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Cold atmospheric-pressure air plasma treatment of C6 glioma cells: effects of reactive oxygen species in the medium produced by the plasma on cell death
Yuyang WANG (汪宇扬)1, Cheng CHENG (程诚)2,4, Peng GAO (高鹏)1,et al.
Plasma Sci. Technol.    2017, 19(2): 025503; doi: 10.1088/2058-6272/19/2/025503
Abstract324)      PDF (535KB)(947)      

An atmospheric-pressure air plasma is employed to treat C6 glioma cells in vitro. To elucidate on the mechanism causing cell death and role of reactive species (RS) in the medium produced by the plasma, the concentration of the long-lived RS such as hydrogen peroxide, nitrate, and ozone in the plasma-treated liquid (phosphate-buffered saline solution) is measured. When vitamin C is added to the medium as a ROS quencher, the viability of C6 glioma cells after the plasma treatment is different from that without vitamin C. The results demonstrate that reactive oxygen species (ROS) such as H2O2, and O3 constitute the main factors for inactivation of C6 glioma cells and the reactive nitrogen species (RNS) may only play an auxiliary role in cell death.

Steady and oscillatory plasma properties in the near-field plume of a hollow cathode
Zun ZHANG (张尊)1, Kan XIE (谢侃)2, Jiting OUYANG (欧阳吉庭)1, et al.
Plasma Sci. Technol.    2018, 20(2): 024010; doi: 10.1088/2058-6272/aa9d7d
Abstract95)      PDF (1617KB)(913)      

Hollow cathodes serve as electron sources in Hall thrusters, ion thrusters and other electric propulsion systems. One of the vital problems in their application is the cathode erosion. However, the basic erosion mechanism and the source of high-energy ions cause of erosion are not fully understood. In this paper, both potential measurements and simulation analyses were performed to explain the formation of high-energy ions. A high-speed camera, a single Langmuir probe and a floating emissive probe were used to determine the steady and oscillatory plasma properties in the near-field plume of a hollow cathode. The temporal structure, electron temperature, electron density, and both static and oscillation of plasma potentials of the plume have been obtained by the diagnostics mentioned above. The experimental results show that there exists a potential hill (about 30 V) and also severe potential oscillations in the near-plume region. Moreover, a simple 2D particle-in-cell model was used to analyze the energy transition between the potential hill and/or its oscillations and the ions. The simulation results show that the energy of ions gained from the static potential background is about 20 eV, but it could reach to 60 eV when the plasma oscillates.

Laser-induced plasma electron number density: Stark broadening method versus the Saha–Boltzmann equation
Arnab SARKAR and Manjeet SINGH
Plasma Sci. Technol.    2017, 19(2): 025403; doi: 10.1088/2058-6272/19/2/025403
Abstract209)      PDF (1337KB)(879)      

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns–Nd:YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha–Boltzmann equation (SBE). Each approach was also carried out by using the Al emission line and Mg emission lines. It was observed that the SBE method generated a little higher electron number density value than the Stark broadening method, but within the experimental uncertainty range. Comparisons of Ne determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for Ne determination, especially when the system does not have any pure emission lines whose electron impact factor is known. Also use of Mg lines gives superior results than Al lines.

Hydrogenation of zirconium film by implantation of hydrogen ions
Yang LIU (刘洋)1, Kaihong FANG (方开洪)2, Huiyi LV (吕会议)1, et al.
Plasma Sci. Technol.    2017, 19(3): 035502; doi: 10.1088/2058-6272/19/3/035502
Abstract190)      PDF (1003KB)(864)      

In order to understand the drive-in target in a D–D type neutron generator, it is essential to study the mechanism of the interaction between hydrogen ion beams and the hydrogenabsorbing metal film. The present research concerns the nucleation of hydride within zirconium film implanted with hydrogen ions. Doses of 30 keV hydrogen ions ranging from 4.30×1017 to 1.43×1018 ions cm−2 were loaded into the zirconium film through the ion beam implantation technique. Features of the surface morphology and transformation of  phase structures were investigated with scanning electron microscopy, atomic force microscopy and x-ray diffraction. Confirmation of the formation of δ phase zirconium hydride in the implanted samples was first made by x-ray diffraction, and the different stages in the gradual nucleation and growth of zirconium hydride were then observed by atomic force microscope and scanning electron microscopy.

Spatiotemporal characteristics of nanosecond pulsed discharge in an extremely asymmetric electric field at atmospheric pressure
Li ZHANG (张丽), Dezheng YANG (杨德正), Sen WANG (王森) and Wenchun WANG (王文春)
Plasma Sci. Technol.    2017, 19(6): 064006; doi: 10.1088/2058-6272/aa632d
Abstract178)      PDF (2616KB)(834)      

In this paper, high resolution temporal-spatial diagnostics are employed to research the optical characteristics of nanosecond pulsed dielectric barrier discharge in needle-plate electrode configuration. Temporal-spatial distributions of discharge images, the emission intensities of optical emission spectra, and plasma vibrational and rotational temperatures are investigated. By analyzing the evolution of vibrational and rotational temperatures in space and time dimensions, the energy distribution and energy transfer process in plasma are also discussed. It is found that a diffuse structure with high density plasma concentrated in the region near the needle tip can be presented in nanosecond pulsed discharge, and an obvious energy transfer from electronic energy to vibration energy can be observed in each discharge pulse.

Effect of cylindrical cavity height on laser-induced breakdown spectroscopy with spatial confinement
Junfeng SHAO (邵俊峰)1, Tingfeng WANG (王挺峰)1, Jin GUO (郭劲)1,et al.
Plasma Sci. Technol.    2017, 19(2): 025506; doi: 10.1088/2058-6272/19/2/025506
Abstract156)      PDF (755KB)(791)      

In this paper, we present a study on the spatial confinement effect of laser-induced plasma with a cylindrical cavity in laser-induced breakdown spectroscopy (LIBS). The emission intensity with the spatial confinement is dependent on the height of the confinement cavity. It is found that, by selecting the appropriate height of cylindrical cavity, the signal enhancement can be significantly increased. At the cylindrical cavity (diameter = 2mm) with a height of 6 mm, the enhancement ratio has the maximum value (approximately 8.3), and the value of the relative standard deviation (RSD) (7.6%) is at a minimum, the repeatability of LIBS signal is best. The results indicate that the height of confinement cavity is very important for LIBS technique to reduce the limit of detection and improve the precision.

Effects of gamma-ray irradiation on electronic and non-electronic equipment of Large Helical Device
K OGAWA1,2, T NISHITANI1, M ISOBE1,2, et al.
Plasma Sci. Technol.    2017, 19(2): 025601; doi: 10.1088/2058-6272/19/2/025601
Abstract143)      PDF (508KB)(785)      

In a deuterium operation on the Large Helical Device, the measurement and control equipment placed in the torus hall must survive under an environment of  radiation. To study the effects of gamma-ray irradiation on the equipment, an irradiation experiment is performed at the Cobalt-60 irradiation facility of Nagoya University. Transient and permanent effects on a personal computer, media converters, programmable logic controllers, isolation ampliers, a web camera, optical flow meters, and water sealing gaskets are experimentally surveyed. Transient noise appears on the web camera. Offset of the signal increases with an increase of the integrated dose on the programmable logic controller. The DeviceNet module on the programmable logic controller is broken at the integrated dose of 72 Gy, which is the expected range of the integrated dose of the torus hall. The other equipment can survive under the gamma-ray field in the torus hall.

Realization of minute-long steady-state H-mode discharges on EAST
Xianzu GONG (龚先祖) 1,Baonian WAN (万宝年) 1,Jiangang LI (李建刚) 1, et al.
Plasma Sci. Technol.    2017, 19(3): 032001; doi: 10.1088/2058-6272/19/3/032001
Abstract276)      PDF (1063KB)(782)      

In the 2016 EAST experimental campaign, a steady-state long-pulse H-mode discharge with an ITER-like tungsten divertor lasting longer than one minute has been obtained using only RF heating and current drive, through an integrated control of the wall conditioning, plasma configuration, divertor heat flux, particle exhaust, impurity management, and effective coupling of multiple RF heating and current drive sources at high injected power. The plasma current (Ip ∼0.45 MA) was fully-noninductively driven (V loop <0.0 V) by a combination of ∼2.5 MW LHW, ∼0.4 MW ECH and ∼0.8 MW ICRF. This result demonstrates the progress of physics and technology studies on EAST, and will benefit the physics basis for steady state operation of ITER and CFETR.

The influence of grounded electrode positions on the evolution and characteristics of an atmospheric pressure argon plasma jet
Bo ZHANG (张波), Ying ZHU (朱颖), Feng LIU (刘峰) and Zhi FANG (方志)
Plasma Sci. Technol.    2017, 19(6): 064001; doi: 10.1088/2058-6272/aa629f
Abstract232)      PDF (2318KB)(776)      

An atmospheric pressure plasma jet (APPJ) in Ar with various grounded electrode arrangements is employed to investigate the effects of electrode arrangement on the characteristics of the APPJ. Electrical and optical methods are used to characterize the plasma properties. The discharge modes of the APPJ with respect to applied voltage are studied for grounded electrode positions of 10 mm, 40 mm and 80 mm, respectively, and the main discharge and plasma parameters are investigated. It is shown that an increase in the distance between the grounded electrode and high-voltage electrode results in a change in the discharge modes and discharge parameters. The discharges transit from having two discharge modes, dielectric barrier discharge (DBD) and jet, to having three, corona, DBD and jet, with increase in the distance from the grounded to the high-voltage electrodes. The maximum length of the APPJ reaches 3.8 cm at an applied voltage of 8 kV. The discharge power and transferred charges and spectral line intensities for species in the APPJ are influenced by the positions of the grounded electrode, while there is no obvious difference in the values of the electron excited temperature (EET) for the three grounded electrode positions.

Numerical analysis of the static performance of an annular aerostatic gas thrust bearing applied in the cryogenic turbo-expander of the EAST subsystem
Tianwei LAI (赖天伟)1, Bao FU (付豹)2, Shuangtao CHEN (陈双涛)1,et al.
Plasma Sci. Technol.    2017, 19(2): 025604; doi: 10.1088/2058-6272/19/2/025604
Abstract200)      PDF (1276KB)(773)      

The EAST superconducting tokamak, an advanced steady-state plasma physics experimental device, has been built at the Institute of Plasma Physics, Chinese Academy of Sciences. All the toroidal field magnets and poloidal field magnets, made of NbTi/Cu cable-in-conduit conductor, are cooled with forced flow supercritical helium at 3.8 K. The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of coils, structures, thermal shields, bus-lines, etc. The high-speed turbo-expander is an important refrigerating component of the EAST cryogenic system. In the turbo-expander, the axial supporting technology is critical for the smooth operation of the rotor bearing system. In this paper, hydrostatic thrust bearings are designed based on the axial load of the turbo-expander. Thereafter, a computational fluid dynamics-based numerical model of the aerostatic thrust bearing is set up to evaluate the bearing performance. Tilting effect on the pressure distribution and bearing load is analyzed for the thrust bearing. Bearing load and stiffness are compared with different static supply pressures. The net force from the thrust bearings can be calculated for different combinations of bearing clearance and supply pressure.

Analytical study of seashell using laser-induced breakdown spectroscopy
Ying LI (李颖), Yanhong GU (谷艳红), Ying ZHANG (张莹), et al.
Plasma Sci. Technol.    2017, 19(2): 025501; doi: 10.1088/2058-6272/19/2/025501
Abstract155)      PDF (709KB)(760)      

Seashell has been applied as an indicator for ocean research and element analysis of the seashell is used to track biological or environmental evolution. In this work, laser-induced breakdown spectroscopy (LIBS) was applied for elementary analysis of an ezo scallop-shell, and a graphite enrichment method was used as the assistance. It was found that LIBS signal intensity of Ca fluctuated less than 5%, in spite of the sampling positions, and Sr/Ca was relatedtothe shellgrowth. Asimilar variationwas also foundwhenusing adirect LIBS analysis on the shell surface, and it might be more practicable to track shell growth by investigating Sr/Ca ratio with Sr ionic line at 421.6 nm. The obtained results prove that calcium (Ca) is quali?ed as an internal reference for shell analysis, and LIBS is a potential analytical method for seashell study.

Modelling effect of magnetic field on material removal in dry electrical discharge machining
Abhishek GUPTA and Suhas S JOSHI
Plasma Sci. Technol.    2017, 19(2): 025505; doi: 10.1088/2058-6272/19/2/025505
Abstract173)      PDF (1143KB)(741)      

One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining (EDM) is confinement of plasma due to Lorentz forces. This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single-and multiple-discharge EDM process. The model incorporates three main effects of the magnetic field, which include plasma confinement, mean free path reduction and pulsating magnetic field effects. Upon the application of an external magnetic field, Lorentz forces that are developed across the plasma column confine the plasma column. Also, the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes. As the mean free path of electrons reduces, more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs. The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%–10% over the respective experimental values.

Parametric study on the characteristics of a SDBD actuator with a serrated electrode
Guoqiang GAO (高国强), Kaisheng PENG (彭开晟), Lei DONG (董磊), Wenfu WEI (魏文赋)1 and Guangning WU (吴广宁)
Plasma Sci. Technol.    2017, 19(6): 064010; doi: 10.1088/2058-6272/aa5b39
Abstract182)      PDF (2115KB)(738)      

Active flow control based on surface dielectric barrier discharge (SDBD) has become a focus of research in recent years, due to its unique advantages and diverse potential applications. Compared with the conventional SDBD with straight electrodes, the serrated electrode-based SDBD has a great advantage due to its 3D flow topology. It is believed that the boundary layer separation of moving objects can be controlled more effectively with this new type of SDBD. In SDBD with a serrated electrode, the R (tip sharpness) and N (tip number per unit length) have a great influence on the discharge and induced airflow characteristics. In this paper, a parametric study of the characteristics of SDBD with a serrated electrode has been conducted with different ranges of R and N. Aspects of the power consumption, the steady medium temperature distribution, and the maximum induced airflow velocity have been investigated. The results indicate that there is a critical value of R and N where the maximum power consumption and induced airflow velocity are achieved. The uniformity of the steady temperature distribution of the medium surface is found to be more dependent on N. We found that the accelerating effects of the induced airflow can be evaluated with the Schlieren technique, which agree well with the results from the pitot tube.

Simulated and experimental studies on the array dielectric barrier discharge of water electrodes
Lele WANG (王乐乐),XiutaoHUANG (黄修涛), Junfeng CHEN (陈俊峰), et al.
Plasma Sci. Technol.    2017, 19(3): 035402; doi: 10.1088/2058-6272/19/3/035402
Abstract222)      PDF (1050KB)(736)      

A kind of dielectric barrier discharge (DBD) device composed of water electrodes with 3×3 forms can produce large-area low-temperature plasmas at atmospheric pressure. To reflect the discharge characteristics of DBD better, a dynamic simulation model, which is based on the voltage controlled current source (CCS), is established, then the established model in Matlab/ Simulink is used to simulate the DBD in air. The voltage–current waves and Lissajous at a voltage of 10 kV, 11 kV and 12 kV peak value with a frequency of 15 kHz are studied. The change of the discharge power of DBD with a different amplitude and frequency of applied voltage is also analyzed. The result shows the voltage–current waves, Lissajous and discharge power of DBD under different conditions from the simulation agree well with those of the experiment. In addition, we propose a method to calculate the dielectric barrier capacitance Cd and the gap capacitance Cg, which is valid through analyzing the variation of capacitance at different voltage amplitudes.

Preliminary results of in situ laser-induced breakdown spectroscopy for the first wall diagnostics on EAST
Zhenhua HU (胡振华)1, Cong LI (李聪)2, Qingmei XIAO (肖青梅)2,et al.
Plasma Sci. Technol.    2017, 19(2): 025502; doi: 10.1088/2058-6272/19/2/025502
Abstract236)      PDF (947KB)(718)      

Post-mortem methods cannot fulfill the requirement of monitoring the lifetime of the plasma facing components (PFC) and measuring the tritium inventory for the safety evaluation. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising method for the in situ study of fuel retention and impurity deposition in a tokamak. In this study, an in situ LIBS system was successfully established on EAST to investigate fuel retention and impurity deposition on the first wall without the need of removal tiles between plasma discharges. Spectral lines of D, H and impurities (Mo, Li, Si, K ) in laser-induced plasma were observed and identified within the wavelength range of 500–700 nm. Qualitative measurements such as thickness of the deposition layers, element depth profile and fuel retention on the wall are obtained by means of in situ LIBS. The results demonstrated the potential applications of LIBS for in situ characterization of fuel retention and co-deposition on the first wall of EAST.

Evolution of plasma parameters in an Ar–N2/ He inductive plasma source with magnetic pole enhancement
Maria YOUNUS1, N U REHMAN2, M SHAFIQ1, et al.
Plasma Sci. Technol.    2017, 19(2): 025402; doi: 10.1088/2058-6272/19/2/025402
Abstract172)      PDF (1182KB)(713)      

Magnetic pole enhanced inductively coupled plasmas (MaPE-ICPs) are a promising source for plasma-based etching and have a wide range of material processing applications. In the present study Langmuir probe and optical emission spectroscopy were used to monitor the evolution of plasma parameters in a MaPE-ICP Ar–N2/He mixture plasma. Electron density (ne) and temperature (Te), excitation temperature (Texc), plasma potential (Vp), skin depth (δ) and the evolution of the electron energy probability function (EEPF) are reported as a function of radiofrequency (RF) power, pressure and argon concentration in the mixture. It is observed that ne increases while Te decreases with increase in RF power and argon concentration in the mixture. The emission intensity of the argon line at 750.4 nm is also used to monitor the variation of the ‘high-energy tail’ of the EEPF with RF power and gas pressure. The EEPF has a ‘bi-Maxwellian’ distribution at low RF powers and higher pressure in a pure N2 discharge. However, it evolves into a ‘Maxwellian’ distribution at RF powers greater than 70 W for pure N2, and at 50 W for higher argon concentrations in the mixture. The effect of argon concentration on the temperatures of two electron groups in the ‘bi-Maxwellian’ EEPF is examined. The temperature of the low-energy electron group TL shows a decreasing trend with argon addition until the ‘thermalization’ of the two temperatures occurs, while the temperature of high-energy electrons TH decreases continuously.

The dynamics of an ion acting on two monochromatic obliquely propagating Alfvén waves
Limin YU (虞立敏)1, Zhengmao SHENG (盛正卯)2, Xianmei ZHANG (张先梅)1, et al.
Plasma Sci. Technol.    2017, 19(7): 075001; doi: 10.1088/2058-6272/aa6617
Abstract157)      PDF (4571KB)(710)      
The interaction between a magnetized ion and two monochromatic shear Alfvén waves propagating obliquely to an ambient magnetic field is investigated both analytically and numerically. According to the Hamiltonian of this system, the invariant of motion at the lowest order and the half-island widths at the corresponding resonances are obtained analytically using the Lie transformation method. It is shown that these theoretical results agree with the numerical ones from the Poincaré surface of section. The regular motions from the invariant and the transition to stochasticity due to resonance overlapping are demonstrated. Compared to the case of a single wave, there may be a lower stochastic threshold in the multiple-wave problem.
Influence of the axial magnetic field on sheath development after current zero in a vacuum circuit breaker
Yi CHEN (陈毅), Fei YANG (杨飞), Hao SUN (孙昊), Yi WU (吴翊),Chunping NIU (纽春萍) and Mingzhe RONG (荣命哲)
Plasma Sci. Technol.    2017, 19(6): 064003; doi: 10.1088/2058-6272/aa65c8
Abstract176)      PDF (652KB)(707)      

After current zero, which is the moment when the vacuum circuit breaker interrupts a vacuum arc, sheath development is the first process in the dielectric recovery process. An axial magnetic field (AMF) is widely used in the vacuum circuit breaker when the high-current vacuum arc is interrupted. Therefore, it is very important to study the influence of different AMF amplitudes on the sheath development. The objective of this paper is to study the influence of different AMF amplitudes on the sheath development from a micro perspective. Thus, the particle in cell-Monte Carlo collisions (PIC-MCC) method was adopted to develop the sheath development model. We compared the simulation results with the experimental results and then validated the simulation.We also obtained the speed of the sheath development and the energy density of the ions under different AMF amplitudes. The results showed that the larger the AMF amplitudes are, the faster the sheath develops and the lower the ion energy density is, meaning the breakdown is correspondingly more difficult.

Statistical characteristics of transient enclosure voltage in ultra-high-voltage gas-insulated switchgear
Yuanji CAI (蔡元纪), Yonggang GUAN (关永刚)1 and Weidong LIU (刘卫东)
Plasma Sci. Technol.    2017, 19(6): 064011; doi: 10.1088/2058-6272/aa65c7
Abstract182)      PDF (1945KB)(705)      

Transient enclosure voltage (TEV), which is a phenomenon induced by the inner dielectric breakdown of SF6 during disconnector operations in a gas-insulated switchgear (GIS), may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage (UHV)substations. In this paper, the statistical characteristics of TEV at UHV level are collected from field experiments, and are analyzed and compared to those from a repeated strike process. The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first. Then, statistical characteristics, such as the pulse number, duration of pulses,frequency components, magnitude and single pulse duration, are extracted. The transmission line theory is introduced to analyze the TEV and is validated by the experimental results. Finally,the relationship between the TEV and the repeated strike process is analyzed. This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage. The results contribute to the definition of the standard testing waveform of the TEV, and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.

The Characteristics of CLHS Driving for High Luminance Efficiency in AC PDP
Gun-Su KIM1, Chi-Hyung AHN2, Seok-Hyun LEE3
Plasma Sci. Technol.    2016, 18(11): 1116-1122; doi: 10.1088/1009-0630/18/11/10
Abstract158)      PDF (510KB)(705)      

This paper proposes a CLHS (Capacitor Less Half Sustain) driving method that is applied to a long gap panel to reduce the power consumption. In order to reduce the power consumption in moving images, the luminous efficiency should be improved at the low discharge load (<25%). The weight of reactive power consumption tends to increase as the low discharge load decreases. Thus, it is very important to improve the luminous efficiency at low discharge load. It is well known that a long gap panel improves the luminance and the luminous efficiency but it is very difficult to drive the panel due to high driving voltage. It is confirmed that the main factors which cause a long gap panel to increase the minimum driving voltages are not only a long discharge gap but also self-erasing discharge. Self-erasing discharge is generated between the address and sustain electrodes in a sustain period. The CLHS driving method can reduce the reactive power consumption in a sustain period because energy recovery capacitors were removed in the sustain circuit. The CLHS driving method can reduce the minimum driving voltage of the long gap panel because the self-erasing discharge was prevented. When the CLHS driving method was applied to the panel with an ITO gap of 100 µm, VS and VA minimum voltages are reduced by about 9 V and 12 V compared with those of the normal driving method. The luminance and the luminous efficiency also increased by about 24.3% and 33.3% at the discharge load of 4% compared with those at the normal condition.