中国先进研究堆中子散射科学平台介绍

中子散射技术作为人类认知世界不可或缺的独特手段,多年来在诸多领域得到了广泛应用并成绩显著。文章以新建成的中国先进研究堆中子散射科学平台谱仪为例,较为详细地介绍了中子散射技术和谱仪的基本原理和特点,并对其未来的应用进行了展望。     

中子散射:理解工程材料的必要工具

在工程材料领域,建立材料内部微结构与宏观性能之间的关系是极具挑战的课题。中子是目前唯一真正意义上的体探针,它能无损地获取材料内部微结构与三维内应力分布。中子衍射应力分析与小角散射技术在工程领域极具应用价值,文章简述了这两种技术的现状、应用与发展趋势。未来将全面建成的中子散射科学装置必将为中国多学科领域用户提供创新平台,并为国家的重要工程领域持续发挥基础作用。     

NeuDATool：支持GPU硬件加速和计算机集群跨节点并行的开源中子散射数据分析软件

实验势精修是20世纪80年代英国散裂中子源无定型材料组开发的用于分析中子散射实验数据的软件. 实验势精修的目标是根据中子散射数据重建样品的三维原子结构. 在过去的几十年，实验势精修被广泛用于中子散射实验数据分析，为实验用户提供了可靠的分析结果. 但是实验势精修是基于共享内存并行计算(OpenMP)的Fortran程序，不支持计算机服务器集群跨节点并行加速和GPU加速；这限制了它的分析速度. 随着计算机服务器集群的广泛建设和GPU加速技术的普遍使用，有必要重新编写EPSR程序以提高运算速度. 本文使用面向对象的C++语言，开发了一套实现EPSR算法的开源软件包NeuDATool；软件通过MPI和CUDA C实现了计算机集群跨节点并行和GPU加速. 使用液态水和玻璃态二氧化硅的中子散射实验数据对软件进行了测试. 测试显示软件可以正确重建出样品的三维原子结构；并且模拟体系达到10万原子以上时，使用GPU加速可以比串行的CPU算法提高400倍以上的模拟速度. NeuDATool为中子实验用户尤其是对熟悉C++编程并希望定义特殊分析算法的实验科学家提供了一种新的选择.     

中子半影成像的散射中子对点扩展函数的影响

基于ICF中子半影成像分辨力的要求,利用蒙特卡罗方法,模拟了4种系统模型的点扩展函数,分析半影孔装置、靶室和中子束流通道的钢管、高密度内爆靶丸的散射中子对点扩展函数的影响;模拟了平面中子源在4种模型中的半影成像,并用维纳滤波方法重建,分析了散射中子对中子半影成像诊断的影响。模拟结果表明:半影孔装置、靶室等的散射中子不会造成点扩展函数的变形,仅仅增加本底,对诊断的影响可以忽略;高密度内爆靶丸的散射中子会造成点扩展函数的平滑,但对诊断的影响有限。     

中子散射技术及其应用

热中子的波长和凝聚态物质的原子／分子间距具有相同的量级，而其能量又和原子／分子的热运动能量相近．因此，利用热中子的弹性和非弹性散射效应，可以从微观层次上获取物质的结构和动力学知识。目前，中子散射技术在物理、化学、化工、生物和材料科学等研究领域的应用已经获得了许多用其他方法无法得到的知识，文章介绍了中子散射的基本原理和特点，并列举了中子散射技术在相关研究领域中的典型应用     

中子活化分析法测定病人体内磷元素

应用中子活化分析方法测定了 2 1位肿瘤病人体内磷元素含量 ,为中子辐照技术在医学诊断方面提供有益参考。     

应用于13T中子散射超导磁体的低温系统设计

作为样品环境极端条件之一,中子散射超导磁体系统产生的强磁场为凝聚态量子材料等磁性前沿研究提供了理想的工具平台。对国内自主研制的第一台中子散射磁体关键部件——低温容器结构及制冷方式进行了介绍,对该方案的结构系统传热进行Ansys仿真模拟与分析,验证了结构的合理性;在传热模拟的基础上,对各部件进行了热负荷计算,完成了制冷机的选型。     

中国散裂中子源小角散射谱仪

正作为中国散裂中子源(CSNS)首批建设的三套谱仪之一,小角散射谱仪用于探测物质体系在1~100 nm尺度内的微观和介观结构。它的实验应用范围将涵盖化学、物理、生物、材料、地质等广泛学科,服务于国家能源、环境、生物和新材料等诸多高科技研发领域。中国散裂中子源小角散射谱仪建成后,能为图1所示例的诸多科学探索与技术研发工作,提供必需的实验方法及其技术手段。一、中子散射技术的缘起与现状     

241Am-Be中子参考辐射的蒙特卡罗模拟研究

研究用于校准场所中子剂量监测仪表的241Am-Be中子参考辐射场计量特性。采用蒙特卡罗方法模拟了空气自由中子参考辐射(FRNR),GB/T 14055规定的最小尺寸中子参考辐射(SRNR)和实际中子参考辐射(ARNR)中不同检验点处中子周围剂量当量率、散射中子占比和能谱分布特征。研究结果表明,空气对FRNR中的剂量率和能谱分布影响小,近似为理想中子参考辐射;采用5%含硼聚乙烯作屏蔽的最小尺寸SRNR可减少热中子,降低散射中子占比,影锥法不适用于小尺寸中子参考辐射中对散射中子的修正;ARNR中的散射中子更少、占比更低,影锥法所得散射中子占比与理论值基本一致。     

极化中子照相磁场量化技术方案比较与分析

极化中子照相技术通过分析极化中子束的自旋相移对样品磁场进行成像,目前已发展出多种成像技术方案,其中能量选择法和自旋回波法极化中子成像技术从不同的原理出发,解决了极化中子照相中磁场量化的周期解问题,同时避免装置极化效率等参数的影响,可以实现较高的量化精度.本文对两种极化中子照相技术方案进行研究,通过对单色器能量分辨率和装置极化效率等关键参数的分析和模拟,确定在研究堆上开展相关实验的可行性,并初步明确其量化能力和适用范围.相关结果可为极化中子照相的实验数据处理技术研究及装置设计提供参考.     

Neutron-based characterization techniques for lithium-ion battery research

During the past decades, Li-ion batteries have been one of the most important energy storage devices. Large-scale energy storage requires Li-ion batteries which possess high energy density, low cost, and high safety. Other than advanced battery materials, in-depth understanding of the intrinsic mechanism correlated with cell reaction is also essential for the development of high-performance Li-ion battery. Advanced characterization techniques, especially neutron-based techniques,have greatly promoted Li-ion battery researches. In this review, the characteristics or capabilities of various neutron-based characterization techniques, including elastic neutron scattering, quasi-elastic neutron scattering, neutron imaging, and inelastic neutron scattering, for the related Li-ion-battery researches are summarized. The design of in-situ/operando environment is also discussed. The comprehensive survey on neutron-based characterizations for mechanism understanding will provide guidance for the further study of high-performance Li-ion batteries.     

Basic to industrial research on neutron platform in Japan

The co-location of reactor- and accelerator-based neutron sources offers a great opportunity for complementary use of steady and pulsed neutron beams in a wide variety of neutron science and technology areas ranging from basic research to industrial applications. In Japan, such a balance of two kinds of neutron sources has a long tradition and now we are entering into a new era with the commissioning of the world’s most intense pulsed neutron beams at JSNS/J-PARC plus the existing JRR-3 reactor both co-located within 1 km of each other in Tokai. The joint operation of these neutron facilities in close proximity under a program called ‘neutron platform’, will allow neutron beam access not only to professional users, familiar with both pulsed and steady state techniques but also to first-time academics and industrial researchers to neutron scattering.      

Editorial: Winds of Change

When compared to developments occurring at synchrotron radiation facilities, the neutron scattering world often gives the impression of moving in slow motion. This was perhaps true a decade ago, but is certainly not the case anymore. Such positive dynamics could be clearly felt during the recent American Conference on Neutron Scattering (see page 4) where approximately 500 scientists from all over the world gathered in the Washington, D.C. area. Aside from a very exciting science program, the future of neutron scattering worldwide was discussed as well. While third generation sources are being built in the United States and Japan, major upgrades are being made at almost all running facilities.     

极紫外、X射线和中子薄膜光学元件与系统

极紫外、X射线和中子光学为现代科学的发展提供了高精度的观测手段,但这些手段的实现需要大量高性能薄膜光学元件和系统的支撑。由于短波长和材料光学常数的限制,短波光学元件的结构、性能和制作技术明显区别于长波光学元件。近二十年来,同济大学精密光学工程技术研究所建立了以短波反射镜为基底的精密加工检测平台,发展了超薄薄膜界面生长调控方法和大尺寸薄膜镀制技术,提出了高效率/高分辨率多层膜微纳结构的衍射理论和制备方法,初步阐明了短波辐照损伤的物理机制,形成了短波薄膜和晶体聚焦成像系统的高精度全流程研制技术,并将该技术成功应用于国内和国际短波光子大科学装置中。本文简要介绍本课题组在上述短波元件和系统领域中的研究进展。     

Nanometric confinement: Toward new physical properties and technological developments

In numerous real life situations, molecular systems are not found in bulk but instead trapped in limited volumes of nanometric size: this is nanometric confinement. The complex interplay of the confinement topology, dimensionality (3D to 1D) and surface/volume ratio significantly affects the physical properties of the confined material. After decades of intense fundamental research, we are now entering a time when the unusual properties of fluids under confinement may be tuned to target specific technological objectives. In this paper, we highlight few situations, all related to the fields of energy production or storage, where diverse neutron scattering techniques (imaging, small angle scattering, diffraction, inelastic and quasi-elastic scattering) may help to bridge basic science and applied research.     

Advanced imaging techniques: A new deal for neutron physics

Among non-destructive evaluations and methodologies—the important set of analyses which preserve the integrity of the tested object—neutron imaging techniques, and neutron computerized tomography in particular, represent powerful tools. Although they have been considered more an amusement for scientists rather than an effective tool for engineers until few years ago, it can be stated that they can now provide valuable quantitative results in many circumstances of interest, being the only available choice in some specific cases. This wider interest and the attempt to give neutron imaging a certain prominence reflect themselves in the birth of an international group of people involved in the field of neutron research; the so-called ENRWG (European Neutron Radiography Working Group). Connected to a general interest and a diffuse curiosity in the fascinating interactive world of INTERNET there is also the possibility, since last year, to get information about neutron radiography state of the art and current projects from a free-access WWW site. As a consequence of these fervent activities, a new deal in studies of advanced materials, sources, detectors and algorithms is now growing to promote and to develop the capabilities of neutron imaging techniques after a long period during which the interest in neutron physics and in their applications was limited to selected specialists involved in the nuclear-energy production. The results of this effort will not be limited to improved technological processes, but will include an improved knowledge in relevant fields of nuclear and material science.     

Radiometry with synchrotron radiation at the PTB laboratory at Bessy ii

A workshop on Engineering Applications of Neutrons and Synchrotron Radiation took place on September 13–14, 2004, at the ESRF in Grenoble, France. The workshop brought together around 100 leading scientists and engineers who discussed the application of synchrotron X-ray and neutron central facilities for engineering problems. The event was organized by the FaME38 materials engineering facility at ILL-ESRF. FaME38 is jointly funded by the UK research council EPSRC and ILL-ESRF and provides support to enable materials engineers to make the best use of the advanced synchrotron X-ray and neutron scientific facilities at ILL-ESRF.

The programme included formal presentations, a poster session, informal workgroup sessions and an opportunity to meet staff at the ILL-ESRF materials science beamlines. The formal presentations were structured into three sessions entitled Progress, Complementarity, and Applications chaired by Giovanni Bruno (ILL), Thomas Buslaps (ESRF), and Darren Hughes (FaME38).     

Percy W. Bridgman's second century

Percy Williams Bridgman's impact on science began in 1909 with his first three experimental papers. These publications on high pressure calibration, techniques, and compressibility, together with the many articles that followed, established his influence on the course of modern high pressure research. Grounded in classical thermodynamics and practical mechanics, his developments showed how the variable of pressure leads to myriad transformations in materials. Studies carried out under a broader range of conditions now provide unprecedented insights into chemical and physical properties at multimegabar pressures and temperatures from millikelvins to thousands of degrees, where novel electronic, magnetic, and superconducting phases are now being discovered. With careful attention to experimental techniques and material performance, Bridgman extended the available pressure range that could be achieved in the laboratory with the development of new devices. We are now witness to continued refinement of static and dynamic compression methods and in situ measurement techniques, including the marriage of high pressure methods with large facilities such as synchrotron, neutron, and laser sources. Bridgman showed the broad range of implications of this work; the modern field of high pressure research now spans physics and chemistry, geosciences and planetary science, materials science and technology, and biology. Selected examples illustrate Bridgman's impact and legacy in this, his second century. For dense hydrogen, new insights have been obtained from high P–T measurements as well as studies of alloys and compounds of hydrogen, leading to the creation of new metallic and superconducting phases. Studies of other hydrogen-rich systems provide both tests of fundamental theory and potentially useful materials for hydrogen storage. High pressure studies of oxides have led to new ferroelectric and multiferroic materials and phases with remarkable properties that guide the design and fabrication of new devices. With the discovery of super-Earths outside our solar system, the high pressure properties of silicates, oxides, volatiles, and the full complement of planetary materials are now problems of cosmic importance well beyond the conditions found on and within the Earth. Developments in high pressure biology are addressing the question of the depth of the biosphere, the processes and reservoirs of carbon in our planet, and new insights into the origins of life as we know it, as well as the possibility of extraterrestrial life. Improved materials that can withstand high P–T conditions and other extreme environments include new forms of diamond, which are advancing experimental methods and finding numerous applications in advanced technology. These developments dovetail with synergetic advances in a broad spectrum of radiation techniques including coherent X-ray, intense neutron, and ultrabright laser sources.     

Recent neutron scattering research and development in India

A national facility for neutron beam research is operated at the research reactor Dhruva at Trombay in India. The research activities involve various nanoscale structural, dynamical and magnetic investigations on materials of scientific interest and technological importance. Thermal neutron has certain special properties that enable, e.g., selective viewing of parts of an organic molecule, hydrogen or water in materials, investigations on minerals and ceramics, and microscopic and mesoscopic characterization of bulk samples. The national facility comprises of eight neutron-scattering spectrometers in the reactor hall, and another four spectrometers in the neutron-guide laboratory. In addition, a neutron radiography facility and a detector development laboratory are located at APSARA reactor. All the instruments including the detectors and electronics have been developed within BARC. A new powder diffractometer (PD-3) is being developed by UGC-DAE-CSR. The national facility is utilized in collaboration with various universities and other institutions.     

VITESS polarized neutron suite: allows for the simulation of performance of any existing polarized neutron scattering instrument

As neutron simulations packages are used for analysis of the expected performance for practically all newly built neutron instruments, possibilities for simulations with polarized neutrons have been relatively underdeveloped.During the last years we developed a new approach for the representation of time-dependent magnetic fields (both in magnitude and direction) for the VITESS simulation package. This allowed us to simulate the neutron spin dynamics in practically all polarized neutron devices (RF neutron flipper, adiabatic gradient RF flipper, the Drabkin resonator, etc.). In this article the above-mentioned VITESS instrument components (modules) will be presented and the simulated performance of a number of polarized neutron scattering instruments (NRSE, MIEZE, SESANS, etc.) will be demonstrated.Thus, we practically complete the polarized neutron suite of the VITESS, which seems sufficient for the simulation of performance of any existing polarized neutron scattering instrument. Future work will be concentrated on developments of dedicated sample modules (kernels) to allow for virtual experiments with VITESS.