The magnetic structure of TbNiSiD1.78

TbNiSiD_1.78 has been studied by powder neutron diffraction below 100 K. The compound takes the hexagonal room temperature structure at 100 and 50 K (P6₃/mmc). At 2 K, below the antiferromagnetic ordering temperature of 10 K, there is a small orthorhombic distortion of the lattice. The refined unit-cell dimensions at 2 K (space group Pnma) are a=7.9505(2), b=4.02502(14), c=6.9823(2) Å. The magnetic moments of Tb are 8.71(6) μ_B, and are ordered antiferromagnetically along a.     

界面流法计算反应堆六角形燃料组件中子通量密度分布

利用界面流法计算两维六角形轻水堆燃料组件中子通量密度分布。子区内中子源在空间上采用二次分布近似，还考虑了六角形组件周边水隙对组件内中子通量密度的影响。根据提出的模型，编制了TPHEX－E程序，并对一些轻水堆六角形组件问题作了计算，计算结果与蒙特卡罗方法计算结果进行了比较，符合良好。本程序可用于六角形轻水堆燃料组件计算。     

中子寿命测井在评价管外窜槽中的应用

管外窜槽已成为制约中原油田注水开发的障碍，并造成了严重的经济损失。文中分析了管外窜槽的形成机理，重点介绍了注硼中子寿命测井技术用于管外窜槽监测的原理、工艺及解释方法。结合中原油田的应用实例，论证了中子寿命测井评价管外窜槽的有效性，为油藏动态监测提供了有效手段。     

中子辐照金刚石生成卡宾碳

金刚石在中子辐照下发生相转变,得到了线性结构的卡宾碳。所得产物为覆盖金刚石表面的黑色薄膜状物质,其拉曼光谱在2191cm-1处有强峰,归属于C≡C伸缩振动;同时,其俄歇电子谱的峰位与金刚石相比有5eV的位移,证实了卡宾碳的存在。在中子辐照条件下,金刚石向卡宾碳的转化可能是通过碳原子堆垛形式发生变化而实现的。     

中子产额大于1.5×10^10n／s的密封中子管

报道了一种中子产额大于１．５×１０１０ｎ／ｓ、靶和离子源都可拆卸的密封中子管，以它为核心研制的密封中子发生器已被用于中子照像等领域，并取得了较好的结果。     

铑自给能中子探测器的灵敏度

本文给出了铑自给能探测器的热中子灵敏度和中子灵敏度的理论计算公式、燃耗修正公式以及不同中子温度下的换算公式。运用这些公式对ZTRh 123型铑自给能探测器的热中子灵敏度和中子灵敏度进行了理论计算,并在反应堆中对其进行了实验验证。其结果表明,理论计算值和实验标定值是相吻合的。其偏差:热中子灵敏度为8.5％,中子灵敏度为3.9％。     

Systematic analysis of neutron yields from thick targets bombarded by heavy ions and protons with moving source model

A simple phenomenological analysis using the moving source model has been performed on the neutron energy spectra produced by bombarding thick targets with high energy heavy ions which have been systematically measured at the Heavy-Ion Medical Accelerator (HIMAC) facility (located in Chiba, Japan) of the National Institute of Radiological Sciences (NIRS). For the bombardment of both heavy ions and protons in the energy region of 100–500 MeV per nucleon, the moving source model incorporating the knock-on process could be generally successful in reproducing the measured neutron spectra within a factor of two margin of accuracy. This phenomenological analytical equation is expressed having several parameters as functions of atomic number Z_p, mass number A_p, energy per nucleon E_p for projectile, and atomic number Z_T, mass number A_T for target. By inputting these basic data for projectile and target into this equation we can easily estimate the secondary neutron energy spectra at an emission angle of 0–90° for bombardment with heavy ions and protons in the aforementioned energy region. This method will be quite useful to estimate the neutron source term in the neutron shielding design of high energy proton and heavy ion accelerators.     

Neutron Stress Measurement of W‐Fiber Reinforced Cu Composite

Stress measurement methods using neutron and X‐ray diffraction were examined by comparing the surface stresses with internal stresses in the continuous tungsten‐fiber reinforced copper‐matrix composite. Surface stresses were measured by X‐ray stress measurement with the sin²ψ method. Furthermore, the sin²ψ method and the most common triaxal measurement method using Hooke's equation were employed for internal stress measurement by neutron diffraction. On the other hand, microstress distributions developed by the difference in the thermal expansion coefficients between these two phases were calculated by FEM. The weighted average strains and stresses were compared with the experimental results. The FEM results agreed with the experimental results qualitatively and confirmed the importance of the triaxial stress analysis in the neutron stress measurement.     

Specular reflection of thermal neutrons from Gd-containing layers and optimization of antireflective underlayers for polarizing coatings

A detailed analysis of specular neutron reflection from an absorbing medium is given. The experimental studies revealed that oxidation and roughness of the surface are the main factors that determine the neutron reflectivity of Gd-containing layers. It is concluded that the empirical approach used at present does not guarantee optimization of underlayer parameters (composition and thickness) and technological regimes. An algorithm of optimization is proposed, in which account is taken of the substrate potential, the dependence of the underlayer potential on the thermal neutron wavelength, the polarizing coating imperfections that enhance reflection of neutrons with the undesired spin. The antireflective TiZrGd underlayer for CoFe/TiZr supermirrors produced at the magnetron facility DIOGEN (PNPI, Gatchina) is optimized.