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.
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.
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.
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.
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.
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。
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。
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。
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.
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。
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。
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。
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
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.
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。
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。
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.
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.
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。
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.
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