您选择的条件: 核物理学
  • Structure and 2p decay mechanism of $^{18}Mg$

    分类: 物理学 >> 核物理学 提交时间: 2024-05-24

    摘要: The recently discovered, extremely proton-rich nuclide18Mg exhibits ground-state decay via two sequential two-proton (2p) emissions through the intermediate nucleus,16Ne. This study investigates the structure and the initial2pdecay mechanism of18Mgby examining the density and correlations of the valence protons using a three-body Gamow-coupled-channel method. The results show that the ground state of18Mgis significantly influenced by the continuum, resulting in a significants-wave component. However, based on the current frame- work, this does not lead to a significant deviation in mirror symmetry in either the structure or spectroscopy of the18Mg-18Cpair. Additionally, the time evolution analysis of the18Mgground state suggests a simultaneous2pemission during the first step of decay. The observed nucleon–nucleon correlations align with those of the light–mass2pemitters, indicating a consistent decay behavior within this nuclear region.

  • Design and high power testing of offline conditioning cavity for CiADS RFQ high power coupler

    分类: 物理学 >> 核物理学 提交时间: 2024-05-23

    摘要: 为验证RFQ腔体功率输入耦合器设计的合理性和减少腔体污染,设计了低损耗离线锻炼腔体,并进行了高功率试验。离线锻炼腔由两个耦合口和两个调谐器口组成。此外,耦合环的安装角度和调谐器的插入深度可以用来低腔体的功率损耗。对该离线锻炼腔体进行了电磁结构和多物理场模拟,结果表明该腔体的最小理论功率损耗为4.3%。当腔体频率变化为110kHz时,理论功率损耗增加到10%。因此,调谐器在调节过程中始终处于运动状态。多物理场模拟表明,腔体温度的升高对频率变化没有影响。当离线高功率锻炼平台建成后,测量了该系统的传输性能,功率损耗为6.3%,大于理论计算值。高功率离线锻炼采用了高效的自动扫福和驻波谐振锻炼方法。为了充分锻炼高功率输入耦合器,选择了13个驻波点。最大连续波功率大于20kW,优于预期目标。

  • Development of an enhanced online tritium monitoring system using plastic scintillation fiber array

    分类: 物理学 >> 核物理学 提交时间: 2024-05-20

    摘要: Tritium, a radioactive nuclide discharged by nuclear power plants, poses challenges for removal. Continuous online monitoring of tritium in water is crucial for real-time radiation data, given its predominant existence in the environment as water. This paper presents the design, simulation, and development of a tritium monitoring device utilizing a plastic scintillation fiber (PSF) array. Experimental validation confirmed the device’s detection efficiency and minimum detectable activity. The recorded detection efficiency of the device is 1.6 × 10−3 , which exceeds the theoretically simulated value of 4 × 10−4 by four times. Without shielding, the device can achieve a minimum detectable activity of 3165 Bq L−1 over a 1600-second measurement duration. According to simulation and experimental results, enhancing detection efficiency is possible by increasing the number and length of PSFs and implementing rigorous shielding measures. Additionally, reducing the diameter of PSFs can also improve detection efficiency. The minimum detectable activity of the device can be further reduced using the aforementioned methods.

  • TMSR熔盐泵实时异常监测系统设计与开发

    分类: 物理学 >> 核物理学 提交时间: 2024-05-20

    摘要: 熔盐泵是2 MW液态燃料钍基熔盐堆(Thorium Molten Salt Reactor-Liquid Fuel,TMSR-LF1)回路系统的主要设备之一,承担着驱动熔盐在回路中循环的重要职责。熔盐泵运行的安全性和可靠性直接影响到反应堆运行的安全性和经济性,而状态监测是保证系统运行安全性和经济性的有效手段。为了能够及时发现设备及系统的运行异常,帮助操作员更快速掌握设备运行情况信息,为视情检修提供依据,基于Windows呈现基础(Windows Presentation Foundation, WPF)框架,采用MVVM(Model-View-ViewModel)模式开发了熔盐泵实时异常监测系统,实现了熔盐泵监测模型管理、实时监测与报警、异常信号定位、日志查询等功能。测试结果表明,该系统准确有效,且具有较高的稳定性,能够为操作和运行人员提供有效信息,辅助运行决策。相较于传统的DCS阈值报警,提高了异常检测的及时性和有效性,为后续智能运行支持的应用实现奠定基础。

  • Sustainability-oriented prioritization of nuclear fuel cycle transitions in China: A holistic MCDM framework under uncertainties

    分类: 物理学 >> 核物理学 提交时间: 2024-05-17

    摘要: A sustainability-oriented assessment of the nuclear energy system can provide informative and convincing decision-making support for nuclear development strategies in China. In our previous study, four authentic nuclear fuel cycle (NFC) transition scenarios were proposed, featuring different development stages and exhibiting distinct environmental, economic, and technical characteristics. However, because of the multiple and often conflicting criteria embedded therein, determining the top-priority NFC alternative for a sustainability orientation remains challenging. To address this issue, this study proposed a novel hybrid multi-criteria decision-making framework comprising fuzzy Analytic Hierarchy Process (AHP), Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE)-Geometrical Analysis for Interactive Aid (GAIA), and MOORA. Initially, an improved fuzzy AHP weighting model was developed to determine criteria weights under uncertainty and investigate the influence of various weight aggregation and defuzzification approaches. Subsequently, PROMETHEE-GAIA was used to address conflicts among the criteria and prioritize alternatives on a visualized k-dimensional GAIA plane. As a result, the alternative for direct recycling pressurized water reactor spent fuel in fast reactors is considered the most sustainable. Furthermore, a sensitivity analysis was conducted to examine the influence of criteria weight variation and validate the screening results. Finally, using MOORA, some significant optimization ideas and valuable insights were provided to support decision-makers in shaping nuclear development strategies.

  • Passive Neutron Multiplicity Device for 240Pu Measurement Based on FPGA

    分类: 物理学 >> 核物理学 提交时间: 2024-05-17

    摘要: A passive neutron multiplicity measurement device, FH-NCM/S1, based on field-programmable gate arrays(FPGAs), is developed specifically for measuring the mass of plutonium-240 (240Pu) in mixed oxide fuel. FHNCM/S1 adopts an integrated approach, combining the shift-register analysis mode with the pulse-positiontimestamp mode using an FPGA. The optimal effective length of the 3He neutron detector was determined tobe 30 cm, and the thickness of the graphite reflector was ascertained to be 15 cm through MCNP simulations.After fabricating the device, calibration measurements were performed using a 252Cf neutron source; a detectionefficiency of 43.07% and detector die-away time of 55.79 μs were observed. Nine samples of plutoniumoxide were measured under identical conditions using the FH-NCM/S1 in shift-register analysis mode and aplutonium-waste multiplicity counter. The obtained double rates underwent corrections for detection efficiency(ε) and double gate fraction (f d), resulting in corrected double rates (Dc), which were used to validate the accuracyof the shift-register analysis mode. Furthermore, the device exhibited fluctuations in the measurementresults, and within a single 20-s measurement, these fluctuations remained below 10%. After 30 cycles, therelative error in the mass of 240Pu was less than 5%. Finally, correlation calculations confirmed the robustconsistency of both measurement modes. This study holds specific significance for the subsequent design anddevelopment of neutron multiplicity devices.

  • Reliable calculations of nuclear binding energies by the Gaussian process of machine learning

    分类: 物理学 >> 核物理学 提交时间: 2024-05-11

    摘要: Reliable calculations of nuclear binding energies are crucial for advancing the research of nuclear physics. Machine learning provides an innovative approach to exploring complex physical problems. In this study, the nuclear binding energies are modeled directly using a machine-learning method called the Gaussian process. First, the binding energies for 2238 nuclei withZ >20andN >20are calculated using the Gaussian process in a physically motivated feature space, yielding an average deviation of 0.046 MeV and a standard deviation of 0.066 MeV. The results show the good learning ability of the Gaussian process in the studies of binding energies. Then, the predictive power of the Gaussian process is studied by calculating the binding energies for 108 nuclei newly included in AME2020. The theoretical results are in good agreement with the experimental data, reflecting the good predictive power of the Gaussian process. Moreover, theα-decay energies for 1169 nuclei with50≤Z≤110are derived from the theoretical binding energies calculated using the Gaussian process. The average deviation and the standard deviation are, respectively, 0.047 MeV and 0.070 MeV. Noticeably, the calculatedα-decay energies for the two new isotopes204Ac M. H. Huanget al.,Phys. Lett. B834, 137484 (2022) and207Th H. B. Yanget al.,Phys. Rev. C105, L051302 (2022) agree well with the latest experimental data. These results demonstrate that the Gaussian process is reliable for the calculations of nuclear binding energies. Finally, theα-decay properties of some unknown actinide nuclei are predicted using the Gaussian process. The predicted results can be useful guides for future research on binding energies andα-decay properties.

  • 中国散裂中子源上的一种双束团数据解析方法

    分类: 物理学 >> 核物理学 提交时间: 2024-05-10

    摘要: 中国散裂中子源(CSNS)可提供0.3 eV至300 MeV的白光中子束流,总束流强度可达107n/s/cm2,为中子俘获反应截面的测量提供了一个优秀的实验平台。CSNS在正常的运行模式下会由加速器产生两个间隔410 ns的质子束团先后打靶,因此产生的中子束流也由间隔为410 ns的两个束团混合而成。为避免两个束团的效应相互干扰,影响中子俘获截面的能量精度,需要对实验数据进行解析和重构,还原单个束团的效应。现有的解析方法可以得到非常精细的解谱结果,但相对复杂,具有一定使用门槛。本工作提出了一种简化的双束团解谱方法,在保证中子能量精度的情况下适用于中子能量低于1.2 MeV的数据,为同类型的实验工作提供一种新的数据处理思路。

  • 重离子辐照CMOS图像传感器导致的永久损伤效应

    分类: 物理学 >> 核物理学 提交时间: 2024-05-08

    摘要: 互补型金属氧化物半导体(Complementary Metal Oxide Semiconductor, CMOS)图像传感器有着体积小,质量轻,功耗低,高集成度等特点正逐步取代CCD图像传感器,在空间辐射环境中有着质子,重粒子,γ射线,电子等大量的高能粒子,CMOS图像传感器会受到重离子的辐射效应并对其有着永久损伤的影响。本文主要是针对CMV4000在重离子辐照下的永久损伤机制。CMV4000在经过重离子辐照过后其图像有着明显的热像素(暗电流尖峰高于其他像素暗电流尖峰数倍通常表现为该像素的灰度值是其他正常像素的数倍),在下一帧图像以及后续图像中热像素也并不会消失,因此热像素并不是暂时的。本文还将考虑 CMOS图像传感器在辐照前后各像参数的对比并揭示各项参数的退化机理。

  • IGFBP-3蛋白对重离子辐射损伤小鼠的防护作用研究

    分类: 物理学 >> 核物理学 分类: 生物学 >> 放射生物学 提交时间: 2024-05-06

    摘要: 我国载人航天和核技术应用正处于快速发展阶段,辐射与核安全仍将长期成为国家重大需求,持续开发新的辐射防护分子靶标和相关药物具有重要价值。先前的研究已发现电离辐射暴露后小鼠血液中的胰岛素样生长因子结合蛋白3(IGFBP-3)的水平显著上升,但是,IGFBP-3蛋白的功能及其血液水平的变化对小鼠辐射损伤的影响仍不清楚。本研究在小鼠肝脏巨噬细胞(Kupffer细胞,MKC)中建立了Igfbp3基因过表达和敲低细胞模型,利用CCK-8、EdU掺入、克隆形成和微球吞噬实验对碳离子照射后不同细胞模型的增殖活力、DNA复制活性和吞噬能力进行检测;在小鼠模型中,通过在照射前2小时尾静脉注射重组IGFBP-3蛋白提前升高血液IGFBP-3蛋白水平,检测致死剂量(5 Gy)碳离子全身照射后小鼠的生存曲线。结果显示,过表达IGFBP-3蛋白显著提高了MKC细胞在辐射暴露后的DNA复制活性、细胞活力、克隆形成率和对微球的吞噬能力,相反地,敲低IGFBP-3蛋白表达则降低了以上检测指标。碳离子辐射暴露前尾静脉注射IGFBP-3蛋白可以显著延缓急性放射损伤小鼠的死亡时间。以上结果从细胞和动物水平表明了IGFBP-3蛋白具有减轻辐射损伤的作用和作为辐射防护药靶的巨大潜力。通过增强小鼠体内Kupffer细胞的辐射抗性和吞噬能力来降低辐射暴露后的感染风险可能是IGFBP-3蛋白发挥辐射防护作用的机制之一。

  • A real-time calibration method based on time-to-digital converter for accelerator timing system

    分类: 物理学 >> 核物理学 提交时间: 2024-04-28

    摘要: The high-intensity heavy-ion accelerator facility (HIAF) is a scientific research facility complex composed ofmultiple cascade accelerators of different types, which pose a scheduling problem for devices distributed overa certain range of 2 km, involving over a hundred devices. The White Rabbit (WR), a technology-enhancingGigabit Ethernet, has shown the capability of scheduling distributed timing devices but still faces the challengeof obtaining real-time synchronization calibration parameters with high precision. This study presents a calibra#2;tion system based on a time-to-digital converter implemented on an ARM-based System-on-Chip (SoC). Thesystem consists of four multi-sample delay lines, a bubble-proof encoder, an edge controller for managing datafrom different channels, and a highly effective calibration module that benefits from the SoC architecture. Theperformance was evaluated with an average RMS precision of 5.51 ps by measuring the time intervals from 0to 24000 ps with 120000 data for every test. The design presented in this study refines the calibration precisionof the HIAF timing system. This eliminates the errors caused by manual calibration without efficiency loss andprovides data support for fault diagnosis. It can also be easily tailored or ported to other devices for specificapplications and provides more space for developing timing systems for particle accelerators, such as whiterabbits on HIAF.

  • The SLEGS beamline of SSRF

    分类: 物理学 >> 核物理学 提交时间: 2024-04-28

    摘要: 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° to 160°. γ-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° 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 (γ,γ’), (γ,n), and (γ,p α). 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.

  • Construction and performance test of charged particle detector array for MATE

    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: 2024-04-28

    摘要: A charged particle array, named MATE-PA, which serves as an auxiliary detec#2;tor system to the Multi-purpose Active-target Time projection chamber for nuclear astrophysical and exotic beam Experiments (MATE) has been con#2;structed. The array is composed of twenty single-sided strip-silicon detectors, covering around 10% of the solid angle. It is dedicated for the detection of reaction-induced charged particles which penetrate the MATE active volume. The performance of MATE-PA has been experimentally studied using an alpha source, and a 36-MeV 14N beam injected into the chamber of MATE, filled with a mixture gas of 95% 4He and 5% CO2 under the pressure of 500 mbar, at the Radioactive Ion Beam Line in Lanzhou (RIBLL). The results demonstrate good separation of light charged particles with the forward double-layer silicon detectors of MATE-PA. The energy resolution of the Si detectors was deduced to be about 1% (σ) for an energy loss of about 10 MeV by the α particles. The inclusion of MATE-PA helps improve particle identification, and increases the dynamic range for the kinetic energy of charged particles, in particular that of α particles up to about 15 MeV.

  • Reliability of DC-link capacitor in pulsed power supply for accelerator magnet

    分类: 物理学 >> 核物理学 提交时间: 2024-04-28

    摘要: Capacitors are widely used in pulsed magnet power supplies to reduce ripple voltage, store energy, and decrease power variation. In this study, DC-link capacitors in pulsed power supplies were investigated. By deriving an analytical method for the capacitor current on the H-bridge topology side, the root-mean-square value of the capacitor current was calculated, which helps in selecting the DC-link capacitors. The proposed method solves this problem quickly and with high accuracy. The current reconstruction of the DC-link capacitor is proposed to avoid structural damage in the capacitor’s current measurement, and the capacitor’s hot spot temperature and temperature rise are calculated using the FFT transform. The test results showed that the error between the calculated and measured temperature increases was within 1.5 ◦C. Finally, the lifetime of DC-link capacitors was predicted based on Monte Carlo analysis. The proposed method can evaluate the reliability of DC-link capacitors in a non-isolated switching pulsed power supply for accelerators and is also applicable to film capacitors.

  • Possibilities for the synthesis of superheavy element Z = 121 in fusion reactions

    分类: 物理学 >> 核物理学 提交时间: 2024-04-18

    摘要: Based on the dinuclear system model, the calculated evaporation residue cross sections matched well with the current experimental results. The synthesis of superheavy elements Z = 121 was systematically studied through combinations of stable projectiles with Z = 21–30 and targets with half-lives exceeding 50 d. The influence of mass asymmetry and isotopic dependence on the projectile and target nuclei was investigated in detail. The reactions 254Es (46Ti, 3n) 297121 and 252Es (46Ti, 3n) 295121 were found to be experimentally feasible for synthesizing superheavy element Z = 121, with maximal evaporation residue cross sections of 6.619 and 4.123 fb at 219.9 and 223.9 MeV, respectively.

  • 在同质异位素碰撞中通过双平面方法寻找手征磁效应

    分类: 物理学 >> 核物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2024-04-15

    摘要: 在相对论重离子碰撞中寻找手征磁效应(CME)有助于我们理解强相互作用中的CP对称性破缺和量子色动力学(QCD)真空的拓扑性质。基于CME的背景和信号相对于旁观者平面和参与者平面有不同的相关性,实验上提出了一种双平面方法提取CME信号。利用具有不同强度CME的多相输运模型,我们在质心碰撞能量为200 GeV的同质异位素碰撞中重新探讨了双平面方法,发现相对于两个不同平面的CME信号和背景效应的比值系数是不同的,这与目前实验测量中的假设不一致。这种差异来自于相对于旁观者和参与者平面的CME的退关联,它源于末态的相互作用。我们的发现表明,目前的实验测量可能高估了在相对论性重离子碰撞中观测到的末态CME信号的比例。

  • 𝑁 = 28 附近奇 𝐴 核 Co 同位素的晕态研究

    分类: 物理学 >> 核物理学 提交时间: 2024-04-12

    摘要: 奇$A$核$^{53-65}$Co负宇称晕态能级结构的系统性比较表明,$^{55}$Co存在能级$9/2^-$与$11/2^-$反转,且$^{53,57}$Co可能存在较强的集体效应。基于GXPF1A有效相互作用的壳模型计算较好地再现这些核的晕态能级,及相应的磁矩和电四极矩实验值。壳模型计算结果展示$^{53-65}$Co基态$7/2^-$波函数中质子主要组态成分均为$ pi left(1f_{7/2} right)^7$。$^{55}$Co中激发态$9/2^-$与$11/2^-$中$1f_{7/2}$质子激发和$1f_{7/2}$中子激发之间存在竞争,从而导致两能级反转。此外,利用Constrained Hartree-Fock(CHF)方法研究了$^{53,55,57}$Co四极形变特征,结合壳模型计算得到的平均占据数和组态,分析了$^{55}$Co激发态能量相较于其他Co同位素更高的原因。

  • 原子核巨单极共振的统一描述与核物质不可压缩系数

    分类: 物理学 >> 核物理学 提交时间: 2024-04-08

    摘要: 原子核同位旋标量巨单极共振的研究是约束核物质不可压缩系数 $K_ infty$ 的重要途径,对理解核天体物理现象提供了重要的信息。目前巨单极共振研究中存在的主要问题是 Pb 和 Sn 中巨单极共振不能够同时描述的矛盾,它阻碍了核物质不可压缩系数的精确约束。本文综述了准粒子无规相位近似理论和准粒子振动耦合理论对该问题的研究进展。

  • Comparison of different kernel functions in nuclear charge radius predictions by the kernel ridge regression method

    分类: 物理学 >> 核物理学 提交时间: 2024-04-01

    摘要: Using two nuclear models, i) the relativistic continuum Hartree-Bogoliubov (RCHB) theoryand ii) the Weizs acker-Skyrme (WS) model WS$^ ast$,the performances of nine kinds of kernel functions in the kernel ridge regression (KRR) methodare investigated by comparing the accuracies of describing the experimental nuclear chargeradii and the extrapolation abilities.It is found that, except the inverse power kernel, other kernels can reach the same levelaround 0.015-0.016~fm for these two models with KRR method.The extrapolation ability for the neutron rich region of each kernel depends on the trainning data.Our investigation shows that the performances of the power kernel and Multiquadric kernel arebetter in the RCHB+KRR calculation, and the Gaussian kernel is better in the WS$^ ast$+KRR calculation.In addition, the performance of different basis functions inthe radial basis function method is also investigated for comparison.The results are similar to the KRR method.The influence of different kernels on the KRR reconstruct function is discussedby investigating the whole nuclear chart.At last, the charge radii of some specific isotopic chains have been investigatedby the RCHB+KRR with power kernel and the WS$^ ast$+KRR with Gaussian kernel.The charge radii and most of the specific features in these isotopic chainscan be reproduced after considering the KRR method.

  • 用于逆运动学 (3He, t) 电荷交换反应实验的探测系统的设计与模拟优化

    分类: 物理学 >> 核物理学 提交时间: 2024-03-28

    摘要: 中能区电荷交换反应可以从自旋-同位旋激发的角度研究原子核复杂结构。利用中国科学院近代物理研究所的放射性束流线,利用逆运动学方法进行电荷交换反应实验,可以将研究的对象核素拓展至丰中子核乃至不稳定核。基于此,设计了用于电荷交换反应实验的探测器系统,该系统主要包括了3He气体靶、TPC和CsI(Tl) 阵列,其中TPC和CsI(Tl) 阵列构成ΔE-E系统。利用Geant4、Garfield++等模拟软件,优化了TPC的工作条件,确定了实验研究的运动学区间和探测器的基本设计,考察了探测系统的粒子鉴别能力。基于模拟优化,搭建了探测系统。