分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2024-07-18
摘要： 本文介绍了惯性力这一物理学史上长期引发争论的概念在揭示本质方面的新进展。在此基础上，系统地介绍了这一概念性的突破对改进物理教学的意义。首先，经典力学框架下的所有定理原则上都可以推广到任何的平动参考系，前提是将原表述中质点受力项的物理意义从统计全部受力替换为统计相对的受力。其次，在分析力学中，由于在一般情况下，与势能相对应的保守力通常是作用在质点上的力的一部分，因此只需确保将参考原点选在与势能相对应的保守力的矢量和始终为零的位置即可。然而，在一般平动参考系的情况下，必须在拉格朗日量和哈密顿量的表达式中加入一个因作用在参考物上的力而导致的势能修正项。最后，质点动力学的对称新方程同样可以自然推广到质点系。在平动参考系中建立推广的质心运动定理和推广的定轴转动定理。最后，为体现实用上的改进优势， 讨论了多体动力学。原则上，在传统方案中通过引入质心参考系来应用牛顿第二定律，看似严格，不过带来了步骤上的迂回。相比之下，通过应用牛顿动力学的对称新方程，行星摄动方程的推导一步到位直截了当。更重要的是，多体系统的质心参考系严格地说仍然只是对惯性系的更高阶近似， 因此，通过考虑非引力相互作用，乃至天体系统外的其他受力，只有对称新方程才可以真正严格地得到行星摄动方程在经典力学框架下的所有可能修正。
分类： 物理学 >> 核物理学 提交时间： 2024-07-17
摘要： We present a theoretical study of the medium modifications on the $p_T$ balance ($x_J$) of dijets in Xe+Xe collisions at $sqrt{s_{NN}}$ = 5.44 TeV. The initial production of dijets is carried out by the POWHEG+PYTHIA8 prescription, which matches the next-to-leading order (NLO) QCD matrix elements with the parton shower (PS) effect. The in-medium evolution in nucleus-nucleus collisions is described by the SHELL model with a transport approach. The theoretical results of the dijet $x_J$ in Xe+Xe collisions exhibit more imbalanced distributions than that in p+p, consistent with the 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 investigate 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 qg component plays a key role in the increased imbalance of the dijet $x_J$ , and especially the $q_1g_2$ (quark-jet-leading) dijets experience more significant asymmetric energy loss than the $g_1q_2$ (gluon-jet-leading) dijets as traversing the QGP. By comparing the $∆⟨x_J⟩$ of inclusive, ccbar and bbbar dijets in Xe+Xe collisions, we observe $∆⟨x_J⟩_{incl.} > ∆⟨x_J⟩_{ccbar} > ∆⟨x_J⟩_{bbbar}$. Moreover, $ρ_{Xe,Pb}$, the ratios of nuclear modification factors of dijets in Xe+Xe to that in Pb+Pb, are calcualted, which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe due to the larger radius of the lead nucleus.
分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2024-07-16
摘要： This paper presents a new development in revealing the nature of the inertial force, a concept that has long stimulated discussion in the history of physics. On this basis, its implications are systematically introduced for the improvement of physics teaching. Firstly, all the theorems in the framework of classical mechanics can be form-invariant generalized to any translational frame of reference, provided that the physical meaning of the force term of the particle in the original formulation is replaced from the total forces to the forces being relatively accounted for. Secondly, in analytical mechanics, since in general the conservative force corresponding to the potential energy is typically a part of the forces acting on the particle, it is enough to ensure that the reference origin is chosen at a position where the vector sum of the conservative forces corresponding to the potential energy is always zero. However, in the case of a general translational reference frame, a correction term for the potential energy due to the forces acting on the reference object must be included in the expression of the Lagrangian and Hamiltonian quantities. Thirdly, the symmetric new equation is applied to the system of particles. The generalized center-of-mass motion theorem and the generalized fixed-axis rotation theorem in the translational reference frame are developed. Finally, for instance, the multi-body dynamics is discussed. In principle, the detour that is introduced by the center-of-mass reference frame can be directly omitted and crossed. To illustrate this, the planetary perturbation equation is demonstrated to be derived in a single step by applying the symmetric new equation of Newtonian dynamics. Besides, the introduction of the symmetric new equation has led to further improvements and refinements in the planetary perturbation equation.
分类： 物理学 >> 核物理学 提交时间： 2024-07-13
摘要： 加速器电子束参数的无损间接测量是一个难题，储存环上传统的X射线针孔成像（X-ray pinhole imaging）方法和直线加速器上的狭缝衍射法（ODR）都存在不足之处。激光康普顿散射（Laser Compton Scattering，简称LCS）装置是利用相对论电子与低能光子相互碰撞产生高能伽马束的新光源。文中提出了一种基于激光康普顿散射光源测量能谱提取电子束参数的方法，该研究旨在通过自主开发的基于Geant4的蒙特卡洛程序模拟重建出与实验测量能谱符合一致的模拟谱，从而获得电子束参数，包括水平方向束斑尺寸、电子能量和发射度。在对上海同步辐射装置（SSRF，简称上海光源）的激光伽马光束线站（SLEGS）上的多碰撞角度伽马测量能谱做了一致性的验证,结果表明：提取的上海光源储存环电子束参数与理论值符合得较好。这证明了激光康普顿散射是一个有效的电子束参数无损间接测量方法，为后续其他电子束的提取奠定基础。
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.
分类： 物理学 >> 核物理学 提交时间： 2024-06-28
Yong Sun
Qi-Biao Wang
Peng-Cheng Li
Ming Xia
Bin Liu
He-Yong Huo
Wei Yin
Yang Wu
Sheng Wang
Chao Cao
Xin Yang
Run-Dong Li
Hang Li
Bin Tang
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.
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。
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.
分类： 物理学 >> 核物理学 提交时间： 2024-06-24
Zhi-Jun Chi
Hong-Ze Zhang
Jin Lin
Xuan-Qi Zhang
Hao Ding
Qi-Li Tian
Zhi Zhang
Ying-Chao Du
Wen-Hui Huang
Chuan-Xiang Tang
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.
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.
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.
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
Xiaozhou Yu
Xiyang Wang
Weihu Ma
Shihong Fu
Pengfei Sun
Jinxing Song
Wanbin He
Yang Shen
Long Ma
Jinhui Chen
Huan Zhong Huang
Siguang Wang
Jing Zhou
Xiaomei Li
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.
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.
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。
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2024-06-15
摘要： 受来自引力的全息理论以及 AdS/CFT 对偶性中所揭示的量子纠缠与时空间可能存在深刻联系的启发，本文尝试在量子测量、量子纠缠以及时空间建立一种联系，提出了一种“多时空”方案。在该方案下，可以同时解决量子测量中的优先基矢问题和明确结果问题。并且揭示出了经典时空来源于量子测量。但该方案的一个衍生结果是宇宙中的经典时空数量不是唯一的，而是可能存在很多个。“多时空”方案使测量仪器或观察者沦为了普通地位，以及被测系统和测量仪器间的地位是平等的。然而目前这种方案的提出仍然是框架性的或认识性的，它的检验依赖于量子引力的建立，但同时也为未来量子引力在同时处理经典时空、量子测量和量子纠缠问题时提供了一种可能的方向。
分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2024-06-14
摘要： 本文研究了具有磁矩和磁荷静态中子星的引力透镜效应。在该中子星时空中，光子的偏转角与中子星磁荷和质距比成正比，与中子星磁矩成反比。特别的，当磁荷取 0.5 时，偏转角为定值，与磁矩的变化无关；当磁矩和磁荷都趋向零时，所有参数都会回归到 Schwarzschild 情况。
分类： 物理学 >> 核物理学 提交时间： 2024-06-11
Yu-Ning Yang
Fang Yan
Zi-Hao Wang
Xiang-Yu Tan
Wen-Jie Wu
Xiang-Rong Fu
Jun Lei
Guo-Ping Lin
Gang Xu
Wei-Min Pan
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。
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2024-06-11
摘要： We propose a simple, direct and verifiable explanation for the neutrino oscillations. This explanation is based on the exchange effect between identical particles. Specifically, the experimental neutrinos acquire a tiny potential energy inversely proportional to their energy by exchanging with the Cosmic Neutrino Background (CνB). This exchange occurs both between neutrinos of the same flavour and between neutrinos of different flavours, and the latter makes the three potential energy eigenstates of the experimental neutrinos different from the three flavour eigenstates. In terms of the effect on the phase factor of the wave function, a neutrino having a tiny potential energy inversely proportional to its energy is equivalent to it having a tiny apparent mass, and the potential eigenstates being a mixture of flavour eigenstates is equivalent to the mass eigenstates being a mixture of flavour eigenstates. We calculate the potential eigenvalues and eigenstates of the potential energy matrix expressed by the exchange amplitudes between the experimental neutrinos and the CνB, and determine the matrix (with one free parameter) by using the measurement data of the neutrino oscillation experiments. The values of the matrix elements have the features that are consistent with the prediction of the Standard Cosmological Model (SCM) for the distribution of the CνB. In addition, the SCM predicts the magnitude of the background neutrino flux, and according to our theory, if the flux of experimental neutrinos is much larger than that of the background neutrinos, then the neutrino exchange may change the distribution of the background neutrinos, and thus change the apparent mass of the neutrinos as well as the way of mixing. This provides a new and unified perspective to explain various anomalies in experiments involving high-flux neutrino sources. Systematically studying the relationship between these anomalies and the magnitude of neutrino flux through experiments would provide a realistic way to test our theory.
分类： 物理学 >> 地球物理学、天文学和天体物理学 分类： 信息科学与系统科学 >> 信息科学与系统科学基础学科 提交时间： 2024-06-09
Wenlong Sun
Fengfeng Shi
Yuting Lin
Jinfeng Xu
Shaofeng He
Yongxin Lin
Guocheng Wang
Run Zhao
Pei Ma
摘要： The precise estimation of the satellite clock bias (SCB) holds considerable importance in ensuring accurate timekeeping, navigation, and positioning. This studyintroduces a novel SCB prediction approach that integrates variational mode decomposition (VMD) and long short-term memory (LSTM) network techniques, combining signal decomposition with deep learning methodologies. Initially, the raw SCB data undergoespreprocessing, followed by decomposition using the VMD method to generate multiple intrinsic mode functions (IMFs). These decomposed IMFs serve as inputs for LSTM, where several independent LSTM models are established for training and prediction purposes. Subsequently, the predicted outcomes are aggregated and reconstructed to derive the finalSCB prediction. Experimental findings demonstrate notable advancements in clock bias prediction for the spaceborne hydrogen atomic clock for BDS, with prediction accuracies of 0.048 ns, 0.204 ns and 1.397 ns for 6 hours, 3 days and 15 days, respectively. These results exhibit significant enhancements compared to both the LSTM network and the Back Propagation (BP) neural network, with improvements of 56%, 84% and 83% for the aforementioned time intervals in comparison to LSTM, and enhancements of 59%, 82% and 83% relative to the BP neural network.
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.
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