Effects of Low Energy and High Flux Helium／Hydrogen Plasma Irradiation on Tungsten as Plasma Facing Material

The High-Z material tungsten (W) has been considered as a plasma facing material in the divertor region of ITER (International Thermonuclear Experimental Reactor). In ITER, the divertor is expected to operate under high particle fluxes (> 1023 m-2s-1) from the plasma as well as from intrinsic impurities with a very low energy (< 200 eV). During the past dacade, the effects of plasma irradiation on tungsten have been studied extensively as functions of the ion energy, fluence and surface temperature in the burning plasma conditions. In this paper, recent results concerning blister and bubble formations on the tungsten surface under low energy (< 100 eV) and high flux (> 1021 m-2s-1) He/H plasma irradiation are reviewed to gain a better understanding of the performance of tungsten as a plasma facing material under the burning plasma conditions.     

Surface Cracking Behaviors of Ultra-Fine Grained Tungsten Under Edge Plasma Loading in the HT-7 Tokamak

Tests of the candidate plasma facing materials(PFMs) used in experimental fusion devices are essential due to the direct influence of in-situ plasma loading.A type of ultrafine grained(UFG) tungsten sintered by resistance sintering under ultra-high pressure(RSUHP) method has been exposed in the edge plasma of the HT-7 tokamak to investigate its performance under plasma loading.Under cychc edge plasma loading,the UFG tungsten develops both macro and micro cracks.The macro cracks are attributed to the low temperature brittleness of the tungsten material itself,while the micro cracks are generated from local intense power flux deposition.     

Heat Transfer During Radio Frequency Inductively Coupled Plasma Deposition of Tungsten

Particle melting and substrate temperature are important in controlling deposited density and residual stress in thermal plasma deposition of refractory materials. In this paper, both the heating and cooling behaviours of tungsten particles inside a radio frequency inductively coupled plasma （ICP） and the plasma heat flux to the substrate were investigated. The distribution of the plasma-generated heat on device, powder injection probe, deposition chamber, and substrate was determined by measuring the water flow rate and the flow-in and flow-out water temperatures in the four parts. Substrate temperature was measured by a two-colour pyrometer during the ICP deposition of tungsten. Experimental results show that the heat flux to the substrate accounts for about 20% of the total plasma energy, the substrate temperature can reach as high as 2100 K, and the heat loss by radiation is significant in the plasma deposition of tungsten.     

Influence of a Static Magnetic Field on Laser Induced Tungsten Plasma in Air

In this work,laser induced tungsten plasma has been investigated in the absence and presence of 0.6 T static transverse magnetic field at atmospheric pressure in air.The spectroscopic characterization of laser induced tungsten plasma was experimentally studied using space-resolved emission spectroscopy.The atomic emission lines of tungsten showed a significant enhancement in the presence of a magnetic field,while the ionic emission lines of tungsten presented little change.Temporal variation of the optical emission lines of tungsten indicated that the atomic emission time in the presence of a magnetic field was longer than that in the absence of a magnetic field,while no significant changes occurred for the ionic emission time.The spatial resolution of optical emission lines of tungsten demonstrated that the spatial distribution of atoms and ions were separated.The influence of a magnetic field on the spatial distribution of atoms was remarkable,whereas the spatial distribution of ions was little influenced by the magnetic field.The different behaviors between ions and atoms with and without magnetic field in air were related to the various atomic processes especially the electrons and ions recombination process during the plasma expansion and cooling process.     

低能氦等离子体低温条件下钨材料的表面形貌

为研究氦等离子体在钨表面造成的表面纳米结构,利用荷兰基础能源研究所Pilot-PSI直线等离子体发生装置在673 K温度下,对钨材料进行了低能（40 eV）高束流强度（4×10²³ m^-2•s^-1）氦等离子体辐照。实验结果表明,辐照后钨材料表面出现了多种不同形态的纳米结构,表面纳米结构和晶粒的表面法向之间存在明显关联。在表面法向为［111］的晶粒表面出现三角形的纳米结构,在［110］取向的晶粒表面出现条带状的纳米结构,而在［001］取向的晶粒表面没有明显的结构出现。晶粒表面的纳米结构尺寸在50 nm左右,高度起伏在5 nm以下。另外,氦等离子体辐照会造成晶界处的高度差,在25 nm左右。分析推测氦等离子体辐照造成的晶粒表面和晶界的形貌可能是由近表面的气泡所导致的。     

Plasma Density Influence on the Properties of a Plasma Filled Rod Pinch Diode

The rod pinch diode is perfect as a source of accelerators for flash X-ray radiography by virtue of a small and stable spot.But it is not suitable for intensive current drivers because of high diode impendence of 40~60Ω.However,by employing pre-filled plasma into diode prior to the driving current,the diode impendence can be efectively reduced.Plasma density plays an important role in this process,especially for sheath formation and space charge current in the diode.Analysis and simulation results show that a proper range of plasma density could be 1015~1016cm-3.     

Enhanced Work Function of Al-Doped Zinc-Oxide Thin Films by Oxygen Inductively Coupled Plasma Treatment

Al-doped zinc-oxide(AZO) thin films treated by oxygen and chlorine inductively coupled plasma(ICP) were compared. Kelvin probe(KP) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the e?ect of treatment. The results of KP measurement show that the surface work function of AZO thin films can increase up to 5.92 eV after oxygen ICP(O-ICP)'s treatment, which means that the work function was increased by at least 1.1 eV. However, after the treatment of chlorine ICP(Cl-ICP), the work function increased to 5.44 eV, and the increment was 0.6 eV. And 10 days later, the work function increment was still 0.4 eV after O-ICP's treatment, while the work function after Cl-ICP's treatment came back to the original value only after 48 hours. The XPS results suggested that the O-ICP treatment was more e?ective than Cl-ICP for enhancing the work function of AZO films, which is well consistent with KP results.     

Determination of Plasma Parameters in a Dual-Frequency Capacitively Coupled CF4 Plasma Using Optical Emission Spectroscopy

Optical emission spectroscopy measurements of dual-frequency capacitively coupled CF4 plasmas were carried out.The gas temperature(Tg) was acquired by fitting the optical emission spectra of a CF B X system in 201~206 nm.The atomic fluorine concentration and the electron temperature(Te) were obtained by trace rare gas optical emission spectroscopy and a modified Boltzmann plot technique,respectively.It was found that the gas temperature was about 620±30 K at 50 mTorr and the atomic fluorine concentration increased while the electron temperature decreased with increasing gas pressure and power of high frequency(60 MHz).With increasing low frequency(2 MHz) power,the electron temperature also increased,but the atomic fluorine concentration was insensitive to this change.The generation and disappearance mechanisms of F atoms are discussed.     

多接收电感耦合等离子体质谱法对铀同位素丰度的测定

为了对环境监测提供有效、可靠的手段,在多接收电感耦合等离子体质谱(MC-ICP-MS)上建立了铀同位素丰度的分析方法。对影响仪器灵敏度的因素进行了初步探索,对标准物质GBW 04227和3个同位素丰度不同的样品中铀的各种同位素组分比值进行了测量,评价了测定结果的不确定度。结果表明,对丰度为3%、质量分数为2×10-7的235U溶液,R(235U/238U)丰度比的相对实验标准偏差优于0.02%,R(236U/238U)丰度比的相对实验标准偏差优于0.2%。     

Tuning Effect of N2 on Atmospheric-Pressure Cold Plasma CVD of TiO2 Photocatalytic Films

To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TiCl4 should be greater than the stoichiometric ratio (pO2 /pTiCl4>1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 (pO2 /pTiCl4=2.6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.     

Plasma Induced Grafting of PMMA onto Titanium Dioxide Powder

Grafting of polymer of methyl methacrylate （PMMA） onto titanium dioxide powder is investigated in this paper. The graft polymerization reaction is induced by dielectric-barrier- discharge produced N2 plasma treatment of titanium dioxide surfaces. IR, XPS and TGA results show that PMMA is grafted onto the surfaces of titanium dioxide powder. And crystal structure of the titanium dioxide powder observed with XRD spectra is unchanged after plasma graft polymerization.     

Breakdown Voltage Research of Penning Gas Mixture in Plasma Display Panel

Paschen law and equations, which ignore the influence of the Penning ionization on the electron ionization coefficient （α）, are always used as the approximation of the breakdown voltage criterion of the Penning gas mixture in current researches of discharge characteristics of the plasma display panel （PDP）. It is doubtful that whether their results match the facts. Based on the Townsend gas self-sustaining discharge condition and the chemical kinetics analysis of the Penning gas mixture discharging in PDP, the empirical equation to describe the breakdown of the Penning gas mixture is given. It is used to calculate the breakdown voltage curves of Ne-Xe/MgO and Ne-Ar/MgO in a testing macroscopic discharge cell of AC-PDP. The effective secondary electron emission coefficients （γeff） of the MgO protective layers are derived by comparing the breakdown voltage curves obtained from the empirical equation with the experimental data of breakdown voltages. In comparison with the results calculated by the Paschen law and the equation which ignore the influence of the Penning ionization on α , the results calculated by the empirical equation have better conformity with experimental data. The empirical equation characterizes the breakdown of the Penning gas mixture in PDP effectively, and gives a convenient way to study its breakdown characteristics and the secondary electron emission behaviors.     

Preliminary Study on Active Modulation of Polar Mesosphere Summer Echoes with the Radio Propagation in Layered Space Dusty Plasma

Radar echoes intensity of polar mesosphere summer echoes(PMSE) is greatly affected by the temperature of dusty plasma and the frequency of electromagnetic wave about the radar.In this paper,a new method is developed to explain the active experiment results of PMSE.The theory of wave propagation in a layered media is used to study the propagation characteristics of an electromagnetic wave at different electron temperatures.The simulation results show that the variation tendency of the reflected power fraction almost agrees with the results observed by radar in the European Incoherent Scatter Scientific Association(EISCAT).The radar echoes intensity of PMSE greatly decreases with the increase of the radio frequency and the enhancement of the electron temperature.     

Synthesis of Cu-Doped Mixed-Phase TiO2 with the Assistance of Ionic Liquid by Atmospheric-Pressure Cold Plasma

An atmospheric-pressure dielectric barrier discharge(DBD) gas-liquid cold plasma was employed to synthesize Cu-doped TiO_2 nanoparticles in an aqueous solution with the assistance of[C_2MIM]BF_4 ionic liquid(IL) and using air as the working gas.The influences of the discharge voltage,IL and the amount of copper nitrite were investigated.X-ray diffraction,N_2adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples.The results showed that the specific surface area of TiO_2 was promoted with Cu-doping(from 57.6 m~2·g~(-1) to 106.2 m~2·g~(-1) with 3%Cu-doping),and the content of anatase was increased.Besides,the band gap energy of TiO_2 with Cu-doping decreased according to the UV-Vis spectroscopy test.The 3%Cu-IL-TiO_2 samples showed the highest efficiency in degrading methylene blue(MB) dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min~(-1),which was 1.2 times higher than that of non-doped samples.According to the characterization results,the reasons for the high photocatalytic activity were discussed.     

Three-Dimensional Simulation of Plasma Deformation During Contact Opening in a Circuit Breaker,Including the Analysis of Kink Instability and Sausage Instability

A three-dimensional (3-D) transient model has been developed to investigate plasma deformation driven by a magnetic field and its influence on arc stability in a circuit breaker. The 3-D distribution of electric current density is obtained from a current continuity equation along with the generalized Ohm's law; while the magnetic field induced by the current flowing through the arc column is calculated by the magnetic vector potential equation. When gas interacts with an arc column, fundamental factors, such as Ampere's law, Ohm's law, the turbulence model, transport equations of mass, momentum and energy of plasma flow, have to be coupled for aria- lyzing the phenomenon. The coupled interactions between arc and plasma flow are described in the fl'amework of time-dependent magnetohydrodynamic (MHD) equations in conjunction with a K-~ turbulence model. Simulations have been focused on sausage and kink instabilities in plasma (these phenomena are related tO pinch effects and electromagnetic fields). The 3-D sjm- ulation reveals the relation between plasma deformation and instability phenomena, which affect arc stability during circuit breaker operation. Plasma deformation is the consequence of coupled interactions between the electromagnetic force and plasma flow described in simulations.     

Atmospheric-Pressure DBD Cold Plasma for Preparation of High Active Au/P25 Catalysts for Low-Temperature CO Oxidation

Cold plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure was adopted for preparation of commercial TiO2 Degussa P25 supported Au catalysts (Au/P25-P) with the assistance of the deposition-precipitation procedure.The influences of the plasma reduction time and calcination on the performance of the Au/P25-P catalysts were investigated.CO oxidation was performed to investigate the catalytic activity of thc Au/P25 catalysts.The results show that DBD cold plasma for the fabrication of Au/P25-P catalysts is a fast process,and Au/P25-P (4 min) exhibited the highest CO oxidation activity due to the complete reduction of Au compounds and less consumption of oxygen vacancies.In order to form more oxygen vacancies active species,Au/P25-P was calcined to obtain Au/P25-PC catalysts.Interestingly,Au/P25-PC exhibited the highest activity for CO oxidation among the Au/P25 samples.The results of transmission electron microscopy (TEM) indicated that the smaller size and high distribution of Au nanoparticles are the mean reasons for a high performance of Au/P25-PC.Atmospheric-pressure DBD cold plasma was proved to be of great efficiency in preparing high performance supported Au catalysts.     

Surface Decontamination of Chemical Agent Surrogates Using an Atmospheric Pressure Air Flow Plasma Jet

An atmospheric pressure dielectric barrier discharge (DBD) plasma jet generator using air flow as the feedstock gas was applied to decontaminate the chemical agent surrogates on the surface of aluminum, stainless steel or iron plate painted with alkyd or PVC. The experimental results of material decontamination show that the residual chemical agent on the material is lower than the permissible value of the National Military Standard of China. In order to test the corrosion effect of the plasma jet on different material surfaces in the decontamination process, corrosion tests for the materials of polymethyl methacrylate, neoprene, polyvinyl chloride (PVC), polyethylene (PE), phenolic resin, iron plate painted with alkyd, stainless steel, aluminum, etc. were carried out, and relevant parameters were examined, including etiolation index, chromatism, loss of gloss, corrosion form, etc. The results show that the plasma jet is slightly corrosive for part of the materials, but their performances are not affected. A portable calculator, computer display, mainboard, circuit board of radiogram, and a hygrometer could work normally after being treated by the plasma jet.     

量程至MGy的石英剂量计性能研究

为建立剂量可至MGy超高剂量范围的新型剂量计,本研究以石英为敏感材料,利用电子自旋共振（ESR）方法测量样品经γ射线或电子束辐照后产生的信号强度,开展石英种类选择、辐照后的线性、稳定性研究。结果表明,高纯石英适合作为超高剂量范畴的工作剂量计原材料。石英样品辐照后经15 min、300 ℃的热处理,信号强度在一年内能保持较好的稳定性,变化<3% ,且其吸收剂量与石英E′信号强度在10~10³ kGy剂量范围内成一定的函数关系,两者之间的拟合系数>0.99,相比于未经热处理的高纯石英样品,稳定性及拟合函数R²均得到明显提升。以上结果表明,石英剂量计适合作为超高剂量范畴的工作剂量计。     

The Gas Nucleation Process Study of Anatase TiO2 in Atmospheric Non-Thermal Plasma EnhancedChemical Vapor Deposition简

Abstract The gas phase nucleation process of anatase TiO2 in atmospheric non-thermal plasma enhanced chemical vapor deposition is studied. The particles synthesized in the plasma gas phase at different power density were collected outside of the reactor. The structure of the collected particles has been investigated by field scanning electron microscope （FESEM）, X-ray diffraction （XRD）, high resolution transmission electron microscopy （HRTEM） and selected area electron diffraction （SAED）. The analysis shows that uniform crystalline nuclei with average size of several nanometers have been formed in the scale of micro second through this reactive atmo- spheric plasma gas process. The crystallinity of the nanoparticles increases with power density. The high density of crystalline nanonuclei in the plasma gas phase and the low gas temperature are beneficial to the fast deposition of the 3D porous anatase TiO2 film.