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  • 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。

  • 三维EAST离子回旋波传播及其加热模型构建及对比

    分类: 物理学 >> 核物理学 提交时间: 2024-03-27

    摘要: 采用有限元法和热介电张量模拟研究了非一次吸收假设,以及一次吸收假设对EAST四电流带天线少数离子加热波传播和功率沉积的影响。模拟结果显示:在其他参数相同的条件下,当天线电流相位为(0 0 π π)和(0 π π 0)时,两种模型计算的天线附近电场分布基本一致;当天线电流相位为(0 π 0 π)时,两个模型的电场模拟结果出现显著差别。环向传播多圈的离子回旋波是导致结果差异的主要原因。环形聚变装置中,当波的平行波数较大时,一次吸收假设的模拟结果偏小。对于环形聚变装置,一次吸收假设的适用性需要进一步系统的研究。

  • 国内外介子束流实验的发展现状和未来计划

    分类: 物理学 >> 核物理学 提交时间: 2024-03-22

    摘要: 介子束流与原子核碰撞实验在中高能核物理和粒子物理研究领域发挥了重要推动作用,特别是在强子谱研究方面取得了一系列重要实验测量结果。本文对目前国际上几个比较典型的介子束流实验进行了梳理与总结,这包括了位于日本的 J-PARC 实验;欧洲核子中心的 COMPASS 实验、AMBER 实验以及计划中的 HIKE实验;美国 JLab 的 GlueX 实验和 EIC 项目。进一步,我们基于国内的 HIAF 装置对可能产生的次级介子束流的参数指标进行了分析估算,并讨论了可以开展的相关物理测量。通过对这些实验项目的调研分析,旨在为进一步规划和建造我国的介子束流实验装置并开展强子物理方面的研究有所启发和借鉴。

  • Design and Construction of Charged Particle Telescope Array for Study of Exotic Nuclear Clustering Structure

    分类: 物理学 >> 核物理学 提交时间: 2024-03-19

    摘要: The exploration of exotic shapes and properties of atomic nuclei, e.g., α cluster and toroidal shape, is afascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detectingmultiple alpha-particle events was designed and constructed. The detector comprises two layers of double-sidedsilicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers arrayas light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDscouple with cesium iodide crystal arrays are used to distinguish multiple alpha hits. The detector array has acompact and integrated design that can be adapted to different experimental conditions. The detector array wassimulated using Geant4, and the excitation energy spectra of some alpha-clustering nuclei were reconstructedto demonstrate the performance. The simulation results show that the detector array has excellent angularand energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple alpha particleevents. This detector offers a new and powerful tool for nuclear physics experiments and has the potential todiscover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms

  • Feasibility study of the photonuclear reaction cross section of medical radioisotopes using a laser Compton scattering gamma source

    分类: 物理学 >> 核物理学 提交时间: 2024-03-19

    摘要: In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.

  • 预碎片的衰变对中能区重离子碰撞过程中集体流和核阻止本领的影响

    分类: 物理学 >> 核物理学 提交时间: 2024-03-19

    摘要: 重离子碰撞过程中轻粒子的产生对于提取核物质状态方程的信息有着重要的作用。基于极端相对论量子分子动力学(UrQMD)模型,利用统计衰变模型GEMINI++处理预激发碎片的衰变,研究了预碎片的衰变对中能区Au+Au碰撞过程中轻粒子的集体流和核阻止本领的影响。研究发现,由于记忆效应,重离子碰撞过程中的预碎片的衰变产生的子核继承了母核的部分动力学性质,在考虑预碎片的衰变后可以更好地描述实验数据,并且这种效应对观测量的影响随碰撞能量的升高而减弱。结果表明,重离子碰撞过程中预碎片的衰变以及轻粒子的产生对敏感于核物质状态方程的观测量有着一定的影响。在利用这些观测量提取核物质状态方程的信息时应当仔细处理。

  • 转动、堵塞效应和八极形变对 U 和 Pu 同位素对关联的影响

    分类: 物理学 >> 核物理学 提交时间: 2024-03-18

    摘要: 通过在Nilsson势中引入八极关联相互作用,基于推转壳模型(CSM)下的粒子数守恒方法(PNC)处理包含单极和四极对力的哈密顿量,研究了反射不对称(RA)原子核的基态转动带。基于此,PNC-CSM的计算结果重现了轻锕系区偶偶核236,238U和238,240Pu的交替宇称带,以及奇-𝐴核237U和239Pu的宇称带双重带的转动惯量实验值。与相邻偶偶核236,238U和238,240Pu相比,奇-𝐴核237U和239Pu的𝑠=−𝑖内禀转动带的转动惯量增加了50%∼60%。这些增加的转动惯量主要是由费米面附近中子轨道的泡利堵塞效应减弱了中子体系的对关联导致。U和Pu同位素中,转动惯量随着转动频率缓慢增加则可以解释为转动使得体系的对关联减弱。在低频率区,反射不对称原子核的转动惯量明显高于相对应的反射对称(RS)原子核的转动惯量。并且,与反射对称原子核相比,较大的八极形变将导致反射不对称原子核体系的对关联减弱更加明显。

  • Research on Intelligent Search-and-Secure Technology in Accelerator Hazardous Areas Based on Machine Vision

    分类: 物理学 >> 核物理学 提交时间: 2024-03-13

    摘要: Prompt radiation emitted during accelerator operation poses a significant health risk, necessitating a thorough search and securing of hazardous areas prior to initiation. Currently, manual sweep methods are employed. However, the limitations of manual sweeps have become increasingly evident with the implementation of large-scale accelerators. By leveraging advancements in machine vision technology, the automatic identification of stranded personnel in controlled areas through camera imagery presents a viable solution for efficient search and security. Given the criticality of personal safety for stranded individuals, search and security processes must be sufficiently reliable. To ensure comprehensive coverage, 180° camera groups were strategically positioned on both sides of the accelerator tunnel to eliminate blind spots within the monitoring range. The YOLOV8 network model was modified to enable the detection of small targets, such as hands and feet, as well as larger targets formed by individuals near the cameras. Furthermore, the system incorporates a pedestrian recognition model that detects human body parts, and an information fusion strategy is used to integrate the detected head, hands, and feet with the identified pedestrians as a cohesive unit. This strategy enhanced the capability of the model to identify pedestrians obstructed by equipment, resulting in a notable improvement in the recall rate. Specifically, recall rates of 0.915 and 0.82 were obtained for Datasets 1 and 2, respectively. Although there was a slight decrease in accuracy, it aligned with the intended purpose of the search-and-secure software design. Experimental tests conducted within an accelerator tunnel demonstrated the effectiveness of this approach in achieving reliable recognition outcomes.

  • FPGA implementation of 500-MHz high-count-rate high-time-resolution real-time digital neutron-gamma discrimination for fast liquid detectors

    分类: 物理学 >> 核物理学 提交时间: 2024-03-11

    摘要: Fast neutron flux measurements with high count rates and high time resolution have important applications in equipment such as tokamaks. In this study, real-time neutron and gamma discrimination was implemented on a self-developed 500-Msps, 12-bit digitizer, and the neutron and gamma spectra were calculated directly on an FPGA . A fast neutron flux measurement system with BC-501A and EJ-309 liquid scintillator detectors was developed and a fast neutron measurement experiment was successfully performed on the HL-2M tokamak at the Southwestern Institute of Physics, China. The experimental results demonstrated that the system obtained the neutron and gamma spectra with a time accuracy of 1ms. At count rates of up to 1 Mcps, the figure of merit was greater than 1.05 for energies between 50 keV and 2.8 MeV. 

  • 6Li-D热核反应的聚变三乘积计算

    分类: 物理学 >> 核物理学 提交时间: 2024-03-11

    摘要: 聚变三乘积(Fusion triple product)是可自持核聚变反应的重要判据,它利用聚变堆中核燃料的原子核数密度$n$、等离子体约束时间$τ_ mathrm{E}$、燃料温度$T$这三个物理量来判断聚变反应堆是否能满足实现自持核聚变的能量平衡条件。本研究探讨了以$^{6}$Li-D作为核燃料的聚变反应系统,并考虑了相对论效应对轫致辐射的影响以及能量回收效率对能量增益因子$Q$的影响,计算了忽略回旋辐射条件下$^{6}$Li-D聚变反应系统的聚变三乘积($n_ mathrm{i}Tτ_{ mathrm{E}}$= SI{4.9e23}{ per cubic meter kilo electronvolt second})。结果表明,$^{6}$Li-D可以作为核聚变燃料实现正的能量增益,但其实现自持核聚变的点火条件相对于D-T核聚变的点火条件来说更为困难。

  • Feasibility of medical radioisotope production based on the proton beams at China Spallation Neutron Source

    分类: 物理学 >> 核物理学 提交时间: 2024-03-10

    摘要: Theutilization of a proton beam fromthe China Spallation Neutron Source (CSNS) for producingmedical radioisotopes is appealingowing toits high current intensity and high energy. The medical isotope production based on the proton beam at the CSNS is significantfor the development of futureradiopharmaceuticals, particularly for the α-emitting radiopharmaceuticals.The production yield and activity of typical medical isotopes wereestimated using theFLUKA simulation. The results indicate that the 300-MeV proton beam with a power of 100 kW at CSNS-II ishighly suitable for proof-of-principle studies of most medical radioisotopes. In particular, this proton beam offers tremendous advantages for the large-scale production of alpha radioisotopes, such as 225Ac, whose theoretical production yield can reach approximately57 Ci/week. Based on theseresults, we provideperspectives on the use ofCSNS proton beams to produce radioisotopes for medical applications.

  • Application of Deep Learning Methods Combined with Physical Background in Wide Field of View Imaging Atmospheric Cherenkov Telescopes

    分类: 天文学 >> 天文仪器与技术 分类: 物理学 >> 核物理学 分类: 计算机科学 >> 计算机应用技术 提交时间: 2024-03-10

    摘要: The HADAR experiment, which will be constructed in Tibet, China, combines the wide-angle advantages of traditional EAS array detectors with the high sensitivity advantages of focused Cherenkov detectors. Its physics objective is to observe transient sources such as gamma-ray bursts and counterparts of gravitational waves. The aim of this study is to utilize the latest AI technology to enhance the sensitivity of the HADAR experiment. We have built training datasets and models with distinctive creativity by incorporating relevant physical theories for various applications. They are able to determine the kind, energy, and direction of incident particles after careful design. We have obtained a background identification accuracy of 98.6 %, a relative energy reconstruction error of 10.0 %, and an angular resolution of 0.22-degrees in a test dataset at 10 TeV. These findings demonstrate the enormous potential for enhancing the precision and dependability of detector data analysis in astrophysical research. Thanks to deep learning techniques, the HADAR experiment’s observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S. at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies. Additionally, our experiment offers a fresh approach to dealing with strongly connected scattered data.

  • Analytical computation of magnetic field in coil-dominated superconducting quadrupole magnets based on racetrack coils

    分类: 物理学 >> 核物理学 提交时间: 2024-03-10

    摘要: Currently, three types of superconducting magnets are used in particle accelerators: cos2uptheta, CCT, and serpentine. However, all three coil configurations have complex spatial geometries, which make magnet manufacturing and strain-sensitive superconductor applications difficult. Compared with the three existing quadrupole coils, the racetrack quadrupole coil has a simple shape and manufacturing process, but there have been few theoretical studies. In this paper, the two-dimensional and three-dimensional analytical expressions for the magnetic field in coil-dominated racetrack superconducting quadrupole magnets are presented. The analytical expressions of the field harmonics and gradient are fully resolved and depend only on the geometric parameters of the coil and current density. Then, a genetic algorithm is applied to obtain a solution for the coil geometry parameters with field harmonics on the order of 10-4. Finally, considering the practical engineering needs of the accelerator interaction region, electromagnetic design examples of racetrack quadrupole magnets with high gradients, large apertures, and small apertures are described, and the application prospects of racetrack quadrupole coils are analyzed.

  • Opportunities for production and property research of neutron-rich nuclei around N=126 at HIAF

    分类: 物理学 >> 核物理学 提交时间: 2024-03-09

    摘要: The study of nuclide production and its properties in the N=126 neutron-rich region is the frontier and hot topic in nuclear physics and astrophysics research. The upcoming High energy FRagment Separator (HFRS) at the High Intensity heavy-ion Accelerator Facility (HIAF), an in-flight separator at relativistic energies, is characterized by high beam intensity, large ion-optical acceptance, high magnetic rigidity, and high momentum resolution power. It provides an opportunity for the study of the production and properties of neutron-rich nuclei around N=126. In this paper, an experimental scheme is proposed to produce the neutron-rich nuclei around N=126 and simultaneously measure their mass and lifetime based on the HFRS separator, and the feasibility of this scheme is evaluated by the simulations. The results show that under the high resolution optical mode many new neutron-rich nuclei approaching the r-process abundance peak around A=195 can be produced for the first time, and many nuclei with unknown mass and lifetime can be produced with high statistics. Using the time-of-flight corrected by the measured dispersive position and the energy loss information, the cocktails produced from the 208Pb fragmentation can be unambiguously identified. Moreover, the masses of some neutron-rich nuclei in the vicinity of N=126 can be measured with high precision using the time-of-flight magnetic rigidity technique. This indicates that the HIAF-HFRS facility has potential for the production and property research of neutron-rich nuclei around N=126, which is of great significance for expanding chart of nuclides, developing nuclear theories, and understanding the origin of heavy elements in the universe.

  • Development of a scintillating-fiber-based beam monitor for the Coherent Muon-to-Electron Transition experiment

    分类: 物理学 >> 核物理学 提交时间: 2024-03-08

    摘要: COMET is a leading experiment to search for coherent conversion of $ mu^- mathrm{N} to e^- mathrm{N}$ with a high-intensity pulsed muon beamline, produced by the innovative slow extraction techniques. Therefore, it is critical to measure the characteristics of the muon beam. We set up a Muon Beam Monitor (MBM), where scintillation fibers (SciFi) weaved in the cross shape are coupled to silicon photomultipliers (SiPM), to measure the spatial profile and timing structure of the extracted muon beam for COMET. The MBM detector has been tested successfully with a proton beamline in China Spallation Neutron Source (CSNS) and taken data with good performance in the commissioning run called COMET Phase-$ alpha$. Experience of the MBM development, such as the mechanical structure and electronics readout, and its beam measurement results will be shared.

  • Multi-distortion suppression for neutron radiographic images based on generative adversarial network

    分类: 物理学 >> 核物理学 提交时间: 2024-03-08

    摘要: Neutron radiography is a crucial nondestructive testing technology widely used in the aerospace, military, andnuclear industries. However, because of the physical limitations of neutron sources and collimators, the resultingneutron radiographic images inevitably exhibit multiple distortions, including noise, geometric unsharpness,and white spots. Furthermore, these distortions are particularly significant in compact neutron radiography systemswith low neutron fluxes. Therefore, in this study, we devised a multi-distortion suppression network thatemploys a modified generative adversarial network to improve the quality of degraded neutron radiographic images.Real neutron radiographic image datasets with various types and levels of distortion were built for the firsttime as multi-distortion suppression datasets. Thereafter, the coordinate attention mechanism was incorporatedinto the backbone network to augment the capability of the proposed network to learn the abstract relationshipbetween ideally clear and degraded images. Extensive experiments were performed; the results show that theproposed method can effectively suppress multiple distortions in real neutron radiographic images and achievestate-of-the-art perceptual visual quality, thus demonstrating its application potential in neutron radiography.

  • Development of a new irradiation-embrittlement prediction model for reactor pressure-vessel steels

    分类: 物理学 >> 核物理学 提交时间: 2024-03-07

    摘要: Predicting the transition-temperature shift (TTS) induced by neutron irradiation in reactor pressure-vessel (RPV) steels is important for the evaluation and extension of nuclear power-plant lifetimes. Current prediction models may fail to properly describe the embrittlement trend curves of Chinese domestic RPV steels with relatively low Cu content. Based on the screened surveillancedata of Chinese domestic and similar international RPV steels, we have developed a new fluence-dependent model for predicting the irradiation-embrittlement trend. The fast neutron fluence (E> 1 MeV) exhibited the highest correlation coefficient with the measured TTS data; thus, it is a crucial parameter in the prediction model. The chemical composition has little relevance to the TTSresidual calculated by the fluence-dependent model. The results show that the newly developed model with a simple power-law functional form of the neutron fluence is suitable for predicting the irradiation-embrittlement trend of Chinese domestic RPVs, regardless of the effect of the chemical composition.

  • Effect of Multiple Coulomb Scattering on the Beam Tests of Silicon Pixel Detectors

    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: 2024-03-07

    摘要: 在硅像素探测器的研究和开发中,配备高分辨率的像素束望远镜的准直单能带电粒子测试束流对探测器原型验证和性能评估是至关重要的。当束流能量较低时,必须考虑多次库仑散射对被测设备(DUT)测量分辨率的影响,以准确评估像素芯片和探测器的性能。本研究旨在调查多次库仑散射对DUT测量分辨率的影响,特别是在低束流能量下。使用Allpix2软件进行模拟,研究了不同束流能量、物质量和望远镜布局下多次库仑散射的影响。模拟还提供了多次库仑散射影响可忽略的最低能量。与在DESY用电子束测试的的结果相比,模拟结果与束流测试结果一致,验证了模拟的可靠性。