分类： 物理学 >> 核物理学 提交时间： 2023-06-02
摘要：In this study, the rapidity distribution, collective flows, and nuclear stopping power in 197Au+197 Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics (UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.
分类： 物理学 >> 核物理学 提交时间： 2023-06-02
摘要：银纳米团簇(AgNCs)是一种与分子性质相似的新型纳米材料，它具有独特的应用前景。通过将AgNCs与不同的基体材料结合制备AgNC复合材料，可以极大的扩展AgNCs的应用范围。利用辐照技术，我们开发了一种简单的两步法制备银纳米团簇复合材料的合成方法。首先，将聚丙烯酸(PAA)链接枝到PE薄膜表面得到固体模板(PE-g-PAA)。随后，在模板材料表面原位还原银离子，得到AgNC复合材料(AgNCs@PE-g-PAA)。通过调整反应条件，可以很容易地控制AgNCs在复合膜上的负载程度。负载的AgNCs被锚定在PAA的羧基上并包裹在接枝链中。AgNCs的粒径仅为4.38±0.85 nm，粒径分布非常均匀。AgNCs@PE-g-PAA表现出AgNCs的荧光特性。AgNCs@PE-g-PAA的荧光很容易被Cr3+离子猝灭。该复合材料可作为荧光试纸，实现对Cr3+的目视检测。
分类： 物理学 >> 核物理学 提交时间： 2023-06-01 合作期刊: 《Nuclear Science and Techniques》
E. Aboud
S. Ahn
G. V. Rogachev
V.E. Johnson
J. Bishop
G. Christian
E. Koshchiy
C.E. Parker
D.P. Scriven
摘要：Nuclear nonproliferation is of critical importance for global security. Dangerous fissile materials including highly enriched uranium and weapons-grade plutonium are especially important to detect. Active interrogation techniques may result in much better sensitivity but are difficult with conventional portal monitors that rely on detecting thermal neutrons. Also, most conventional portal monitoring systems rely on 3 He, which has a finite and continually decreasing supply. By designing a highly segmented array of organic scintillators, we posit that we can accurately and quickly identify fissile materials, including weapons-grade plutonium and highly enriched uranium, being smuggled. We propose a new design for a fast-neutron detector that overcomes the limitations of the current generation of portal monitors. MCNP6 simulations have been performed in conjunction with the UMPBT statistical model to determine the sensitivity limitations of the proposed detector. Results suggest that the proposed detector may be 10 times more efficient than current-generation thermal neutron detectors and may be able to positively identify a 81 mg 235 U source in as little as 192 seconds utilizing active interrogation techniques.
分类： 生物学 >> 生态学 提交时间： 2023-06-01
Fu, Hui
Ge, Yili
Cai, Guojun
Deng, Jianming
Liu, Huanyao
Wu, Aiping
Li, Youzhi
Li, Wei
Yuan, Guixiang
Erik Jeppesen
摘要：Understanding how phytoplankton interacts with local and regional drivers as well as their feedbacks is a great challenge, and quantitative analyses of the regulating role of human activities and climate changes on these feedback loops are also limited. By using monthly monitoring dataset (2000-2017) from Lake Taihu and empirical dynamic modelling to construct causal networks, we quantified the strengths of causal feedbacks among phytoplankton, local environments, zooplankton, meteorology as well as global climate oscillation. Prevalent bidirectional causal linkages between phytoplankton and the tested drivers were found, providing holistic and quantitative evidence of the ubiquitous feedback loops. Phytoplankton exhibited the highest feedbacks with total inorganic nitrogen and ammonia and the lowest with nitrate. The feedbacks between phytoplankton and environmental factors from 2000 to 2017 could be classified by two groups: the local environments (e.g., nutrients, pH, transparency, zooplankton)-driven enhancement loops promoting the response of the phytoplankton, and the climate (e.g., wind speed)-driven regulatory loops suppressing it. The two counterbalance groups modified the emergent macroecological patterns. Our findings revealed that the causal feedback networks loosened significantly after 2007 following nutrient loading reduction and unsuccessful biomanipulation restoration attempts by stocking carp. The strength of enhancement loops underwent marked decreases leading to reduced phytoplankton responses to the tested drivers, while the climate (decreasing wind speed, warming winter)-driven regulatory loops increased– like a tug-of-war. To counteract the self-amplifying feedback loops, the present eutrophication mitigation efforts, especially nutrient reduction, should be continued, and introduction of alternative measures to indirectly regulate the critical components (e.g., pH, Secchi depth, zooplankton biomass) of the loops would be beneficial.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2023-06-01
Li, Haoqing
Sheng, Liang
Zhang, Changqing
Du, Yingchao
Zhou, Zheng
Weng, Xiufeng
Xiao, Jiahao
Yin, Hongqiao
Sun, Bin
Wei, Kun
Li, Yang
Duan, Baojun
Liu, Yongtang
Zhang, Yanhong
Zhang, Mei
Song, Yan
Zhang, Xiaodong
Liu, Jun
Fu, Zhuming
Xu, Qing
摘要：Image distortion caused by angular misalignment of quadrupole magnets in high energy electron radiography is studied systematically. We propose that the distortion originates from the coupling of the motions of electron in transverse directions based on theoretical analysis via transfer matrix method. The relative angular rotation between the second and third magnetic quadrupoles is identified to be the main contributor to image distortion, which is verified by both beam dynamics simulation and experimental outcomes. In addition, different strategies to mitigate this image distortion are explored, including magnets online tuning, using higher beam energy and larger magnification factor. This study provides some criteria for designing experiments, and paves the way to achieve higher image precision.
分类： 医学、药学 >> 临床医学 提交时间： 2023-06-01
摘要：应用热释光探测器（TLD）检测直线加速器精确放疗下小鼠肝脏照射部位的剂量，并采用单次高剂量照射小鼠肝脏的方法，构建小鼠辐射诱发肝损伤（RILD）的生物模型，以确定在直线加速器下构建小动物精确放疗模型的可行性。在固体水内TLD的位置为计划中的靶体积（PTV）制定了360°弧形旋转调强放疗（VMAT）计划，规定剂量为2Gy，以比较TLD的测量剂量与TPS系统中评估参数的差异。将TLD植入小鼠肝脏，并根据TLD计划VMAT，以比较测量和规定的剂量。C57BL/6J小鼠被随机分为对照组和25Gy辐射组，每天检查体重的变化。它们在辐射后3周和10周被安乐死，并测量肝脏血清酶的水平，如丙氨酸氨基转移酶（ALT）、天冬氨酸氨基转移酶（AST）和碱性磷酸酶（ALP），观察小鼠肝脏受照射区域的任何病理组织学变化。固体水下TLD的测量值在TPS系统中评价参数的Dmean值的±3%以内。25Gy辐射组的小鼠在肝脏照射部位表现出辐射引起的肝脏损伤的病理迹象。小鼠肝脏中TLD的测量剂量和规定剂量的偏差在-1.5%至6%之间；在直线加速器下使用VMAT技术构建RILD的精确模型是可行的。
分类： 物理学 >> 核物理学 提交时间： 2023-06-01
摘要：Compton camera-based prompt gamma (PG) imaging has been proposed for range verification during proton
therapy. However, a deviation between the PG and dose distributions, as well as the difference between the
reconstructed PG and exact values, limit the effectiveness of the approach in accurate range monitoring during
clinical applications. The aim of the study was to realize a PG-based dose reconstruction with a Compton
camera, thereby further improving the prediction accuracy of in-vivo range verification and providing a novel
method for beam monitoring during proton therapy. In this paper, we present an approach based on a subsetdriven origin ensemble with resolution recovery (SD-OE-RR) and a double evolutionary algorithm (DEA) to reconstruct the dose depth profile (DDP) from the gamma events obtained by a Cadmium-Zinc-Telluride
(CZT) Compton camera with limited position and energy resolution. Simulations of proton pencil beams with
clinical particle rate irradiating phantoms made of different materials and the CT-based thoracic phantom were
used to evaluate the feasibility of the proposed method. The results show that for the monoenergetic proton
pencil beam irradiating homogeneous-material box phantom, the accuracy of the reconstructed DDP was within
0.3 mm for range prediction and within 5.2% for dose prediction. In particular, for 1.6-Gy irradiation in the
therapy simulation of thoracic tumors, the range deviation of the reconstructed spread-out Bragg peak was
within 0.8 mm, and the relative dose deviation in the peak area was less than 7% compared to the exact values.
The results demonstrate the potential and feasibility of the proposed method in future Compton-based accurate
dose reconstruction and range verification during proton therapy.
分类： 生物学 >> 遗传学 提交时间： 2023-06-01
摘要：在古人类研究中，骨骼，尤其是头骨性状的测量是获得标本特征信息的主要手段。随着技术的发展，CT技术及三维复原技术为骨骼测量带来了巨大的便利。其中Mimics软件作为常用的三维重建软件之一，在复原过程中为使用者提供了低、中、高、最佳这四种精度的选择。我们希望获知在不同复原精度得到的模型上进行测量得到的结果存在何种程度的差异，以便在未来研究过程中选择最合适的标准。在本研究中，我们选择了顶骨矢状弦、颅周、头盖面积、乳突小房表面积、颅容量、乳突小房体积这六项性状的测量数据作为检测指标，计算同一批现代人标本在Mimics中采用不同精度复原得到的模型间测量数值的差异，根据Mimics的复原模型简化规则，我们选择未精简的最佳精度模型作为标准进行非参数检验、配对t检验及计算测量差异占比。结果表明，这六项的不同简化精度模型测量数据与最佳精度模型测量数据的非参数检验及配对t检验均具有显著差异。顶骨矢状弦、颅周、头盖面积、颅容量的测量差异占比基本均小于3%，而乳突小房表面积的低精度测量差异占比可达到50%以上，乳突小房体积低精度测量差异占比可达120%以上。除去简化过程造成的模型表面膨胀外，乳突小房的多气房结构造成不同精度之间存在的绝对差异比上一整体体量小区域而形成的巨大相对差异提示我们，在三维模型的测量中，对于头骨内部腔窦这样小体量表面粗糙的部分的复原精度选择及数据比较需要格外谨慎。
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-01
摘要：研制用于精确控制电子能量的失谐系统是一个电子靶用于离子储存环的重要挑战。为此，本文为HIAF-SRing的电子靶研制了一种高精度、高电压、失谐系统，使其能在实验中产生精确的电子离子相对能量调制。该系统由辅助电源和高压失谐电源组成。辅助电源级采用工作在软开关状态的LCC谐振变换器和LC滤波器输出正弦波形为高压失谐电源供电。失谐电源由高压脉冲放大器(HVPA)与高压直流(HVDC)模块串联组成。本文介绍了失谐系统的设计与开发，并详细介绍了实验装置，测试结果表明，失谐系统符合双电子复合(DR)实验的技术要求。最后，利用失谐量测量了Fe15+ DR谱，实验数据显示了良好的实验分辨率，验证了该方法的可靠性和可行性。
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-01
分类： 核科学技术 >> 裂变堆工程技术 提交时间： 2023-06-01
摘要：Recent reactor antineutrino experiments have observed that the neutrino spectrum changes with the reactor core evolution and that the individual fissile isotope antineutrino spectra can be decomposed from the evolving data, providing valuable information for the reactor model and data inconsistent problems. We propose a machine learning method by building a convolutional neural network based on a virtual experiment with a typical short-baseline reactor antineutrino experiment configuration: by utilizing the reactor evolution information, the major fissile isotope spectra are correctly extracted, and the uncertainties are evaluated using the Monte Carlo method. Validation tests show that the method is unbiased and introduces tiny extra uncertainties.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
Xu,Miaofu
Zhang,Xiangzhen
Ye,Rui
Wang,Jincan
Bian,Xiaojuan
Gao,Yao
Li,Minxian
Chen,Fusan
Yang,Xiaochen
Ge,Rui
摘要：A 3W1 superconducting wiggler (SCW) with the pole gap of 68 mm was successfully tested and installed in a BEPC II storage ring in November, 2019. The goal of zero liquid helium consumption was achieved, and the cryogenic system exhibited a 12% residual cooling capacity (approximately 0.69 W @4.2K). The 3W1-SCW was set to operate at 2.49 T and has been operating for more than seven months. Three instances of magnet quenching occurred during the normal operation. The evaporated helium gas can be recycled to the helium gas recycling system when the pressure in the helium tank is higher than the parameter value（the setpoint of the presssur value is 1.2 bara）. The cryogenic system can be recovered within 4 h if sufficient liquid helium is available to inject into the cryostat.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：Theoretical uncertainties of single proton transfer cross sections of the (3He,d) and (d,3He) reactions
due to the uncertainties of the entrance- and exit-channel optical model potentials are examined with the
30Si(3He,d)31P, 13B(d,3He)12Be, and 34S(3He,d)35Cl reactions at incident energies of 25 MeV, 46 MeV, and
25 MeV, respectively within the framework of distorted wave Born approximation. Differential cross sections
at the first peaks in the angular distributions of these reactions are found to be uncertain within around 5% due
to the uncertainties of the optical model potentials from an result of 20000 times of calculations with the optical
potential parameters randomly sampled. This amount of uncertainties is found to be nearly independent of the
angular momentum transfer and the target masses within the studied range of incident energies. Uncertainties
of the single proton spectroscopic factors obtained by matching the theoretical and experimental cross sections
at different scattering angles are also discussed.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
Guan Yongjing
Chen Wu
Wang Shenzhen
Hua Yuxin
Jing Qiaoyan
Liu Zhiyong
Huang Chunping
Wang Deyu
Wang Huijuan
He Xianwen
Mario De Cesare
Cui Liangjia
He Hua
Fan Kaidi
Guo Zichen
摘要：The spatial distributions of 239+240Pu and 137Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion. The activity concentrations of 239+240Pu and 137Cs in the surface soils of the paddy fields were in the range of 0.089-0.734 and 1.80-7.88 mBq/g, respectively. The activities of 239+240Pu and 137Cs showed very similar distribution trends, first increasing and then decreasing with increasing elevation. The 240Pu/239Pu atom ratios in the surface soils ranged from 0.162–0.232. The activities of 239+240Pu and 137Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth. The mean soil erosion rates of Longji Rice Terraces estimated by 239+240Pu and 137Cs tracer methods were 5.44 t/(ha·a) and 5.16 t/(ha·a), respectively, which demonstrated that plutonium can replace 137Cs as an ideal tracer for soil erosion research in the future. Landform features are the main factors affecting the distribution of plutonium and 137Cs as well as soil erosion in the Longji Rice Terraces.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：In this work we perform a Bayesian inference of the crust-core transition density ρt of neutron stars based upon the neutron-star radius and the neutron-skin thickness data within a thermodynamical method. The uniform and Gaussian distributions for the ρt prior are adopted in the Bayesian approach. It has a larger probability to have values higher than 0.1 fm 3 for ρt as the uniform prior and the neutron-star radius data are used. We found that this is controlled by the curvature Ksym of the nuclear symmetry energy. This phenomenon will not happen if Ksym is not extremely negative, i.e., Ksym > -200 MeV. The obtained ρt is 0.075+0.005-0.01fm^3 at 68% confifidence level when both the neutron-star radius and the neutron-skin thickness data are taken into account. The strongly anti-correlations between ρt and the slope L, curvature of the nuclear symmetry energy are observed. The dependence of the three L-Ksym correlations predicted in the literature on the crust-core density and pressure is quantitatively investigated. The most probable value of 0.08 fm^3 for ρt is obtained from the L-Ksym relation raised by Holt et al. and the larger values are preferred by the other two relations.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：A simulation code, GOAT, is developed to simulate single-bunch intensity-dependent effects and their interplay in the proton ring (pRing) of the Electron-Ion Collider in China (EicC) project. GOAT is a scalable and portable macroparticle tracking code written in Python and coded by object-oriented programming technology. It allows for transverse and longitudinal tracking, including impedance, space charge effect, electron cloud effect, and beam-beam interaction. In this paper, physical models and numerical approaches for the four types of high-intensity effects, together with the benchmark results obtained through other simulation codes or theories, are presented and discussed. In addition, a numerical application of the cross-talk simulation between the beam-beam interaction and transverse impedance is shown, and a dipole instability is observed below the respective instability threshold. Different mitigation measures implemented in the code are used to suppress the instability. The flexibility, completeness, and advancement demonstrate that GOAT is a powerful tool for beam dynamics studies in the EicC project or other high-intensity accelerators.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：Bonner多球谱仪(BBS)求解中子能谱是一个复杂的多维模型，需要使用复杂的优化算法求解第一类Fredholm积分方程。针对极大似然期望最大化(MLEM)算法容易陷入局部最优，粒子群优化(PSO)算法易得到粒子飞行方向和步长不合理，导致迭代无效，影响效率和精度的问题，提出了一种改进的PSO-MLEM算法用于中子能谱展开。利用动态加速因子平衡全局和局部搜索能力，提高算法的收敛速度和精度。首先，采用蒙特卡罗方法对BBS进行模拟，得到BBS的响应函数和计数率。模拟计数率时，采用了国际原子能机构403号技术报告中的4个参考光谱作为蒙特卡罗方法的输入参数。采用PSO-MLEM算法对中子能谱展开，通过展开能谱与参考能谱的差异进行验证。最后，利用BBS对252Cf中子源进行测量，并采用PSO-MLEM算法展开实验中子谱。与最大熵反卷积(MAXED)、PSO和MLEM算法相比，PSO-MLEM算法参数更少，并自动调整动态加速因子以解决局部最优问题。PSO-MLEM算法的收敛速度分别是MLEM和PSO算法的1.4倍和3.1倍。与PSO、MLEM和MAXED算法相比，PSO-MLEM算法的相关系数分别提高了33.1%、33.5%和1.9%，相对平均误差分别降低了98.2%、97.8%和67.4%。
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：lead-shielded HPGe detector and offline g–ray spectra of the residual product were used to measure the cross-section (CS) and ratios of isomeric CS (sm/sg) in 134Xe(n,2n)133m,gXe reactions at different energies including 13.5, 13.8, 14.1, 14.4, and 14.8 MeV, relative to 93Nb(n,2n)92mNb reaction CS. The target was high-purity natural Xe gas under high pressure. T(d,n)4He reaction was used to produce neutrons. The TALYS code (1.95 version) for nuclear reactions was used for calculations along with the default parameters and various nuclear level density models. The uncertainties present in the measured CS data were thoroughly analyzed using the covariance analysis method. The results were subsequently compared to the theoretical values, evaluation data, and previous experimental findings. Thus, the CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5,13.8 and 14.1 MeV neutron energies are reported for the first time. This work advances our knowledge of pre-equilibrium emission in the (n,2n) reaction channel by resolving inconsistencies in Xe data.
点击量
点击量
下载量
评论
待评议
通过
