Chemical and isotope composition of baltic iron-manganese concretions

Methods of processing iron-manganese concretions from the Gulf of Finland in the Baltic Sea are reported. The relative content of their basic components is found. The concentration of helium isotopes in and the rate of growth of these concretions (7.5 mm/thousand years) are determined. It is shown that the content of the cosmic matter in the concretions can be raised by means of special chemical processing.     

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对ITER包层屏蔽块进行了热工水力学设计及分析,并给出了两套合理的加热方案.分析结果表明,可以通过分阶段改变入口气体温度的方法实现在高效加热屏蔽块的同时满足工程及部件热应力的技术要求,并通过热应力计算验证了加热过程不会对屏蔽块产生不可预期的结构破坏.     

ITER屏蔽块真空热氦检漏装置热工水力学设计与分析

对ITER包层屏蔽块进行了热工水力学设计及分析,并给出了两套合理的加热方案。分析结果表明,可以通过分阶段改变入口气体温度的方法实现在高效加热屏蔽块的同时满足工程及部件热应力的技术要求,并通过热应力计算验证了加热过程不会对屏蔽块产生不可预期的结构破坏。     

冷热坩埚中电子枪加热金属熔池的数值分析

利用NavierStokes方程在一定的边界条件下求解了电子枪加热长槽形冷、热坩埚中的二维熔池流场,获得了熔池流场的速度和温度分布,并且详细地对比研究了冷、热坩埚中金属熔池的蒸发量与电子枪功率、束宽以及坩埚尺寸的关系.电子枪功率越高、束宽越小(除非小于05mm)、坩埚尺寸越大,则蒸发量越大,电子枪能量的有效利用率也越高.当电子枪束宽较大时,热坩埚的蒸发量较大,而当束宽较小时,冷坩埚的蒸发量较大.计算中对铁、铜、钆和铝等金属熔池进行了数值分析,获得了相似的结果. 关键词： NavierStokes方程 热毛细流 浮力流 金属熔池     

Use of a hollow cathode for determining gases in solids by the isotope balancing method

A method for the spectral isotopic determination of gases in solids has been developed. The technique involves the use of a discharge tube of the hot hollow-cathode type with two graphite cathodes. Melting of the specimen for the purpose of isotope balancing takes place in one of the cathodes and excitation of the gas luminescence before and after equalization of the isotope composition takes place in the other. A special device makes it possible to introduce the specimen into the isotope balancing zone without interfering with the vacuum. The mode of source operation and the conditions of isotope balancing and spectrum excitation are investigated.     

高密度氦相变的分子动力学研究

采用分子动力学方法结合对关联函数分析计算了0–1000 K范围内氦的固–液相变曲线, 与实验数据的对比显示, 在0–500 K之间与实验数据符合很好, 500 K以上还没有相应的实验数据. 另外, 计算了钛金属中不同尺寸氦泡的压强, 并与高密度氦的固–液相变曲线进行了对比. 结果显示, 在低温条件下, 随着温度的降低, 钛晶体中可能会出现固态氦泡; 在300 K以上不会存在固态氦泡.     

Melting of aluminum nitride at atmospheric nitrogen pressure

Experimental results on the melting of aluminum nitride heated by an electric arc burning in a nitrogen atmosphere at a pressure of 0.2–0.3 MPa are presented. A qualitative explanation of the dissociation suppression mechanism under arc heating is proposed. It has been shown that the suppression is possible at atmospheric pressure due to the photoactivation of aluminum on the sample surface by resonant radiation of aluminum vapors present in the electric arc.     

Fine structure and hyperfine structure of some excited states of helium

The fine structure and the hyperfine structure for some singly-excited and doubly-excited states of helium atom are calculated using Rayleigh-Ritz variational method with multi-configuration-interaction wave functions. The calculated results of the fine structure for the Rydberg series are in good agreement with other theoretical and experimental data. The hyperfine parameters and the hyperfine coupling constants of ³He are also obtained for this system.Received: 17 January 2003, Published online: 29 July 2003PACS: 32.10.Fn Fine and hyperfine structure - 31.30.Gs Hyperfine interactions and isotope effects, Jahn-Teller effect     

无磁杜瓦粘接接头真空性能的实验研究

采用氦质谱仪测量了不同工况下 ,铝、玻璃钢和不锈钢等材料间螺纹粘接接头处的漏率 ,结果表明螺纹接头可以得到很好的真空性能 ,可以满足无磁杜瓦的技术要求     

Isotope distribution in nuclear multifragmentation

A statistical multifragmentation model is used to analyze the isotope distribution of medium sized nuclei produced in p + Kr reactions at high bombarding energies. The results show that the evaporation processes narrow significantly the primordial hot fragment distributions and washes out almost completely the patterns associated with the isotope distributions in the primary fragments. Thus the calculation supports a scenario in which the formation of hot primary fragments is assumed. From adjustments to the experimental data an excitation energy per nucleon of the initial system is found to range from 3.5 to 7 MeV.     

Stable isotope geochemistry of calcrete nodules and septarian concretions in a Quaternary 'red clay' paleovertisol from Hungary

Calcrete nodules and concretions in unusually large amounts are embedded in the Quaternary clay-rich (Vertisol-type) 'red clay' soil-sedimentary complex at the pediment of the Mátra Mountains (Hungary). Stable isotope signatures were studied in nodules and septarian concretions, uncommon due to their several millimeter sized calcite crystals filling voids and fractures, to reveal their origin. The isotope composition of calcrete covers a wide range: delta18O=-5.9 to-10.4 per thousand and delta13C=-8.9 to-12.3 per thousand (vs. V-PDB). Isotope compositions support pedogenic (sensu stricto) and/or shallow groundwater origin for the calcrete nodules and concretions, the role of 'evolved' (isotopically modified) groundwaters in the formation of secondary carbonate was possibly subordinate. Late-stage, large, Mn-rich euhedral calcite crystals in concretions have the lowest delta13C values, which are interpreted as a result of larger contribution of isotopically light organic carbon due to decomposition of organic matter under reducing conditions. Precipitation of late calcite crystals in concretions occurred in early diagenetic environment after shallow burial of the 'red clay' paleovertisol.     

Single-nucleon and heavy recoil spectra in intermediate energy heavy-ion reactions

We study the nucleon emission spectra from a local large-volume hot zone formed in intermediate energy (～ 20–100 MeV/nucleon) heavy-ion reactions. The hot zone is continuously being cooled by nucleon emission while the cold nuclear matter surrounding the hot zone is being heated up by nucleon absorption until full thermal equilibrium is reached. The sequential evaporation from the equilibrated reaction complex is followed up. The recoil properties of the residual heavy fragments are also investigated.     

冷坩埚磁悬浮熔炼的电磁场分析

针对冷坩埚熔炼过程的悬浮特性问题,利用准三维耦合电流算法,就坩埚结构、电磁频率及感应圈电流等影响因素进行分析,为冷坩埚结构和磁悬浮熔炼的优化设计提供依据。结果显示,冷坩埚熔炼时,电磁场频率和冷坩埚结构决定坩埚的透磁能力,随频率上升,坩埚内磁通密度下降,且频率高于100kHz时下降趋势加大;其次,冷坩埚的分瓣结构使其涡流损耗降低,且磁场频率越高效果越明显。对100kHz以上的超高频磁场,坩埚应分割为(16~20)瓣;对(10~100)kHz的高频磁场,坩埚可分割为(8~12)瓣;而对低于10kHz的中高频磁场,坩埚只需分割(4~8)瓣。再者,熔体的磁悬浮力与感应圈电流成平方关系,且电磁场频率越高则磁悬浮力越大。     

Aluminum mirror degradation in a vuv laser

Thermal calculations have been made for overcoated aluminum mirror structures of the type used in vacuum uv lasers. The resulting thermal profiles suggest the dominant mechanism for mirror failure to be melting of the aluminum. Design parameters to avoid rapid mirror degradation are discussed.     

Improving the material quality of silicon ingots by aluminum gettering during crystal growth

We present a method for the purification of silicon ingots during the crystallization process that reduces significantly the width of the low charge carrier lifetime region at the ingot top. The back‐diffusion of impurities from the ingot top is suppressed by adding a small amount of pure aluminum into the silicon melt right at the end of the solidification. We study the aluminum gettering effect by instrumental neutron activation analysis (INAA) and Fe_i imaging. Furthermore, we present a model for aluminum gettering of Fe in the silicon ingot that is in agreement with literature data for aluminum gettering at lower temperature. The distribution of iron in the ingots with and without aluminum is fairly well predicted by a combination of this model with a model for Fe contamination from the crucible system. A simulation with varying Al content exhibits further potential for an increased yield of silicon wafers with high charge carrier lifetime. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

电子束激发原子对金属蒸发的影响

在原子蒸气激光同位素分离工程(AVLIS)中,金属受电子束的加热而熔化,并向真空蒸发,蒸气原子通过电子束的过程中,可能与电子发生非弹性碰撞,被激发到高能级.在膨胀的过程中,高能级的原子通过与原子的非弹性碰撞消激发,将原子内的电子能量转换为蒸气的平动能.为了分析电子束与原子作用对蒸气的密度、速度和温度等物理特性的影响,采样直接模拟蒙特卡罗法(DSMC)模拟钆原子蒸发过程.模拟结果表明,电子束与原子的作用使得原子蒸气的速度增加,密度减小,温度升高 关键词： 金属蒸发 AVLIS DSMC 电子枪     

散裂靶中质子束窗的散射效应

 质子束窗是在高功率靶区中的一个分界窗,它将质子输运线上高真空区域和氦容器中的氦环境分开。在其他散裂中子源中质子束窗的热效应以及机械问题都已经被研究过了,但质子束在该窗中散射效应的研究却很少被报导,然而在靶设计中如果没有处理好质子束窗的散射效应会有很大的问题。报导了质子束窗散射效应的模拟计算结果,包括不同质子束窗的材料和结构选择,并以中国散裂中子源（CSNS）为例,介绍了在CSNS一期和二期中质子束窗采用周边水冷的铝合金单层结构,CSNS三期采用中间水冷的铝合金夹层结构。文中给出了不同结构的质子束窗和不同的与靶距离散射效应对靶上经非线性磁铁均匀化的束流分布的影响的模拟计算结果。模拟结果显示质子窗的散射效应对束流损失和靶上的束流分布有重要的影响。     

Calculation of laser-induced temperature field on moving thin metal foils in consideration of Stefan problem

A temperature field on a moving thin sheet heated by a high-quality laser beam (TEM₀₀) is calculated. Effects of melting and solidification of sheet material is taken into account. Convective and radiation cooling is included into a mathematical model. Nonlinear effects connected with temperature dependencies of material properties are considered. An explicit finite-difference numerical method was used to calculate the non-steady-state 2D and 3D Stefan problems. A surface, on which the melting occur, is replaced by a zone of finite thickness. All physical properties in this zone are smoothed and considered as continuous values. Evaporation of liquid metal begins when temperature reaches some critical value. This effect is also included in the developed model. As a result, the geometry of the melting zone can be derived and is compared with a cross section of real laser welding seem.     

基于微束X射线荧光的铸轧7B05铝合金元素偏析研究

材料内部微观尺度上成分、组织结构控制精度低、波动大是制约高铁铝合金国产化进程的重要原因,因此从微观尺度上研究大尺寸铝合金成分均匀性至关重要.鉴于目前研究铝合金偏析的区域通常较小且不连续,定量统计方法过于简单.使用微区分辨率较高的微束X荧光与原位定量统计分布分析技术相结合的方法,从点、线、面、频度分布等方面对成分分布数据...     

晶体生长角和凝固速率对贵金属电子束区域熔炼晶体生长的作用

基于电子束区域熔炼中熔区上力的平衡关系式, 计算获得了基座法、等径区熔法两种工艺下稳定成形熔区高度的表达式, 探讨了试样尺寸、晶体生长角和凝固速率等参数对六种贵金属稳定成形熔区高度的影响. 结果发现, 区熔相同尺寸试样时, 六种贵金属能够稳定成形熔区高度大小依次排序为 Ru> Pd> Ir> Pt> Ag> Au. 同时获得了这六种贵金属的晶体生长角在8.4°-10.7°之间, 而实际的晶体生长角与界面生长机制有关. 在基座法中, 连续生长机制所能支撑的熔区高度最小, 而等径区熔法中连续生长机制支撑的熔区高度大于位错生长机制和小面生长机制. 这三种晶体界面生长机制中连续生长方式对晶体生长角和区熔熔区高度影响较小, 有利于贵金属区熔单晶制备. 另外当凝固速率达到2.4 mm·min^-1, 位错和小面生长机制对区熔熔区高度的影响也变得很小, 预测的工艺参数与Ir和Ru单晶区熔实验报道结果基本符合.