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.     

重离子和γ辐照硼硅酸盐玻璃的辐照效应对比

为研究玻璃固化体在不同辐照方式下的宏观和微观结果及其对应关系,使用重离子和γ辐照硼硅酸盐玻璃,分别测量了辐照后硼硅酸盐玻璃的硬度和模量变化。发现在γ辐照条件下,直到吸收剂量达到6×10~6 Gy,硼硅酸盐玻璃的宏观性质(硬度和模量)均未发生明显改变。在Xe离子辐照条件下,当辐照剂量达到0.1 dpa时,硬度和模量减少达饱和值。此外,测量了γ辐照后的硼硅酸盐玻璃的吸收光谱,得到了辐照后硼硅酸盐玻璃带隙随吸收剂量的变化规律,讨论了辐照产生的微观缺陷来源和产生机理。发现重离子辐照产生的硬度和模量的下降主要来源于玻璃网络结构的断裂,而重离子的核能量沉积是造成网络体结构断裂的主要原因。结合γ辐照样品的吸收光谱结果,通过对比γ射线和重离子辐照后的样品硬度和模量变化不同趋势可发现:γ辐照会在硼硅酸盐玻璃中产生微观缺陷(非桥氧空位色心等),这些缺陷主要来源于网络体末端与钠相连的键的断裂。而网络体末端的断裂不影响硼硅酸盐玻璃的网络体结构,所以γ辐照产生的缺陷不会引起硼硅酸盐玻璃的硬度和模量变化。     

γ射线辐照对MgO单晶的点缺陷组态及磁性的影响

对(100)取向的MgO单晶进行了不同剂量的60Coγ射线辐照,辐照剂量从30 kGy到1 750 kGy。利用同步辐射漫散射技术以及紫外-可见吸收光谱研究了辐照样品的点缺陷情况,并将实验测量的漫散射结果与理论计算结果进行比对,以获得点缺陷组态的信息。利用超导量子干涉仪(Superconducting Quantum Interference Device,SQUID)测量了样品在不同温度下的磁性质。漫散射和吸收光谱的实验结果表明,经γ射线辐照的MgO单晶产生了阴离子弗伦克尔缺陷,并在室温下没有表现出铁磁性,只是在低温下观察到了顺磁信号,且辐照前后样品在零场冷却和加场冷却下的M-T曲线没有变化,说明阴离子空位没有导致MgO的d0铁磁性。     

重离子和γ辐照硼硅酸盐玻璃的辐照效应对比

为研究玻璃固化体在不同辐照方式下的宏观和微观结果及其对应关系，使用重离子和γ辐照硼硅酸盐玻璃，分别测量了辐照后硼硅酸盐玻璃的硬度和模量变化。发现在γ辐照条件下，直到吸收剂量达到6×10⁶ Gy，硼硅酸盐玻璃的宏观性质（硬度和模量）均未发生明显改变。在Xe离子辐照条件下，当辐照剂量达到0.1 dpa时，硬度和模量减少达饱和值。此外，测量了γ辐照后的硼硅酸盐玻璃的吸收光谱，得到了辐照后硼硅酸盐玻璃带隙随吸收剂量的变化规律，讨论了辐照产生的微观缺陷来源和产生机理。发现重离子辐照产生的硬度和模量的下降主要来源于玻璃网络结构的断裂，而重离子的核能量沉积是造成网络体结构断裂的主要原因。结合γ辐照样品的吸收光谱结果，通过对比γ射线和重离子辐照后的样品硬度和模量变化不同趋势可发现：γ辐照会在硼硅酸盐玻璃中产生微观缺陷（非桥氧空位色心等），这些缺陷主要来源于网络体末端与钠相连的键的断裂。而网络体末端的断裂不影响硼硅酸盐玻璃的网络体结构，所以γ辐照产生的缺陷不会引起硼硅酸盐玻璃的硬度和模量变化。     

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.     

3MeV硅离子辐照聚苯乙烯引起的化学改性

在室温下用 3MeV硅离子对聚苯乙烯薄膜进行了辐照注入 ,并对辐照后的样品进行了傅立叶转换红外反射光谱和紫外 /可见透射光谱的测量。测量结果显示 ,材料经 3× 10 13 ions/cm2 以上剂量辐照后 (即吸收剂量在约 4 5MGy以上时 )迅速降解 ,包括苯环在内的大部分特征官能团遭到破坏 ;与此同时 ,材料的光能隙随着剂量的增大逐渐减小 ,在辐照剂量达到 1× 10 14 ions/cm2 和 3× 10 14 ions/cm2 时 ,材料的光能隙分别由原来的 2 .7eV减小到 1.85eV和 1.2eV。     

金红石辐照损伤的分子动力学模拟

为了研究辐照条件下金红石的耐辐照损伤能力，采用GULP软件包拟合出了与实验值吻合的势函数，并采用LAMMPS软件包计算出了金红石的离位阈能和高能粒子反冲条件下的位移级联。通过统计球坐标系下266个出射方向的离位能，利用缺陷形成概率的定义得出Ti和O原子的离位阈能分别为(78.3±1.0) eV和(42.6±2.0) eV。采用VORONOI缺陷统计方法，计算了300 K、10 keV出射能量条件下缺陷数量随辐照时间演化信息，结果表明：Ti原子作为初始出射原子产生的缺陷数量整体高于O原子产生缺陷的数量，在最大无序阶段产生的空位、填隙和不同类型反位缺陷通过空位-填隙复合作用和kick-out机制逐渐减少，有效地降低了晶体的无序度，提高了基材耐辐照损伤性能。     

不同电荷态的7Li离子对质粒DNA链断裂的影响

电离辐射致DNA损伤的程度受到很多因素的影响，如剂量、剂量率、射线种类、DNA浓度等。北京师范大学周宏余课题组利用电子顺磁共振谱仪测量了不同电荷态的低能C离子辐照丙氨酸薄膜后产生的自由基浓度，实验结果发现，当离子注量达到10^13cm-2时，随着离子电荷态的增加，产生自由基相对浓度减少。     

高放废物玻璃固化体的辐照效应研究进展

本文概述了国内外针对玻璃辐照效应所开展的研究及其进展。介绍了α、β、γ射线在玻璃中产生的微观缺陷类型、相对应的表征手段、不同微观损伤与吸收剂量的关系及其在不同温度条件下的稳定性。介绍了玻璃宏观性质随辐照剂量的改变以及饱和现象,提出了宏观性质的改变和无序度的联系来解释实验结果。最后,介绍了玻璃固化体研究所面临的问题和挑战。     

高能氩离子辐照SiO_2玻璃的正电子寿命谱学研究

用 1.15GeV的氩离子在室温下对二氧化硅玻璃样品进行了辐照 ,并通过正电子寿命测量技术研究了辐照后材料微观结构的变化。结果表明 ,在未辐照二氧化硅玻璃中有近 81%的正电子是以正电子素的形式湮灭的 ;根据o -Ps的撞击湮灭寿命确定出未辐照样品的自由体积分布在0 .0 2— 0 .13nm3的区域里 ,平均自由体积半径约为 2 .5nm。辐照后材料的自由体积分布函数变窄 ,峰位下移 ,显示样品经辐照后有密度增大的现象。随着剂量的增大 ,第二正电子寿命成分的强度逐渐增加 ,而相应于o -Ps的寿命成分的强度逐渐减小 ,这被认为是由于辐照产生的电离电子在自由体积中漫游 ,使正电子与这些漫游电子发生湮灭的几率增大 ,从而减小了正电子素的形成几率。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.     

Non-FDG PET imaging of brain tumors

Due to relatively high uptake of glucose in the brain cortex, the use of FDG PET imaging is greatly limited in brain tumor imaging, especially for low-grade gliomas and some metastatic tumours. More and more tracers with higher specificity were developed lately for brain tumor imaging. There are 3 main types of non-FDG PET tracers： amino acid tracers, choline tracers and nucleic acid tracers. These tracers are now widely applied in many aspects of brain tumor imaging. This article summarized the general use of non-FDG PET in different aspects of brain tumor imaging.     

基于NPL-NMC系统的γ测量子系统的建模与优化

在军控核查中,核部件的质量、丰度、年龄属性需采用无损方法进行核查,NPL-NMC系统是一套利用中子多重性测量核部件质量属性的装置,为建立完善的属性测量系统,还需在NPL-NMC系统的基础上建立γ测量子系统。本文通过设计γ测量子系统在NPL-NMC系统上的布局及对中子屏蔽的优化,使系统能对铀部件的丰度、年龄属性进行测量。模拟计算结果表明,该γ测量子系统能很好地满足军控核查对铀部件丰度、年龄属性测量的要求。     

Improvement of carbon fiber surface properties using electron beam irradiation

Carbon fiber-reinforced advance composites have been used for structural applications,mainly on account of their mechanical properties.The main factor for a good mechanical performance of carbon fiber-reinforced com- posite is the interfacial interaction between its components,which are carbon fiber and polymeric matrix.The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite.EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests.Experimental results showed that EB irradiation improved the ten- sile strength of carbon fiber samples.The maximum value in tensile strength was reached using doses of about 250 kGy.After breakage,the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated car- bon fibers were evaluated.SEM micrographs showed modifications on the carbon fiber surface.     

Measurement system for SSRF pulsed magnets

This paper describes the magnetic field measurement system for pulsed magnets in SSRF.The system consists of magnetic probes,analog active integrator,oscilloscope,stepper motor and a controller.An application pro- gram based on LabVIEW has been developed as main control unit.After the magnetic field mapping of a septum magnet prototype,it is verified that the test results accord with the results of theoretical calculation and computer simulation.     

旁路阀调节对高温气冷堆闭式布雷顿循环瞬态特性影响研究

闭式布雷顿循环是第4代高温堆核能系统的关键技术之一,其典型的动态过程是旁路阀调节。为分析这一过程,建立了循环中关键部件的动态模型,其中压气机在径向平衡模型基础上耦合了对附面层发展的预测,兼顾了计算效率与准确性;换热部件模型基于双曲型守恒律方程,对工质的热物性和参数的快速变化有较好的适应性。在此基础上根据回路的质量守恒和压力平衡原则将各部件的模型耦合,建立了系统的动态模型。由于旁路阀调节是氦气透平发电系统主要的功率快速调节手段,瞬态效应较为显著,以模块式高温气冷堆（HTR-10GT）旁路阀开启后的过渡过程作为算例,分析了主要循环参数的响应特性,并通过分析,给出了降低输出功率的机制。计算结果表明：系统的容积惯性对旁路阀调节的响应速度影响较大,而阀门的开度则决定了系统在末态的输出功率;回热器的温度冲击现象可能发生在调节过程中,但可通过两旁路阀联动的方式缓解;反应堆出口温度变化幅度很小,因此反应堆模型的准确程度对结果基本无影响。     

CEFR 100%额定功率运行汽轮机发电能力分析

中国实验快堆(CEFR)首次100%额定功率发电运行中,实际电功率较设计值相差较多。为判断影响机组实际发电能力的主要原因,以现场采集的运行数据和汽轮机厂商提供的设计资料为基础,进行了相应的计算分析。对汽轮机内效率进行修正,绘制汽轮机近似热力过程曲线,并通过实测的各段抽汽压力,在热力过程曲线上获得抽汽焓值;利用换热器的能量守恒和流量守恒的基本方程进行除氧器和各加热器的热平衡计算,获得各段抽汽的流量;利用汽轮机的功率计算方程,得到汽轮机发电功率的计算值。通过计算值与实际值的比较分析,得出主蒸汽参数不达标是影响CEFR汽轮机发电能力的主要因素。