使用山嵛酸银标定中子小角散射谱仪的关键参数

为了快速标定中子小角散射谱仪的关键参数:速度选择器的选择波长和波长分辨率以及谱仪布局下的Q分辨率,采用实验方法对山嵛酸银粉末的中子小角散射实验数据进行了拟合.首先,确定谱仪布局,包括准直光阑孔径大小、准直长度、样品到探测器之间的距离;其次,在中子小角散射谱仪的机械速度选择器设置在3 000、4 000、5 000和6 000r·min-1 4种不同转速下,测定山嵛酸银粉末的中子小角散射谱;最后,对实验数据进行反演分析.通过分析,计算出该机械速度选择器常数为2 329.2 r· m-1·nm,从而得到了4种不同转速所对应的选择波长分别为0.776、0.582、0.466、0.388 nm;通过对实验数据的拟合还得到了该速度选择器的波长分辨率(23.75％),以及在此谱仪布局下的Q分辨率曲线.结果表明,使用山嵛酸银粉末的中子小角散射能够较好地标定谱仪的关键参数,从而支持对中子小角散射数据的正确分析和反演.     

SANS准直器的蒙特卡罗模拟

本文采用基于蒙特卡罗方法的谱仪设计软件VITESS，对中子小角散射谱仪上三种不同形状的准直器进行了模拟。比较了这三种不同准直器在输入条件相同的情况下，它们出口处的中子注量率、水平面和竖直面的中子角分布。通过分析，采用具有超镜因子m=1．5的bender类型的准直器可以获得较高的中子注量率，但是其水平面角分布相对其它两种稍微偏大。这为中子小角散射谱仪设计中准直器的选择提供了一个参考。     

用于中子小角散射的中子反射镜聚焦性能评价

中子因具有极强的穿透力被广泛应用于材料与生物试样微观结构检测,但由于中子束强度显著弱于X射线,通常采用聚焦的方式来实现对中子束的有效利用。针对前期基于高性能制造思想研发的金属材质部分回转椭球中子反射镜进行了聚焦和中子小角散射实验测试。结果表明,聚焦中子束的最大强度能够达到漫散射强度的103,实现了与前端针孔尺寸几乎相等的圆形焦斑。通过远离最佳焦平面的聚焦实验,获得了不同镜心到探测器距离的束流剖面,该束流剖面的半峰全宽与基于几何光学的理论计算值吻合良好,分析了直射中子束和反射中子束的波长分布,中子的反射率达到了60%,峰值强度超过了1 000个计数/像素(0.1 mm×0.1 mm)。以介孔二氧化硅(MCM-41)为标样,获得了中子小角散射的初步结果。结果表明,该中子反射镜具有良好的聚焦性能,能够应用于中子小角散射。     

高效液相色谱-蒸发光散射法测定马鞭草中齐墩果酸与熊果酸的含量

建立了高效液相色谱一蒸发光散射检测法测定马鞭草药材中齐墩果酸和熊果酸含量的方法,色谱柱为PinnacleⅡ C18（250min×4．6mm,5m）,流动相为甲醇-0．2％冰醋酸（体积比82．5：17．5）;淋洗速度1mL／min;柱温35℃;蒸发光散射检测器检测,漂移管温度为85℃;气体流速为2．2L／min。齐墩果酸在0．317～1．585μg范围内（r=0．9997）,熊果酸在0．585～2．925g范围内（r=0．9999）线性关系良好。药材中齐墩果酸和熊果酸的回收率（n=6）分别为100．4％和97．6％,标准偏差分别为1．84％和2．34％。所建方法准确,重现性好,可作为马鞭草药材的质量控制方法。     

用于能量传输的生物体植入式MEMS电感线圈的设计

为了能得到植入在生物体内，用于体内微型电子系统与体外设备信号和能量传输的高品质因数Q值和高电感量L值的MEMS电感线圈，本文首先对MEMS电感模型做了理论分析，然后在充分考虑功率传输要求、植入器件体积的限制以及制作工艺的可实现性的情况下，用高精度的3D电磁仿真软件HFSS，对电感的主要参数如圈数N、线宽W、导线间隙S、导线厚度H、导线材料M和衬底电导率σ作了优化设计。最终确定N=10、W＝25μm、S=50μm、H=48μm、M为Cu、σ=0．1S／m。数值仿真的结果显示Q=17．6，L=55nH，fQMAX=240MHz，fself=1．2GHz，它们能很好地符合能量传输的功率要求和信号传输的带宽要求。     

中子应力谱仪准直器的模拟计算

为了能具体了解准直器系统对中子应力谱仪的性能参数如:样品处中子注量率、谱仪分辨率等主要指标的影响,对安装于中子应力谱仪上的准直器系统进行模拟和计算.通过设定和优化各个准直器参数.分析它们对谱仪性能指标的影响.模拟过程中,我们主要采用了McStas软件来进行建模及优化计算工作,通过对第一、第二准直器等主要部件的发散度参数α1、α2和长度的组合变化来发现它们对谱仪整体的影响,并且计算它们引起的分辨率改变,最终我们得到在α1:α2=30'下样品处水平方向中子注量率可以达到2.3×106n·cm-2·s-1,垂直方向可达3.5×106n·cm-2·s-1,并且当第一、第二准直器发散角α1:α2=10'时谱仪可以得到它的最好分辨率Fw=0.2,它所对应的应变误差值是应力谱仪测量的最小误差.     

叶顶间隙对离心叶轮气动性能影响研究

使用非结构化网格上的有限体积法，数值研究一半开式离心压缩机叶轮的内部流场、气动性能随叶顶间隙的变化规律。对原始叶轮相对间隙α=1．8％，数值计算所得到的气动性能参数与实验值符合非常好；对大范围叶顶相对间隙α=0．9％。7．0％内6种不同叶顶间隙下该叶轮的气动性能进行数值预测，随着叶顶间隙增大，离心叶轮气动效率、压比及转矩均降低，但变化曲线与线性函数相距甚远，呈现出典型的双平台变化关系。对所研究模型，综合考虑气动及强度振动因素，叶顶相对间隙最佳值取为2．6％，计算结果对离心压缩机设计具有一定的工程指导意义。     

中温碱性化学镀镍磷实用新工艺研究

用正交试验设计法和中心组合规则研究了以硫酸镍、次亚磷酸钠为主盐的化学镀液优 化配方,通过SAS8．2进行模拟得到二次多项式回归方程数学模型。研究了镀液中微量光亮 剂对镀速的影响。结果表明:在施镀温度为62．7℃,pH值为8．0,装载量为1 dm2／L,NiSO4· 6H20 36．03 g／L,NH4Ac 36．96 g／L,NaF 6．3 g／L,Na3C6H5O7·2H2O 23．52 g／L,NaH2PO2 42．4 g／L条件下,施镀1h,所得到的平均镀速为14．65μm／h,且镀层光亮,镀层含磷量为 7．8％～8．2％,镀层硬度为HV457,镀液可循环利用7个周期,能满足生产的实际需要。     

中子反射谱仪的闸门与会聚导管组合设计

为提高水平散射几何中子反射谱仪的前端束流特性，针对前端闸门与会聚中子导管的组合设计进行了优化计算。根据闸门通道截面、会聚导管入出口截面及相应内表面超镜因子不同分成多组，采用数值方法对多个组合设计进行优化计算，结合水平散射几何中子反射谱仪的特点需求通过比较分析，选取比较理想的组合。计算结果表明：会聚导管的最佳组合最好采用上下面会聚，垂直面不会聚，宽度为10mm,闸门内表面超镜因子为2，会聚导管上下面超镜因子为3，左右面超镜因子为2。通过多组比较分析，获得了水平散射几何中子反射谱仪的前端闸门与会聚导管的相关物理参数的优化组合，为谱仪的概念设计奠定了理论基础。     

用计算器快速求反渐开线函数值

在计算渐开线齿轮或花键几何尺寸过程中,通常是先计算渐开线函数值invα,再进一步求出其反函数值a。常规办法是用渐开线函数表,先查出inva接近的角度值,再用插值法算出余下部分的角度值。这不仅费时,而且计算误差偏大。为此,我在实际工作中,总结出一种用函数计算器快速求反渐开线函数的方法,现介绍如下。 如今工程技术人员普遍配有函数计算器,用它求反渐开线函数值α,不少人进行了探索,也积累了一些经验。例如用迭代法求a,迭代公式为α1=arctg(invα α0),设α0=3invα-0.385inva。我们用上面公式计算了inva=2.7100355×10-3～0.1422883中…     

Optimized design for time-of-flight total neutron scattering instrumentation using Monte Carlo simulations with application for the characterization of disordered macromolecules

Abstract

A time-of-flight neutron total scattering instrument for the China Spallation Neutron Source (CSNS) was designed. The instrument is designed for disordered macromolecular systems with characteristic lengths below 10?nm. The coupled hydrogen moderator of CSNS was selected to ensure the favorable statistics at the smallest scattering vector of 0.01?Å^?1. The optics and geometry of the instrument were optimized to cover a wide range of scattering vectors from 0.01 to 70?Å^?1. The performance of the instrument was examined using a series of Monte Carlo simulations, which demonstrate that the flux on the sample, the resolution, and the range of the scattering vectors are comparable to those of other advanced neutron total instruments. Finally, a virtual experiment was performed with silica powder. The resulting scattering pattern is consistent with both the numeric calculation and the estimated resolution of the instrument. The designed total scattering instrument at CSNS allows the simultaneous observation of both atomic and nanometer scale structures, having the potential to become a powerful tool for studying the structure of disordered materials in the fields of polymers, biology, and condensed matter physics.     

A study of structure inhomogeneities using a neutron double-crystal spectrometer according to the Warren technique: A review

A technique for examining inhomogeneities of materials on a neutron beam using a double-crystal spectrometer is described. The parameters of inhomogeneities are determined from the measured integrated attenuation due to small-angle scattering (the Warren technique for X rays). The theoretical basis for adaptation of this technique to neutron flux measurements is presented, and the scope of its applicability is outlined. Results from examining different materials using this technique are described. Proposals for developing a stationary express method for serial small-angle measurements are formulated.     

Development of neutron spectrometer toward deuterium plasma diagnostics in LHD

Neutron spectrometer based on coincident counting of associated particles has been developed for deuterium plasma diagnostics on Large Helical Device (LHD) at the National Institute for Fusion Science. Efficient detection of 2.5 MeV neutron with high energy resolution would be achievable by coincident detection of a scattered neutron and a recoiled proton associated with an elastic scattering of incident neutron in a plastic scintillator as a radiator. The calculated neutron spectra from deuterium plasma heated by neutral beam injection indicate that the energy resolution of better than 7% is required for the spectrometer to evaluate energetic deuterium confinement. By using a prototype of the proposed spectrometer, the energy resolution of 6.3% and the detection efficiency of 3.3×10(-7)?count/neutron were experimentally demonstrated for 2.5 MeV monoenergetic neutron, respectively.     

Electron crystal structure analysis of small organic molecules

Electron crystallography of small organic molecules, i.e., electron diffraction crystal structure analysis, has been long recognized to possess definite advantages over neutron and x-ray diffraction techniques for the investigation of microcrystalline preparations. Quantitative application of the technique to real structural problems, on the other hand, had been hindered initially by an inadequate theoretical model. Yet, as demonstrated in this review of the methodology, the adequate recognition of limiting factors due to n-beam dynamical scattering and crystal deformation permits design of optimal diffraction experiments which yield intensity data suitable for ab initio structure analysis. Representative crystallographic analyses discussed here underscore the utility of this technique as a probe of organic molecular structure at atomic resolution.     

A SMALL-ANGLE X-RAY SCATTERING STATION AT BEIJING SYNCHROTRON RADIATION FACILITY

This article presents the development and current state of a small-angle X-ray scattering station at beamline 1W2A of the Beijing Synchrotron Radiation Facility, China. The source of the beamline is introduced from a 14-pole wiggler. A triangular bending Si(111) crystal is used to horizontally focus the beam and provide a monochromatic X-ray beam (8.052 keV). A bending cylindrical mirror coated with rhodium downstream from the monochromator is used to vertically focus the beam. The X-ray beam is focused on the detector which is fixed at 30 m from the source. The focused beam size (full width at half maximum) is 1.4 × 0.2 mm² (horizontal × vertical) with a flux of 5.5 × 10¹¹ phs/s at 2.5 GeV and 250 mA. Besides the routine mode of small-angle X-ray scattering, the combination of small- and wide-angle X-ray scattering, grazing incidence small-angle X-ray scattering, and time-resolved small-angle X-ray scattering in sub-second level are also available for the users. Dependent on the measurement requirements, several detectors can be chosen for the collection of scattering signals. Furthermore, multiple sample environments, including temperature, stress-strain, and liquid sampling are available for in situ measurements. In a typical camera length of 1.5 m, the small-angle X-ray scattering resolution is about 115 nm. The steady operation of the small-angle X-ray scattering station at Beijing Synchrotron Radiation Facility not only provides the small-angle X-ray scattering beam time for users, but also promotes the development and application of these techniques in China.     

Elastic incoherent neutron scattering operating by varying instrumental energy resolution: principle, simulations, and experiments of the resolution elastic neutron scattering (RENS)

The main aim of this paper is to present the scientific case of the resolution elastic neutron scattering (RENS) method that is based on the collection of elastic neutron scattering intensity as a function of the instrumental energy resolution and that is able to extract information on the system dynamical properties from an elastic signal. In this framework, it is shown that in the measured elastic scattering law, as a function of the instrumental energy resolution, an inflection point occurs when the instrumental energy resolution intersects the system relaxation time, and in an equivalent way, a transition in the temperature behavior of the measured elastic scattering law occurs when the characteristic system relaxation time crosses the instrumental energy resolution time. With regard to the latter, an operative protocol to determine the system characteristic time by different elastic incoherent neutron scattering (EINS) thermal scans at different instrumental energy resolutions is also proposed. The proposed method, hence, is not primarily addressed to collect the measured elastic scattering intensity with a great accuracy, but rather relies on determining an inflection point in the measured elastic scattering law versus instrumental energy resolution. The RENS method is tested both numerically and experimentally. As far as numerical simulations are concerned, a simple model system for which the temperature behavior of the relaxation time follows an Arrhenius law, while its scattering law follows a Gaussian behavior, is considered. It is shown that the system relaxation time used as an input for the simulations coincides with the one obtained by the RENS approach. Regarding the experimental findings, due to the fact that a neutron scattering spectrometer working following the RENS method has not been constructed yet, different EINS experiments with different instrumental energy resolutions were carried out on a complex model system, i.e., dry and D(2)O hydrated lysozyme, in an extended temperature range. The resulting temperature behavior of the system relaxation time, obtained with RENS method, agrees very well with the one obtained in literature, for the same system, following the quasi-elastic neutron scattering (QENS) approach. The proposed scientific case puts into evidence the challenges of an RENS spectrometer working by varying the instrumental energy resolution; in particular, in comparison with QENS, the proposed RENS method requires a smaller amount of sample, which is an important point in dealing with biological and exotic systems; it is not affected by the use of model functions for fitting spectra as in QENS, but furnishes a direct access to relevant information.     

The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.     

BioRef: a versatile time-of-flight reflectometer for soft matter applications at Helmholtz-Zentrum Berlin

BioRef is a versatile novel time-of-flight reflectometer featuring a sample environment for in situ infrared spectroscopy at the reactor neutron source BER II of the Helmholtz Zentrum Berlin fu?r Materialien und Energie (HZB). After two years of design and construction phase the instrument has recently undergone commissioning and is now available for specular and off-specular neutron reflectivity measurements. BioRef is especially dedicated to the investigation of soft matter systems and studies at the solid-liquid interface. Due to flexible resolution modes and variable addressable wavelength bands that allow for focusing onto a selected scattering vector range, BioRef enables a broad range of surface and interface investigations and even kinetic studies with subsecond time resolution. The instrumental settings can be tailored to the specific requirements of a wide range of applications. The performance is demonstrated by several reference measurements, and the unique option of in situ on-board infrared spectroscopy is illustrated by the example of a phase transition study in a lipid multilayer film.