Eine einfache Mehrprobenrotationsanordnung zur Aktivierungsanalyse am Neutronengenerator

Es wird eine Anordnung beschrieben, die es gestattet, bis zu 7 Proben unter identischen Bedingungen rotationssymmetrisch zu aktivieren. Die Proben rotieren um zwei parallele Achsen. Es wird über Erprobungsmessungen durch Aktivierung von Cu-und N-haltigen Proben berichtet.     

Fermi能区核－核碰撞的平衡前中子发射

利用ＢＵＵ模型模拟核－核碰撞３６Ａｒ＋１０８Ａｇ（３５Ｍｅｖ／ｕ）、１４Ｎ＋１０８Ａｇ（３５ＭｅＶ／ｕ）中的平衡前中子发射．模拟结果与唯象的运动源拟合给出的中等速度源成份相吻合．这说明中等速度源成份产生于核－核碰撞的早期，对应平衡前发射．并从级联碰撞的角度定量地研究了平衡前发射的持续时间     

Transmutation of 129I, 237Np, 238Pu, 239Pu, and 241Am using neutrons produced in target-blanket system ‘Energy plus Transmutation’ by relativistic protons

Target-blanket facility ‘Energy + Transmutation’ was irradiated by proton beam extracted from the Nuclotron Accelerator in Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction yields (residual nuclei production yields) have been determined using γ-spectroscopy. Neutron field's energy distribution has also been studied using a set of threshold detectors. Results of transmutation studies of ¹²⁹I, ²³⁷Np, ²³⁸Pu, ²³⁹Pu and ²⁴¹Am are presented.      

Characteristic variations in the effect of diluents on polymer crystallization and melting observed for a sample of poly(ethylene-co-octene)

Melting points in mixtures of a crystallizable polymer with a low-molar-mass diluent depend on both, the diluent fraction and the crystal thickness. A differentiation of the two factors can be achieved by temperature-dependent SAXS experiments. A corresponding study, complemented by DSC, dilatometry, microscopy and AFM-imaging, was carried out for mixtures of a poly(ethylene-co-octene) with n-C₁₆H₃₄, c-C₁₆H₃₂ and methyl-anthracene, respectively. All diluents lead for a constant crystal thickness to melting point depressions in agreement with Raoult's law. On the other hand, the effect of the diluents on the thickness of the crystals formed at a fixed crystallization temperature varies. While in the presence of the two alkanes thicker crystals form, no effect arises for the methyl-anthracene—as was previously found for the octene-co-units. We consider these observations as a further support for our view that polymer crystallization follows a multi-stage route which includes a passage through an intermediate mesomorphic phase. Under such conditions crystal thicknesses would only be affected if the diluent is still present in the mesomorphic phase and stay invariant if the diluent molecules are already rejected when this intermediate phase forms.     

Acceleration Effect in the Field of Neutron Star with Electric and Magnetic Charge and Magnetic Moment

The expression of acceleration in the external gravitational field of neutron star with electric and magnetic charge and magnetic moment is obtained. And some gravitational effects and properties of the field are discussed respectively from the contributions of the electric and magnetic charge and magnetic moment on the acceleration.     

D-T中子源n-γ密度测井规律的蒙特卡罗模拟

根据D-T反应中子的能谱和角分布数据,建立了中子源模型;根据石灰岩地层标准刻度井群数据,建立了井模型。采用MCNP程序模拟了井中中子和射线的输运,得到了不同地层密度、不同源距处NaI探测器中的混合能谱和非弹能谱。在混合能谱2.5~4.5 MeV能区开窗,混合射线相对计数随源距的变化曲线显示,源距应选择在20~80 cm,密度与混合射线计数之间呈现非线性关系。在非弹能谱1.0~8.0 MeV能区开窗,非弹射线相对计数随源距的变化数据显示,源距应选择在20~40 cm或80 cm附近,密度与非弹射线计数之间成近似线性关系。     

用于位置灵敏型中子探测器的6LiF/ZnS（Ag）闪烁体性能研究

研究了掺杂6LiF的ZnS(Ag)闪烁体对中子、γ射线的发光特性和EJ426闪烁体样品的热中子探测效率、出射光产额和γ灵敏度。EJ426的热中子探测效率为32.4%,出射光产额为8.01×103光子/中子,70 mV阈值时的γ灵敏度小于10-7,表明EJ426是较理想的闪烁体型位置灵敏中子探测器材料。     

核爆发电问题中核燃料循环的中子学研究

研究核爆聚变电站中的一类中子学问题——如何利用核爆炸产生的大量中子生产核燃料.首先,根据核爆中子场的特点,确定可以利用的中子能量范围.用慢化理论对慢化材料的厚度进行估计,并用MCNP程序进行数值计算.研究如何利用中子反照效应减少造材料层的厚度,最后提出一个较合理的造材料技术路线.     

粮仓效应的圆盘堆积模型

为研究圆筒中颗粒堆内部的应力分布,将颗粒堆简化为规则的二维圆盘堆积模型.对圆盘堆积中力的传递进行分析后给出了圆盘堆积中力的传递规律,利用计算机模拟了圆盘对容器底部的压力,发现底部压力随圆盘层数增加会达到饱和,并将二维圆盘堆积的规律推广到三维颗粒堆,从理论上推导出容器底部平均压强p与颗粒填充高度Z的关系.     

Crystal structure and magnetic ordering of RNi Si compounds

The element distributions and the magnetic ordering behaviour of compounds RNi₁₀Si₂ (R = Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize in an ordered variant of the ThMn₁₂ structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively, corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn₁₂ structure. TbNi₁₀Si₂ orders antiferromagnetically below T _N = 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi₁₀Si₂ do not carry any ordered magnetic moments. The compounds with R = Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively. Received 10 July 2002 / Received in final form 12 September 2002 Published online 29 October 2002