Critical angles for axial channeling

The critical angle for axial proton channeling has been measured as a function of temperature for a number of different crystals. The results are consistently below the values predicted from simple analytical estimates. The magnitude of this discrepancy does not seem to depend on the specific lattice structure. In point of fact, all the results are consistent with a relationship ψ_1/2 = α(p/a). ψ₁, where ψ₁ is Lindhard's characteristic angle, and α(p/a)is a function of the thermal vibrational amplitude p, measured in units of the Thomas-Fermi screening distance a. A formula for α(p/a), derived by Barrett from computer simulations, on the average predicts the magnitude of α quite well, but the observed functional dependence on p/a is considerably stronger than predicted.     

Dielectric relaxation investigations of 100 MeV Ag-ion-irradiated polyetherimide using thermally stimulated discharge current techniques

The thermally stimulated discharge current technique (TSDC) has been used to elucidate various dielectric relaxation processes in 100 MeV Ag-ion-irradiated polyetherimide (PEI). The irradiated PEI samples (85 μm thickness, area 0.12 cm²) were polarized at different temperatures ranging from 50–200 °C under various biasing fields (50–300 kV/cm). TSDC spectra, in general, consist of four current maxima namely γ, β, α and ρ in ascending order of temperature, appearing around 40, 110, 200 and 230 °C, respectively. The origin of γ - and β -peaks has been attributed to the dipolar nature of ether linkages and carbonyl groups, respectively, whereas α- and ρ-maxima have been attributed to the space charge polarization process. The absence of γ-peak in irradiated samples is attributed to the significant loss in ether linkages due to irradiation. The free radical formation, demerization of carbonyl groups and cross-linking of imide groups due to ion irradiation in PEI have been held to be responsible for the behavior of these relaxation processes. In the vicinity of the β-relaxation, a new relaxation process, termed δ-relaxation, is also observed.     

Critical approach distances and critical angles for channelling

The critical angles and critical approach distances, which determine the limits for the channelling of energetic ions, down open crystal directions are established by the methods of computer simulation and compared with simple analytical models. For non-vibrating rows or planes a good agreement between the two is obtained. The complicating effects of thermal vibrations can be accounted for by empirical formulae.     

高能Pb离子辐照注碳SiO2的红外谱研究

室温下，先用120keV的C离子注入二氧化硅薄膜样品至剂量2.0×1017、5.0×1017或8.6×1017ions/cm2，再用950MeV的Pb离子分别辐照至剂量5.0×1011、1.0×1012或3.8×1012 ions/cm2，然后测量样品的傅里叶变换红外(FTIR)光谱. 通过分析测量得到的傅里叶变换红外谱，发现Pb离子辐照在注碳SiO₂样品中可引起大量的Si－C和Si (C)－O－C等化学键的形成，大剂量Pb离子辐照可在大剂量注碳的SiO₂中产生分子CO₂. 大量的Si－C键的存在和分子CO₂的形成，预示着高能Pb离子辐照在注碳SiO₂样品中有可能形成了纳米Si团簇和/或SiC晶粒.     

中能重离子微束辐照装置的研制

微束辐照装置是将辐照样品的束斑缩小到微米量级, 能够对辐照粒子进行准确定位和精确计数的实验平台, 是开展辐照材料学、辐照生物学、辐照生物医学以及微加工的有力工具. 中国科学院近代物理研究所(IMP)正在研制中能重离子微束辐照装置. 该装置以兰州重离子加速器(HIRFL)系统提供的中能和低能重离子束流为基础, 采用磁聚焦方式形成微米束. 束运线上两台铅垂方向的偏转磁铁辅以四极磁铁构成对称消色差系统, 将束流导向地下室, 再用高梯度的三组合四极透镜强聚焦形成微米束斑, 在真空中或大气中辐照样品. 它将成为国内首台能够提供从低能(10MeV/u)到中能(100MeV/u)的重离子微束的公共实验平台, 用于定位、定量照射靶物质(生物细胞、组织或其它非生物材料等), 有助于深入揭示重离子与物质相互作用的本质, 也为探索重离子辐照效应的应用提供新的手段.     

辐射免疫学研究进展

近年来辐射免疫学作为一门新兴学科进展迅速，特别是在低剂量辐射兴奋效应研究方面有较大发展，同时重离子辐射生物效应的研究在治疗肿瘤方面也有了明显进步。综述了国内、外辐射免疫学的现况，其目的是寻找出一种综合疗法，从而达到既可以较好的治疗肿瘤，又对病人损伤较小的目的。Radiation immunology as a new subject has made a great progress in recent years, especially in the radiation hormesis. At the same time, the research of radiobiological effect on heavy ions has played an important role in the cancer therapy, especially on the radiation immunology of heavy ions in the outer space. In this review, we summaried the status and development of radiation-immunology, and try to find out some better ways which can increase efficient killing on tumours, but reduce the damages on normal tissues.     

高能Xe离子辐照引起的注碳a:SiO2中新结构的形成

先用120keV的碳离子注入非晶二氧化硅a:SiO2薄膜，再用能量为1754MeV的Xe离子辐照。注碳量为5．0×10^16—8．6×10^17ion／cm^2，Xe离子辐照剂量为1．0×10^11和5．0×10^11ion／cm^2。辐照后的样品中形成的新结构用显微傅立叶变换红外光谱仪进行测试分析。结果表明，Xe离子辐照引起了注碳a:SiO2中Si—C，C—C，Si—O—C键以及CO和CO2分子的形成与演化。在注碳量较高时，Xe离子辐照在样品中产生了大量的Si—C键。与注入未辐照和辐照的低注碳量样品比较，增强的Si—C键的形成，预示着辐照可引起注碳a:SiO2样品中的SiC结构相变。Amorphous silicon-dioxide （a:SiO2） films were firstly implanted at room temperature （RT） with 120 keV C-ions to doses ranging from 5.0 × 10^16 to 8.6 × 10^17 ion/cm^2, and then the C-doped a:SiO2 films were irradiated at RT with 1 754 MeV Xe ions to 1.0 × 10^11 and 5.0 × 10^11 ion/cm^2, respectively. The information of new tex- ture formation in the C-doped SiO2 films after high-energy Xe ion irradiation was investigated using micro-FTIR measurements. The obtained results showed that Si--C, C--C, Si--O--C bonds as well as CO and CO2 molecules were formed in the C-doped a-SiO2 films after Xe ion irradiation. Furthermore, Xe-ion irradiation induced a plenteous formation of Si--C bonds in the high dose C-ion implanted a:SiO2 films. Compared with the C-implanted sampies without Xe-ion irradiation and the low dose C-implanted samples with Xe-ion irraddiation, the enhanced and plenty of Si--C bond formation implied that the phase of SiC structures may be produced by Xe-ion irradiation in the high dose C-ion implanted a:SiO2 films.     

25 MeV/u Kr辐照下PET薄膜的损伤机制研究

通过25 MeV/u 86 Kr离子辐照叠层结晶聚对苯二甲酸乙二醇酯膜（PET）, 在不同的电子能损（3.40-7.25 keV/nm）和离子注量(5×1011----3×1012 ions/cm2)辐照条件下, 对Kr离子在PET中引起的辐照损伤效应进行了研究。借助傅里叶变换红外光谱分析,通过对样品的红外吸收峰进行扣除基底后的Lorentz拟合,分析了与主要官能团对应的吸收峰强度的变化趋势, 研究了化学结构与组分在重离子辐照下的变化规律; 利用X射线衍射光谱仪测量, 研究了Kr离子在PET潜径迹中引起的非晶化过程,并通过对吸光度和非晶化强度随离子注量的指数衰减规律的分析, 获得了不同电子能损离子辐照PET时主要官能团的损伤截面和非晶化截面及对应的潜径迹半径。 At room temperature, polyethylene terephthalate(PET) foil stacks were irradiated by 25 MeV/u Kr ions in the electronic stopping power range(3.3--7.66 keV/nm) and the fluence range from 5×1011 to 3×1012 ions/cm2. The behaviour of the main function groups with fluence and electronic stopping power were studied by using Fourier transform infrared(FTIR) spectroscopy, the degradation of the function group was investigated with the Lorentz fitting subtracted baseline. The amorphous processes in the latent tracks of PET were studied by X ray diffraction(XRD) measurements. The Kr ion induced degradation cross section and amorphisation cross sections(radii) for different electronic energy loss were acquired from the experimental data(FT IR and XRD) by exponential decay function respectively.      

Impact of the displacement damage in channel and source/drain regions on the DC characteristics degradation in deep-submicron MOSFETs after heavy ion irradiation

This paper mainly reports the permanent impact of displacement damage induced by heavy-ion strikes on the deep-submicron MOSFETs.Upon the heavy ion track through the device,it can lead to displacement damage,including the vacancies and the interstitials.As the featured size of device scales down,the damage can change the dopant distribution in the channel and source/drain regions through the generation of radiation-induced defects and thus have significant impacts on their electrical characteristics.The measured results show that the radiation-induced damage can cause DC characteristics degradations including the threshold voltage,subthreshold swing,saturation drain current,transconductance,etc.The radiation-induced displacement damage may become the dominant issue while it was the secondary concern for the traditional devices after the heavy ion irradiation.The samples are also irradiated by Co-60 gamma ray for comparison with the heavy ion irradiation results.Corresponding explanations and analysis are discussed.     

粲夸克辐射的死区效应

基于轻夸克辐射能量谱, 考虑夸克质量对部分子辐射能量损失的影响, 利用死区因子把轻部分子辐射能量损失谱推广到重部分子辐射能量损失的情形. 研究结果表明, 利用与夸克质量相关的死区因子推广轻夸克辐射能量损失谱得到的重夸克辐射能量损失谱, 与直接利用微扰QCD计算所得到的Djordjevic-Gyulassy(D-G)谱的结果一致, 且极大简化了重夸克辐射能量损失的计算.     

重离子诱变酵母培养基的优化与研究

利用12C6+离子诱变技术对面包酵母菌种进行诱变,得到一株粗蛋白含量达到55% 以上的菌株,借助Minitab16.0,采用Plackett-Burman 实验设计法及响应面分析法,对诱变后面包酵母菌发酵培养基的成分进行了优化,得到3 个最为显著的主要影响因子:葡萄糖、酵母抽提物和硫酸镁。利用最陡爬坡实验逼近最大响应区域后,利用Box-Behnken 实验设计及响应面分析法进行回归分析。通过求解回归方程,得到优化发酵的条件为,葡萄糖:11.03 g/L、酵母抽提物:6.53 g/L、硫酸镁:5.59 g/L。面包酵母生物量为4.84 g/L,相比未进行优化时的生物量提高了15%。A mutant bread yeast strain with high protein content of 55% was gained by use of 12C6+ ions. The MINITAB 16.0 software, Plackett-Burman experimental design and response surface methodology were applied to optimize the culture medium for the irradiated yeast. The most important three factors which influenced the culture results were identified as glucose, magnesium sulphate and yeast extract. The path of the steepest ascent was undertaken to approach the optimal region of the three significant factors. Box-Behnken design and response surface methodology were used for the regression analysis. Finally, the optimal fermentation conditions were identified as glucose 11.03 g/L, yeast extract 6.53 g/L and magnesium sulphate 5.59 g/L by the regression analysis. It was found that the biomass of the bread yeasts reached 4.84 g/L and increased by 15% compared to original conditions.     

快重离子辐照对非晶态SiO2薄膜光致发光谱的影响

用湿氧化法在单晶硅表面生长了非晶态SiO2薄膜,再用高能Pb和Xe离子对薄膜进行辐照,最后用荧光光谱分析了辐照参数(剂量、电子能损值)与发光特性改变的相关性.研究发现,快重离子辐照能显著影响薄膜的发光特性,进一步分析显示,辐照导致了SiO2薄膜内O-Si-O缺陷、缺氧缺陷和非桥式氧空位缺陷的产生,且缺氧缺陷和非桥式氧空...     

SiO2水玻璃微球辐射增强扩散研究

激光惯性约束聚变使用的玻璃微球经中子辐照后,产生辐射增强扩散效应,Ar在玻璃微球中的扩散性能显著改善,获得了常规加热加压扩散方式无法得到的扩散效果。而带电离子辐照玻璃微球后Ar的扩散性能却没有明显改善。研究了中子和其它带电粒子辐射增强扩散效应的差异。After being radiated by neutron, the glass microspheres, which used in ICF research, have greatly increased the ability of Ar diffusion in it because of the radiation-enhanced diffusion. Such results cannot be achieved by means of thermal diffusion. But after being radiated by charged particles, the ability of Ar diffusion in glass has not increased very much. The differences of the radiation-enhanced diffusion caused by neutron and ions are presented.     

Materials modification at zirconium–silicon interface using swift heavy ions

The reactivity of the Zr/Si interface induced by swift heavy ion beams of Au has been investigated in the present work. Zirconium was evaporated on a clean silicon substrate in ultra high vacuum (UHV) at a pressure of 10^?8 Torr by the electron beam evaporation technique and the final layer was a thin film of Au to avoid oxidation of zirconium. The Zr/Si system was irradiated by 350 MeV Au²⁶⁺ ions at liquid nitrogen temperature at different fluences (0.46×10¹⁴, 1.85×10¹⁴ and 4.62×10¹⁴ ions/cm²). Rutherford back scattering (RBS) spectroscopy using 2 MeV He ions was used to monitor the Zr and Si concentration profiles and interdiffusion at the interfaces. The irradiation at the Zr/Si interface showed mixing. X-ray diffraction measurements confirmed the formation of the ZrSi₂ phase. Thermal spike formation and melting in the tracks was found to be the dominant process at the interfaces.     

介质对部分子劈裂几率的影响

利用部分子在热密QCD介质中的辐射谱, 研究部分子在热密介质中的演化规律. 研究结果表明, 在相同能量下介质诱导效应使得部分子在介质中的劈裂几率大于部分子在真空中的劈裂几率; 高密度介质中的部分子劈裂几率大于低密度介质中的劈裂几率. 本文研究结果与美国BNL/RHIC相对论重离子碰撞实验中观测到的高横动量强子产额压低现象一致, 揭示了在RHIC能区已经生成高温高密物质.     

先进核能系统结构材料辐照性能研究

首先简要介绍第一代到先进的第四代核能系统的发展、与核能系统发展密切的抗辐照结构材料研发进展、第四代核能系统结构材料辐照性能研究新方法。第四代核能系统发展中,辐照引起材料性能退化是一个需要研究和解决的瓶颈问题。现有中子源都不能满足第四代核能系统结构材料高剂量中子辐照性能研究的要求。为此,发展了用于核能系统结构材料高剂量辐照性能快速检测加速器重离子辐照方法和第四代核能系统实际辐照工况模拟的重离子与氢和氦三束同时辐照新方法,文中进行了详细的介绍。最后介绍了中国原子能科学研究院核能系统结构材料辐照性能研究现状和近期发展计划。该院在HI-13串列加速器器上建立了多种不同用途的重离子辐照装置、三个独立加速器构成的重离子与氢和氦三束同时辐照实验平台,开展了一系列核能结构材料,例如国产改进型奥氏体钢、CLAM钢、1515钢、钽、钨等的辐照性能的系统测试和研究。为了更好地开展核能结构材料性能研究,从国外引进了一台超导直线加速器和一台可变能量重离子回旋加速器。结合现有2×13 MeV,2×1.7 MV串列加速器、30 MeV和100 MeV质子回旋加速器、高压倍加器,中国实验快堆、中国先进研究堆、微堆等,CIAE将建成一个比较完整和先进的核能系统结构材料辐照实验平台系统供国内外用户使用。This paper introduces briefly the development of nuclear energy systems from the GEN I to the advanced GEN IV, the progress of manufacturing radiation resistant materials associated with the development of nuclear energy systems and the new methods of investigating radiation properties of the structural materials for the GEN IV nuclear energy systems at first. Irradiation induced deterioration of materials properties is a bottle neck problem, which must be investigated and solved for the development of the GEN IV nuclear energy systems. Unfortunately, all the currently available neutron sources cannot meet the requirements of investigating radiation properties of structural materials irradiated by high dose neutron irradiation in the GEN IV nuclear energy systems. Therefore, two new methods of the accelerator heavy ion irradiation that simulates the high-dose neutron irradiation and the triple beam irradiation that mimics the real neutron irradiation environment in the GEN IV nuclear energy systems have been developed. These two methods are introduced in this paper. The present status of the study on radiation properties of structural materials for nuclear energy systems of the new generation and the near future development plan at China Institute of Atomic Energy (CIAE) are described also. The accelerator heavy ion irradiation facilities for different applications and the simultaneous triple beam irradiation platform with three separate accelerators or implanters have been established at the HI-13 tandem accelerator of CIAE. A series of structural materials for nuclear energy systems, such as the home-made modified austenic steel, CLAM steel, 1515 steel, Tantalum, Tungsten, etc. have been tested and investigated systematically. A superconducting linear accelerator and a variable energy heavy ion cyclotron have been imported from abroad for a better performance of the study. Combined with the currently existing facilities of 2×13 MeV and 2×1.7 MV tandem accelerators, 30 and 100 MeV proton cyclotrons, China experimental fast reactor, China advance research reactor, Miniature neutron source reactor, etc. a comprehensive and advanced system of experimental irradiation platform for structural materials of nuclear energy systems will be established in the near future for both domestic and foreign users.     

Stoichiometry dependent changes in the optical properties and nanoscale track formation of PECVD grown a-SiNx:H thin films upon 100 MeV Au8+ ion irradiation

a-SiN_x:H thin films of different stoichiometry grown by PECVD were subjected to irradiation by 100 MeV Au⁸⁺ ions with various fluences to understand the effect of stoichiometry on properties of thin films upon irradiation. Ellipsometry and UV–Vis study suggest the variation in the refractive index of thin films with fluence. The evolution of Hydrogen due to irradiation is quantified with the help of ERDA. RBS was probed to study the change in thin films' composition upon irradiation, which further helps understand the change in thin films' optical properties. Quenching of photoluminescence in the films with all stoichiometries was also observed due to ion irradiation. X-TEM images show the formation of discontinuous ion tracks of radius 2.5 nm in the film closer to silicon nitride stoichiometry. However, Si rich film does not show the clear formation of tracks. Results are explained in the framework of the Thermal spike mechanism of ion-solid interaction.     

HIRFL辐照终端照射野均匀度与离子通量的关系

采用固体核径迹探测器聚碳酸脂膜,测定了兰州重离子研究装置提供的55MeV/u40Ar和80MeV/u20Ne离子束经辐照终端束流均匀化扫描装置后照射野均匀度与离子通量之间的关系.结果表明:对于40Ar和20Ne离子束,离子通量小于1×106和2×107ions/cm2时,横向照射野均匀度缓Ne离子束照射慢增加;当离子通量分别介于1×106—1×107和2×107—1×108ions/cm2时,40Ar和20野均匀度逐渐增加;离子通量达到1×107和1×108ions/cm2时,40Ar和20Ne离子束照射野均匀度分别约为58%和61%.从而说明,辐照终端束流扫描装置对束流的均匀化程度目前并不能满足辐照生物效应、辐射育种和重离子治癌等研究工作的需要,须对其性能做进一步的提高. Using 55 MeV/u 40Ar and 80 MeV/u20Ne ion beams delivered by the Heavy Ion Research Facility at Lanzhou (HIRFL), the relationships between the irradiation homogeneities in irradiation fields generated by the beam scanning device located at the irradiation terminal of the HIRFL and ion fluence were measured respectively with 100 μm polycarbonate films by means of nuclear track detection. The results show that the homogeneity increases when the ion fluence are lower than ........     

Asymptotic laws for the winding angles of planar Brownian motion

Using constrained path integrals, we study the winding angle distribution of a two-dimensional Brownian motion around a given point. By a careful analysis of the spectral properties of some Schrödinger-like Hamiltonians, we obtain a generalization of the Messulam-Yor law. Various limiting cases are considered.     

强流加速器材料研究

加速器技术的快速发展以及科学技术研究和应用的不断需求,使得高流强和高品质成为新一代加速器装置的最重要的指标。目前大型科学实验装置如重离子束驱动的惯性约束聚变装置、对撞机、中微子及介子工厂、散裂中子源等都需要强流加速器。详细介绍了强流加速器中涉及的材料问题以及强流加速器在聚变堆材料研究中的作用和前景。With the increasing development of accelerator technology and the growing requirements from scientific and technical researches as well as applications, high intensity and high performance become the most important characters of the new accelerator facilities. Currently, many large-scale scientific experimental facilities such as the heavy-ion driven inertial confined fusion facility, the collider, the neutrino and muon factories, the spallation neutron source and so on all need the high intensity accelerators. In this paper, the material issues relevant to the high intensity accelerators and the applications of high intensity accelerators are introduced.