反应截面。实验结果能够很好的符合以前的实验结果。由于缺少实验数据,这项工作为相关数据库的评价及数据库研制提供了重要参考。

  • Study of Primordial Deuterium Abundance in Big Bang Nucleosynthesis

    分类: 物理学 >> 核物理学 提交时间: 2024-02-19

    摘要: Big Bang nucleosynthesis (BBN) theory predicts the primordial abundances of the light elements 2H (referred to as deuterium, or D for short), 3He, 4He, and 7Li produced in the early universe. Among these, deuterium, the first nuclide produced by BBN, is a key primordial material for subsequent reactions. To date, the uncertainty in predicted deuterium abundance (D/H) remains larger than the observational precision. In this study, the Monte Carlo simulation code PRIMAT was used to investigate the sensitivity of 11 important BBN reactions to deuterium abundance. We found that the reaction rate uncertainties of the four reactions d(d, n)3He, d(d, p)t, d(p, γ)3He, and p(n, γ)d had the largest influence on the calculated D/H uncertainty. Currently, the calculated D/H uncertainty cannot reach observational precision even with the recent LUNA precise d(p, γ)3He rate. From the nuclear physics aspect, there is still room to largely reduce the reaction-rate uncertainties; hence, further measurements of the important reactions involved in BBN are still necessary. A photodisintegration experiment will be conducted at the Shanghai Laser Electron Gamma Source (SLEGS) Facility to precisely study the deuterium production reaction of p(n, γ)d.

  • 2023-84N终稿

    分类: 物理学 >> 核物理学 提交时间: 2024-02-18

    摘要: 基于强子-夸克偶素模型和色磁相互作用口袋模型分别计算了含有奇异夸克的隐重味四夸克系统 𝑞 ̄𝑠𝑄𝑄和 𝑠 ̄𝑠𝑄𝑄 的质量谱。强子-夸克偶素模型的计算结果表明当重夸克偶素 𝑄𝑄 处于激发态时, 奇异介子和 𝑄𝑄 之间的束缚能较大,可能会形成紧致的结构,因此实验上可以通过 𝑄𝑄 激发态至基态的衰变过程来识别。对于
    基态的奇异隐重味四夸克态,色磁相互作用口袋模型的计算结果支持紧致的四夸克态,尤其对实验上发现的𝑍𝑐𝑠(4000) 和 𝑍𝑐𝑠(4220) ,计算结果相差仅 20 MeV 左右,对 𝑠 ̄𝑠𝑄𝑄 的质量计算结果和实验的部分结果也非常接近,据此我们支持含有奇异夸克的四夸克态可能具有更多紧致的结构。