Application of neutron activation tracer sediment technique on environmental science

Field and laboratory inverstigations were carried out to study the transport and dispersion law of polluted sediments near wastewater outlet using neutron activation tracer technique.The direction of transport and dispersion of polluted sediments,dispersion amount in different directions,sedimentary region of polluted sediment and evaluation of polluted risk are given.This provided a new test method for the study of environmental science and added a new forecasted content for the evaluation of environmental influence.     

Energy and angular distribution of recoil proton of fast neutron in scintillation fiber： a simulation study

Due to their low cost,big reaction cross-section with neutrons,flexibility,and convenience for long distance data transfer,plastic scintillation fibers (PSF) have been increasingly used as detectors or sensors for high-energy neutron radiography.In this paper,Geant4 Monte Carlo simulation tool was used to obtain some chalacteristics of energy and angular distributions of recoil protons in plastic scintillation fibers irradiated by fast neutrons.The plastic fiber with BCF-20 as the core and an acrylic outer cladding was used in the simulation.The results show that there is a big range of energy and angular distribution of recoil protons in energies varying inversely with the recoil angle.     

Elemental analysis of rain－and fresh water by neutron activation analysis

Analysis of rain-and fresh water for trace constitutents is a mandatory part of environmental monitoring.This text gives a survey of neutron activation analysis(NAA) within the framework of current environmental water research programmes.based on the practice developed in co-operation with the Dutch Energy Research Centre at Petten(ECN).While the procedures reported in literature cover obout thirty five elements,our routine procedures of instrumental neutron activation analysis(INAA) is limited to ten to fifteen elements.THe use of some dedicated radiochemical separations(RNAA) adds another six,some of which are speciated as well.Current contributions of NAA to water analysis center on determination and speciation of anionic trace elements,notably Br.I,As,and Se,on the assay of some ultra traces like Ag,Au and Hg and on validation.     

Measurement of fast－neutron capture cross sections for ^75As

The cross sections of the ^75As(n,γ)^76As reaction were measured in the neutron energy range from 0.50 to 1.50 MeV by using the activation technique.Neutrons were produced via the T(p,n)^3He reaction and the cross sections of the ^197Au(n,γ)^198Au reaction were used to determine the absolute neutron flux.Present results are compared with existing measurements and evaluations.     

Hidden substances identification by detection of fast neutron induced γ rays using associated α particle technique

Measurements have been made of characteristic gamma rays spectra from A(n,n^′γ)A reactions induced by 14.1 MeV neutrons on bulk samples of different substances: C, H₂O, SiO₂, C₃H₆N₆ and samples of soil. Background radiation was reduced by the associated alpha particle technique.     

Improved activation tests of fusion structural materials with a deuteron–beryllium neutron source

In the framework of the European Activation File (EAF) task of the European Fusion Technology Programme, the EAF data relevant to the steel types F82H-mod and MANET-2 were benchmarked experimentally. Samples were activated in an intense neutron field produced in a thick beryllium target by a 19-MeV deuteron beam of the Karlsruhe Isochron-Zyklotron. The irradiated samples were investigated by γ spectrometry. The results were compared with calculations using the FISPACT code, the EAF-4.1 library and the source neutron spectrum as measured by activation foil dosimetry. Calculation-over-experiment ratios between 0.96 and 1.19 are found for the more important medium-halflife radionuclides produced in F82H-mod. Similar values are found for MANET-2.     

ICRF Experiments and GAMMA 10 Potential Formation on the Tandem Mirror

Target plasmas, on which the formation of the electrostatic potentials and the improvement of the confinement are studied, are produced with ICRF in the GAMMA 10 tandem mirror. The ion temperature of more than 10 keV has been achieved in relatively low density plasmas. When the strong ICRF heating is applied, it is observed that the high frequency and the low frequency fluctuations are excited and suppress the increase of the plasma parameters. Recently, a new high power gyrotron system has been constructed and the ECRH power in plug extends up to 370 kW. The improvement of the confinement due to the formation of the potential in the axial direction and the strong radial electric field shear has been observed.     

Simulation and experimental study of a random neutron analyzing system with （252）~Cf neutron source

Experiments were performed on a high-speed online random neutron analyzing system(HORNA system)with a 252Cf neutron source(up to 1 GHz sampling rate and 3 input data channel),to obtain time-and frequencydependent signatures which are sensitive to changes in the composition,fissile mass and configuration of the fissile assembly.The data were acquired by three high-speed synchronized acquisition cards at different detector angles,source-detector distances and block sizes.According to the relationship between 252Cf source and the ratio of power spectral density,Rpsd,all the signatures were calculated and analyzed using correlation and periodogram methods.Based on the results,the simulated autocorrelation functions were utilized for identifying different fissile mass with Elman neural network.The experimental results show that the Rpsd almost remains at constant amplitude in frequency range of 0-100 MHz,and is only related to the angle and source-detector distance.The trained Elman neural network is able to distinguish the characteristics of autocorrelation function and identify different fissile mass.The average identification rate reached 90% with high robustness.     

Experiments on X—ray—ablated C8H8 samples

The behavior of materials heated by X rays to high energy density state is a very interesing and active research field for application in inertial fusion,astrophysics and so on.Some new experiments on X-ray-ablated C8H8 samples were designed and performed on Xingguang one beam frequency-tripled Nd:galass laser faciltiy.The ablation velocity and the mass absorption coefficient of C8H8 foam,and the self-cmission spectrum of C8H8 foil were experimentally obtained.The experiments and results are briefly descrided.     

快中子照相的实验研究

快中子照相是一种优良的无损检测技术,它有着X射线、热中子照相等所不具有的独特优势。本文介绍了作者分别采用^241Am-Be同位素中子源和中子发生器进行的快中子照相研究,并利用自制的Gd2O2S：Tb快中子转换发光屏进行探测,成功实现照相。     

回旋加速器快中子治癌装置的研究

就30MeV回旋加速器上建立快中子治癌装置的几个主要方面,如中子束特性参数、中子屏蔽准直器、中子靶、中子剂量监测及中子治癌控制等进行了可行性的研究。     

活化法测量溅射Au原子的各向异性

溅射的空间分布和溅射率的研究不仅是检验各种溅射机制的重要手段而且与许多溅射的应用问题紧密相联。如利用溅射刻绘集成电路所需的复杂图样、单晶表面加工和薄靶制备技术等。此外一些分析技术也有赖于溅射的角分布和能量分布知识。 有关溅射理论的基础是由Sigmund在1969年提出的线性级联碰撞理论。根据他的理论引致的空间溅射角分布是余弦形状的对称分布,但一些实验表明这一理论与实验有明显的偏     

微型堆辐照座内快中子通量谱的测定

用Ａｌ，Ｆｅ，Ｉｎ和Ｎｉ作探测片，用阈探测片活化法测定了中国原子能科学研究院微型堆内，外辐照孔道的快中子能量。用平均截面法求得内外辐照孔道的快中子与热中子能量比分别为０．１９８和０．０７７，用有效阈能法计算了不同能量区间的快中子通量，同时也对四个内辐照等之间及内、外辐照管内径向和轴向快中子通量的不均匀度进行了测定。     

Contrast sensitivity in 14 MeV fast neutron radiography

Fast neutron radiography (FNR) is an effective non-destructive testing technique.Due to the scattering effect and low detection efficiency,the detection limit of FNR under certain conditions cannot be determined.In order to obtain the minimum detectable thickness by FNR,we studied the contrast sensitivity of FNR lead samples,both theoretically and experimentally.We then clarified the relationship between pixel value and irradiation time,and sample materials and thickness.Our experiment,using a 4-cm-thick lead sample,verified our theoretical expression of FNR contrast sensitivity.     

多探测器快中子飞行时间谱仪

描述了一台串列加速器HI-13上的多探测器快中子飞行时间谱仪,并与国际上同类谱仪进行了比较。本谱仪主要用于能量大于8 MeV的快中子散射实验、次级中子双微分截面及带电粒子引起的出射中子能谱的测量。简要介绍了谱仪各主要部分(包括零信号拾取筒、氘气体靶、探测器、电子学等)的结构和特性及其在快中子实验中的应用。     

铝外壳Si（Au）面垒探测器受快中子辐照后性能恢复的研究

本文研究了探测器经注量＜10^15n/cm^2的快中子辐照后，在重新加偏压过程中它们的反向电流猛增而使性能变坏的原因，然后采用慢加偏压的方式恢复了探测器的性能，延长了使用寿命。     

固体径迹探测器测量快裂变因子

介绍了利用固体径迹探测器测量快裂变因子的原理,方法和实验结果,并将实验结果与理论计算结果进行了比较,两在误差范围内相符合。