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  • Electromagnetic Fields of Moving Point Sources in the Vacuum

    分类: 信息科学与系统科学 >> 信息科学与系统科学基础学科 分类: 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类: 天文学 >> 天文学 提交时间: 2024-05-22

    摘要: The electromagnetic fields of point sources with time varying charges moving in the vacuum are derived using the Liénard-Wiechert potentials. The properties of the propagation velocities and the Doppler effect are discussed based on their far fields. The results show that the velocity of the electromagnetic waves and the velocity of the sources cannot be added like vectors; the velocity of electromagnetic waves of moving sources are anisotropic in the vacuum; the transverse Doppler shift is intrinsically included in the fields of the moving sources and is not a pure relativity effect caused by time dilation. Since the fields are rigorous solutions of the Maxwell’s equations, the findings can help us to abort the long-standing misinterpretations concerning about the classic mechanics and the classic electromagnetic theory. Although it may violate the theory of the special relativity, we show mathematically that, when the sources move faster than the light in the vacuum, the electromagnetic barriers and the electromagnetic shock waves can be clearly predicted using the exact solutions. Since they cannot be detected by observers in the region outside their shock wave zones, an intuitive and reasonable hypothesis can be made that the superluminal sources may be considered as a kind of electromagnetic blackholes.

  • 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.

  • Non-perturbative corrections to the planetary perturbation equation

    分类: 天文学 >> 天体力学 分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-05-16

    摘要: 本文简要介绍新的对称形式的质点动力学方程对天体动力学理论的系统性改进。 首先,对于开放的多体系统,无法找到近似程度非常高的惯性系,在传统理论中不得不引入惯性系的近似,而对称新方程因为可以直接适用于任意的平动参考系而避免了惯性系的近似,从而可以提高理论预言的精度。其次,对于束缚的多体系统,传统理论的动力学应用是先引入质心参考系,在质心参考系中应用牛顿第二定律,然后通过坐标变换再转化到实体参考系,比如太阳系的行星摄动方程。 但是,应用对称新方程则可以一步到位推导得到行星摄动方程。最后,如果进一步考虑行星受到临时推力或者冲击力,甚至为了进一步提高计算精度进而考虑来自束缚系统外的作用力,则一个可以叠加非微扰作用力的行星摄动的修正方程在本文得到了确立。

  • Turing’s thinking machine and ’t Hooft’s principle of superposition of states

    分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 分类: 计算机科学 >> 计算机科学技术其他学科 提交时间: 2024-05-14

    摘要: In his 1950 paper 11 , Turing proposed the notion of a thinking machine, namely a machine that can think. But a thinking machine has to follow a certain law of physics, provided it is realized physically. In this paper, we show that Turing’s thinking machine necessrily obeys ’t Hooft’s principle of superposition of states, which was presented by ’t Hooft 8 in 2016 beyond the usual one as described by Dirac 4 in the conventional quantum mechanics. Precisely, Turing’s thinking machine must be a quantum machine, while ’t Hooft’s principle characterizes its thinking behavior in a probabilistic way.

  • 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。

  • 统计流体力学:湍流力学 I

    分类: 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 提交时间: 2024-05-09

    摘要: 工程中必须处理的以及人们在自然中碰到的流体,其流动在绝大多数情况下是湍动的,对这些流动的描述需要一种统计性的方法。容易描述的层流(Laminar flow)异常少见。我们相信,流体力学不能只局限于这些很少碰到的特殊情形,并且个别层流的经典描述虽然无疑重要而有价值,但是只能作为真正湍流理论的导引章节。在湍流理论中,研究的目标是宏观上相同外界条件下的流动系综的性质。

  • 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。

  • Ultra-low-noise transimpedance amplifier with a single HEMT in pre-amplifier for measuring shot noise in cryogenic STM

    分类: 工程与技术科学 >> 物理学相关工程与技术 分类: 工程与技术科学 >> 仪器仪表技术 分类: 电子与通信技术 >> 电子技术 分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2024-05-06

    摘要: 本文提出了一种用于低温扫描隧道显微镜(CryoSTM)的跨阻放大器(TIA)设计方案。在CryoSTM中带有尖端样品成分的TIA称为CryoSTM-TIA。该CryoSTM-TIA的跨阻增益在1Gohm,而其带宽大于300kHz。所提出的CryoSTM-TIA的独特特点是其前置放大器由单个低温高电子迁移率晶体管(HEMT)制成,因此在100kHz时仪器等效输入噪声电流功率谱密度低于4(fA)2/Hz。此外,应用“偏置冷却法”可用于原位控制HEMT掺杂区冻结DX-中心的密度,改变其结构以降低器件噪声。利用该仪器,可以进行高能量分辨率的快速扫描隧道光谱测量。并且,它能够测量各种量子系统在原子尺度上的扫描隧道散粒噪声谱(STSNS),即使散粒噪声非常低。它为通过测量STSNS来研究新的量子态提供了一个强大的工具,例如检测拓扑量子系统中马约拉纳束缚态的存在。

  • Low-noise large-bandwidth high-gain transimpedance amplifier for cryogenic STM at 77 K

    分类: 电子与通信技术 >> 电子技术 分类: 工程与技术科学 >> 仪器仪表技术 分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 分类: 物理学 >> 凝聚态:电子结构、电、磁和光学性质 提交时间: 2024-05-06

    摘要: In this work, we design and fabricate the transimpedance Amplifier (TIA) following the design mentioned in Ref. cite{Liang2024}. In the TIA, the preamplifier (Pre-Amp) is made of a junction field effect transistor (JFET) that can work at 77 K. The post-amplifier is made of an operational amplifier (OPA). Cascade Pre-Amp and Post-Amp to form the inverting-amplifier (Inv-Amp). The gain-bandwidth product of Inv-Amp with the gain about 50,000 is higher than 10 GHz. With a 1.13 Gohm feedback network, the gain of TIA is 1.13 Gohm and its bandwidth is about 97 kHz. The equivalent input noise voltage power spectral density of TIA is not more than 9 (nV)2/Hz at 10 kHz and 4 (nV)2/Hz at 50kHz, and its equivalent input noise current power spectral density is about 26 (fA)2/Hz at 10 kHz and 240(fA)2/Hz at 50 kHz. The measured transport performances and noise performances of TIA are consistent with the simulations and calculations, verifying the feasibility for the design of low-noise large-bandwidth TIA proposed in Ref. 1 . And, TIA with various performances that meet various needs can be designed according to the design methods in Ref. 1,2 . With the same gain, the bandwidth of the TIA in this work is much larger than the present TIA and its noises are much lower than those of present ones. The TIA in this work is perfect for the cryogenic STM working at 77 K (i.e. liquid nitrogen temperature).

  • 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.

  • Understanding Fivefold Symmetry in Electron-Diffraction Patterns

    分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2024-04-22

    摘要: Electron-diffraction patterns with5-fold rotational symmetry of experimental alloy phases are assumedto be produced by periodic structures. Two three-dimensionalperiodic structures are presented based on regular pentagonal dodecahedrons. These structures can be used as atomic models todescribe the alloy phases. The Fourier-transform patterns of themodels are found to be similar to the correspondingelectron-diffraction patterns of these alloy phases. Details of themotivations and approaches that lead to thesemodels are also discussed. 

  • Correction to the quantum relation of photons involved in the Doppler effect in the framework of a special Lorentz violation model

    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: 2024-04-22

    摘要: In this paper we followed the idea in Ref. 1 to discuss the Doppler frequency shift of photons and the Compton scattering between photons and electrons, pointing out that followingthe idea we have to modify the usual quantum relation of massless particle. But due to limitedinformation and knowledge, we couldn’t yet determine the specific expression for the correctioncoefficient of the quantum relation of massless particle. However, the phenomenon of spontaneous radiation in a cyclotron maser give us an opportunity to see what the expression for this correctioncoefficient might look like, as the phenomenon of spontaneous radiation in a cyclotron maser canbe explained by the effect of Doppler frequency shift of virtual photons and Compton scatteringbetween virtual photons and electrons. Therefor, under some restrictive conditions, we construct a very concise expression for this correction coefficient by discussing different cases. And then we used this expression to analyze the wavelength of radiation in the cyclotron maser, which tends toa limited value at v→c, rather than to 0 as in the Lorentz model. This paper still inherits the idea inRef. 1 that the energy and momentum of particles cannot be infinite, otherwise it will make some equations meaningless, and this view is also from the idea in some quantum gravity models. This paper also provides us with a possible experimental scheme to determine the value of Qin Ref. 1 , but it still requires extremely high experimental energy.