Westcott $g$ Factors Extended to Arbitrary Neutron Energy Spectra
Nuclear Science Division, Lawrence Berkeley National Laboratory(劳伦斯伯克利国家实验室核科学部);Department of Nuclear Engineering, University of California at Berkeley(加州大学伯克利分校核工程系);Theoretical Division, Los Alamos National Laboratory(洛斯阿拉莫斯国家实验室理论部)
西科特g因子用于中子活化分析(NAA)和即时伽马射线活化分析(PGAA)中,以评估某些核素的中子捕获截面非1/v行为对活化产物产率的影响。这种非1/v行为源于中子捕获截面中存在与低能(<5 eV)中子源谱重叠的中子共振。历史上,用于NAA和PGAA应用的西科特g因子是基于假设麦克斯韦中子速度分布和给定平均温度的计算结果。在本研究中,我们使用这种方法,结合更新的中子捕获截面数据(Evaluated Nuclear Data File,版本VIII.1,ENDF/B-VIII.1)来列出适用于广泛麦克斯韦分布温度范围的西科特g因子值,并将其结果与现有国际原子能机构表格和其他来源的g因子进行比较。在此次分析中发现,某些设施使用引导热中子束和冷中子束时,需要一种基于任意非麦克斯韦谱评估西科特g因子的方法。在本文中,我们提出了一种计算基于用户指定中子谱的g因子的方法,并应用这些方法得到布达佩斯研究反应堆和慕尼黑二研究反应堆的引导热中子束和冷中子束的西科特g因子。本研究还开发了开源软件,可用于PGAA和NAA实验中的这些计算。
英文摘要:
Westcott $g$ factors are used in Neutron Activation Analysis (NAA) and Prompt Gamma-ray Activation Analysis (PGAA) to evaluate the impact of non-$1/v$ behavior in the neutron-capture cross sections of certain nuclei on activation product yields. This non-$1/v$ behavior arises from the presence of neutron resonances in the neutron-capture cross sections that overlap with the source neutron spectrum at low ($<5$~eV) energies. Historically, Westcott $g$ factors that have been cataloged for NAA and PGAA applications are the result of calculations that assume a Maxwellian neutron velocity distribution with a given average temperature. In this study, we use this approach with updated neutron-capture cross sections from the Evaluated Nuclear Data File, version VIII.1 (ENDF/B-VIII.1) to tabulate Westcott $g$ factor values for a broad range of Maxwellian distribution temperatures, comparing the results against currently-available $g$ factors from International Atomic Energy Agency tables and other sources. It was discovered during this analysis that the use of guided thermal and cold-neutron beams at certain facilities necessitates an approach for evaluating Westcott $g$ factors based on arbitrary non-Maxwellian spectra. In this paper, we present an approach for calculating $g$ factors with user-specified neutron spectra, and we apply these methods to obtain Westcott $g$-factors for guided- and cold-neutron beams at the Budapest Research Reactor and the Forschungsreaktor M{ü}nchen II reactor. Open-source software has been developed as part of this study that can be used to perform these calculations for applications in PGAA and NAA experiments
PINO - a tool for simulating neutron spectra resulting from the 7Li(p,n) reaction
7 Li(p,n)反应与3.7 MV的Van de Graaff加速器相结合,在FZK常规使用,以进行激活以及keV区域中子的飞行时间测量。计划中的具有更高质子电流的新装置(如SARAF和FRANZ)以及液体锂靶技术的可用性将引发这种方法的复兴。详细了解中子能谱不仅在实验计划阶段很重要,而且在活化实验分析过程中也很重要。因此,基于蒙特卡罗的程序PINO(质子在中子出)的开发,它允许考虑设置的几何形状和质子能量分布的中子谱的模拟。
The CTOF measurements and Monte Carlo analyses of neutron spectra for backward direction from iron target irradiated by protons with energies from 400 to 1200 MeV
Unfolding the Neutron Spectra from a Water-Pumping-Injection Multi-layered Concentric Sphere Neutron Spectrometer Using a Self-Adaptive Differential Evolution Algorithm
建立了一种自适应差分演化中子谱展开算法(SDENUA),用于对抽注式多层同心球中子谱仪(WMNS)的中子谱进行展开。通过对中子注量边界的估计,加快了算法的收敛速度,并将最优解与输入中子计数之间的最小误差限制在10-6以内,避免了无效计算。此外,交叉概率和比例因子自适应控制。用FLUKA Monte Carlo模拟了WMNS在(1)Cf-252能谱和(2)慢化后能谱、(3)BNCT能谱和(4)反应堆能谱下的读数,并用SDENUA展开了测量的中子计数。SDENUA考虑了测量中子数和响应矩阵的不确定性,不需要复杂的参数调整和先验默认谱。结果表明,SDENUA的解比UMG 3.1中的MAXED和GRAVEL的解更符合IAEA的谱图,计算结果的误差在12%以内。所建立的SDENUA对WMNS的去折叠光谱具有潜在的应用价值。
Shielding Experiments Under JASMIN Collaboration at Fermilab(IV) - Measurement and Analyses of High-Energy Neutron Spectra in the Anti-Proton Target Station
Neutron and proton energy spectra from the non-mesonic weak decays of 5_Lambda-He and 12_Lambda-C
我们同时测量了5_Lambda-He和12_Lambda-C超核通过(pi^+,k^+)反应产生的非介子弱衰变中发射的中子和质子的能谱,其统计量比以前的实验高得多。在高能量阈值(60 MeV)下,两个超核的中子与质子产额比近似等于2,这表明中子和质子诱导的衰变通道的比率Gn(λ n -> nn)/Gp(λ p -> np)约为0.5。在中子能谱中,我们发现低能分量的产额出乎意料地大,即使是5 λ He。
CTOF Measurements and Monte Carlo Analyses of Neutron Spectra for the Backward Direction from a Copper Target Irradiated with 800, 1000, and 1200 MeV Protons
The influence of cluster emission and the symmetry energy on neutron-proton spectral double ratios
采用改进的量子分子动力学模型,在核物质状态方程中引入两种不同的对称能密度依赖关系,模拟了124 Sn +124 Sn和112 Sn +112 Sn反应中心碰撞的自由中子和质子发射.两个反应系统的中子质子比的构造的双比率被发现是敏感的EOS中的对称项。团簇形成的影响进行了研究,发现影响的双倍比主要在低能量区。为了更好地利用输运模型提取关于对称能量的信息,因此重要的是在高能量区域中具有准确的数据,该区域也受顺序衰变的影响最小。
Measurement of the ambient neutron flux and spectral distribution at the Canfranc Underground Laboratory
Instituto de Física Corpuscular, CSIC-Universidad de Valencia(瓦伦西亚大学与西班牙国家研究委员会粒子物理研究所);Technical University of Catalonia (UPC)(加泰罗尼亚理工大学);Universidad Complutense de Madrid(马德里康普顿斯大学);Helmholtz-Zentrum Dresden-Rossendorf (HZDR)(德累斯顿-罗斯多夫亥姆霍兹中心);Universidad de Granada(格拉纳达大学);TRIUMF(特柳芬实验室)