利用HIRFL高能重离子束的核能材料辐照损伤研究

载能重离子与高能中子在材料中能够产生相似的级联碰撞损伤,加之重离子具有大的离位损伤截面和在材料样品中低的感生放射性,载能重离子束成为模拟先进核能装置内部结构材料辐照损伤的重要手段。HIRFL能区的重离子在结构材料中的射程一般远大于晶粒尺寸,因此能够产生材料体损伤,借助小样品技术可以获得材料力学性能变化（尤其辐照脆化）的有用信息,为探讨材料辐照损伤微结构和宏观力学性能变化的关联提供了重要条件。本文简要介绍了近年来我们基于HIRFL高能离子束开展的聚变堆候选材料辐照损伤的研究,包括低活化钢的辐照脆化行为、氧化物弥散强化（ODS）铁素体钢的结构优化对于抗辐照性能的影响、不同载能粒子辐照条件下铁素体/马氏体钢的辐照肿胀数据的关联,以及高能重离子辐照的钨材料中氢同位素的滞留行为。研究表明,结合特殊的测试技术及数据分析方法,高能重离子可作为核能结构材料辐照损伤研究及评估的有效手段。Because of the similarity in cascade damage structure in materials produced by energetic heavy ions and by fast neutrons, and the high displacement rate and low induced radioactivity of samples by heavy ions, heavy ion beam becomes an important tool to simulate radiation damage by energetic neutrons in materials in advanced nuclear energy systems. The ranges of heavy ions provided by HIRFL (Heavy Ion Research Facility in Lanzhou) are generally much larger than the mean dimensions of grains in alloys candidate to advanced nuclear reactors, and is capable of producing radiation damage in bulk scale. It therefore makes possible the evaluation of change of mechanical properties including the radiation induced embrittlement from the irradiated specimens by using miniaturized specimen techniques. In the present paper, we provide an introduction of our recent studies of radiation damage of materials candidate to future fusion reactors by utilizing heavy ion beams in HIRFL.The studies include issues as follows:ductility loss of RAFM steels causes by high-energy Ne ions, impact of oxide dispersoids on the radiation resistance of ODS ferritic steels, correlation of void swelling of ferritic/martensitic steels under different particle irradiation, and behavior of deuterium retention in tungsten under irradiation with high-energy heavy ions. The results show that high-energy heavy ions can be used as a tool to efficiently investigate or evaluate radiation damage in structure materials if combined with some special test techniques and data analysis.     

同步辐射显微技术在高分子材料结构研究中的应用

高分子材料以其优异的性能广泛应用于人类生活的每个角落,但其发展受限于研究手段.基于同步辐射先进光源的研究方法(如散射、吸收和成像等)具有高的空间、时间和能量分辨的优势,是揭示高分子材料多尺度结构形成和演化动力学最有效的工具之一.文章结合作者和国内外同行的工作,以具体案例的形式介绍了同步辐射技术在高分子材料结构研究中的应用.希望能起到抛砖引玉的作用,吸引更多的从事高分子材料结构研究的同行利用同步辐射开展科学研究,同时希望更多的进行物理学研究的同行来帮助回答高分子物理的一些基本科学问题.     

正电子发射成像回旋加速器屏蔽材料防护性能

计算了11 MeV 正电子发射成像回旋加速器18O(p, n)18F反应的双微分截面数据,并采用蒙特卡罗模拟计算方法,分析了单一材料及复合结构对特定辐射源的防护性能。采用单一材料,质量分数为73.8%的重混凝土的防护效果最佳,经过90 cm厚屏蔽层的衰减,距离辐射源正前方1 m处的总剂量降低约5个量级;复合结构采用多层结构,材料选用铁及硼酸溶液,同样厚度即可达到与重混凝土相同的防护效果,密度可降低至少20%。     

环状烯烃聚合物基底材料的太赫兹复介电常数和损耗特性研究

太赫兹时域光谱(THz-TDS)已被用于研究包括液体,半导体,爆炸物和气体等多种材料。然而自由空间太赫兹光谱系统存在着一些检测局限性,如微量物质难以被检测、系统尺寸难以实现微型化、空气中水的强烈吸收引起的信号衰减较大等问题。为了解决这些问题,研究人员设计了基于金属波导传输线结构的太赫兹芯片集成器件,通过飞秒红外激光激励传输线上的光电导材料实现太赫兹波的产生和检测。然而,在这些芯片上传输的太赫兹信号的频谱宽度很难达到自由空间太赫兹时域光谱系统的频带宽度,一个重要原因是由于传输信号受到随频率增加的传输线损耗所导致的衰减。通常这些损耗主要由三个部分组成：导体损耗,介电损耗和辐射损耗。研究表明：使用低介电常数材料作为共面传输线的衬底,将减少这种介电常数的失配,从而避免冲击波辐射损失;使用具有低损耗角正切的基底材料可以减少太赫兹传输线的损耗。环烯烃聚合物(COP)是一种具有环状烯烃结构的非晶性透明共聚物的材料,在太赫兹波段具有很高的透射率,为了探究这种材料是否能用于共面传输线的衬底,需要通过太赫兹时域光谱技术和介电函数理论分析它在太赫兹频段的光谱和介电特性,以及对这种材料作为基底时用在太赫兹传输线的传输特性进行仿真计算分析。使用透射式太赫兹时域光谱系统,对三种COP、熔融石英和PMMA进行了光谱测试,提取了它们的透射时域信号,采用Dorney和Duvillaret等提出的物理模型计算复介电函数。实验表明：与其他两种材料相比,COP材料在1 THz处的透过率更高,可以达到94.5%,同时介电损耗和介电常数更低,其中介电损耗在1 THz处达到4.31×10-4,因此将COP作为传输线基底材料时能有效减少基底的介电损耗。同时COP材料的介电常数在0.2～2.8 THz范围内维持在约2.3的水平,也有效减弱了辐射损耗。对实验材料基底组成的共面波导传输线进行了HFSS模拟,获得了它们的正向传输衰减系数(S₂₁ parameter),并对由基底引起的介电损耗和辐射损耗进行了计算分析。模拟和计算结果也表明在同一传输线结构下,与其他材料相比COP作为基底时的损耗更小。通过太赫兹时域光谱法与介电响应分析,表明了在太赫兹波段具有较低介电常数的COP材料更适合作为太赫兹传输线结构的基底材料,它可以有效的降低因基底引起的介电损耗和辐射损耗。这为太赫兹传输线的设计过程中衬底材料的选择与应用提供了实验和理论依据。     

Photoelectron spectroscopy in the energy region 30 to 800 eV using synchrotron radiation

With the advent of synchrotron radiation, the photoemission techniques were extended to a continuous range of excitation energies in the far ultraviolet and soft x-ray regions, adding tremendously to the usefulness of photoemission as a probe of the electronic structure of materials. In this paper, we discuss the application of photoelectron spectroscopy using synchrotron radiation to the studies of oxygen chemisorption/oxidation of Si surfaces, metal overlayers on III-V semiconductor surfaces, chemisorption on transition metal surfaces, and the surface electronic structure of CuNi alloys.     

Scattering contrast of X-ray radiation

It is experimentally established that, in the majority of cases, the X-ray radiation scattered on different constituent parts of a weakly absorbing object provides sufficient information on inner structure, different types of structural inhomogeneities, and morphological characteristics, such as shapes, sizes, and location of invisible defects of the object. In this study, a new method for investigation of the inner structure of noncrystalline materials is developed. The method is based on recording of the scattered X-ray radiation. It is demonstrated that the image contrast, formed by the X-ray radiation scattered on weakly absorbing objects, can be considerably higher than the absorption contrast.     

Monitoring of the process of formation of epitaxial films with the use of ultrasoft x-ray spectroscopy

The distinctive features of the atomic and electronic structure of thin surface layers of substances in the process of formation of epitaxial silicon films on silicon are studied using the procedures of reflection and scattering of ultrasoft x-ray radiation. The angular distribution of the scattered x-ray radiation (the scattering indicatrices) and the near fine structure of SiL_2,3 spectra of reflection are investigated. The assumption of the sensitivity of the observed peak of anomalous scattering (the Yoneda peak) of x-ray radiation to the presence, in the surface regions of the materials, of extended double-boundary defects, the defects of packing, grain boundaries, dislocations, etc. is made. It is shown that the experimental procedure used makes it possible to obtain information on the surface layers of substances. Translated from Zhurnal Priklaldnoi Spektroskopii, Vol. 67, No. 4, pp. 496–498, July–August, 2000.     

Enhancement of efficiency of storage and processing of food raw materials using radiation technologies

The work is dedicated to improvement of efficiency of storage and processing of food raw materials using radiation technologies. International practice of radiation processing of food raw materials is presented and an increase in the consumption of irradiated food products is shown. The prospects of using radiation technologies for the processing of food products in Russia are discussed. The results of studies of radiation effects on various food products and packaging film by γ radiation and accelerated electrons are presented.     

面向空间高能重离子与辐射屏蔽材料的反应截面地基研究

空间辐射尤其是高能重离子辐射可造成生物机体的严重损伤, 所以对高能重离子进行恰当的辐射屏蔽, 成为实现载人航天的关键性因素之一。 研究表明, 由于高能重离子与不同屏蔽材料发生相互作用, 所产生的核碎片等次级粒子, 直接影响空间辐射屏蔽材料的屏蔽性能研究和屏蔽结构设计。 介绍了太空辐射的分类与组成, 综述了国际地基辐射屏蔽材料与实验现状。 根据文献中的地基实验数据, 重点描述了被动式屏蔽方法: 以相近能量多种重离子, 不同能量的56Fe和28Si重离子分别与C, H, Al和Cu材料相互作用的总反应截面和碎片产生截面, 并结合510 MeV/u 56Fe与不同厚度CH2相互作用产生的碎片通量分布、 碎片平均LET分布和不同厚度CH2的单位入射离子剂量减少量等方面, 系统讨论分析了C, H, Al, Cu和CH2等常用空间辐射屏蔽材料的屏蔽性能。 Cosmic radiation, particularly the high energy heavy ion radiation, may cause serious injury on living organism. Therefore, it is one of critical restriction factor in Manned Spaceflight. Studies show that high energy heavy ions interacting with the shielding materials can produce numerous kinds of fragments and secondaries. These particles have a direct impact on evaluation of shielding properties of different shielding materials, the optimal shielding structure design and low dose evaluation after shielding materials. From perspectives of divisions of cosmic rays and passive shielding methods, this paper introduces the ground based research of shielding materials. The passive shielding method was discussed, based on the experimental data of the total cross sections and fragment（production） cross sections of the aspects of different heavy ions with approximately same energy and 56Fe, 28Si heavy ions with different energies on H, C, CH2, Al and Cu radiation shielding materials. In addition, the fragment fluency distribution, the average LET distribution and the dose reduction per particle of 510 MeV/u 56Fe in different depth of CH2 material were also discussed.     

Analysis of low-dose radiation shield effectiveness of multi-gate polymeric sheets

Computed tomography (CT) uses a high dose of radiation to create images of the body. As patients are exposed to radiation during a CT scan, the use of shielding materials becomes essential in CT scanning. This study was focused on the radiation shielding materials used for patients during a CT scan. In this study, sheets were manufactured to shield the eyes and the thyroid, the most sensitive parts of the body, against radiation exposure during a CT scan. These sheets are manufactured using silicone polymers, barium sulfate (BaSO₄) and tungsten, with the aim of making these sheets equally or more effective in radiation shielding and more cost-effective than lead sheets. The use of barium sulfate drew more attention than tungsten due to its higher cost-effectiveness. The barium sulfate sheets were coated to form a multigate structure by applying the maximum charge rate during the agitator and subsequent mixing processes and creating multilayered structures on the surface. To measure radiation shielding effectiveness, the radiation dose was measured around both eyes and the thyroid gland using sheets in three different thicknesses (1, 2 and 3 mm). Among the 1 and 2 mm sheets, the Pb sheets exhibited greater effectiveness in radiation shielding around both eyes, but the W sheets were more effective in radiation shielding around the thyroid gland. In the 3 mm sheets, the Pb sheet also attenuated a higher amount of radiation around both eyes while the W sheet was more effective around the thyroid gland. In conclusion, the sheets made from barium sulfate and tungsten proved highly effective in shielding against low-dose radiation in CT scans without causing ill-health effects, unlike lead.     

纳米光学辐射传热:从热辐射增强理论到辐射制冷应用

热辐射作为一种无处不在的物理现象,对于科学研究和工程应用都具有重要意义.传统上对热辐射的理解主要是基于普朗克定律,它描述了物体通过辐射交换能量的能力.而近年来的研究表明,由于微纳光学材料在尺寸上远小于热辐射峰值波长,它们的热辐射性质往往很大程度上有别于传统黑体辐射理论所描述的宏观物体.更重要的是,微纳光学材料的热辐射性质可以通过改变它们的几何尺寸和微观构型进行定量的优化设计与精确调控.纳米光学材料与辐射制冷效应的结合,给热辐射效应在能源和环境等相关领域的应用提供了极具前景的应用价值.本文首先从热辐射的基本原理和规律出发,介绍纳米结构热辐射增强的发展进程和最新进展,包括二维材料间的近场热辐射机理以及尺寸效应导致的远场热辐射增强;其次,介绍了近年来纳米光学材料在辐射制冷应用中的重大进展,包括可以实现高效日间辐射制冷的各种纳米光学材料设计;最后,进一步介绍了日间辐射制冷的各种实际应用,包括建筑物制冷、冷凝水收集、舒适衣物与太阳能电池降温等.此外,展望了纳米光学材料的辐射制冷技术在推动荒漠生态环境的治理与改造方面的广阔未来.     

On the acoustic radiation efficiency of local resonance based stop band materials

The application of materials with stop bands is emerging as a novel way of creating meta-materials with good vibrational behaviour. The acoustic radiation efficiency in these stop band zones is often not investigated. This paper formulates an uncoupled vibro-acoustic unit cell model of a plate with local resonant stop band behaviour, based on the addition of a grid of tuned resonators. The results are compared with a vibro-acoustic coupled model for a finite equivalent of the infinite structure. It is shown that the beneficial vibration reduction that is achieved in a stop band can be acoustically reduced or enhanced by the change in radiation efficiency of the structure. When care is taken in the design of the stop band, a stop band material with good vibro-acoustic behaviour can be achieved.     

The use of carbonaceous materials as field-emission cathodes

The advantages and disadvantages of carbon fibers and graphite plates with a developed surface as field-emission cathode materials are discussed. Experimental data for the chemical composition of the materials and the effect of thermal annealing on their structure and emission properties are presented. A correlation between the work function and the amount of cesium implant is studied. The feasibility of preparing planar cold cathodes with a developed surface by means of radiation technologies is considered, and the evolution of the emitting surface during bombardment by low-energy residual gas ions is traced. Cold cathode designs for various applications are recommended.     

Glow and bulk expansion of oxidized graphites stimulated by electromagnetic radiation

The results of studies on the interaction of oxidized graphites and electroconductive materials with the electromagnetic radiation of a microwave oven are presented. The effects of glow and expansion of oxidized graphites stimulated by microwave radiation in air and an inert atmosphere are studied. Differences in the character of expansion of oxidized graphites and conductive materials on a dielectric and metal substrate under the influence of electromagnetic radiation are examined.     

Solar radiation concentrators paired with multijunction photoelectric converters in ground-based solar power plants (Part II)

The present work is devoted to determining the conditions of the joint operation of photoelectric converter–solar concentrator pairs, which are used in solar power plants with concentrators. Three-cascade photoconverters based on A³B⁵ materials with different distributions of solar radiation in spectral ranges are studied. Concentrators of solar radiation are designed as the Fresnel lenses with silicon-on-glass structure. Refractive lens profile fabricated on the basis of Wacker RT604 silicone rubber is characterized by significant changes in refractive index with temperature. The effect of geometric parameters of the Fresnel lenses and their operating temperature on characteristics of solar radiation concentration in specified spectral intervals have been examined. The parameters of concentrators being paired with a photoelectric converter, which may ensure the efficient functioning of the solar power plant, have been calculated.     

Strandlike microstructures in the charge-density wave states of orthorhombic TaS3

Strandlike domains are observed in the commensurate charge-density wave states of orthorhombic TaS₃ using dark field electron microscopy. The images of the strandlike domains are found to be time-dependent and sensitive to the radiation damage induced by the incident high energy electrons. Our observation suggests that the appearance of the strandlike structure may be common to this class of materials regardless of the commensurability of the charge-density waves.     

Numerical investigations of a multi-walled carbon nanotube-based multi-segmented optical antenna

Motivated by the fabrication potential of multi-walled carbon nanotube structures, we numerically investigated a paired structure consisting of two metallic spheres each grown on one end of a multi-walled nanotube. The paired two-segmented structure is capable to convert free-space radiation into an intense near-field, and, hence, acting as an optical antenna. Vice versa the presence of the two nanotubes enable a current source at the antenna feed to more efficiently energy into the radiation modes, resulting e.g. in correspondingly altered luminescence lifetimes when an excited single molecule is placed in the feed point. Furthermore, the structure represents a mean to localize light on a sub-wavelength scale within different materials, which is interesting in the context of a fabrication technology for integrated nanophotonic components with different material combinations. The optical properties of the nano-antenna are analyzed by means of numerical simulations using the finite element method. Our investigations have revealed that the field enhancement, the resonances, and the radiation patterns can be easily tuned since all these quantities strongly depend on the size of the nanotubes and the metallic spheres, as well as on their material properties The structure we propose here carries a great potential for bio-sensing, for tip-enhanced spectroscopy applications, and for interfacing integrated photonic nano circuits.     

纳米硫化锌球壳的高压相变研究

 采用同步辐射能量色散X射线衍射（EDEX）技术和金刚石对顶砧高压装置,对纳米硫化锌球壳进行了原位高压X射线衍射实验。最高压力达33.3 GPa。常压下纳米硫化锌球壳为纤锌矿结构和闪锌矿结构共存的混相结构。压力达到11.2 GPa时,纳米硫化锌空心球中的纤锌矿结构全部转变为闪锌矿结构。压力达到16.0 GPa时,发生了由闪锌矿结构向岩盐矿结构的相变,在17.5 GPa和21.0 GPa时分别出现未知峰,33.3 GPa时基本完全转变为岩盐矿结构。两个相变均为可逆相变。     

Statistical second-order two-scale analysis and computation for heat conduction problem with radiation boundary condition in porous materials

This paper discusses a statistical second-order two-scale(SSOTS) analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configuration for the structure with random distribution is briefly characterized.Secondly,the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell.Then,the statistical prediction algorithm based on the proposed two-scale model is described in detail.Finally,some numerical experiments are proposed,which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of porous materials and demonstrating its significant applications in actual engineering computation.