您选择的条件: 核物理学
  • Testing Validity of the Isobaric Multiplet Mass Equation in 𝑇 = 3 Isospin Septet

    分类: 物理学 >> 核物理学 提交时间: 2024-07-09

    摘要: The validity of the isobaric multiplet mass equation (IMME) is of fundamental importance due to the basicconcept of isospin. Recently, a serious breakdown was found in the 𝐴 = 54 𝑇 = 3 isospin septet, the largest isospinsystem where the validity of IMME have been tested up to now. Motivated by this previous study, the masses of specificisobaric analogue states have been revisited using recent results from advanced mass measurement experiments. It isfound that the IMME holds well in 𝐴 = 50 and 46 isospin septets and the coefficients of IMME also follow the systematictrends. Mass excess values for 50Ni and 46Fe, are predicted to be -3932(20) keV and 898(67) keV, respectively.

  • Indirect neutron radiography experiment on dummy nuclear fuel rods for pressurized water reactors at CMRR

    分类: 物理学 >> 核物理学 提交时间: 2024-06-28

    摘要: Nuclear energy is a vital source of clean energy that will continue to play an essential role in global energy production for future generations. Nuclear fuel rods are core components of nuclear power plants, and their safe utilization is paramount. Due to its inherent high radioactivity, indirect neutron radiography (INR) is currently the only viable technology for irradiated nuclear fuel rods in the field of energy production. This study explores the experimental technique of indirect neutron computed tomography (INCT) for radioactive samples. This project includes the development of indium and dysprosium conversion screens of different thicknesses and conducts resolution tests to assess their performance. Moreover, a pressurized water reactor (PWR) dummy nuclear fuel rods have been fabricated by self-developing substitute materials for cores and outsourcing of mechanical processing. Experimental research on the INR is performed using the developed dummy nuclear fuel rods. The sparse reconstruction technique is used to reconstruct the INR results of 120 pairs of dummy nuclear fuel rods at different angles, achieving a resolution of 0.8 mm for defect detection using INCT.

  • 基于特征伽马谱线测量的中子俘获截面测量方法研究

    分类: 物理学 >> 核物理学 提交时间: 2024-06-25

    摘要: 传统的中子俘获反应截面测量主要通过测量靶核与中子反应后生成的所有伽马射线,再利用理论方法计算目标反应的比例进而得到中子俘获截面。这类方法对理论具有依赖性,并且多种反应道的综合效应会掩盖目标反应的结构特征,在理论预测的共振区得到的也是平滑的截面数据。利用能量分辨高的伽马探测器针对可以代表反应产额的特征伽马谱线进行测量,可以排除其它反应道的干扰,得到准确的中子俘获反应的截面。本文以91Zr(n,gamma) 92Zr反应为例,在中国散列白光中子源上利用此方法对反应截面进行了测量。在理论预测的共振区测到了明显的共振现象,在非共振区的结果与前人的数据在误差范围内保持一致。这表明此方法具有可靠性,并比传统方法具有更高的准确性,希望为其它反应截面的测量提供一种新的思路。

  • Improved isochronous mass spectrometry with tune measurement

    分类: 物理学 >> 核物理学 提交时间: 2024-06-25

    摘要: In conventional isochronous mass spectrometry (IMS) performed at a storage ring, the precision of mass measurement for short-lived nuclei depends on the precise determination of the revolution times (Ts) of stored ions. However, the resolution of T inevitably deteriorates due to the magnetic rigidity spread of the ions, resulting in limited mass resolving power. In this work, we measure the betatron tune Q (the number of betatron oscillations within a single revolution) of the ions, and construct a correlation between T and Q. From this correlation, the T are transformed corresponding to a fixed Q with higher resolution. Using the transformed Ts, we re-determine the masses of 63Ge, 65As, 67Se, and 71Kr, which agree well with the mass values measured by the newly developed IMS (Bρ-IMS). We also study the systematics of Coulomb displacement energies (CDEs) and find that the anomalous staggering in CDEs is removed using the new mass values. This method of T transformation is very useful for the conventional IMS equipped with a single time-of-flight detector.

  • Simultaneous fluorescence and Compton scattering computed tomography based on linear polarization X-ray

    分类: 物理学 >> 核物理学 提交时间: 2024-06-24

    摘要: Owing to the Thomson scattering between relativistic electrons and a laser, continuously polarization-tunable X-rays can be easily generated, providing an excellent probe for advanced X-ray imaging. In this paper, a method for simultaneous fluorescence and Compton scattering computed tomography is proposed using linearly polarized X-rays. The proposed method feasibility was verified using Monte Carlo simulations. In the simulations, the phantom is a polytetrafluoroethylene (Teflon) cylinder inside which are cylindrical columns containing aluminum, water, and gold (Au)-loaded water solutions with Au concentrations ranging between 0.5--4.0 wt%, and a parallel hole collimator imaging geometry was adopted. By adjusting the incident X-ray polarization direction, both the X-ray fluorescence computed tomography (XFCT) and Compton scattering computed tomography (CSCT) images of the phantom were accurately reconstructed using a maximum-likelihood expectation maximization algorithm. A similar attenuation contrast problem for the different cylindrical columns in the phantom can be resolved in the XFCT and CSCT images. The interplay between XFCT and CSCT was analyzed and the contrast-to-noise ratio (CNR) of the reconstruction was improved by correcting for the mutual influence between the two imaging modalities. Compared with K-edge subtraction imaging, XFCT exhibits a CNR advantage for the phantom.

  • Analysis and optimization of performance parameters of the 220Rn chamber in flow-field mode using computational fluid dynamics method

    分类: 核科学技术 >> 辐射防护技术 分类: 物理学 >> 核物理学 提交时间: 2024-06-23

    摘要: The impact of the radiation dose produced by 222Rn/220Rn and its progeny on human health has garneredincreasing interest in the nuclear research field. The establishment of robust, regulatory, and competent 220Rnchambers is crucial for accurately measuring radioactivity levels. However, studying the uniformity of the 220Rnprogeny through experimental methods is challenging, because measuring the concentration of 220Rn and itsprogeny in multiple spatial locations simultaneously and in real time using experimental methods is difficult.Therefore, achieving precise control of the concentration of 220Rn and its progeny as well as the reliable samplingof the progeny pose significant challenges. To solve this problem, this study uses computational fluid dynamicsto obtain the flow-field data of the 220Rn chamber under different wind speeds and progeny-replenishment rates.Qualitative analysis of the concentration distribution of the progeny and quantitative analysis of the progenyconcentration and uniformity of the progeny concentration are conducted. The research findings indicatedthat the progeny-concentration level is primarily influenced by wind speed and the progeny-complement rate.Wind speed also plays a crucial role in determining progeny-concentration uniformity, whereas the progeny-complement rate has minimal impact on uniformity. To ensure the accuracy of 220Rn progeny-concentrationsampling, we propose a methodology for selecting an appropriate sampling area based on varying progenyconcentrations. This study holds immense importance for enhancing the regulation and measurement standardsof 220Rn and its progeny.

  • Performance of the plastic scintillator modules for the top veto tracker of the Taishan Antineutrino Observatory

    分类: 物理学 >> 核物理学 分类: 工程与技术科学 >> 工程通用技术 提交时间: 2024-06-21

    摘要: For tracking and tagging the cosmic-ray muon (CR-muon), the Taishan Antineutrino Observatory (TAO) experiment is equipped with a top veto tracker (TVT) system composed of 160 modules, each consisting of plastic scintillator (PS) strip as target material, embedded wavelength shifting fiber (WLS-fiber) as photon collection and transmission medium, and silicon photomultipliers (SiPMs) at both ends as read-out. This article introduces the unique design of the module and reports the excellent performance of all modules, providing guidance and important reference for the process design of scintillation detectors with WLS-fibers. In general, when the CR-muon hits the center of plastic scintillator and without optical grease, the most probable value of the signal amplitude at one end of the PS strip is greater than 40.8 p.e. and 51.5 p.e. for all the 2 m-length modules and 1.5 m-length modules respectively. The CR-muon tagging efficiency of PS module is measured to be more than 99.3%, which meets the requirement of TAO.

  • Production and Test of sPHENIX W/SciFiber Electromagnetic Calorimeter Blocks in China

    分类: 物理学 >> 基本粒子与场物理学 分类: 物理学 >> 核物理学 提交时间: 2024-06-20

    摘要: The sPHENIX experiment is a new generation of large acceptance detector at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory with scientific goals focusing on probing the strongly interacting Quark-Gluon Plasma (QGP) with hard probes of jets, open heavy flavor particles and $ Upsilon$ production. The EMCal detector, covering the pseudo-rapidity region of $ eta leq 1.1$, is an essential subsystem of sPHENIX. In this paper, we focus on the production and test for the EMCal blocks covering a pseudo-rapidity of $ eta in 0.8 , 1.1 $. These, in conjunction with central pseudo-rapidity EMCal blocks, significantly enhance the sPHENIX physics capability of jet and $ Upsilon$ particle measurements. In this paper, detector module production and testing of the sPHENIX W-powder/Scintillating Fiber (W/ScFi) Electromagnetic Calorimeter Blocks are presented. Selection of the tungsten powder, mold fabrication, QA procedures and cosmic ray test results are discussed.

  • Towards adaptable synchrotron image restoration pipeline

    分类: 物理学 >> 核物理学 提交时间: 2024-06-20

    摘要: Synchrotron microscopic data commonly suffer from poor image quality with degraded resolution incurred by instrumentation defects or experimental conditions. Image restoration methods are often applied to recover the reduced resolution, providing improved image details that can greatly facilitate scientific discovery. Among these methods, deconvolution techniques are straightforward, yet either require known prior information or struggle to tackle large experimental data. Deep learning (DL)-based super-resolution (SR) methods handle large data well, however data scarcity and model generalizability are problematic. In addition, current image restoration methods are mostly offline and inefficient for many beamlines where high data volumes and data complexity issuesare encountered. To overcome these limitations, an online image-restoration pipeline that adaptably selects suitable algorithms and models from a method repertoire is promising. In this study, using both deconvolution and pretrained DL-based SR models, we showthatdifferent restoration efficacies can be achieved on different types of synchrotron experimental data. We describe the necessity, feasibility, and significance of constructing suchan image-restoration pipeline for future synchrotron experiments.

  • 离子回旋共振法同位素分离研究进展综述

    分类: 物理学 >> 核物理学 提交时间: 2024-06-15

    摘要: 离子回旋共振同位素分离(Ion Cyclotron Resonance Isotope Separation, ICR-IS)方法自上世纪提出以来,受到了世界各国研究者和产业界的广泛关注。本文基于国内外研究者公开发表的有关ICR-IS的研究成果,综述了ICR-IS方法的基本原理、装置基本结构、产生显著同位素分离效应需要满足的主要约束条件,以及用于不同种类同位素分离的ICR理论与实验研究进展,进而简要探讨了推动该方法走向实际工程应用仍需深入研究的关键科学问题。

  • Vibration Attenuation on HEPS Bare Ground with Different Frequencies

    分类: 物理学 >> 核物理学 提交时间: 2024-06-11

    摘要: 高能光子源 (HEPS) 对存储环板的振动水平有严格的限制。如果振动水平超过规格限值,会影响设备的正常运行,影响实验终端的采样效率。随着周边城市基础设施建设的不断扩大,为了控制外部振动源,有必要研究HEPS场地的振动传播特性。为了评估外部振动对HEPS关键组件的影响,已经进行了一系列测量。振动台用于人工生成频率为 7Hz 至 100 Hz 的垂直正弦激励。沿裸露地面测量振动响应,分析不同频率的振动衰减。根据测量数据的拟合结果,得到衰减公式和关键参数范围。同时,通过在HEPS现场行驶的50吨起重机的振动数据验证了衰减公式。测量数据与上述拟合公式非常吻合。测量数据与拟合曲线之间的差异在 $35 %$ 以内。本研究将为HEPS校园周边外部行驶载荷的相关调控奠定基础,同时为地面振动传播的研究方法提供参考。

  • Improved mass relations of mirror nuclei

    分类: 物理学 >> 核物理学 提交时间: 2024-06-04

    摘要: In this study, we revisit the previous mass relations of mirror nuclei by considering 1/N- and1/Z-dependent terms and the shell effect across a shell. The root-mean-squared deviation is 66 keVfor 116 nuclei with neutron number N ≥ 10, as compared with experimental data compiled in theAME2020 database. The predicted mass excesses of 173 proton-rich nuclei, including 98 unknownnuclei, are tabulated in the Supplemental Material herein with competitive accuracy.

  • The medium temperature dependence of jet transport coefficient in high-energy nucleus-nucleus collisions

    分类: 物理学 >> 核物理学 提交时间: 2024-06-03

    摘要: The medium temperature $T$ dependence of jet transport coefficient $ hat q$ is studied via nuclear modification factor $R_{AA}(p_{ rm T})$ and elliptical flow parameter $v_2(p_{ rm T})$ for large transverse momentum $p_{ rm T}$ hadrons in high-energy nucleus-nucleus collisions. Within a next-to-leading order perturbative QCD parton model for hard scatterings with modified fragmentation functions due to jet quenching controlled by $ hat q$, we check the suppression as well as the azimuthal anisotropy for large $p_{ rm T}$ hadrons, and extract $ hat q$ by global fits to $R_{AA}(p_{ rm T})$ and $v_2(p_{ rm T})$ data in $A+A$ collisions at RHIC and the LHC, respectively. Numerical results from the best fits show that $ hat q/T^3$ goes down with the local medium temperature $T$ in the parton jet trajectory. Compared with the case of a constant $ hat{q}/T^3$, the going-down $T$ dependence of $ hat{q}/T^3$ makes a hard parton jet to lose more energy near $T_c$ and therefore strengthens the azimuthal anisotropy for large $p_{ rm T}$ hadrons. As a result, $v_2(p_{ rm T})$ for large $p_{ rm T}$ hadrons is enhanced by about 10 % to fit data better at RHIC/LHC. Considering the first-order phase transition from QGP to the hadron phase and additional energy loss in the hadron phase, $v_2(p_{ rm T})$ is again enhanced by 5-10 % at RHIC/LHC.

  • Simulation and reconstruction of particle trajectories in the CEPC drift chamber

    分类: 物理学 >> 核物理学 提交时间: 2024-06-02

    摘要: The Circular Electron Positron Collider (CEPC) is designed to precisely measure the properties of the Higgs boson, study electroweak interactions at the Z-boson peak, and search for new physics beyond the Standard Model. As a component of the 4th Conceptual CEPC detector, the drift chamber facilitates the measurement of charged particles. This study implemented a Geant4-based simulation and track reconstruction for the drift chamber. For the simulation, detector construction and response were implemented and added to the CEPC simulation chain. The development of track reconstruction involved track finding using the Combinatorial Kalman Filter method and track fitting using the tool of GenFit. Using the simulated data, the tracking performance was studied. The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.

  • Fast X-ray Imaging Beamline at SSRF

    分类: 物理学 >> 核物理学 提交时间: 2024-05-29

    摘要: The fast X-ray imaging beamline (BL16U2) at Shanghai Synchrotron Radiation Facility (SSRF) is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales, spanning from 100 ps to μs and ms. This beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena, such as the deformation and failure of materials subjected to intense dynamic loads. In addition, it enables the study of high-pressure and high-speed fuel spray processes in automotive engines. The light source of this beamline is a cryogenic permanent magnet undulator (CPMU) that is cooled by liquid nitrogen. This CPMU can generate X-ray photons within an energy range of 8.7-30 keV. The beamline offers two modes of operation: monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator (DCM) and pink beam mode with the first crystal of the DCM out of the beam path. Four X-ray imaging methods were implemented in BL16U2: single-pulse ultrafast X-ray imaging, microsecond-resolved X-ray dynamic imaging, millisecond-resolved X-ray dynamic micro-CT, and high-resolution quantitative micro-CT. Furthermore, BL16U2 is equipped with various in situ impact loading systems, such as a split Hopkinson bar system, light gas gun, and fuel spray chamber. Following the completion of the final commissioning in 2021 and subsequent trial operations in 2022, the beamline has been officially available to users from 2023.

  • Rutherford’s Atomic Nucleus versus Landau’s Gigantic Nucleus: Does Nature favor flavor symmetry?

    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: 2024-05-29

    摘要: It is hypothesized that, though atomic nuclei are made of nucleons, strongly interacting matter with baryon number from $A simeq 10^{3-9}$ to $ sim 10^{57}$ would be composed of strangeons if Nature favors always the flavor symmetry of quarks.According to that logic, strangeon matter with $A sim 10^{57}$ could manifest in the form of pulsar-like compact stars, and multi-messenger observations with advanced facilities (e.g., China’s FAST) could eventually provide a disproof/proof.It is worth emphasizing that this point of view, based on established “old physics”, may have particular consequences for understanding our material world, for both normal luminous matter and the dark sector.

  • 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。