Surface Structure Modification and Deuterium Retention in Tungsten under Pulsed Plasma Loads

Modification of the surface layer and deuterium accumulation in tungsten targets under plasma irradiation in a quasi-stationary plasma accelerator with an intrinsic magnetic field QSPA-T, which reproduces the conditions (plasma thermal load of 0.2-5 MJ/m2, pulse duration of 0.1-1.2 ms) typical of ELM events in ITER, are studied. Using a scanning electron microscope, structure modifications at the surface and in the bulk after deuterium plasma irradiation are analyzed. The observed changes in the near-surface layer are compared with the calculated data on the change in the internal structure of tungsten under intense thermal action obtained as a result of the numerical solution of the heat conduction problem. The total deuterium retention in the samples was measured using thermal desorption spectroscopy, and it was in the range of (3-4) × 1016 particles/cm2 for the samples melted during plasma exposure. These numbers exceed by an order of magnitude the values obtained for samples without traces of melting.     

Deuterium-ion implantation into composite structures with tungsten coatings

The results of studying the accumulation and thermal desorption of ion-implanted deuterium from tungsten films deposited on various composite substrates are presented. The influence of the tungsten-film thickness and irradiation dose with D⁺ ions of intermediate energy on the amount of trapped deuterium and the shape of the spectra of the thermal desorption of deuterium in vacuum are studied. Possible mechanisms of these processes are discussed.     

Ion-implanted deuterium accumulation in a deposited tungsten coating

The effects of trapping of ion-implanted deuterium and its thermal desorption on the structure and stressed state of a tungsten coating deposited on a composite substrate is studied. The amount of accumulated deuterium, macrostresses of the coating, and the shape of thermal desorption spectra are shown to depend on the D⁺ ion fluence and the irradiation temperature. Possible mechanisms of these processes are proposed.     

Deuterium accumulation in tungsten under low-energy high-flux plasma exposure

The accumulation of deuterium implanted in tungsten is simulated within the framework of kinetic diffusion theory. The influence of the tungsten microstructure (dislocation density and impurity concentration) on the process of deuterium capture and accumulation is considered. It is established that, under the chosen irradiation conditions, deuterium accumulation in the near-surface region is determined by capture at defects formed during implantation. The deuterium concentration gradient, together with the material microstructure, determines its accumulation in tungsten. Variation in the dislocation density and impurity concentration does not affect the simulation results, which is, first, related to the fact that the model used does not contain alternative mechanisms for the formation and growth of vacancy clusters under the subthreshold irradiation mode. The simulation results are compared with experimental data, and ways of improving the model are discussed in order to explain the deuterium-saturation effect for high fluences (more than 10²³ m^?2).     

Mobilization of tungsten dust by electric forces and its bearing on tritiated particles in the ITER tokamak

Experimental investigations on the electric field strength required to overcome the adhesion forces of micron size tungsten metallic dust as well as silver and aluminum oxide in powdery form deposited on a conductive surface are presented. The results reveal a strong influence of particulate surface properties on the detachment threshold, especially for tungsten particles which exhibit a thin surface oxide layer that screens their electrical conductivity. Such tungsten particles makes possible that electrostatic self-charging occurs when tritiated because of their dielectric properties even if there are deposited on a conductive grounded surface.     

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculated when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.     

强激光场中氘团簇双重膨胀引发核聚变

在超强fs激光与氘团簇的相互作用中, 分析了可以引发核聚变的高能氘核产生的原因,提出了团簇双重膨胀的机制,计算了氘核动能及团簇解体的时间, 为选取合适的激光脉冲宽度参数提供参考. Considering the Coulomb explosion induced by the interaction of a deuterium cluster target with ultra intensity femtosecond laser,the causation which generate energetic deuterium nuclei for the fusion has been analyzed. The mechanism for the dual explosion of deuterium cluster is proposed, and hence the velocity of deuterium nuclei and the expansion time of deuterium ion clusters have been estimated.     

Deuterium High-Pressure Target

The design of deuterium high-pressure target of 76 cm³ volume developed to study muon catalyzed fusion in diffusion-pure deuterium over an 80–800 K temperature range at up to 150 MPa pressure is presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hydrogen Retention in Tungsten Alloys Developed for Fusion Facilities (Review)

This review is focused on the effect of doping with various elements on retention in tungsten. Although tungsten is one of the most promising plasma-facing materials (PFMs), it still has a number of drawbacks. Doping is proposed as a way to make tungsten more suitable for PFM applications. A considerable number of tungsten alloys have already been developed in the course of fusion research. Doping may alter the parameters of hydrogen retention in tungsten, and this should be taken into account in selecting the materials for fusion facilities.     

Study of the impact of steady-state plasma on radiation-damaged tungsten

Experimental studies of tungsten (as a candidate plasma-facing material for a fusion reactor) whose properties will degrade as a result of its contact with near-wall plasma and irradiation with neutrons are performed. The effect of a high level of radiation damages (1–100 displacements per atom) on deuterium accumulation and erosion caused by tungsten irradiation with deuterium plasma was studied. Radiation damages are obtained as a result of the irradiation of tungsten samples with high-energy ions in an accelerator (He⁺², C⁺³, 4–10 MeV). Then the samples are exposed to steady-state deuterium plasma at the LENTA facility (National Research Centre Kurchatov Institute). The effects of the erosion of tungsten and accumulation of hydrogen isotopes in it are studied. Modification of the surface microstructure and radiation swelling is observed. The helium and deuterium concentrations were measured using the methods of nuclear elastic backscattering and elastic recoil detection analysis. An increased accumulation of deuterium in the damaged layer to a depth of about 5 μm is revealed.     

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In part one published in the last issue, the tritium retention and the total tritium inventory in PFC materials of FEB-E fusion reactor had been calculated. The tritium well depth, tritium well time during the FEB-E fusion reactor start-up and initial operation phase had been obtained. In this part, how to improve tritium recovery efficiency in the ITER TBM solid breeder blanket with using purge gas has been discussed. Some new innovative schemes for reducing tritium retention and improving tritium recovery efficiency are proposed. Such as, sponge mechanism based on deuterium saturated PFC materials; deuterium and beryllium co-deposition layer created on first wall surface; SPB scheme for enhancing tritium recovery efficiency of purge gas in ceramic breeder blanket based on the electrical polarization rotations catalyzing isotope exchange rate enhancement resulted from applied low frequency electric-field, of Li4SiO4 grain and purge gas molecular particles and so on, are explored.     

聚变堆氚系统设计中的一些重要问题研究(Ⅱ)

在文献[1]中,计算了FEB-E 聚变堆PFC 材料内的氚滞留量、堆系统总的氚投料量、启动运行开始阶段的氚坑深度和氚坑时间大小。这里将讨论在ITER 的TBM 氚增殖包层内固体氚增殖剂中的氚如何高效率地被载氚气体带出并且以高效率地提取回收。本部分将进行创新的探索性研究并且提出某些减少氚滞留量和改善氚提取回收效率的新方案,例如：基于氘饱和的海绵效应;第一壁表面建立氘和铍的伴同沉积层;基于在低频外电场作用下载氚气分子和硅酸锂颗粒电极化旋转催化同位素交换速率的增强载氚气提取氚效率“SPB 方法”。     

Deuterium Distribution in Crude Oil

Abstract

The aim of this paper is to rehabilitate informative potential of using deuterium as a natural tracer in geofluids investigations and to illustrate how the deuterium concentration from geological fluid links the micro-scale effects to the macro-scale processes.

Research on the deuterium concentration of crude oils formerly has highlighted the role of deuterium as a natural tracer during diagenesis. We discuss how the deuterium abundance in oil and water from sedimentary basins provides information on dynamics of hydrocarbons reservoirs.

We can obtain qualitative and quantitative information about the dynamics of fluids from deposit by deuterium concentration monitoring from geofluids (gas-oil-water).     

Efficiency of Tungsten Dust Collection of Different Types of Dust Particles by Electrostatic Probe

Formation of dust particles and clusters is observed in almost every modern thermonuclear facility. Accumulation of dust in the next generation thermonuclear installations can dramatically affect the plasma parameters and lead to the accumulation of unacceptably large amounts of tritium. Experiments on collection of dust particles by a model of electrostatic probe developed for collection of metallic dust at ITER are described in the article. Experiments on the generation of tungsten dust consisting of flakes formed during the destruction of tungsten layers formed on the walls of the plasma chamber sputtered from the surface of the tungsten target by plasma ions were conducted. The nature of dust degassing at elevated temperatures and the behavior of dust in an electric field were studied. The results obtained are compared with the results of the experiments with dust consisting of crystal particles of simple geometric shapes. The effectiveness of collection of both types of dust using the model of an electrostatic probe is determined.     

钨中氢同位素热脱附实验的速率理论模拟研究

本文采用基于速率理论的模拟方法研究钨材料中氢同位素氘的热脱附谱. 热脱附数据来源于520 K下受等离子体辐照的多晶钨, 入射离子能量为40 eV, 剂量为1× 10²⁶ D/m². 通过调节速率理论中的俘获能、俘获率等参数, 最终获得与实验相符合的热脱附拟合谱. 拟合结果表明, 钨中俘获的氘存在于三种俘获态, 俘获能分别为1.14 eV, 1.40 eV和1.70 eV, 相应脱附温度峰值为500 K, 600 K和730 K. 这三个俘获能分别应对应于第一原理计算得到的空位俘获第3–5个氢原子的俘获能(含零点振动能修正)、空位俘获第1–2个氢原子的俘获能, 空位团簇对氢原子的俘获能. 模拟结果表明, 在本辐照实验条件下, 钨中空位及空位团簇是氘在钨中的主要俘获态.     

Accumulation of deuterium in radiation-damaged tungsten

Experimental studies have been performed to determine the effect of high-level radiation damage on the accumulation of deuterium and erosion of tungsten samples exposed to deuterium plasma. Tungsten samples were exposed first to fast helium ions having an energy of 3–4 MeV (providing from one to ten displacements per atom) and then to deuterium plasma up to a dose of 10²⁵ ion/m². The effects of deformation and modification of the surface microstructure have been observed. The concentrations of helium and deuterium have been measured by the methods of elastic nuclear proton backscattering and nuclear recoil detection of helium ions. A high concentration of deuterium in the damaged layer of a tungsten sample has been measured, and helium has been detected in a layer ～5 μm thick. The proposed method shows promise for determining the lifetime of materials used in fusion reactors and measuring the concentration of tritium accumulated in these materials.     

北京市区绿色空间滞尘分布反演研究

北京市作为中国政治中心和京津冀特大型城市,近40年来城市化进程迅速,大气颗粒物和尘埃粒子污染问题较为突出,发挥绿色空间滞尘功能具有重要现实意义。将高光谱技术与遥感技术相结合,反演了市域尺度绿色空间滞尘分布。以北京市区绿色空间常见植被大叶黄杨(Euonymus japonicus)为研究对象,通过室外采样与室内试验获取叶片样本的滞尘量、光谱反射率和叶面积等数据,比较叶片滞尘前后的原始光谱曲线和反射率一阶导数特征,分析不同滞尘量对光谱反射率的影响,探究对叶片滞尘量高度敏感的波段。利用光谱响应函数将地面采集的窄波段光谱反射率数据分别转化遥感卫星的宽波段光谱反射率数据,建立对应卫星波段植被指数比值与滞尘量的回归模型,选取拟合效果最好的回归模型作为滞尘反演模型。结合GF-2影像所提取北京市区绿色空间范围,采用滞尘反演模型获取北京市区绿色空间滞尘分布。进而插值得到北京市区尘埃污染分布,采用空间自相关模型检验其空间聚集特性。结果表明：740～1 870 nm波段,滞尘后光谱反射率明显低于滞尘前反射率,滞尘对红边、黄边、蓝边位置没有明显影响,对“红边幅值”和“红边面积”影响较明显,利用Sentinel...     

Hydrogen interaction with Al2O3-coated tungsten under plasma irradiation

The effect of amorphous films of Al₂O₃ on deuterium trapping in polycrystalline tungsten under plasma irradiation (150 eV/D) and high fluence (up to 4 × 10²⁴ D/m²) was studied by the methods of nuclear reaction product spectroscopy and thermal desorption spectroscopy. It was determined that the hydrogen permeation blocking properties of aluminium oxide lead to a great increase in deuterium trapped in tungsten. With the complete erosion of the film, this effect continues but with a lower amplitude. Extrapolation of this property to beryllium oxide implies that the presence of beryllium oxide on the surface of the tungsten tiles of the ITER leads to a considerable increase in the tritium inventories accumulated in them.     

Sputtering of tungsten, tungsten oxide, and tungsten-carbon mixed layers by deuterium ions in the threshold energy region

An original experimental method is developed for determining the sputtering coefficients of electrically conducting materials during bombardment by light gas ions at threshold energies. This information is very valuable in both purely scientific and practical terms. The basis of the method is a special field-ion-microscopic analysis regime. The procedure for measuring the sputtering coefficients includes cleaning the surface by field desorption and evaporation, with the subsequent work on an atomically clean and atomically smooth surface. The method permits identification of single vacancies on the irradiated surface, i.e., it is possible to count individual sputtered atoms. The method is tested on commercially pure tungsten, tungsten oxide, and a W-C mixed layer on tungsten under deuterium ion bombardment. The energy dependences of the sputtering coefficients of these materials for sputtering by deuterium ions at energies of 10–500 eV are obtained and analyzed. An important relationship between the energy threshold for sputtering and the conditions for oxidation of tungsten is found. The energy threshold for sputtering of an oxidized tungsten surface is 65 eV. The energy threshold for sputtering of the W-C mixed layer is almost equal to the corresponding value for pure tungsten. Zh. Tekh. Fiz. 69, 137–142 (September 1999)     

Electron impact desorption of hydrogen on tungsten: I. Pure hydrogen lasers

The electron impact induced desorption of H⁺ ions from hydrogen layers on thermally annealed polycrystalline tungsten ribbons has been investigated mass spectrometrically. In agreement with Benninghoven et al. (1972) and Madey (1973) the more strongly bound β₂-state has been found to have a higher EID cross section than the more weakly bound β₁-state. Ionic and total desorption cross sections have been measured at 100 eV; the obtained values agree with the lower values published to data, which suggests that the much higher values reported by some authors do not apply to pure hydrogen layers. The contributions of the different states have also been investigated using partial coverage with deuterium. The implications of the findings for the understanding of the adsorption states of hydrogen on tungsten and for the mechanism of EID are discussed.