Mössbauer study of amorphous alloys irradiated with energetic heavy ions

Mössbauer spectroscopy was applied to study radiation damage in amorphous alloys irradiated with ⁴⁰Ar ($\text{E = 225}\text{MeV}$) or ¹³²Xe ($\text{E = 120}\text{MeV}$) ions at room temperature. In the magnetically split Mössbauer spectra dose dependent decreases of the intensity of the 2nd and 5th lines as well as of the average hyperfine magnetic field were observed. The changes were also analysed using the hyperfine field distribution obtained from the spectra. The results are interpreted in terms of defect creation and structural changes of short range order of irradiated amorphous alloys.     

Mechanical properties of cubic zirconia irradiated with swift heavy ions

The modifications of the mechanical properties of cubic (yttria-stabilized) zirconia induced by swift heavy ion irradiation are investigated. Polycrystalline pellets were irradiated at room temperature with 940 MeV Pb ions at the GANIL accelerator in Caen at fluences ranging from 5 × 10¹¹ to 4 × 10¹³ cm⁻². The microhardness and the fracture toughness of irradiated YSZ were studied by Vickers micro-indentation. Although YSZ is damaged by irradiation, an increase of the microhardness and fracture toughness with increasing ion fluence is observed. A strengthening of YSZ, associated with residual compressive stresses induced in the surface layer by irradiation, explain these results.     

Electrical properties of silicon diodes with pn junctions irradiated with Au swift heavy ions

Electrical properties of silicon diodes with p⁺n junctions irradiated with ¹⁹⁷Au⁺²⁶ swift heavy ions (energy E = 350 MeV, fluences of 10⁷ cm⁻² and 10⁸ cm⁻²) and silicon diodes irradiated with electrons (energy E = 3.5 MeV, fluences of 10¹⁵ cm⁻², 5 × 10¹⁵ cm⁻² and 10¹⁶ cm⁻²) have been investigated. Frequency dependences of the impedance, current-voltage characteristics and switching characteristics of these devices have been studied. Irradiation of the diodes with ¹⁹⁷Au⁺²⁶ ions at a fluence of 10⁸ cm⁻² leads to the formation of a quasi-continuous layer of irradiation-induced defects that enable a combination of characteristics such as a reverse resistance recovery time and direct voltage drop that are better than those for electron-irradiated diodes. Still, the irradiation of high-energy ions results in an increase in recombination currents that are larger than those obtained with electron irradiation, and causes more complicated frequency dispersion of the diode parameters.     

Inactivation cross section of yeast cells irradiated by heavy ions

1IntroductionThecalculationsofinactivationcrosssectionsforheavyionsinthetrackwidthregaldisplayingthindownforE.ColtB/randBs-1,andforBaciUusSubtilusarestraightforwardforthese1-hitdetectorsbasedontheKatztracktheory.[1]CalculationsforV-79hamstercellsaremorecomplex.Theyfollowtheoriginaldevelopmentofitusmodelforeucaryoticcens,andmalleuseofthecrosssectionscalculatedforhypotheticalinternaltargetswhicharethenassertedtobeproportionaltothemeasuredcellularinactivationcrosssections.Inmaxnmallancensinac…     

Microstructure evolution and degradation mechanisms of reactor internal steel irradiated with heavy ions

Structure evolution and degradation mechanisms during irradiation of 18Cr-10Ni-Ti steel (material of VVER-1000 reactor internals are investigated). Using accelerator irradiations with Cr³⁺ and Ar⁺ ions allowed studying effects of dose rate, different initial structure state and implanted ions on features of structure evolution and main mechanisms of degradation including low temperature swelling and embrittlement of the 18Cr-10Ni-Ti steel. It is shown that differences in dose rate at most irradiation temperatures mainly exert their influence on the duration of the swelling transient regime. Calculations of possible transmutation products during irradiation of this steel in a VVER-1000 spectrum were performed. It is shown that gaseous atoms (He and H), which are generated simultaneously with radiation defects, stabilize the elements of radiation microstructure and influence the swelling. The nature of deformation under different temperatures of irradiation and of mechanical testing is investigated. It is shown that the temperature sensitivity of swelling behaviour in the investigated steel, with different initial structures can be connected with the dynamic behaviour of point defect sinks.     

Inactivation cross sectiopn of yeast cells irradiated by heavy ions

Inactivation cross sections for haploid yeast cell strain 211a have been calculated as 1-ht detector based on the track theory in an extended target mode and a numerical calculation of radial dose distribution.In the calculations,characteristic dose D0 is a fitted parameter which is obtained to be 42Gy,and “radius” of hypothetical target a0 is chosen to be 0.5μm which is about the size of nucleus of yeast cells for obtaining an overall agreement with experimental cross sections.The results of the calculations are in agreement with the experimental data in igh LEF(linear energy transfer)including the thindown region.     

Multiply charged ions from solids produced under energetic, heavy ion impact

Multiply charged ions from solids under energetic, heavy ion impact have been observed and compared with those from gas atoms and molecules. It is found that the production of multiply charge ions from most metallic solids is significantly reduced, compared to that from gas targets, meanwhile metallic ions from solids of oxided materials seem to be produced in a way similar to that from gas targets. It is also pointed out that impurities adsorbed on surface play an important role in the production of ions from metallic surfaces. Possible applications of energetic, heavy ion bombardment to study of desorption from solid surfaces are discussed.     

Structural changes in anatase TiO2 thin films irradiated with high-energy heavy ions

In order to investigate possible structural changes due to high-density electronic excitation, anatase TiO₂ thin film specimens were irradiated with 230 MeV ¹³⁶Xe¹⁵⁺ ions and 200 MeV ¹⁹⁷Au¹³⁺ ions. X-ray diffraction (XRD) patterns were measured before and after irradiation. The intensity of the XRD peak assigned to the (0 0 4) planes of anatase TiO₂ decreases in an exponential manner as a function of ion-fluence. This result can be explained by the formation of the cylindrical damaged regions (i.e. ion tracks) with diameters of 9.6 and 16.3 nm for 230 MeV Xe and for 200 MeV Au ion irradiations, respectively. The difference in the track diameter between Xe ion irradiation and Au ion irradiation can be attributed to the difference in the electronic stopping power (and to the ion-velocity effect, if any). For 200 MeV Au ion irradiation, splitting of the (0 0 4) peak is observed. The original (0 0 4) TiO₂ peak remains in the same position, but the new peak shifts to higher angles as fluence increases.     

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.     

Anisotropy of disorder accumulation and recovery in 6H-SiC irradiated with Au ions at 140 K

Single crystal 〈0 0 0 1〉-oriented 6H-SiC was irradiated with Au²⁺ ions to fluences of 0.032, 0.058 and 0.105 ions/nm² at 140 K and was subsequently annealed at various temperatures up to 500 K. The relative disorder on both the Si and C sublattices has been determined simultaneously using in situ D⁺ ion channeling along the 〈0 0 0 1〉 and 〈〉 axes. A higher level of disorder on both the Si and C sublattices is observed along the 〈〉. There is a preferential C disordering and more C interstitials are aligned with 〈0 0 0 1〉. Room-temperature recovery along 〈〉 occurs, which is associated with the 〈0 0 0 1〉-aligned interstitials that annihilate due to close-pair recombination. Disorder recovery between 400 and 500 K is primarily attributed to annihilation of interstitials that are misaligned with 〈0 0 0 1〉 and to epitaxial crystallization. Effects of stacking order in SiC on disorder accumulation are insignificant; however, noticeable differences of low-temperature recovery in Au²⁺-irradiated 6H-SiC and 4H-SiC are observed.     

12C6+重离子辐照胡麻种子初步研究

本文研究了6×108 cm-2、1.8×109 cm-2和3.6×109 cm-2的12C6 重离子束辐照对胡麻种子M1代生物学性状和DNA分子多态性等方面的影响.6×108 cm-2辐照处理可引起胡麻发芽率提高,促进植株株高,增强花粉活力.同时辐照处理使胡麻种子千粒重和含油量有不同程度提高,辐射剂量越高,两者数值越大,3.6×109cm-2辐射剂量的胡麻种子千粒重和含油量与对照组的相比分别高出了16.5%和19.9%,此外在此剂量处发现了花粉发生了形态变化.辐照处理对胡麻DNA分子也产生了影响,筛选出的14个随机引物可以扩增出清晰、稳定、重复性好的DNA片段,有52个是多态性DNA片段,比率为52.5%.     

Vickers hardness change of the Chinese low-activation ferritic/martensitic steel CLF-1 irradiated with high-energy heavy ions

In the present work, the irradiation hardening behavior of a Chinese low-activation ferritic/martensitic steel CLF-1, a candidate for fusion reactor blankets, is studied. Specimens were irradiated with high-energy~(14)N and~(56)Fe ions at the terminal of a cyclotron to three successively increasing damage levels of 0.05, 0.1 and 0.2 displacements per atom(dpa) at about-50 °C. The energy of the incident ions was dispersed to 11 successively decreasing grades using an energy degrader, thereby generating an atomic displacement damage plateau in the specimens from the surface to a depth of 25 μm, which is sufficiently broad for the Vickers hardness test. Eight different loads(i.e. 98 mN, 196 m N, 490 m N, 980 m N, 1.96 N, 4.9 N, 9.8 N and 19.6 N) were applied to the specimens to obtain the depth profiles of the Vickers hardness by using a microhardness tester. Hardening was observable at the lowest damage level, and increased with increasing irradiation dose. A power-law correlation of the Vickers hardness with the damage level(HV_0=1.49+0.76 dpa~(0.31)) is proposed. Testing with a nano-indentation technique was also performed, and a linear relationship between the Vickers micro-hardness and the nanohardness(HV_0=0.83 H_0) was observed. A comparison with other RAFM steels(CLAM, JLF-1,F82 H, EUROFER97 etc.) under neutron or charged particle irradiation conditions shows that most of the RAFM steels exhibit similar power-law exponents in the dose dependence of irradiation hardening. The difference in the irradiation hardening may be attributed to differences in microstructure prior to irradiation.     

12C6+离子束照射不同肿瘤细胞显示重离子治疗癌症的明显优势

通过观察两种人恶性肿瘤细胞(人肝癌细胞SMMC-7721和人黑色素瘤细胞A375)对高LET12C6 离子和γ射线辐照的敏感性及其差异,考察重离子治疗肿瘤的可行性及优势.以这两种体外培养的来源于人体不同组织的具有高辐射抗性的恶性肿瘤细胞为实验对象,分别进行12C6 和γ射线0-6Gy内不同剂量点的单次和分次照射,采用克隆存活法统计细胞的存活分数.结果显示,无论是单次还是分次照射,12C6 照射后两种细胞的存活分数均明显低于γ射线照射,而且两种细胞的辐射敏感性差异明显降低,同时分次照射细胞的存活分数没有明显提高.结果表明,高LET重离子照射对肿瘤细胞能明显提高杀伤能力,同时降低了不同细胞辐射敏感性的差异且导致细胞低的修复.以上特点与重离子剂量深度分布相结合,使得重离子在治疗肿瘤时具有特殊的优势.     

高能铁离子辐照二氧化硅玻璃产生的缺陷研究

室温下用紫外-可见吸收光谱、荧光光谱和电子顺磁共振技术测量分析1.157 GeV56Fe离子辐照的二氧化硅玻璃,研究了高能重离子辐照产生缺陷的规律.紫外-可见吸收光谱测量结果显示,高能铁离子辐照产生了包括E'心、非桥连氧空穴心(NBOHC)和缺氧心ODC(Ⅱ)在内的多种缺陷结构.随着离子辐照量的增加,各类缺陷的数量逐渐增大并在高辐照量时趋于饱和.用单离子饱和损伤模型对实验结果进行拟合,获得了各类缺陷的产生截面在90-140 nm2.根据缺陷相对数量的变化关系探讨了E心和NBOHC的产生机制.荧光光谱显示,当以5 eV的紫外光激发辐照样品时,观测到三个荧光发射峰,分别位于4.28 eV(α带)、3.2 eV(β带)和2.67 eV(γ带),α带和γ带的存在证实辐照产生了ODC(Ⅱ)缺陷.实验发现β带是二氧化硅玻璃中的一种固有缺陷,高能离子辐照可使其部分脱色.电子顺磁共振测量进一步证实了E'心的产生规律.     

Trapping of energetic hydrogen ions in reactive metals

A model is proposed to describe the trapping of a beam of energetic ions of hydrogen isotopes by targets of reactive metals in which the incident ions dissolve exothermically. The model considers the ions free to diffuse inside the metal, and to escape from the surface at a rate determined from the known solubility data.It has been shown that in the case of semi-infinite geometry the trapping efficiency can be expressed in analytic form as a function of dose. However, in the two dimensional case appropriate for beam experiments, radial diffusion becomes important and a numerical solution has been found to be necessary. The model has been compared with experimental results on the trapping of 18 keV deuterons by targets of Nb, Zr, Ti and Pd in the temperature range 230–1000 K and in general good agreement has been obtained.     

低速高电荷态重离子在GaN单晶中引起的辐照损伤研究

利用Rutherford沟道背散射分析研究了低速高电荷态重离子(Xe26 )在氮化镓(GaN)晶体中辐照损伤的产生对剂量的依赖关系,比较了垂直照射和60°倾斜照射的差异.基于"库仑爆炸"模型对结果进行了解释.