51例夜光粉描绘工人发中~(210)Po 含量分析

本文报道了51例表面夜光粉描绘工人发中~(210)Po 含量,发现其水平大大超过正常人群发样中~(210)Po 含量(男性组P=0.0025;女性组P<0.0005),并指出水平与接触工龄有关。     

Temporal changes in vertical distribution of 137Cs in litter and soils in mixed deciduous forests in Fukushima,Japan

Downward migration of ¹³⁷Cs in soils was studied in three mixed deciduous forests c.a. 40 km northwest of the Fukushima Daiichi Nuclear power plant (FDNPP), Japan. We selected three different types of forest regarding to environmental condition such as slope inclinations and snow coverage conditions at the time of deposition. We examined temporal changes in the vertical distribution of ¹³⁷Cs from litter layers to 10 cm soil depth for two years (2.3 to 4.3 years after the FDNPP accident in 2011). At all three study sites, the ¹³⁷Cs in the litter layer had largely migrated to surface soil by 2013. After 2014, about 80% of the ¹³⁷Cs in forest soils (litter layer to 10 cm soil depth) remained within 0–5 cm soil layer. The vertical distribution had not changed substantially since 2014, suggesting that changes to the downward migration rates of ¹³⁷Cs in soils drastically decreased with time. In addition, small amounts of migrating ¹³⁷Cs could not be detected by the present method because there was a large spatial variation in the distribution of soil ¹³⁷Cs. The results showed similar patterns of soil ¹³⁷Cs distribution among the three study sites although there were differences in the environmental conditions.     

哈尔滨燃煤电厂周围土壤放射性水平的分析

煤炭燃烧过程中,放射性核素会不同程度的在飞灰和炉渣中富集,进而随着飞灰和炉渣进入土壤环境中,对土壤造成不同程度的放射性污染。本文以哈尔滨群力燃煤电厂和呼兰燃煤电厂为研究对象,在距电厂1 km范围内布设采样点,每个采样点土壤分3层采样,即A层深度:0～10 cm,B层深度:10～20 cm,C层深度:20～30 cm。利用高纯锗γ谱仪测量土样中的天然放射性核素,分析了燃煤电厂周围土壤样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K的含量,并与黑龙江省土壤天然放射性核素测量结果进行了比较。结果表明,在群力电厂和呼兰电厂1 km范围内周围土壤中,除了天然放射性核素²³⁸U以外,其他3种核素含量都未超出全省含量最大值,其中核素²³²Th的含量甚至低于全省大部分地区;燃煤电厂的长期运行给土壤环境带来了一定的放射性影响,土壤本底的放射性核素含量发生了一些变化,这种变化在呼兰电厂周围的土壤中表现得更为明显,但是并未超出国家规定的标准,污染程度在可接受的范围内。     

Diffusion and strain relaxation in Si/Si1−xGex/Si structures studied with Rutherford backscattering spectrometry

The thermal stability of strained Si/Si_1−xGe_x/Si structures grown by molecular beam epitaxy was investigated by resistive heating and in situ Rutherford backscattering spectrometry. Ge profiles obtained from a 50 nm Si_1−xGe_x layer on a Si(100) substrate capped with 50 nm Si were evaluated for different Ge concentrations after sequential heating periods at a particular temperature between 850 and 1010° C. The diffusion coefficients, calculated from the increase in signal in the tail of the Ge profile, proved to be comparable to the value for Ge in bulk Si. A more pronounced decrease of the signal at the center of the Ge profile indicated a faster diffusion within the SiGe layer which was confirmed by analysis of the FWHM of the Ge profile. Ion channeling measurements were used to characterize tetragonal strain in the buried SiGe layers. Angular scans through the 111 direction were interpreted with Monte Carlo channeling calculations and used to study strain relaxation in dislocation-free and partially relaxed layers.     

Oxygen diffusion in the Zr-1% Nb alloy during high-temperature oxidation in water vapor (steam)

Conclusions The kinetics of the processes of high-temperature oxidation of the Zr-1% Nb alloy was studied. The distribution of oxygen (concentration profile) in the layer located below the oxide layer was established according to the method of mass-spectrometry of secondary ions using a SMI-300 ion analyzer. The diffusion parameters were calculated on an ES-1055 computer using a specially written program in the FORTRAN-4 language.Translated from Atomnaya Energiya, Vol. 65, pp. 321–326, November, 1988.     

Nd0.5Sr0.4Pb0.1Mn0.96Fe0.04O3微观结构的中子衍射

采用固相反应法制备了混价钙钛矿型锰氧化物多晶样品Nd0.5Sr0.4Pb0.1Mn0.96Fe0.04O3,在室温下进行了中子粉末衍射测量并用Rietveld峰形精修程序Fullprof2k对实验数据进行了拟合。结果表明:Nd0.5Sr0.4Pb0.1Mn0.96Fe0.04O3样品具有正交的GdFeO3型结构,空间群为Pnma,Nd(Sr、Pb)原子占据4c晶位,Mn(Fe)原子占据4b晶位,O原子分别占据4c和8d两个不等价的晶位,并得到了MnO6八面体中Mn—O—Mn键角和Mn—O键的键长。     

用~(14)N(d,α_1)~(12)C核反应研究注入氮在纯铁和GCr15钢中的深度分布

本文描述了利用~(14)N(d,a_1)~(12)C核反应测量固体样品表面层内氮原子含量及深度分布的方法。在Si_3N_4标准样品中,所得到的表面处的深度分辨为48nm。利用该分析手段,研究了在不同注入温度条件下,氮离子注入纯铁和GCr15钢的保留量及深度分布的变化情况。     

RNRA and neutron threshold analyses of thick lithium coatings deposited by sputter evaporation

Li coatings on various substrates have numerous applications: Boron neutron capture therapy, super conducting tokamak, etc.Unfortunately the main difficulty using Li is its reactivity in air and diffusion into metals. It is the only metal that reacts with nitrogen at room temperature and it tarnishes and oxidizes rapidly in air.In this work, we investigate how to profile thick Li layers (50 μm) deposited on SiO₂ substrates by a method based on plasma sputtering, involving both DC sputtering and evaporation simultaneously.A thick Li layer (≈10 μm) was covered with a thin stainless steel layer to prevent oxidation during transfer of the sample from the sputtering chamber and the accelerator. Li coatings were investigated by RNRA and neutron threshold reaction to obtain interdiffusion profiles of the different components and their concentration. The depth profile using the ⁷Li(p,γ)⁸Be^∗ resonance nuclear reaction occurring at 440 keV allows us to obtain Li concentration versus depth up to 50 μm.Preliminary results indicate that homogeneous Li layers can be obtained and protected against air, even though it diffuses into the encapsulated layers.     

Local studies in horizontal gas–liquid slug flow

The axial liquid-phase velocity profile development in a horizontal air–water plug/slug flow-pattern was experimentally investigated by simultaneously using two hot-film anemometers. One of the probes which was kept in a fixed location was exclusively used as a phase identifier while the other probe was traversed vertically for local velocity measurements. The experimental observations were focused on the intermittent and transient characteristics of the slug flow-pattern. It was shown that the velocity rapidly develops into an asymmetric but nearly fully-developed profile within liquid slug with the maximum value occurring below the pipe center line. On the other hand it was documented that the velocity never develops into a quasi-fully-developed profiles within the liquid layer below a passing slug. At a given location the velocity gradually decelerates toward the gas slug tail, but rapidly accelerates towards the wake of the gas slug.     

Depth resolution enhancement by combined DSIMS and TOF-LEIS profiling

A combination of dynamic secondary ion mass spectroscopy (DSIMS) and time-of-flight low-energy ion scattering (TOF-LEIS) has been applied to acquire a composition depth profile of MoSi multilayers. During the sequential Ar⁺ sputtering secondary ions were monitored while in-between the sputtering cycles the TOF-LEIS spectra of scattered He neutrals were acquired. All the measured TOF-LEIS spectra versus sputtering time were displayed in one bitmap from which the depth profiles for different scattering depths were derived and analyzed. Analyzing the TOF-LEIS spectra of He particles scattered from the areas below the layer altered by ion-beam mixing led to an improvement of the depth resolution. In this way the resolution limits due to mixing phenomena can be overcome. Finally, the direct comparison of the DSIMS and TOF-LEIS depth profiles was carried out.     

Development of a Double Layered Scintillator for Separating and Detecting Low Energy Protons and Electrons

A scintillator system consisting of a thin (5,000 ? - 15,000 ?) CsI(Tl) layer evaporated onto a plastic scintillator (NE-102) has been developed for the purpose of distinguishing low energy protons from electrons and measuring the energy of each species. Evaporations in a high vacuum (10-8 Torr) produced layers of CsI(Tl) that scintillate with an efficiency comparable to optimally doped bulk material, If the CsI(Tl) layer thickness is 15,000 ?, it stops protons with energies below 170 keV and electrons with energies below 18 keV. Thus, protons with energies between about 25 and 250 keV can be distinguished from electrons with energies above 18 keV by examining the shape of the light pulse generated in the dual scintillator. Results obtained with protons and electron beams will be presented.     

Microbeam analysis of lateral inhomogeneity in depth penetration of Pd in porous silicon

Porous silicon (PS) is widely utilized in gas sensors. Palladium is a good choice to sensitize the surface of PS to hydrogen. Ideally for highest sensitivity of the sensor, all the pores of PS should be completely covered with palladium. Rutherford backscattering spectroscopy (RBS) technique is routinely used to determine depth profile of elements in thin layers. By using microbeam analysis as a complementary technique, we clearly observed the lateral image of penetrated Pd in depth. In this work, we used electrochemically anodized-silicon wafer doped with Pd by the electroless process. In our analysis, we intentionally characterized both the area of PS where Electric Field is applied during silicon etching (EF area) and the Field Free region (FF area) of the sample. Microbeam analysis show that EF area of the sample is covered with thicker palladium layer, but the pores are rarely filled in this area, while in the FF area of the sample, there is a thin palladium film on the silicon surface, but the pores are partially filled. We used a computational simulation method based on columnar pore structure and linear variation of Pd depth profile in pores and determined the lateral variation of Pd penetration in pores in both parts of the sample. These simulations showed that there are 180 ± 80 nm thick Pd layer with 300 ± 200 nm penetration in pores in EF region and 80 ± 40 nm thin Pd layer with 800 ± 200 nm penetrate in pores in FF region.     

Peculiarities of defect generation in Si+-implanted GaAs (2 1 1)

Peculiarities of the defect generation during implantation of (2 1 1) GaAs with Si⁺ ions and doses below the amorphisation dose of GaAs have been investigated by X-ray diffraction, the secondary ion mass-spectroscopy (SIMS) and transmission electron microscopy. It was shown, that in such implanted layers less radiation defects will be formed and these defects are more easily annealed by rapid photon annealing (RPA) than in (1 0 0)-oriented wafers.     

Synthesis of single-crystalline Al layers in sapphire

Single-crystalline, buried aluminium layers were synthesized by 180 keV high-dose Al⁺ ion implantation into sapphire at 500°C. The approximately 70 nm thick Al layers exhibit in XTEM investigations locally abrupt interfaces to the single-crystalline Al₂O₃ top layer and bulk, while thickness and depth position are subjected to variations. The layers grow by a ripening process of oriented Al precipitates, which at low doses exist at two different orientations. With increasing dose, precipitates with one out of the two orientations are observed to exist preferentially, finally leading to the formation of a single-crystalline layer. Al outdiffusion to the surface and the formation of spherical Al clusters at the surface are found to be competing processes to buried layer formation. The formation of Al layers is described by Rutherford Backscattering Spectroscopy (RBS), Cross-section transmission electron microscopy (XTEM) and Scanning electron microscopy (SEM) studies as a function of dose, temperature and substrate orientation.     

Depth profiling of carbon in silicon using the C(p, p′γ) reaction

An analytical method has been developed for the measurement of a carbon depth profile of the region a few tens of μm from the surface, using a ¹²C(p, p′γ) reaction. Measurements for a SiC sample coated with a silicon layer and a carbon-implanted silicon sample were performed using this method. Two charged particle detectors and two γ-ray detectors were utilized for the coincident detection of scattered protons and γ-rays from the first excited state (E_x = 4.4 MeV) of ¹²C. The measured depth profiles agree well with results obtained using a surface profiler and an Auger microprobe. These results demonstrate that this method is useful for the non-destructive analysis of carbon at depths of a few tens of μm from the surface.     

陨石中宇宙成因核素~(53)Mn的放化中子活化分析

本文介绍了陨石中宇宙成因核素~(53)Mn的放化中子活化分析方法,给出吉林陨石钻孔样品~(53)Mn的分析结果。     

Relaxation of strain during solid phase epitaxial growth of Ge+ ion implanted layers in silicon

Formation of Si_1−xGe_x-alloy layers by solid phase epitaxial growth (SPEG) of Ge⁺ ion implanted silicon has been studied. The ion implantations were performed with 40, 100, 150, 200 and 300 keV ⁷⁴Ge⁺ ions and various ion doses. The SPEG of the ion implanted layers was carried out in a conventional furnace at 850°C for 20 min under a flow of nitrogen gas. The Si_1−xGe_x-alloy layers were characterised by Rutherford backscattering spectrometry and transmission electron microscopy (TEM). For a given ion energy, a Si_1−xGe_x-alloy layer with no observable extended defects can be manufactured if the ion dose is below a critical value and strain-induced defects are formed in the alloy layer when the ion dose is equal to or above this value. The critical Ge⁺ ion dose increases with ion energy, while the critical maximum Ge concentration decreases. For ion energies ⩽150 keV, the defects observed in the alloy layers are mostly stacking faults parallel to the {1 1 1} planes. For higher ion energies, 200 keV and above, the majority of defects in the alloy layer are hairpin dislocations. In the whole ion energy range, the critical ion dose and the depth position of the nucleation site for the stacking faults obtained from the measurements are in good agreement with theoretical predictions. Extended defects are formed in the alloy layer during the SPEG when the regrowth of the crystalline/amorphous interface has reached the depth position in the crystal where the accumulated strain energy density is equal to the critical value of 235 mJ/m².     

我国膳食中~(90)Sr、~(137)Cs、~(226)Ra、~(228)Ra、~(210)Pb 和~(210)Po含量及其所致内照射剂量

作为1990年全国总膳食调查的放射性物质部分,本文报道了组成我国膳食的各类食品中~(90)Sr、~(137)Cs、~(226)Ra、~(228)Ra、~(210)Pb 和~(210)Po 含量的测定结果;按调查所得膳食组成和食品中核素含量,估算了我国居民(成年男子)当前这些核素经食入所致年摄入量和待积有效剂量当量。结果表明,每年食入所致总待积有效剂量当量约为0.24 mSv,贡献较大的食品是蔬菜、水产品和谷类,贡献较大的核素为~(210)Pb、~(210)Po 和~(228)Ra。这些结果更新了我国膳食中这些核素的资料,补充了来自饮水的数据。文中还讨论了我国膳食组成的地区差异及其对居民摄入量和所致内照射剂量的影响。     

狗经氡子体暴露后血、毛中~(210)Pb 和~(210)Po 含量的动态变化

本文叙述了实验狗经氡子体暴露后血、毛中~(210)Po、~(210)Pb 含量、~(210)po/~(210)Pb 比率及血中~(210)Po,~(210)Pb 排出的动态变化。