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Molecular Dynamics Study on the Diffusion Properties of Hydrogen Atoms in Bulk Tungsten
YU Xingang (余新刚),GOU Fujun (苟富均)
Plasma Sci. Technol.    2013, 15(7): 710-715; doi: 10.1088/1009-0630/15/7/19
Abstract346)      PDF (10814KB)(10452)      

Molecular dynamics simulations were performed to study the diffusion behavior of hydrogen atoms in body-centered cubic(bcc) tungsten(W). The energy distribution of a single hydrogen atom in the (001) plane of tungsten lattice was computed. The values of diffusion barriers agree well with other theoretical and experimental results. The interaction between an H atom and a vacancy was simulated, which shows evidence of strong binding effect. The temperature effect on the diffusion behavior of hydrogen atoms was investigated. The critical temperature for an H atom to diffuse in bulk W with and without vacancies were calculated to be 950 K and 450 K, respectively, which is supported by several experimental results. In addition, the diffusion coefficient of hydrogen atoms in tungsten was evaluated and analyzed.

Electromagnetic Particle-in-Cell Simulations of Electron Holes Formed During the Electron Two-Stream Instability
WU Mingyu (吴明雨), LU Quanming (陆全明), ZHU Jie (朱洁),WANG Peiran (王沛然), WANG Shui (王水)
Plasma Sci. Technol.    2013, 15(1): 17-24; doi: 10.1088/1009-0630/15/1/04
Abstract464)      PDF (28766KB)(7206)      

Previous electrostatic particle-in-cell (PIC) simulations have pointed out that elec- tron phase-space holes (electron holes) can be formed during the nonlinear evolution of the electron two-stream instability. The parallel cuts of the parallel and perpendicular electricfield have bipolar and unipolar structures in these electron holes, respectively. In this study, two-dimensional (2D) electromagnetic PIC simulations are performed in the x- y plane to investigate the evolution of the electron two-stream instability, with the emphasis on the magnetic structures associated with these electron holes in di®erent plasma conditions. In the simulations, the background magnetic field (Bo = Bo ~ ex) is along the x direction. In weakly magnetized plasma (­e <ωpe, where ­e and !pe are the electron gyrofrequency and electron plasma frequency, respectively), several 2D electron holes are formed. In these 2D electron holes, the parallel cut of the fluctuating magneticfield ±Bx and ±Bz has unipolar structures, while the flctuating magneticfield ±By has bipolar structures. In strongly magnetized plasma (­e >ωpe), several quasi-1D electron holes are formed. The electrostatic whistler waves with streaked structures of Ey are excited. The fluctuating mag- netic field δBx and δBz also have streaked structures. The fluctuating magneticfield δBx and δBy are produced by the current in the z direction due to the electric field drift of the trapped elec- trons, while the fluctuating magneticfield δBz can be explained by the Lorentz transformation of a moving quasielectrostatic structure. The influences of the initial temperature anisotropy on the magnetic structures of the electron holes are also analyzed. The electromagnetic whistler waves are found to be excited in weakly magnetized plasma. However, they do not have any significant effects on the electrostatic structures of the electron holes.

Effect of Cold Plasma Treatment on Seed Germination and Growth of Wheat
JIANG Jiafeng(蒋佳峰), HE Xin(何昕) , LI Ling(李玲) , LI Jiangang(李建刚) , SHAO Hanliang(邵汉良) , XU Qilai(徐启来) , YE Renhong(叶仁宏) , DONG Yuanhua(董元华)
Plasma Sci. Technol.    2014, 16(1): 54-58; doi: 10.1088/1009-0630/16/1/12
Abstract512)      PDF (222KB)(4942)      

This study investigated the effect of cold helium plasma treatment on seed germina- tion, growth and yield of wheat. The effects of different power of cold plasma on the germination of treated wheat seeds were studied. We found that the treatment of 80 W could significantly improve seed germination potential (6.0%) and germination rate (6.7%) compared to the control group. Field experiments were carried out for wheat seeds treated with 80 W cold plasma. Compared with the control, plant height (20.3%), root length (9.0%) and fresh weight (21.8%) were improved significantly at seedling stage. At booting stage, plant height, root length, fresh weight, stem diameter, leaf area and leaf thickness of the treated plant were respectively increased by 21.8%, 11.0%, 7.0%, 9.0%, 13.0% and 25.5%. At the same time, the chlorophyll content (9.8%), nitrogen (10.0%) and moisture content (10.0%) were higher than those of the control, indicating that cold plasma treatment could promote the growth of wheat. The yield of treated wheat was 7.55 t·ha −1 , 5.89% more than that of the control. Therefore, our results show that cold plasma has important application prospects for increasing wheat yield.

Dry Etching Characteristics of Amorphous Indium-Gallium-Zinc-Oxide Thin Films
ZHENG Yanbin1(郑艳彬), LI Guang1(李光), WANG Wenlong1(王文龙),LI Xiuchang1(李秀昌),JIANG Zhigang2(姜志刚),
Plasma Sci. Technol.    2012, 14(10): 915-918; doi: 10.1088/1009-0630/14/10/11
Abstract672)      PDF (4031KB)(4913)      
Amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) backplane technology is the best candidate for flat panel displays (FPDs). In this paper, a-IGZO TFT structures are described. The effects of etch parameters (rf power, dc-bias voltage and gas pressure) on the etch rate and etch profile are discussed. Three kinds of gas mixtures are compared in the dry etching process of a-IGZO thin films. Lastly, three problems are pointed out that need to be addressed in the dry etching process of a-IGZO TFTs.
Sterilization of Staphylococcus Aureus by an Atmospheric Non-Thermal Plasma Jet
LIU Xiaohu (刘小虎), HONG Feng (洪枫), GUO Ying (郭颖),ZHANG Jing (张菁), SHI Jianjun (石建军)
Plasma Sci. Technol.    2013, 15(5): 439-442; doi: 10.1088/1009-0630/15/5/09
Abstract251)      PDF (8560KB)(3410)      

An atmospheric non-thermal plasma jet was developed for sterilizing the Staphylo- coccus aureus (S. aureus). The plasma jet was generated by dielectric barrier discharge (DBD), which was characterized by electrical and optical diagnostics. The survival curves of the bacteria showed that the plasma jet could effectively inactivate 106 cells of S. aureus within 120 seconds and the sterilizing efficiency depended critically on the discharge parameter of the applied voltage. It was further confirmed by scanning electron microscopy (SEM) that the cell morphology was seriously damaged by the plasma treatment. The plasma sterilization mechanism of S. aureus was attributed to the active species of OH, N2 + and O, which were generated abundantly in the plasma jet and characterized by OES. Our findings suggest a convenient and low-cost way for sterilization and inactivation of bacteria.

Electron Density and Optical Emission Measurements of SF6/O2 Plasmas for Silicon Etch Processes
M. M. MORSHED, S. M. DANIELS
Plasma Sci. Technol.    2012, 14(4): 316-320; doi: 10.1088/1009-0630/14/4/09
Abstract642)      PDF (1482KB)(2887)      
This work investigates internal plasma process parameters using a hairpin resonance probe and optical emission spectroscopy. The dependence of electron density and atomic fluorine on the percentage of oxygen in an SF6/O2 discharge was measured using these methods. An RIE Oxford Instruments 80 plus chamber was used for the experiments. Two different process powers (100 and 300W) at a constant pressure (100 mTorr) were used, and it was found that the optical emission intensity of the 703.7 and 685.6 nm lines of atomic fluorine increased rapidly as oxygen was added to the SF6 discharge, reached their maximum at an O2 fraction of 20% and then decreased with further addition of oxygen. The plasma electron density was also strongly influenced by the addition of O2.
Water Content Effect on Oxides Yield in Gas and Liquid Phase Using DBD Arrays in Mist Spray
CHEN Bingyan (陈秉岩)1,2,3,4, ZHU Changping (朱昌平)3,5,FEI Juntao (费峻涛)4,5, et al.
Plasma Sci. Technol.    2016, 18(1): 41-50; doi: 10.1088/1009-0630/18/1/08
Abstract534)      PDF (1784KB)(2853)      

Electric discharge in and in contact with water can accompany ultraviolet (UV) radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals (OH), oxygen radical (O), ozone (O3) and hydrogen peroxide (H2O2). In this paper, a non-thermal plasma processing system was established by means of dielectric barrier discharge (DBD) arrays in water mist spray. The relationship between droplet size and water content was examined, and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O3 and nitrogen dioxide (NO2) in DBD room decreased with increasing water content. Moreover, the concentrations of H2O2,O3 and nitrogen oxides (NOx) in treated water decreased with increasing water content, and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last, the water containing phenol was tested in this system for the concentration from 100 mg/L to 9.8 mg/L in a period of 35 min.

Standardization of tritium water by TDCR method
WU Yongle1,2 (吴永乐) , LIANG Juncheng3 (梁珺成) , LIU Jiacheng3(柳加成),XIONG Wenjun1(熊文俊), YAO Shunhe1(姚顺和), GUO Xiaoqing1(郭晓清),CHEN Xilin1(陈细林), YANG Yuandi3(杨元第), YUAN Daqing1(袁大庆)
Plasma Sci. Technol.    2012, 14(7): 644-646; doi: 10.1088/1009-0630/14/7/17
Abstract453)      PDF (336KB)(2797)      
The triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting is an absolute measurement method of radioactivity. The formulation of the TDCR method and the established TDCR liquid scintillation counter are presented in this paper. The NIST SRM of tritium water was measured to verify the performance of the TDCR liquid scintillation counter.
Feature Scale Simulation of PECVD of SiO 2 in SiH 4 /N 2 O Mixture
LIU Xuan(刘璇), GE Jie(葛婕), YANG Yi(杨轶), SONG Yixu(宋亦旭), REN Tianling(任天令)
Plasma Sci. Technol.    2014, 16(4): 385-389; doi: 10.1088/1009-0630/16/4/15
Abstract84)      PDF (1576KB)(2461)      

In this paper, to simulate the process of PECVD (plasma enhanced chemical vapor deposition) of SiO 2 , the plasma chemistry and plasma density of SiH 4 /N 2 O mixture have been studied with an inductive coupled plasma model, and the level set methodology has been used to obtain the feature scale variation during the process. In this simulation, the goal is to fill a trench. We studied how ion sputtering and chamber pressure affect the feature scale model. After the simulation, we found that the trench will close up at the top after a few steps, and if we add the ion sputtering into the surface reactions, the trench top will close up a little later. When the chamber pressure is improved, the plasma density will increase, so the trench top will close up earlier. In semiconductor device manufacture, people can control the trench’s feature scale through adjusting these two parameters.

The Calculation of Prompt Fission Neutron from 233U(n, f) Reaction by Multi-Modal Los Alamos Model
ZHENG Na (郑娜),ZHONG Chunlai (钟春来), FAN Tieshuan(樊铁栓)
Plasma Sci. Technol.    2012, 14(6): 521-525; doi: 10.1088/1009-0630/14/6/19
Abstract586)      PDF (6009KB)(2425)      
An attempt is made to improve the evaluation of the prompt fission neutron emission from 233U(n, f) reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass (usually named “sawtooth” data) are calculated independently for the three most dominant fission modes (standard I, standard II and superlong), and the total spectra and are synthesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.
Characteristics of a Normal Glow Discharge Excited by DC Voltage in Atmospheric Pressure Air
LI Xuechen (李雪辰),ZHAO Huanhuan (赵欢欢),JIA Pengying (贾鹏英)
Plasma Sci. Technol.    2013, 15(11): 1149-1153; doi: 10.1088/1009-0630/15/11/13
Abstract233)      PDF (4308KB)(2304)      

Atmospheric pressure glow discharges were generated in an air gap between a needle cathode and a water anode. Through changing the ballast resistor and gas gap width between the electrodes, it has been found that the discharges are in normal glow regime judged from the current- voltage characteristics and visualization of the discharges. Results indicate that the diameter of the positive column increases with increasing discharge current or increasing gap width. Optical emission spectroscopy is used to calculate the electron temperature and vibrational temperature. Both the electron temperature and the vibrational temperature increases with increasing discharge current or increasing gap width. Spatially resolved measurements show that the maxima of electron temperature and vibrational temperature appeared in the vicinity of the needle cathode.

Calculation of the Critical Speed and Stability Analysis of Cryogenic Turboexpanders with Different Structures
CHEN Shuangtao (陈双涛), ZHAO Hongli (赵红利), MA Bin(马斌), HOU Yu, (侯予)
Plasma Sci. Technol.    2012, 14(10): 919-926; doi: 10.1088/1009-0630/14/10/12
Abstract389)      PDF (3126KB)(2259)      
A modularized code based on the Finite Element QZ (FEQZ) method is developed, for a better estimate of the critical speed and a more convenient method of rotor-dynamic stability analysis for a gas bearing high speed turboexpander rotor system with actual structure and application of a cryogenic turboexpander. This code is then validated by the experimental data of a gas bearing turboexpander, with a rotor diameter of 25mm and a rated speed of 106,400 rpm. With this code, four rotors with different structures, available to the turboexpander, are parametrically analyzed by the available speed range, vibration modes and logarithmic attenuation rate. The results suggest that the rotor with a structure of two thrust collars on the system exhibits a better performance in the designed conditions.
Carbon Dioxide Reforming of Methane to Syngas by Thermal Plasma
SUN Yanpeng(孙艳朋), NIE Yong(聂勇), WU Angshan(吴昂山), JI Dengxiang(姬登祥), YU Fengwen(于凤文), JI Jianbing(计建炳
Plasma Sci. Technol.    2012, 14(3): 252-256; doi: 10.1088/1009-0630/14/3/12
Abstract743)      PDF (274KB)(2250)      
Experiments were conducted on syngas preparation from dry reforming of methane by carbon dioxide with a dc arc plasma at atmospheric pressure. In all experiments, nitrogen gas was used as the working gas for thermal plasma to generate a high-temperature jet into a horizontal tube reactor. A mixture of methane and carbon dioxide was fed vertically into the jet. In order to obtain a higher conversion rate of methane and carbon dioxide, chemical energy efficiency and fuel production efficiency, parametric screening studies were conducted, in which the volume ratio of carbon dioxide to methane in fed gases and the total flux of fed gases were taken into account. Results showed that carbon dioxide reforming of methane to syngas by thermal plasma exhibited a larger processing capacity, higher conversion of methane and carbon dioxide and higher chemical energy efficiency and fuel production efficiency. In addition, thermodynamic simulation for the reforming process was conducted. Experimental data agreed well with the thermodynamic results, indicating that high thermal ef?ciency can be achieved with the thermal plasma reforming process.
Simulation Study of Quantitative X-Ray Fluorescence Analysis of Ore Slurry Using Partial Least-Squares Regression
LIN Caishou(林才寿)1,2, MAO Li(毛莉)1, HUANG Ning(黄宁)1, AN Zhu(安竹)1
Plasma Sci. Technol.    2012, 14(5): 427-430; doi: 10.1088/1009-0630/14/5/22
Abstract629)      PDF (2759KB)(2186)      
X-ray fluorescence (XRF) in combination with partial least-squares regression (PLS) was employed to analyze the ore slurry grade. Using the Monte Carlo simulation code PENELOPE, X-ray fluorescence spectra of ore samples were obtained. Good accuracy was achieved when this method was used to analyze elements with concentrations of several percent or above. It was demonstrated that the more the number of X-ray fluorescence spectra used to calibrate, the better the obtained accuracy. In this method detector resolution was found to have little or no effect on the results of quantitative analysis. The effect of the concentration of water was investigated as well, and it was found to have little influence on the results.
Atmospheric Pressure Radio Frequency Dielectric Barrier Discharges in Nitrogen/Argon
LIU Zhongwei (刘忠伟), YANG Lizhen (杨丽珍), WANG Zhengduo (王正铎), et al.
Plasma Sci. Technol.    2013, 15(9): 871-874; doi: 10.1088/1009-0630/15/9/07
Abstract204)      PDF (6319KB)(2183)      

This work reports the experimental results on the characteristics of radio frequency dielectric barrier N 2 /Ar discharges. Depending on the nitrogen content in the feed gas and the input power, the discharge can operate in two different modes: a homogeneous glow discharge and a constricted discharge. With increasing input power, the number of discharge columns increases. The discharge columns have starlike structures and exhibit symmetric self-organized arrangement. Optical emission spectroscopy was performed to estimate the plasma temperature. Spatially resolved gas temperature measurements, determined from NO emission rotational spectroscopy were taken across the 4.4 mm gap filled by the discharge. Gas temperature in the middle of the gas gap is lower than that close to the electrodes.

Linear Plasma Sources for Large Area Film Deposition: A Brief Review
WEI Yu(魏钰), ZUO Xiao(左潇), CHEN Longwei(陈龙威), MENG Yuedong(孟月东), FANG Shidong(方世东), SHEN Jie(沈洁), SHU Xingsheng(舒兴胜)
Plasma Sci. Technol.    2014, 16(4): 356-362; doi: 10.1088/1009-0630/16/4/10
Abstract89)      PDF (1105KB)(2175)      

By utilization of different excitation power sources, linear plasma sources can be differentiated into DC, RF, VHF, microwave and dual frequency types. Through installing several linear plasma sources in parallel or adopting the so-called roll-to-roll (air-to-air) process, scale uniform linear plasma sources were realized and successfully applied to the deposition of large area uniform dielectric thin films. Furthermore, the magnetic field system can effectively reduce the recombination losses on the wall of the vacuum chamber and enhance the plasma density. Linear plasma sources with approximately one square meter deposition area with the plasma density of 10 11 cm −3 have been developed, some of which have been used for the deposition of dielectric layers and large area plasma etching.

Decomposition of Nitrogen Trifluoride Using Low Power Arc Plasma
Jee-Hun KO, Sooseok CHOI, Hyun-Woo PARK, and Dong-Wha PARK
Plasma Sci. Technol.    2013, 15(9): 923-927; doi: 10.1088/1009-0630/15/9/17
Abstract245)      PDF (4452KB)(2164)      

The low power arc plasma is characterized by extremely high enthalpy and temper- ature and it is easy to generate and control, and thus thermal decomposition process based on the plasma torch is receiving a great attention for decomposing non-degradable greenhouse gases. In order to elevate the economic feasibility, the effects of input power, waste gas flow rate and additive gases on the destruction and removal efficiency (DRE) of NF 3 are examined. Specific energy density (SED) deceases as the flow rate increases, and accordingly, the DRE is reduced. The DRE is basically determined by the specific energy density. The highest DRE of NF 3 was 97% for the waste gas flow rate of 100 L/min at a low input power level of 2 kW with the help of hydrogen additional gas. The inlet and outlet concentration of NF 3 was analyzed using Fourier transform infrared spectroscopy (FT-IR) for DRE of NF 3 evaluation. As a result, large amount of NF 3 can be efficiently decomposed by low power arc plasma systems.

Conceptual Design of Neutral Beam Injection System for EAST
HU Chundong(胡纯栋), NBI Team
Plasma Sci. Technol.    2012, 14(6): 567-572; doi: 10.1088/1009-0630/14/6/30
Abstract622)      PDF (8415KB)(2158)      
Two Neutral Beam Injection (NBI) system will be constructed on the Experimental Advanced Superconducting Tokamak (EAST) in two stages for high power auxiliary plasmas heating and non-inductive current driver. Each NBI can deliver 2~4 MW beam power with 50~80 keV beam energy in 10~100 s pulse length. Each elements of the NBI system are presented in this contribution.
Ultra-Low Breakdown Voltage of Field Ionization in Atmospheric Air Based on Silicon Nanowires
CHEN Yun (陈云),ZHANG Jian (张健)
Plasma Sci. Technol.    2013, 15(11): 1081-1087; doi: 10.1088/1009-0630/15/11/01
Abstract225)      PDF (10187KB)(2119)      

Classic field ionization requires extremely high positive electric fields, of the order of a few million volts per centimeter. Here we show that field ionization can occur at dramatically lower fields on the electrode of silicon nanowires (SiNWs) with dense surface states and large field enhancement factor. A field ionization structure using SiNWs as the anode has been investigated, in which the SiNWs were fabricated by improved chemical etching process. At room temperature and atmospheric pressure, breakdown of the air is reproducible with a fixed anode-to-cathode distance of 0.5 µm. The breakdown voltage is ∼38 V, low enough to be achieved by a battery- powered unit. Two reasons can be given for the low breakdown voltage. First, the gas discharge departs from the Paschen’s law and the breakdown voltage decreases sharply as the gap distance falls in µm range. The other reason is the large electric field enhancement factor (β) and the high density of surface defects, which cause a highly non-uniform electric field for field emission to occur.

FDTD Simulation on Power Absorption of Terahertz Electromagnetic Waves in Dense Plasma
XI Yanbin (奚衍斌), LIU Yue (刘悦)
Plasma Sci. Technol.    2012, 14(1): 5-8; doi: 10.1088/1009-0630/14/1/02
Abstract629)      PDF (2432KB)(2046)      
A finite difference time domain (FDTD) method is used to numerically study the power absorption of broadband terahertz (0.1-1.5THz) electromagnetic waves in a partially ionized uniform plasma layer under low pressure and atmosphere discharge conditions. The power absorption spectra are calculated numerically and the numerical results are in accordance with the analytic results. Meanwhile, the effects on the power absorption are calculated with different applied magnetic fields, collision frequencies and electron number densities, which depend strongly on those parameters. Under the dense strongly magnetized plasma conditions, the absorption gaps appear in the range of 0.3-0.36THz, and are enlarged with the increasing electron number density.