快重离子在聚合物潜径迹中引起的损伤效应研究

在室温和真空环境下利用不同的快重离子(1.158GeV Fe56、1.755GeV Xe136及2.636GeV U238)对多层堆叠的聚对苯二甲酸乙二醇酯(PET)、聚碳酸脂(PC)和聚酰亚胺(PI)进行了辐照,结合X射线衍射(XRD)、傅立叶红外光谱(FTIR)及紫外可见光谱测量技术,在较宽的电子能损(1.9-19.0 keV·nm-1)和注量范围(1×1010-6×1012 cm-2)研究了离子在不同聚合物潜径迹中引起的损伤过程,观测到了主要官能团的降解、炔基生成、非晶化及紫外吸收边缘的红移等现象随辐照注量及电子能损的变化趋势.通过对损伤过程的定量分析,应用径迹饱和模型假设,分别给出了Fe、Xe和U离子在不同电子能损下辐照PC时的平均非晶化径迹半径和炔基形成半径,并用热峰模型对实验结果进行了检验.     

MeV离子辐照聚酰亚胺的化学结构及电性能转变

在室温真空条件下,用北京大学离子注入机提供的3 MeV Si~+对厚度大约25μm的电绝缘聚酰亚胺(PI/Kapton)进行了表面改性,通过紫外可见光谱分析(UV/Visible)、傅立叶转换红外光谱分析(FTIR)及电性能测量,研究了不同离子注量(1×10~(12)—1×10~(15)cm~(-2))下注入层中聚酰亚胺各官能团的化学降解及石墨化结构转变机制。红外结果表明,官能团随离子注入量的增加指数降解,并通过实验点的拟合给出了典型分子键的损伤截面。辐照后聚合物的导电性发生了巨大变化,在我们的实验中,聚酰亚胺的面电阻与未辐照样相比下降了近10个数量级,呈现出半导体的电特性。紫外光谱中吸收边缘从紫外到可见区的红移表明了光能隙的逐渐减小,这是由于芳香团尺寸的增加而引起的。     

高能重离子辐照制备SiOC复合材料的研究

用120 kev碳离子注入非晶SiO2薄膜,再用高能Xe、Pb和U离子辐照.注碳剂量范围为2.0×1017-8.6×1017 cm-2,高能离子辐照剂量1.0×1010-3.8×1012 cm-2.辐照后的样品用傅里叶变换红外光谱仪进行系统分析.实验结果显示,高能离子辐照在注碳非晶SiO2薄膜中形成了大量的Si-O-C键和Si-C键.这些Si-O-C结构具有环链、开链和笼链等多种结构形式.随电子能损、辐照剂量或者沉积能量密度的增加,SiOC结构由类笼向环/开链结构演化.对高能重离子驱动产生SiOC结构的机理进行了简单的讨论.     

高能氩离子辐照聚酰亚胺时的能量沉积效应对光学吸收及电性能的影响

用２２．５ＭｅＶ／ｕ的高能氩离子辐照层聚酰亚胺薄膜，对辐照样品的志电性测量及紫外可见光吸收分析表明，随单位体积中能量沉积的增加，薄膜的导电性增强，光吸收度增大，且光吸收边缘由近ＵＶ区向可见区移动。     

1.23 GeV Fe离子在C60薄膜中形成潜径迹的Raman谱分析

用能量为1.23GeV的快Fe离子辐照了多层堆叠的C60薄膜。用Raman散射技术分析了快Fe离子在C60薄膜中由强电子激发引起的效应，主要包括辐照引起C60分子的聚合及其高温、高压相（HTHP）的形成，和在高电子能损下C60晶体点阵位置上的C60分子向非晶碳的转变。由此演绎出了快Fe离子在C60薄膜中的损伤截面或潜径迹截面σ和潜径迹的半径心，及其随沉积在电子系统中的能量密度的变化而变化的规律。     

高能Ar离子辐照PET膜引起的表面改性研究

采用傅立叶转换的红外光吸收技术在反射方式下分析研究了35MeV/u Ar离子辐照半晶质PET膜引起的表面改性及其对吸收剂量的依赖性。结果表明，辐照导致PET膜中与晶态区域相关的吸收带强度随吸收剂量增加普遍减弱，而与非晶区域相关的吸收带强度随吸收剂量增加逐渐增加，表明辐照使PET膜发生了非晶化转变。化学键断裂主要发生在苯环的对位和酯的C－O键上，而苯环的基本结构在整个辐照过程中变化较小。非晶化效应和化学键断裂同时依赖于离子的照射剂量和样品表面的电子能量沉积。此外，在约5．0MGy以上的吸收剂量，辐照还引起了炔端基团的形成，炔端基团浓度随吸收剂量的增加显著增加。对实验结果进行了定性解释。     

高能铁离子辐照单晶氧化铝产生的色心研究

室温下利用紫外-可见吸收光谱和荧光光谱技术对1.157GeV的56Fe离子注入辐照的单晶三氧化二铝(α-Al2O3)进行了测量分析,研究了辐照产生的阴离子空位的形成和演化规律.测量结果显示,高能Fe离子辐照产生了多种阴离子空位型缺陷,其中包括F、F 、F2 、F22 和F2心.随入射离子剂量的增加,各类缺陷的数量逐渐增大,并在高剂量时趋于饱和,但各类缺陷间的相对数量存在一定的比例,不随剂量的增加而有明显变化.用单离子饱和损伤模型对实验结果进行了拟合,获得各类色心的产生截面在40-90 nm2之间.与TRIM程序计算结果比较后发现,室温下辐照时阴离子单空位的产生速率约是由核能损过程在低温下产生缺陷速率的一半.     

离子在近电子能损阈值能区诱发云母表面小丘形成

利用0.65 MeV的He~+离子轰击白云母膜,并在大气环境下用原子力显微镜(AFM)的轻敲模式分析了辐照后的膜表面。实验结果显示,在不同温度下离子诱导的小丘高度在小于1 nm到几nm之间,且室温条件下能诱发小丘生成的He~+离子电子能损阈值在0.44 keV/nm以下。此外,升高温度至973 K并在其中选取不同温度进行表面辐照来验证观测到的小丘结构。实验发现,相比于室温,小丘直径和高度的统计分布在更高温度下表现出了更大的歧离。分别利用分析热峰模型和双温热峰模型计算了辐照过程中的核能损与电子能损,并选取了用能损在阈值附近的离子辐照所产生的小丘的实验数据与模拟结果相比较,发现实验结果与双温热峰模型吻合较好。     

Xe23+离子辐照Al2O3的光谱特性

本工作研究460 keV、3 MeV和308 MeV Xe23 辐照Al2O3单晶样品的光致发光特性.从经过460 keV Xe23 辐照后样品的光致发光测试结果可看到,波长为380、413和450 nm的发光峰明显增强,在390和564 nm处出现了新的发光峰.从3 MeV的Xe23 辐照后样品谱的变化可看到,在较低剂量条件下,516 nm(2.4 eV)和564 nm(2.2 eV)处的发光峰随辐照剂量增加而增强,且当剂量增到1×1016 cm-2时,564 nm处的发光峰消失,只有516 nm(2.4 eV)处的发光峰较强.从308 MeV Xe23 辐照后样品的光致发光谱中可看到,357 nm(3.47 eV)和516 nm(2.4 eV)处的发光峰随着剂量增加明显增强.辐照后样品的FTIR谱显示:波数在460～510 cm-1和630 cm-1附近的吸收是Al2O3振动模式,经离子辐照后,吸收带展宽;1 000～1 300 cm-1间为Al-O-Al桥氧键的伸缩振动模式,高能辐照后的吸收带向低波数方向移动.     

离子在近电子能损阈值能区诱发云母表面小丘形成

利用0.65 MeV的He⁺离子轰击白云母膜,并在大气环境下用原子力显微镜(AFM)的轻敲模式分析了辐照后的膜表面。实验结果显示,在不同温度下离子诱导的小丘高度在小于1 nm到几nm之间,且室温条件下能诱发小丘生成的He⁺离子电子能损阈值在0.44 keV/nm以下。此外,升高温度至973 K并在其中选取不同温度进行表面辐照来验证观测到的小丘结构。实验发现,相比于室温,小丘直径和高度的统计分布在更高温度下表现出了更大的歧离。分别利用分析热峰模型和双温热峰模型计算了辐照过程中的核能损与电子能损,并选取了用能损在阈值附近的离子辐照所产生的小丘的实验数据与模拟结果相比较,发现实验结果与双温热峰模型吻合较好。     

Atomic energy and energy security

The results of analytical investigations of the dynamics of world energy consumption, which were performed on the basis of a mathematical analysis of series of statistical data on the consumption of primary energy in the world, are presented. The main trends characteristic for the present stage of development of world energy production are determined. It is shown that for any forecasts new energy sources and, first and foremost, atomic energy, will have to be put into active use in the near future. __________ Translated from Atomnaya énergiya, Vol. 101, No. 4, pp. 247–254, October, 2006.     

Measurement of mean excitation energy by energy loss

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Roles of nuclear energy in Japan's future energy systems

The roles of nuclear energy in Japan's future energy systems were analyzed from the viewpoint of securing stable energy supply and reducing carbon dioxide (CO₂) emissions. The MARKAL model, developed in the Energy Technology Systems Analysis Programme (ETSAP) of the IEA, was used for establishing several energy scenarios with different assumptions on the availability of nuclear energy, natural gas, and a CO₂ disposal option. Nuclear energy was assumed to apply for synthetic fuel production as well as for conventional electric power generation. By comparing the CO₂ emission and system costs between these energy scenarios, following results were obtained. Without nuclear energy, the CO₂ emissions will hardly be reduced because of substantial increases in coal utilization. CO₂ disposal will be effective in reducing the emissions, however at much higher costs than the case with nuclear energy. The expansion of natural gas imports, if alone, will not reduce the emissions at enough low levels.     

Requirements for nuclear energy in the 21st century nuclear energy as a sustainable energy source

Nuclear energy must compete against other energy technologies in the 21st century. It must be economical and it must be proven that it fulfills the conditions for sutainability. This means that the requirements of — no short term depletion of resources — extremely low emission of noxious or radioactive substances to the environment — extremely low release of radioactivity from a nuclear plant in case of the most severe accidents and — the present very long term problem of high active waste must be transformed into a few hundred years problem through destruction of plutonium, transmutation of the minor actinides and the most important very long lived fission products.     

能源的需求与核能的未来

石油和天然气可维持人类对能源需要的时间是暂短的,煤储量虽较为丰富,但对环境的污染严重.核能是相对干净的能源,但现有的裂变核能源主要是消耗占天然铀中0.72%的235U,受到铀资源不足的严重制约.聚变能作为能源的利用,还有相当的距离.利用平衡燃料成分反应堆的概念,设计一种可充分利用铀、钍资源,处理高放废物,又可防核扩散的新型快堆的可能途径.介绍了国外类似研究工作的进展和动态.     

Direct energy generation and energy conservation in radiation shielding facilities

In this paper, the experimental and theoretical calculation of direct heat generation from the penetration of 6.20 MeV photons energy through double layer combinations of concrete (Al), steel (Fe) and lead (Pb) shields is described. The results are displayed in curves to show the distribution of heat generation in the shield thickness. The results show good agreement between the measured and calculated values and show also that the heat generation has its maximum value in the first layer of the shield thickness.     

Calculation of proton energy losses in the intermediate energy region

Various binary encounter theories for calculation of proton stopping powers are analysed. It is shown that the influence of the Pauli principle on each electron shell contribution becomes important if the projectile velocity v₁ is of the same order as the considered electron orbital velocity v₂. For projectile velocities much greater and much lower than the electron orbital velocity its influence may be neglected. Furthermore, the effect of electron velocity distribution on the stopping power calculations is considered.     

Thermionic energy transformers

The question of direct transformation of nuclear energy into electricity by thermionic methods is discussed. A comparison is made of the properties of various materials, containing fissionable matter, and at the same time having good thermoemissive properties. Results are given of transformation experiments in the active zone of a reactor. The experiments have shown that in the course of operation, a transformer filled with inert gas is converted into a cesium plasma diode. This eliminates the necessity of introducing cesium vapor into the transformer. In addition, it becomes possible to pump out the gases during operation, which prolongs the useful life and improves the thermionic properties of the transformer.