分类： 物理学 >> 核物理学 提交时间： 2023-05-23
摘要：In this study, we theoretically investigate the feasibility of using laser-wakefield accelerated (LWFA) electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser Plasma Accelerator (CLAPA) laboratory. The experiments at the CLAPA show that a stable electron beam with an energy of 78–135 MeV and a charge of 300-600 pC can be obtained. The bremsstrahlung spectra were simulated using Geant4, which suggests that a bremsstrahlung source with a peak intensity of 1019 photons/s can be generated. Theoretical calculations of isomer production cross-sections from the photonuclear reactions on six target nuclei, 197Au, 180Hf, 159Tb, 115In, 103Rh, and 90Zr were performed and compared with the available experimental data in EXFOR, which suggest that further experiments are required for a series of photonuclear reaction channels. Flux-averaged cross-sections and isomer ratios (IR) resulting from such bremsstrahlung sources are theoretically deduced. The results suggest that IR measurements can be used to constrain nuclear components, such as γ strength function and optical model potential. In addition, the detection of the decay characteristics was evaluated with Geant4 simulations. The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.
分类： 物理学 >> 核物理学 提交时间： 2023-05-19
摘要：How nuclides decay in the superheavy region is key information for investigating new elements beyond oganesson and the island of stability. The Random Forest algorithm is applied to study the competition between different decay modes in the superheavy region, including α decay, β− decay, β+ decay, electron capture and spontaneous fission. The observed half-lives and dominant decay mode are well reproduced. The dominant decay mode of 96.9 % nuclei beyond 212Po is correctly described. α decay is predicted to be the dominant decay mode for isotopes in new elements Z = 119 − 122, except for spontaneous fission in some even-even ones because of the increased Coulomb repulsion and odd-even effect. The predicted half-lives show the existence of a long-lived spontaneous fission island at the southwest of 298Fl caused by the competition of nuclear deformation and Coulomb repulsion. More understanding of spontaneous fission, especially beyond 286Fl, is crucial to search for new elements and the island of stability.
分类： 物理学 >> 核物理学 提交时间： 2023-05-19
摘要：We provide an investigation of the spectroscopic factors of resonance states in $A =5-8$ nuclei using two distinct nuclear models, the Gamow shell model (GSM) and the no-core shell model (NCSM). Configuration mixing is treated exactly in both GSM and NCSM. GSM employs the complex-energy Berggren ensemble, which treats bound, unbound resonance, and non-resonant continuum single-particle states on an equal footing. As a result, continuum coupling is taken into account in GSM, whereas it is absent in NCSM, where the harmonic oscillator basis is used. We first calculate low-lying states of helium isotopes and isotones. The results indicate that GSM can more accurately reproduce the low-lying resonance states than NCSM. The spectroscopic factors of the resonance states are also computed. Results from the GSM and NCSM are compared and show that continuum coupling plays an important role in the calculations of spectroscopic factors of resonance states. Overlap functions related to the resonance states are also systematically calculated by the GSM and NCSM. It is then demonstrated that wave function asymptotes can only be reproduced in GSM, where continuum coupling is taken into account.
分类： 物理学 >> 核物理学 提交时间： 2023-05-16
摘要：N/A
分类： 物理学 >> 核物理学 提交时间： 2023-05-16
摘要：A new approach that using polarized photon-gluon collisions reported by STAR Collaboration is used to do tomography of the ultrarelativistic nucleus.
The collision can be treated as a double-slit experiment at fermi scale, and solves a mystery last over 20 years in extracting the nuclear radius via vector meson photoproduction.
分类： 物理学 >> 核物理学 提交时间： 2023-05-15
摘要：In the R&D for upgrading the KL0 and µ detector (KLM) in Belle II experiment using scintillator and silicon photomultiplier (SiPM), we design a compact preamplifier with high#2;speed and low-noise. The preamplifier has a good gain stability, a baseline noise level of σ ≈ 0.3 mV, a good time resolution that can achieve < 20 ps, and can be applied comprehensively to SiPMs. To reduce the pile-up in using a large size SiPM or an array of SiPMs, which is due to the large capacitance and high dark count rate, we adopt pole#2;zero-cancellation which reduce both the rise time and the fall time of a SiPM signal. The combinations of the preamplifier and several kinds of SiPMs show time resolutions better than 50 ps for most of the cases; when the number of detected photons is larger than 60, a time resolution of about 25 ps can be achieved
分类： 物理学 >> 核物理学 提交时间： 2023-02-25
摘要：
Plastic scintillator (PS) embedding wavelength shifting (WLS) fiber is widely used in high energy particle physics, as muon taggers, and also in medical physics and other applications. In this work, a simulation package is built to evaluate the effects of the diameter and the layout of the optical fiber on the light yield with different configurations. The optimal optical configuration was designed based on the simulation and then validated with two PS prototypes under certain experimental conditions. In the study, the top veto tracker (TVT) of the JUNO#2; TAO experiment, comprised of 4 layers of 160 strips of PS was designed and evaluated. When a muon taggingefficiency of a PS strip is higher than 99%, the threshold is evaluated. The efficiency of 3-layer out of 4-layer of TVT will be higher than 99% even with the tagging efficiency of a single strip as low as 97% using a threshold of 10 p.e. assuming 40% SiPM PDE.
分类： 物理学 >> 核物理学 提交时间： 2023-01-12
自由电子激光(FEL)是一种以高品质电子束在周期磁场中运动产生受激辐射来放大电磁辐射的强相干光源，它有低增益和高增益两种工作模式。本文讨论了自由电子激光的发展概况，给出了一维近似下低增益自由电子激光、高增益自由电子激光的的基本理论。主要讨论了高增益自由电子激光的实验装置。 给出了自由电子激光装置的物理设计基本方法和设计思想。
分类： 物理学 >> 核物理学 提交时间： 2022-07-25
摘要：加速器中带电粒子的运动分为横向运动与纵向运动，加速器中的纵向运动即为相运动，给出了一维近似下的相运动方程，相运动的稳定性物理机制和相位条件。给出了一个纵向运动的标准映射，可用于非线性动力学研究。模拟研究了二台S波段电子直线加速器，验证了相运动的基本理论，模拟结果与基本理论一致，吻合的很好。提出了在常规直流高压电子枪的电子直线加速器中，直接将直流高压电子枪更换成光阴极微波电子枪，并使用
束团压缩器的实验研究方案，同样可以获得高峰值电流的短电子束团。
分类： 物理学 >> 核物理学 提交时间： 2022-06-13
Shanghai Laser Electron Gamma Source (SLEGS) is a powerful gamma source to provide MeV gamma-ray beams for nuclear science and technology. It is developed as one of the sixteen beamline stations in Phase II Project of the Shanghai Synchrotron Radiation Facility (SSRF). The slant-scattering mode is for the first time systematically employed in the laser Compton scattering (LCS) at SLEGS to produce energy-tunable quasi-monoenergetic gamma-ray beams. SLEGS officially completed its commissioning from July to December 2021. Gamma-rays in energy range of 0.25 - 21.7 MeV with the flux of 2.1 × 104 - 1.2 × 107 photons/s and the energy spread of 2 – 15 % are produced during the test. This paper reports results of the commissioning of the SLEGS beamline.
分类： 物理学 >> 核物理学 提交时间： 2022-06-13
本文提出了束团压缩物理的产生背景，束团压缩的基本原理、种类。运用束流光学的基本理论，给出了
束团压缩的基本理论公式，论证了束团压缩的高阶限制。分析讨论了单级压缩、两级压缩中存在的设计
物理问题，总结了束团压缩设计中经常遇见的一些物理问题。关于束团压缩的束流动力学问题，给出了
束团压缩器中的粒子运动方程，以及完整的动力学方程-Vlasov方程。讨论了相干同步辐射效应和微束团
不稳定性。最后，分析了磁压缩器中的误差问题。
分类： 物理学 >> 核物理学 提交时间： 2022-01-21 合作期刊: 《Nuclear Science and Techniques》
Configurational information entropy (CIE) theory was employed to determine the neutron skin thickness of neutron-rich calcium isotopes. The nuclear density distributions and fragment cross-sections in 350 MeV/u 40-60Ca + 9Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model. CIE quantities were determined from the nuclear density, isotopic, mass, and charge distributions. The linear correlations between the CIE determined using the isotopic, mass, and charge distributions and the neutron skin thickness of the projectile nucleus show that CIE provides new methods to extract the neutron skin thickness of neutron-rich nuclei.
分类： 物理学 >> 核物理学 提交时间： 2022-01-21 合作期刊: 《Nuclear Science and Techniques》
By implementing an additional heavy quark–antiquark pair production trigger in a multiphase transport (AMPT) model, we study the effect on anisotropy flows of identified particles with a focus on charged particles and quarkonium (J/Ψ and Υ). A systematic increase in the collision rate for active partons in the AMPT model with such an implementation has been observed. It leads to a slight increase of identified particles anisotropy flows as a function of transverse momentum (pT ) and rapidity, and gives a better description of the experimental data of elliptic flow toward larger pT . Our approach provides an efficient way to study the heavy quark dynamics in the AMPT model at LHC energies.
分类： 物理学 >> 核物理学 提交时间： 2022-01-07
摘要：在改进的量子分子动力学模型框架下，研究了高能氘核在重靶核作用下的碎裂过程，尤其近零度角产生的中子。模拟重现了 102 MeV d+C 反应中实验测量的中子双微分截面。根据模型与实验结果的一致性，论证了通过氘核在碳靶上碎裂而产生高能中子束的可行性。但因氘核内部核子的费米运动，使得包含实验室0°在内的中子能量具有相当大的能量展宽。基于模型计算，通过测量氘核碎裂过程中出射的伴随质子，出射中子能量可约束在5%(1σ)以内。进一步，本工作论证了基于伴随质子测量的单能高能中子束产生的可行性。
分类： 物理学 >> 核物理学 提交时间： 2021-12-31
摘要：Configurational information entropy (CIE) theory was employed to determine the neutron skin thickness of neutron-rich calcium isotopes. The nuclear density distributions and fragment cross-sections in 350 MeV/u 40060Ca + 9Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model. CIE quantities were determined from the nuclear density, isotopic, mass, and charge distributions. The linear correlations between the CIE determined using the isotopic, mass, and charge distributions and the neutron skin thickness of the projectile nucleus show that CIE provides new methods to extract the neutron skin thickness of neutron-rich nuclei.
分类： 物理学 >> 核物理学 提交时间： 2021-12-25
刁昕玥
关分海
王轶杰
秦雨浩
秦智
郭栋
吴强华
司大伟
赵暄
肖圣
张耀鹏
魏向伦
邹海川
杨贺润
马朋
胡荣江
段利敏
Artur, Dobrowolski
Krzysztof, Pomorski
肖志刚
摘要：我们研究了在CSHINE上重建$ 25 MeV/u ^{86}Kr +^{208}Pb$ 反应中快裂变事件的方法。裂变碎片由三个大面积平行板雪崩计数器进行探测，它可以提供碎片的位置和到达的时间信息。起始时间信息由回旋加速器的高频信号给出。我们利用两个裂变碎片的速度，重建了裂变事件。裂变碎片的速度分布和方位差的展宽均随折叠角的增大而减小，这与快速裂变发生的图像一致。同时，裂变轴的各向异性角分布也一致地揭示了裂变事件的动力学特征。
分类： 物理学 >> 核物理学 提交时间： 2021-03-03
摘要： 本文讨论了常规电子直线加速器的设计问题， 并以一台 10 MeV 的电子直线加速器为例穿插其中讨论了常规电子直线加速器的设计。常规电子直线加速器由电子枪、聚束部分、光速部分所组成，而且在直线对撞机装置、自由电子激光装置中经常用到束团压缩部分。我们对每一部分都进行了分析与讨论，主要包括纵向、横向束流动力学方面， 总结了一系列的行之有效的设计思想与方法。
分类： 物理学 >> 核物理学 提交时间： 2021-02-25
摘要：In high energy resolution X-ray spectroscopy beamlines of synchrotron radiation (SR) facilities and laboratory XAS/XES spectrometer, it is important to keep X-ray spectrometer operating in optimal conditions. The adjusting process is normally very time consuming due to the irregular light source beam point, and it is difficult to get global optimum. This study aims to develop an intelligent adjusting system based on global optimization algorithm for spectrometers on SR beamlines and on laboratory x-ray source. First of all, based on the two dimensional experimental data, automatic adjustment process was established. Then the automatic optimization was applied to adjust X-ray spectrometer practically, and upgraded iteratively. The online testing is carried out on a self-developed laboratory XAS spectrometer. Online tests results show that this automatic adjustment process converges to the optimal solution quickly, and the convergence time is about several dozens to hundreds steps, more efficient than manual optimization process. After automatic adjustment, we can get correct X-ray absorption spectrum based on the adjusted spectrometer.
分类： 物理学 >> 核物理学 提交时间： 2018-07-10
摘要： 本文分析讨论了加速器的百年历史， 从思想的萌芽、理论的突破与准备、技术的准备与储存、实验的成功、加速器的未来与展望等几个方面进行了论述。
分类： 物理学 >> 核物理学 提交时间： 2018-06-20
摘要： 本文讨论了加速结构中的解析求解问题， 主要讨论了场和等效电路两种求解方法。
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