Ep≤63 GeV 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。A detailed design of the liquid Pb-Bi spallation target of the Accelerator Driven Systems (ADS) requires powerful and reliable computational tools that can accurately predict particles and nuclides production by the proton induced spallation reactions in the energy range of a few GeV. In this paper, the neutron production double-differential cross sections for Pb and Bi target materials at incident proton kinetic energies between 800 MeV and 3 GeV are studied by calculations with Monte Carlo simulation package Geant4. The simulated results of Geant4 with several physics models are compared with available experimental data. The simulated results generated by QGSP BERT and QGSP INCL ABLA physics models of Geant4 well reproduce the available experimental data. The present results validated that Geant4 Monte Carlo simulation package is suitable for simulations of neutron production double-differential cross sections of proton induced reaction on Pb and Bi targets in the incident energy range up to 3 GeV.     

中能质子引起散裂反应的碎片质量分布研究

对 SHIELD程序进行了部分检验,利用SHIELD程序计算质子入射铅的薄靶产生的靶碎片的截面及质量分布和激发函数 ,计算结果较好地再现了实验数据 .并计算了 1 .6Ge V的质子轰击长 60 cm和直径20cm的铅靶的碎片质量分布. The test of part benchmark of SHIELD code was performed. The cross section, mass distribution and excitation function of the fragments (including residual nuclei) in the proton induced spallation reaction on thin Pb target at intermediate energy have been calculated by SHIELD code. And the results are in good agreement with experimental data. The fragment mass distributions from proton induced spallation reaction on thick Pb traget at incident energy 1.6 GeV were also presented.     

中能质子引起散裂反应的碎片质量分布研究

对 SHIELD程序进行了部分检验,利用SHIELD程序计算质子入射铅的薄靶产生的靶碎片的截面及质量分布和激发函数 ,计算结果较好地再现了实验数据 .并计算了 1 .6Ge V的质子轰击长 60 cm和直径20cm的铅靶的碎片质量分布. The test of part benchmark of SHIELD code was performed. The cross section, mass distribution and excitation function of the fragments (including residual nuclei) in the proton induced spallation reaction on thin Pb target at intermediate energy have been calculated by SHIELD code. And the results are in good agreement with experimental data. The fragment mass distributions from proton induced spallation reaction on thick Pb traget at incident energy 1.6 GeV were also presented.     

20 MeV以下n+6Li反应的理论计算

核反应R矩阵理论是研究轻核反应以及中重和重核共振能区核反应的重要理论方法。包含能级矩阵非对角元贡献的完全R矩阵理论在理论上比较严格。根据不同的假定和近似得到不同的R矩阵计算方法。新编的R矩阵程序FDRR包含了4种计算方法,包括约化道多能级Breit-Wigner 方法、完全约化R矩阵方法、非对角化能级位移约化R矩阵方法及对角化能级位移约化R矩阵方法。可计算轻核各种两体反应道的截面、角分布。利用FDRR程序对n+6Li 反应20 MeV以下能区进行理论分析和计算,理论计算结果与实验数据进行了比较分析,理论计算得到的截面和角分布与实验数据符合得很好。R-matrix theory is an important theory of light, medium and heavy mass nuclide nuclear reaction in the resonance energy range. Full R-matrix formalism contains the un-diagonal element of energy levels matrix and it is rigorous in theory. Because of different assumptions and approximations, many kinds of R-matrix methods are obtained. The new R-matrix code FDRR is presented and includes 4 kinds of R-matrix methods, reduced multi-level Breit-Wigner R-matrix method, full reduced R-matrix method, un-diagonal energy shift reduced Rmatrixn method, and diagonal energy shift reduced R-matrix method. It can be used for calculating integral cross sections and angular distributions of 2-bodies reactions. The cross sections and angular distributions of n+6Li reaction are calculated and analyzed by FDRR code below 20 MeV. The calculation results are compared with the experimental data, and the cross sections and angular distributions are in good agreement with experimental data.     

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.     

基于ImIQMD模型对近垒重系统准裂变反应的研究

利用改进的同位旋相关的量子分子动力学(ImIQMD)模型程序,对能量在库仑位垒附近的48Ca+208Pb反应系统进行了模拟。 计算得到的俘获截面、 准裂变截面和碎片分布及其发生的时间分布等结果与实验数据符合较好。 同时还得到了准裂变过程中发射第三个较大碎片的截面, 并简单讨论了它们的发射机制。Based on the improved isospin dependent quantum molecular dynamics (ImIQMD) model,the reaction of 48Ca+208Pb at energies near the Coulomb barrier was investigated systematically. The capture cross section,the quasi fission cross section, the mass distribution of the quasi fission fragments and the time for quasi fission happened were obtained. According to the comparison with experimental data,the calculated capture cross sections and the fragment distributions of the quasi fission were reasonable. Additionally,we got the cross sections of the third largest fragment,and the emission mechanism was also discussed briefly.     

波包宽度对弹核碎裂反应截面的影响

运用改进的量子分子动力学(ImQMD)模型嫁接GEMINI统计衰变模型对波包宽度与弹核碎裂反应截面之间的关系进行了理论分析,分析了不同的波包宽度对400 AMeV 36Ar+C,20Ne与C,Al,Cu,Sn弹核碎裂反应截面的影响,分析了同位素36Ar,40Ar与Al反应在不同的波包宽度下的同位素分布。分析结果表明:波包宽度的选择影响着弹核碎裂的反应截面,并且与核反应体系有关。当σ2_r = 2 fm2时的计算结果与实验结果一致;而σ_r =(0.88+0.09 A1/3) fm的计算结果与体系有很大的关系,对弹核碎裂的反应截面影响明显。不的波包宽度对丰中子核40Ar的弹核碎裂反应截面的影响要小于对36Ar的弹核碎裂反应截面的影响,而且随体系分布的波包宽度计算的同位素要比σ2_r =2 fm2时计算的同位素多。The relations between wave packet width and projectile fragmentation cross sections are studied in theory by using the improved quantum molecular dynamics (ImQMD) and GEMINI models. The effect of different wave packet width for projectile fragmentation cross sections is analyzed for the reaction 36Ar on C, 20Ne on C, Al, Cu, Sn at 400 AMeV, the isotope distributions with different wave packet width are studied for reactions 36Ar, 40Ar on Al. The results show that the projectile fragmentation cross sections are affected by the choice of the wave packet width, and are related to the system of nuclear reaction. The calculation results of σ2_r =2 fm2are in agreement with the experimental results, but the results of σ_r = (0.88+0.09A1/3) fm have a strong relation with reaction system and the projectile fragmentation cross sections are affected obviously. The influence of wave packet width for 40Ar projectile fragmentation cross sections is smaller than that for 36Ar.Moreover isotope distributions with system-size-dependent wave packet width are larger than with σ2_r =2 fm2.     

尿嘧啶、水合尿嘧啶的结构和振动性质研究

基于从头计算方法和半经验势分子动力学,通过计算尿嘧啶分子及其水合尿嘧啶分子运动轨迹的速度自关联函数的傅立叶变换,给出了这些分子的振动频率。通过求解Hessian矩阵,鉴别出这些分子每一个振动频率的振动模式。对孤立的尿嘧啶分子,计算结果能够和实验数据符合。对水合尿嘧啶分子中,尿嘧啶分子的结构和振动频率的改变做了讨论。Based on an ab initio calculation and a semiempirical method, the structural and vibrational frequencies of Uracil and hydrated Uracil are studied by using the Fourier transform of velocity autocorrelation function of trajectories of molecular dynamics simulations. The finite difference harmonic method is also used to assign the vibrational frequency of each mode. It is found the calculation frequencies are in good agreement with the experiment data. The structural and vibrational frequencies of Uracil in hydrated form is discussed.     

10B中子非弹性散射的理论计算

本文介绍了根据直接作用模型,采用DWBA方法,对~(10)B快中子非弹性散射的一组实验数据进行分析,获得了与实验数据符合较好的理论结果及一组参数,由所得参数,计算了入射中子能量为7.54～20MeV的~(10)B(n,n′)~(10)B~0.717MeV激发态非弹性散射的积分截面和角分布,补充了实验所缺的数据。 In this paper, we analysed the experimental data of reaction cross sections induced byfast neutron on ~(10)B by using the direct nuclear reaction theory and the DWBA method. We obtainedthe results in agreement with experimental data and reported a set of parameters. Furthermore, byusing the set of parameters we have calculated systematically the inelastic integrated cross sectionsand angular distribution of ~(10)B(n, n′) ~(10)B 0.717 MeV excited state for incident neutron energiesfrom 7.54 MeV to 20.0 MeV. ...     

Pairing-energy coefficients of neutron-rich fragments in spallation reactions

The ratio of pairing-energy coefficient to temperature(a_p/T)of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model.A series of spallation reactions,0.5A and 1A Ge V~(208)Pb+p,1A Ge V~(238)U+p,0.5A Ge V~(136)Xe+d,0.2A,0.5A and 1A Ge V~(136)Xe+p,and~(56)Fe+p with incident energy ranging from 0.3A to 1.5A Ge V,has been analysed.An obvious odd-even staggering is shown in the fragments with small neutron excess(I≡N-Z),and in the relatively small-A fragments which have large I.The values of a_p/T for the fragments,with I from 0 to36,have been found to be in a range from-4 to 4,and most values of a_p/T fall in the range from-1 to 1.It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions.It is also concluded that the method proposed in this article is not good for fragments with A/A_s85%(where A_(s )is the mass number of the spallation system).     

利用MSDM分析p+208Pb散裂反应产物

多步动力学模型(MSDM)研究中、高能质子引起的散裂反应分为3个过程:核内级联、粒子预平衡发射以及通过蒸发粒子和裂变方式的剩余激发核退激发过程.利用Ignatyuk能级密度公式代替MSDM模型中的费米气体能级密度公式,改进其研究质子入射引起散裂产物的形成截面.采用Ignatyuk能级密度公式MSDM研究p+208Pb散裂产物的电荷、质量分布以及产物核形成截面,结果很好地再现了实验数据,且比利用费米气体能级密度的MSDM结果好得多. The level density of Ignatyuk formula is introduced into the Many stages dynamics model ( (MSDM)) instead of Fermi-gas formula to improve the simulation of spallation fragments. The results of (MSDM) with Ignatyuk formula reproduced the experimental data well for the mass and charge distributions, the formation cross sections of isotopic product of proton-induced spallation on~(208)Pb. The calculations are in agreement with the experimental data and better than some simulations by MSDM with Fermi-gas ...     

Adhesion measurement of thin films by a modified laser spallation technique: theoretical analysis and experimental investigation

Laser driven shocks can lead to a dynamic failure, called film spallation. Here, we use a modified laser spallation set-up to measure the dynamic adhesion of thin films and we propose a novel diagnostic technology. Based on correlation theory, new spallation criteria for characterizing the progressive damage at the interface between the film and the substrate are established, such as interface delamination, film spallation and film expulsion. With the help of the theory, the degree of damage and the dimension of damage (i.e. fracture), such as the minimum width of delamination radius, the thickness of the film etc., are estimated. Experiments are carried out on epoxy/stainless steel and epoxy/Al, and the experimental results show that their dynamic bonding strengths are about 25 MPa and 20 MPa, respectively. The detailed results, analyses and discussions are presented in this paper. Received: 6 February 2001 / Accepted: 3 December 2001 / Published online: 11 February 2002     

A Bayesian-neural-network prediction for fragment production in proton induced spallation reaction

Fragment production in spallation reactions yields key infrastructure data for various applications. Based on the empirical SPACS parameterizations, a Bayesian-neural-network (BNN) approach is established to predict the fragment cross sections in proton-induced spallation reactions. A systematic investigation has been performed for the measured proton-induced spallation reactions of systems ranging from intermediate to heavy nuclei systems and incident energies ranging from 168 MeV/u to 1500 MeV/u. By learning the residuals between the experimental measurements and SPACS predictions, it is found that the BNN-predicted results are in good agreement with the measured results. The established method is suggested to benefit the related research on nuclear astrophysics, nuclear radioactive beam sources, accelerator driven systems, proton therapy, etc.     

Study of the H＋HS reaction on a newly built potential energy surface using the quasi-classical trajectory method

<正>The quasi-classical trajectory（QCT） method is used to study the H+HS reaction on a newly built potential energy surface（PES） of the triplet state of H₂S（³A″） in a collision energy range of 0-60 kcal/mol.Both scalar properties, such as the reaction probability and the integral cross section（ICS）,and the vector properties,such as the angular distribution between the relative velocity vector of the reactant and that of the product,etc.,are investigated using the QCT method.It is found that the ICSs obtained by the QCT method and the quantum mechanical（QM） method accord well with each other.In addition,the distribution for the product vibrational states is cold,while that for the product rotational states is hot for both reaction channels in the whole energy range studied here.     

中国散裂中子源多功能反射谱仪屏蔽设计

本文介绍了利用蒙特卡罗粒子输运程序MCNPX2.5.0进行中国散裂中子源多功能反射谱仪屏蔽设计的屏蔽需求、辐射源项、计算方法和设计结果等内容.在计算中考虑慢化器泄漏源项、中子导管损失源项等不同辐射源项,使用分步计算和源项角度偏移、源项能量偏移、几何分裂等多种减方差方法,在保证计算结果精度的同时提高计算速度.在谱仪束线传输段、第二中子开关、散射室等的屏蔽计算中,通过比较了不同条件下的所需屏蔽确定最终屏蔽设计,确保谱仪屏蔽外人员可到达区域的剂量低于安全限值2.5μSv/h.     

核反应总截面和奇异结构研究

本总结了晕和皮等奇异核子结构研究的现状,介绍了发现晕和皮现象的实验证据。然后集中介绍了利用奇异核反应总截面的实验测量和理论模型,从中提取奇异核物质半径,核内核子分布以及介质中的核子－核子碰撞截面等重要信息,我们将特别强调通过实验测量和理论模型之间的联系来研究奇异结构性质。     

Ultrasound assisted synthesis of polyacrylic acid–nanoclay nanocomposite and its application in sonosorption studies of malachite green dye

Synthesis of nanoclay nanocomposite has been undertaken by using polyacryalic acid (PAA) in aqueous medium and ultrasound environment and its application in dye removal has been investigated. The synthesized product was characterized by using FTIR and XRD techniques. The sonosorption capacity of the product namely PAA–nanoclay composite was determined by choosing malachite green (MG) dye as a model pollutant. The effects of various parameters such as nanocomposite loading, pH, various process conditions etc. have been studied. On comparing the results obtained with that of nanoclay as an adsorbent, it was found for an initial concentration of 500 mg/l, the PAA–nanoclay nanocomposite exhibited higher percentage of pollutant removal (68%) and for nanoclay it was 54%. The adsorption data has been correlated using Langmuir and Freundlich models. The fit of the Freundlich isotherm model was found to be good in the entire range of concentration for the experimental sorption data obtained on the nanoclay nanocomposite. A plausible reaction mechanism for use of PAA–nanoclay nanocomposite as an adsorbent is also proposed.