E_p≤3GeV质子入射铅、铋引起的中子产生双微分截面的模拟(英文)

加速器驱动次临界系统(ADS)液态Pb-Bi散裂靶的设计中,需要可靠的理论计算工具精确地预言几个GeV能量范围的质子引起的散裂反应产生的各种粒子和核素。利用蒙特卡罗模拟软件包Geant4计算研究了800 MeV至3 GeV质子入射铅、铋材料引起的中子产生双微分截面。比较了Geant4不同物理模型得到的模拟结果与现有的实验数据。其中,Geant4的QGSP BERT和QGSP INCL ABLA物理模型模拟结果很好地再现了实验数据。本工作证实了Geant4蒙特卡罗模拟软件包适合用于能量高达3 GeV的质子入射铅、铋引起的中子产生双微分截面的模拟计算。     

利用GEANT4和FLUKA研究质子诱发散裂反应出射中子双微分截面

在中高能质子诱发散裂反应相关核工程设计中,可靠的蒙特卡罗模拟程序结合核反应理论模型具有较好的理论指导意义。本工作中,利用GEANT4耦合INCL4和ABLA理论模型以及FLUKA耦合PEANUT模型模拟计算了几百MeV至几个GeV质子轰击Be,Al,Fe,W,U等靶后30°,60°,120°,150°出射角产生的散裂中子双微分截面,并与现有实验数据进行了比较。结果发现,FLUKA和GEANT4模拟计算较好地再现了Al,Fe,W,U等靶实验测量数据。然而,模拟结果明显低估了Be靶出射中子能量小于10 MeV能区的实验数据。For the design of nuclear engineering related with medium-high energy proton induced spallation reaction,the reliable Monte Carlo simulation codes coupled with nuclear reaction models have a good theoretical guidance.In this work,the production spallation neutron double differential cross sections at 30°,60°,120°,150°emission angle for Be,Al,Fe,W,U target materials at incident proton energies between several hundred MeV and GeV are theoretically calculated by using the GEANT4 coupled INCL4 and ABLA,and the FLUKA coupled PEANUT.The calculated results were compared with the available experimental data.It is found that the GEANT4 and FLUKA calculations well reproduced the experimental measurement of Al,Fe,W,U target materials.However,calculations obviously underestimated the emission neutrons of Be target for lower than 10 MeV energy range.     

利用QMD分析中高能质子入射208Pb的(p,xn)反应双微分截面

中高能质子入射重金属靶产生散裂中子是加速器驱动洁净核能系统的一个关键部分.利用量子分子动力学(QMD)模型研究入射质子能量在300MeV—1.5GeV,散裂靶为²⁰⁸Pb的(p,xn)核反应的双微分截面,QMD计算结果很好再现了实验数据,且QMD的计算结果明显优于HETC和LAHET.QMD在较宽的能区和核区满足加速器驱动洁净核能系统散裂靶物理计算的要求.     

加速器驱动次临界系统散裂靶参数优化计算

采用国际开源程序包Geant4,构建高能质子束轰击加速器驱动次临界系统(ADS)散裂靶的物理模型,模拟计算质子轰击液态金属铅、铅-铋合金和汞靶的泄漏中子谱分布,以及计算不同能量质子对应的铅靶泄漏中子产额和轴向积分分布,获得1 Ge V质子对应的铅圆柱靶优化参数,考虑入射质子的利用率和整个堆芯的体积质量,优化靶半径范围为16～24 cm,靶高为100 cm,相关研究结果可为(ADS)散裂靶的物理和工程设计提供理论依据。     

能量到250MeV质子入射Pb,Bi,Hg反应出射粒子能谱的理论研究

在光学模型、预平衡激子模型、蒸发模型、核内级连、PICK-UP机制等理论的基础上, 对入射能到250MeV质子入射中重核²⁰⁴Pb, ²⁰⁶Pb,²⁰⁷Pb,²⁰⁸Pb,²⁰⁹Bi, ¹⁹⁶Hg,¹⁹⁸Hg,¹⁹⁹Hg,²⁰⁰Hg, ²⁰¹Hg,²⁰²Hg和²⁰⁴Hg反应进行了系统的计算, 重点对出射粒子能谱进行了仔细的研究. 结果表明, 能量较高时预平衡反应机制占主导地位, 出射粒子的能谱形状在很大程度上决定于激子模型参数DK和激子态密度, 本文给出了能量相关的单粒子态密度修正经验公式; 考虑了PICK-UP机制后复杂粒子(α,D,T,³He)的能谱有很大改善.     

Calculations of Double-Differential Neutron and Proton Emission Cross Sections on 19F at 14.2-MeV Incident Neutron Energy

Physics of Atomic Nuclei - In the present paper, the double-differential cross sections (d2σ/dΩdε) of emission spectra for the 19F(n, xn) and 19F(n, xp) structural fusion materials...     

替代反应法测量锕系核(n,f)和(n,xn)截面

对于某些中子反应截面,在直接测量上存在困难。为了获得那些对核能发展极其重要的核数据,人们提出替代反应法,即利用带电粒子代替中子进行反应,从而实现中子反应截面间接测量的方法。现有替代反应一般采用非弹激发、转移等周边反应,涉及的角动量远比中子反应的大,需要理论修正,这造成了一定的困难。有鉴于此,提出利用轻带电离子的俘获反应作为替代反应,其复合核自旋与中子反应的相当,有效避免了自旋修正的困难。根据这个思路,采用236U的（α,f）和（α,2n）反应作为替代反应,成功提取了239Pu的（n,f）和（n,2n）反应截面,与ENDFB7评价库数据在误差范围内符合较好,表明了替代反应法的优越性,可以在核数据测量中推广应用。There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.     

Preequilibrium neutron emission in109Ag(3He,xn) and111Cd(p,xn) reactions

Excitation functions of the reactions¹⁰⁹Ag(³He,xn) and¹¹¹Cd(p, xn) have been measured with stacked foil techniques for projectile energies E≦45 MeV and multiplicitiesx≦4 populating ground and spin isomeric states in^112?x In. Preequilibrium (PE) contributions are more pronounced for thep than for the³He entrance channel and for low multiplicitiesx and can be reproduced with the (geometry dependent) hybrid model. The observed isomeric cross section ratios require a reduced population for the high spin state (as compared with the expectation for equilibrated systems) whenever PE emission contributes significantly. Calculations for a full statistical model with a PE decay mode and approximate angular momentum conservation indicate PE neutron emission to be stretched in angular momentum space. For the (p, xn) reactions a more detailed coupling scheme is imperative whereas the (³He,xn) data suggest the competitive PE emission of complex particles.     

Reaction mechanism for208Pb(3He,p)210Bi

The double-stripping (³He,p) reaction has been studied on a target of²⁰⁸Pb at 40.8 MeV. Data for the lowest multiplet ofπ h _9/2?v g _9/2 states are compared to a one-step DWBA prediction, a two step sequential single stripping prediction and to a coherent sum of these mechanisms. The two-step mechanism is shown to be much less important than the single step excitation, but its proper inclusion does provide an important improvement to the magnitudes of the predictions. To within a factor of two these calculations account for the magnitudes of the data for final states of spins 0^? through 8^?.     

Comparison of K−p Topological Cross Sections at 32 and 33.8 GeV/c with Lower Energy Data

The K⁻p experiments at 32.1 GeV/c and 33.8 GeV/c in the Mirabelle bubble chamber are reviewed and the resulting topological cross sections are compared to lower energy data with beam momenta between 4.2 and 16 GeV/c. Some quantities characterizing the multiplicity distributions are compiled for these data and their energy dependence is compared to results from pp experiments. Studying the scaling behavior of the K⁻p multiplicity distributions, “quasi scaling” is observed for data with p_Lab ≧ 8.25 GeV/c.     

Pion PT Distribution and a Test of Scaling Hypothesis at an Incident Proton Energy of 24 GeV

The transverse momentum distribution of 900 secondary pions produced in interactions of 24 GeV protons with emulsion nuclei is seen to agree fairly well with the HAGEDORN distribution for a' = 3/2 and b' adjusted to 133 MeV. A satisfactory fit of FEYNMANS scaling idea is also observed at this incident energy.     

The Estimation of the Difference Between d(d,n)3He and d(d,p)T Cross Sections in the Cold Fusion

The difference between two reaction cross sections of d(d, p)T and d(d, n)³He has been estimated in the cold fusion. It is caused by the different potential wall transmission and the angular distribution due to the structure.of deuterons. The rough estimation indicates that the branching ratio b about two orders of magnitude.