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1.
Very Small Angle Neutron Scattering(VSANS) is an upgrade of the traditional Small Angle Neutron Scattering(SANS) technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, D11 in Grenoble, was built in 1972, new collimation techniques,focusing optics(multi-beam converging apertures, material or magnetic lenses, and focusing mirrors) and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed.In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source(CSNS) is thereby presented. 相似文献
2.
中子照相是一种重要的无损检测技术,它能用于火工产品、毒品和核燃料元件等的检测。基于紧凑型D-T中子发生器,完成了一个用于快中子照相的准直屏蔽体系统(BSA)的物理设计。根据D-T中子源的能谱和角分布建立了中子源模型,采用MCNP4C蒙特卡罗程序,模拟了准直屏蔽体系统中中子和γ射线的输运,准直中子束相对于单位源中子的中子注量可以达到9.30×10-6 cm-2,准直中子束中主要是能量大于10 MeV的快中子;在设置的样品平面直径14 cm的照射视野范围,准直束中子注量的不均匀度为4.30%,准直束中中子注量与γ注量的比值为17.20,中子通量和中子注量比值J/Φ为0.992,说明准直中子束有好的平行性;准直屏蔽体外的泄露中子注量率与准直束中子注量率相比降低了2个量级。所设计的准直屏蔽体能满足快中子照相的要求。Neutron radiography is an important nondestructive testing technique. It can be used to detect the explosive devices, drug and the nuclear fuel element, etc. A beam-shaping-assembly (BSA) based on a compact D-T neutron generator is designed for fast neutron radiography in this paper. D-T neutron source model is constructed based on the neutron energy spectrum and angular distribution data. The transportation of neutron and γ-ray in the BSA is simulated using MCNP4C code. The neutron fluence of the collimated neutron beam with respect to the neutron source of the unit source is 9.30×10-6 cm-2. The collimated neutron beams is mainly fast neutrons with energies greater than 10 MeV. In the irradiation field range with a diameter of 14 cm, the neutron fluence uniformity of the collimated beam is 4.3%, the ratio of the neutron fluence to the gamma fluence in the collimated beam is 17.20, and the neutron flux and the neutron fluence ratio (J/Φ) is 0.992 which indicates that the collimated neutron beam has good parallelism. The leakage neutron fluence in outside of BSA is two orders of magnitude lower than that of the collimated neutron beam. The designed BSA can meet the need of fast neutron radiography. 相似文献
3.
鲍杰 陈永浩 张显鹏 栾广源 任杰 王琦 阮锡超 张凯 安琪 白怀勇 曹平 陈琪萍 程品晶 崔增琪 樊瑞睿 封常青 顾旻皓 郭凤琴 韩长材 韩子杰 贺国珠 何泳成 何越峰 黄翰雄 黄蔚玲 黄锡汝 季筱路 吉旭阳 江浩雨 蒋伟 敬罕涛 康玲 康明涛 兰长林 李波 李论 李强 李晓 李阳 李样 刘荣 刘树彬 刘星言 马应林 宁常军 聂阳波 齐斌斌 宋朝晖 孙虹 孙晓阳 孙志嘉 谭志新 唐洪庆 唐靖宇 王鹏程 王涛峰 王艳凤 王朝辉 王征 文杰 温中伟 吴青彪 吴晓光 吴煊 解立坤 羊奕伟 杨毅 易晗 于莉 余滔 于永积 张国辉 张旌 张林浩 张利英 张清民 张奇伟 张玉亮 张志永 赵映潭 周良 周祖英 朱丹阳 朱科军 朱鹏 《物理学报》2019,68(8):80101-080101
中国散裂中子源(CSNS)已于2018年5月建设完工,随后进行了试运行.其中的反角白光中子束线(Back-n)可用于中子核数据测量、中子物理研究和核技术应用等多方面的实验.本文报道对该中子束的品质参数测量实验过程以及最终实验结果.实验主要采用中子飞行时间法,利用~(235)U,~(238)U裂变室和~6Li-Si探测器测量了中子能谱和中子注量率,又利用闪烁体-互补金属氧化物半导体探测系统测量了中子束斑的剖面,得到了该束线的初步实验测量结果.其中白光中子的全能谱测量范围eV—100 MeV,给出了不确定度分析;给出了中子注量率两个实验厅位置的满功率值;给出了白光中子在直径60 mm情况下的全能区束斑.通过与模拟结果的比较探讨了以上结果的合理性,并提出了改进计划.这些实验结果为以后该束线的核数据测量和探测器标定实验奠定了基础. 相似文献
4.
Small angle neutron scattering studies (SANS) were carried out to understand the formation of third phase in DHDECMP-dodecane-UO2(NO3)2/HNO3 system. It was observed that third phase formation takes place due to the formation of UO2(NO3)2.DHDECMP reverse micelles in the dodecane phase. SANS data obtained were interpreted with particle interaction model using
Baxter sticky spheres model.
相似文献
5.
SMARTer, a 36-meter small angle neutron scattering (SANS) spectrometer was installed at the Neutron Scattering Laboratory
(NSL), National Nuclear Energy Agency of Indonesia — BATAN in Serpong, Indonesia and has performed the experiment for studying
the magnetic structures of Cu(NiFe), CuCo and FeSiBNbCu metal alloys. The experiments were conducted at room temperature and
up to 1 T (10 kOe) of external magnetic field. At zero fields, isotropic scattering identified as nuclear scattering is dominant.
When a magnetic field is applied in a horizontal direction perpendicular to the neutron beam, the response of the magnetic
scattering permits extraction of the field-induced re-arrangement of the magnetic moment. With increasing field the distortion
is more pronounced and the magnetic scattering dominates the intensity and affects the peak position. Radial and angular averaging
from experimental data are given to show the details of magnetic structures.
相似文献
6.
用3He球形4中子探测器,通过直接反应法可以对核素的(n,2n)反应截面进行测量。在此类实验中,要求对中子束进行很好的准直。好的准直器设计要求能够提高样品处的中子注量率的均匀性,同时保证中子束流边缘处的下降幅度,能够降低低能中子所占份额。本工作采用FLUKA和MCNPX对圆柱形准直器、单锥形准直器及三种不同斜率的双锥形准直器对中子注量率的均匀性和低能中子所占份额进行了对比研究,结果表明,低斜率的双锥形准直器可以满足实验对这两方面的要求。同时,在有样品和无样品两种条件下,对探测系统经由这五种不同准直器准直后的中子束流的响应做了对比,结果显示,经过低斜率的双锥形准直器准直的中子束流,探测系统在有样品时表现为较高的计数率,在无样品时表现为较低的本底。除此之外,对准直器出口处的斜率对准直效果的影响也做了比较。最终中子准直器选用为这种低斜率的双锥形准直器,材料选用为紫铜、不锈钢、聚乙烯和铅。准直孔开口处直径为2.64 cm,长度为137 cm,经准直后样品处的中子束斑直径为3.2 cm。 相似文献
7.
C. K. Nisha Sunkara V. Manorama Souvik Maiti K. N. Jayachandran V. K. Aswald P. S. Goyal 《Pramana》2004,63(2):315-320
The interaction of cationic random copolymers of methoxy poly(ethylene glycol) monomethacrylate and (3-(methacryloylamino)propyl) trimethylammonium chloride with oppositely charged surfactant, sodium dodecyl sulphate, and the influence of surfactant association on the polymer conformation have been investigated by small-angle neutron scattering. SANS data showed a positive indication of the formation of RCPSDS complexes. Even though the complete structure of the polyion complexes could not be ascertained, the results obtained give us the information on the local structure in these polymer-surfactant systems. The data were analysed using the log-normal distribution of the polydispersed spherical aggregate model for the local structure in these complexes. For all the systems the median radius and the polydispersity were found to be in the range of 20 ± 2 Å and 0.6 ± 0.05, respectively. 相似文献
8.
Spherical micelles in ionic micellar solutions, often aggregate to form spherical, cylindrical or chain-like aggregates on
addition of salt to the solution. It is known that the technique of small angle neutron scattering (SANS) can be used to distinguish
spherical and cylindrical aggregates. To examine if SANS can be used to distinguish the latter two aggregation processes,
we have calculated the angular distribution of scattered neutrons from 0.002 M CTAB solutions. These calculations show that
aggregation of CTAB micelles results in large changes in SANS spectra. The shapes of SANS spectra are different for the above
three types of aggregates, suggesting that technique of SANS can indeed be used to distinguish the three aggregation processes.
The size of the aggregate can also be obtained from such studies. 相似文献
9.
Small angle neutron scattering (SANS) measurement has been performed on the reentrant ferromagnet Cr60Fe20Mn20 alloy. An increase in the SANS intensity is observed below 100 K coinciding with an increase in the magnetization. It exhibits a maximum at 40 K and shifts to lower temperatures with increase in Q. The magnetic part of the SANS intensity fits to a Lorentzian at all temperatures. The temperature dependence of the inverse correlation length exhibits a minimum at 40 K. In the antiferromagnetic spin-glass phase at 15 K ferromagnetic correlations of ~40 Å is observed. 相似文献
10.
对国际上用于单粒子效应(SEE)研究的准单能中子源进行了相关调研,对产生准单能中子源的7Li(p, n)7Be核反应、装置布局以及表征中子场性质的中子注量率、中子能谱、中子束流轮廓及其均匀性、热中子本底等参数的理论计算及实验测量进行了系统的介绍。进行准单能中子SEE实验要求中子源有较高的中子注量率水平、较大的束流轮廓、较好的束流均匀性以及较低的热中子本底,并且能测量出精确的中子能谱。对准单能中子SEE实验过程以及三种中子SEE截面的尾部修正方法进行了介绍。 相似文献
11.
The aggregation behaviour of a hydrotrope, sodiumn-butyl benzene sulfonate (Na-NBBS), in aqueous solutions is investigated by small-angle neutron scattering (SANS). Nearly
ellipsoidal aggregates of Na-NBBS at concentrations well above its minimum hydrotrope concentration were detected by SANS.
The hydrotrope seems to form self-assemblies with aggregation number of 36–40 with a substantial charge on the aggregate.
This aggregation number is weakly affected by the hydrotrope concentration. 相似文献
12.
The state of intermolecular aggregates and that of folded gelatin molecules could be characterized by dynamic laser light and small-angle neutron scattering experiments, which implied spontaneous segregation of particle sizes preceding coacervation, which is a liquid-liquid phase transition phenomenon. Dynamic light scattering (DLS) data analysis revealed two particle sizes until precipitation was reached. The smaller particles having a diameter of ~50 nm (stable nanoparticles prepared by coacervation method) were detected in the supernatant, whereas the inter-molecular aggregates having a diameter of ~400 nm gave rise to coacervation. Small-angle neutron scattering (SANS) experiments revealed that typical mesh size of the networks exist in polymer dense phase (coacervates) [1]. Analysis of the SANS structure factor showed the presence of two length scales associated with this system that were identified as the correlation length or mesh size, ξ = 10.6 Å of the network and the other is the size of inhomogeneities = 21.4 Å. Observations were discussed based on the results obtained from SANS experiments performed in 5% (w/v) gelatin solution at 60°C (ξ = 50 Å, ζ = 113 Å) and 5% (w/v) gel at 28°C (ξ = 47 Å, ζ = 115 Å) in aqueous phase [2] indicating smaller length scales in coacervate as compared to sol and gel. 相似文献
13.
We report a combined use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) to the study of
counterion condensation in ionic micelles. Small-angle neutron and X-ray scattering measurements have been carried out on
two surfactants cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium chloride (CTACl), which are similar but
having different counterions. SANS measurements show that CTABr surfactant forms much larger micelles than CTACl. This is
explained in terms of higher condensation of Br− counterions than Cl− counterions. SAXS data on these systems suggest that the Br− counterions are condensed around the micelles over smaller thickness than those of Cl− counterions. 相似文献
14.
利用中子飞行时间技术和BC501A液体闪烁探测器的粒子分辨特性,测量了0°方向、20 MeV氘束轰击厚金属铍靶反应产生的中子源能谱,测量的中子能谱范围为0.7~25.0 MeV。在60°方向放置芪晶体闪烁探测器,由刻度好的BC501A液体闪烁探测器归一校正后,用于中子源强度监测。利用Be(d, n) 反应中子源,采用单粒子灵敏度标定方法,实验标定了0.75~15.75 MeV能量范围内的薄膜闪烁探测器中子能量响应曲线,实验结果与蒙特卡罗模拟计算结果在8%的不确定度范围内一致。 相似文献
15.
Mesoscopic density fluctuations in liquid phase sintered silicon carbide have been investigated using small angle neutron
scattering (SANS). The increase in the additives results in the modification in the pore size distribution and to some extent
the total porosity. SANS revealed a mass fractal nature of the agglomerated matrix microstructure. The fractal dimension of
the matrix does not change appreciably with the additives although the upper cut-off value of the fractal decreases significantly
with the increase in the additives. The liquid phase sintering due to the presence of additives helps to achieve higher level
of densification. However, the agglomeration hinders achievement of the fully dense pellets.
相似文献
16.
利用中子飞行时间技术和BC501A液体闪烁探测器的粒子分辨特性,测量了0°方向、20 MeV氘束轰击厚金属铍靶反应产生的中子源能谱,测量的中子能谱范围为0.7~25.0 MeV。在60°方向放置芪晶体闪烁探测器,由刻度好的BC501A液体闪烁探测器归一校正后,用于中子源强度监测。利用Be(d, n) 反应中子源,采用单粒子灵敏度标定方法,实验标定了0.75~15.75 MeV能量范围内的薄膜闪烁探测器中子能量响应曲线,实验结果与蒙特卡罗模拟计算结果在8%的不确定度范围内一致。 相似文献
17.
Polyamide nanocomposite films were prepared from nanometer-sized silica particles having particle radius of gyration (R g) of about 66 Å and trimesoyl chloride-m-phenylene diamine-based polyamides having macromolecular units of about 100–140 Å. The nanoscale morphology of the samples was characterized using small angle neutron scattering (SANS). SANS reveals that silica nanoparticles interact well with the polyamide units only at limited silica loading. 相似文献
18.
19.
A. K. Patra P. U. Sastry Srirupa T. Mukherjee Vinila Bedekar A. K. Tyagi 《Pramana》2008,71(5):1057-1061
Ceria powders were prepared by gel combustion process using cerium nitrate and hitherto unexplored amino acids such as aspartic
acid, arginine and valine as fuels. The powders have been characterized by X-ray and laser diffraction. Cold pressed compacts
of these powders have been sintered at 1250°C for 2 h. Internal pore microstructure of the sintered compacts has been investigated
by small angle neutron scattering (SANS) over a scattering wave vector q range of 0.003–0.17 nm−1. The SANS profiles indicate surface fractal morphology of the pore space with fractal dimensionality lying between 2.70 and
2.76.
相似文献
20.
中国散裂中子源(CSNS)反角白光中子源束线主要由中子束窗、中子开关、中子准直器和真空管道等组成。为了保证CSNS反角白光中子源束线安全、稳定、可靠地运行,研制了基于EPICS(Experimental Physics and Industrial Control System)软件架构的控制系统。该系统主要由中子束窗、中子开关及中子准直器的运动控制系统、真空控制系统和控制室三部分组成,实现了对反角白光中子源束线主要设备的远程监测和控制。测试结果表明,该系统具有稳定可靠性高、人机交互友好的特点,很好地满足了反角白光中子源束线运行的需要。 相似文献