Study of neutron spectra in a water bath from a Pb target irradiated by 250 MeV protons

Spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with a cadmium (Cd) cover. According to the measured activities of the foils, the neutron flux at different resonance energies were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code. The comparison showed that the simulation could give a good prediction for the neutron spectra above 50 eV, while the finite thickness of the foils greatly effected the experimental data in low energy. It was also found that the resonance detectors themselves had great impact on the simulated energy spectra.     

HIRFL-CSR系统中RIBLLⅡ上中子墙设计的模拟计算

HIRFL-CSR系统中RIBLLⅡ外靶实验终端上的中子探测装置是用来开展放射性束物理以及利用放射性束开展非对称核物质性质等研究的一个重要的探测装置. 介绍了在RIBLLⅡ上计划建造的中子墙的探测原理以及基于Geant4对其所进行的蒙特卡罗模拟, 给出了中子墙的设计方案、优化的设计参数以及中子探测的性能指标.     

Configuration of the valence neutrons of 17B

The reaction cross section of ¹⁷B on ¹²C target at (43.7±2.4)MeV/u has been measured at the Radioactive Ion Beam Line in Lanzhou (RIBLL). The root-mean-square matter radius (R_rms) was deduced to be (2.92±0.10)fm, while the R_rms of the core and the valence neutron distribution are 2.28fm and 5.98fm respectively. Assuming a ``core plus 2n' structure in ¹⁷B, the mixed configuration of (2s_1/2) and (1d_5/2) of the valence neutrons is studied and the     

铕(Ⅲ)离子光谱探针Eu(DBM)_32AP络合物中Eu(Ⅲ)格位

在77K测得的激发光谱说明Eu(DBM)_32AP(DBM:二苯甲酸甲烷根,AP:安替吡啉)络合物中Eu~(3+)离子仅有一种晶格格位.~5D_O→~7F_J(J=0-4)跃迁光谱说明中心Eu~(3+)离子具有C_(2v)格位对称性.实验测得的配位体总电荷为-2.75,与理论计算值-3.00吻合较好.     

大学电磁学视角下的高考电磁学问题研究

随着高中物理新教材的使用以及新高考在全国的陆续施行，对高中物理教学而言，无论是教学内容还是教学形式都出现了许多新的课题。这就使得站在高观点下(即大学普通物理学角度)研究高中物理，不仅成为教学改革的迫切任务，也成为了新课程下物理教学改革的一个主流方向。本文将结合2道高考试题，浅谈如何在大学电磁学视角下对高中电磁学问题进行深入研究，旨在引导高中物理教师和物理专业的师范生加强挖掘高中物理问题背后隐藏的知识，从而提高自己的物理素养，形成全面、扎实、灵活的学科知识结构。     

一例具有显著单分子磁体行为的双核镝配合物

使用多齿席夫碱H₂L（H₂L=（E）-N''-（3-乙氧基-2-羟基亚苄基）-3-羟基吡啶甲酰肼）为配体,与Ln（dbm）₃·2H₂O（Ln=Dy（1）、Nd（2）;dbm^-=1,3-dioxo-1,3-diphenylpropan-2-ide）反应,通过溶剂热法,成功得到了2例新的双核稀土配合物[Ln₂（dbm）₂（L）₂（C₂H₅OH）₂]。单晶X射线衍射结构表明：配合物1和2的结构主要由2个Ln（Ⅲ）离子、2个dbm^-、2个L^2-及2个C₂H₅OH组成,中心Ln（Ⅲ）离子通过2个μ₂-O原子相互连接,形成一个平行四边形的Ln₂O₂核心。磁性研究表明,配合物1中Dy（Ⅲ）离子间存在铁磁耦合作用,且1表现出显著的单分子磁体行为。     

Study of neutron activation yields in spallation reaction of 400 MeV/u carbon on a thick lead target

The spallation-neutron yield was studied experimentally by bombarding a thick lead target with 400 MeV/u carbon beam. The data were obtained with the activation analysis method using foils of Au, Mn, Al, Fe and In. The yields of produced isotopes were deduced by analyzing the measured γ spectra of the irradiated foils. According to the isotopes yields, the spatial and energy distributions of the neutron field were discussed. The experimental results were compared with Monte Carlo simulations performed by the GEANT4+FLUKA code.     

基于ITO/聚甲基丙烯酸甲酯/Al的有机阻变存储器SPICE仿真

探索了ITO/PMMA/Al器件的阻变机理及其SPICE电路仿真, 通过优化聚甲基丙烯酸甲酯(PMMA)层退火温度, 器件可实现连续擦-读-写-读操作. 基于不同退火温度PMMA薄膜的表面形貌研究, 构建了单层有机阻变器件的非线性电荷漂移模型, 以及描述该模型掺杂区界面移动的状态方程, 并通过反馈控制积分器建立了SPICE仿真电路. 最后, 代入器件实际测量参数, 得到与器件实际结果基本一致的电流-电压模拟曲线. 结果验证了单层有机器件的阻变机理, 说明该非线性电荷漂移模型的SPICE仿真在有机阻变器件仿真中同样适用. 关键词： 有机阻变存储器 非线性电荷漂移 SPICE仿真     

Angular Dispersion and Deflection Function for Heavy Ion Elastic Scattering

The differential cross sections for elastic scattering products of ^17F on ^208Pb have been measured. The angular dispersion plots of ln（dσ/dθ） versus θ^2 are obtained from the angular distribution of the elastic scattering differential cross sections. Systematical analysis on the angular dispersion for the available experimental data indicates that there is an angular dispersion turning angle at forward angular range within the grazing angle. This turning angle can be clarified as nucleal rainbow in classical deflection function. The exotic behaviour of the nuclear rainbow angle offers a new probe to investigate the halo and skin phenomena.     

STRUCTURE-PROPERTY RELATIONSHIP OF POLYELECTROLYTES AND ITS APPLICATION IN STABILIZING DRILLING-MUD IN PRESENCE OF SALTS

A new polyelectrolyte (SPU) has been prepared. It can depress the water-loss of drilling-mud much more effective than the commonly used acrylic polyelectrolytes even in 30% NaCl solution. SPU has phenyl group in the backbone with -SO_3~- in the side chain while the acrylic polyelectrolytes have C—C and -COO~- respectively, there exists an intrinsic relationship between the structure of polymer and its tolerance to salts, it has been found: 1) The adsorption amount of polymer on clay is related closely to the flexibility of polymer chain. 2) The salt-tolerance of -SO_3~- is superior to -COO-. 3) Both SPU-mud and HPAN-mud are plastic fluids. The dependence of yield point on salts relates to the molecular weight of polymer and hydration of ionogenic group, which is quite different for SPU-mud and HPAN-mud. 4 ) The extent of raising zeta-potential of base-mud by SPU is greater than by HPAN, but the extent of dropping zeta-potential of SPU-mud by NaCI is smaller than HPAN-mud. According to these results we suppose the salt-tolerance of SPU-mud is attributed mainly to hydration of -SO_3~- and that of HPAN-mud mainly to network structure formed in the drilling-mud.