不均匀电场下加压气体中弥散放电和火花放电的形成(英文)

Diffuse and spark discharges are formed and studied during breakdowns with nonuniform electric field in nitrogen,air,and argon at elevated pressures and pulse repetition frequency of 400 Hz.Negative-polarity voltage pulses of the amplitude 20 kV,width at the base of 15 ns and rise time of 2 ns are applied to the electrode with a small radius of curvature.In the conditions of generation of runaway electron beams and X-rays,a CCD camera records the time of the diffuse discharge formation and its duration prior to its transition to a spark one.In all three gases,the diffuse discharge is formed during the time not exceeding 1 ns,when the bright spots appear on cathode in argon and air resulting in the beginning of the spark channel propagation.     

氩气与氨气混合下的大气压介质阻挡放电(英文)

In this paper,the influence of ammonia admixture on argon discharge properties is investigated.Electrical measurements,as well as ten-nanoseconds-exposure photographs taken by an intensified charge-coupled device(ICCD)camera,are employed to confirm the existence of atmospheric pressure glow discharge(APGD)in Ar/NH3mixture.The breakdown voltage and transition voltage between APGD and filamentary discharge are studied at various ammonia concentrations.The results show that a small amount of NH3can lead to APGD due to the Penning ionization of NH3molecules by metastable argon,and the breakdown voltage increases with the growth in NH3concentrations owing to the electronegative feature of NH3.The optical emission spectrum of Ar/NH3APGD is analyzed.Besides,gas temperature is estimated at 327 K by the diagnoses of the OH(A-X)(0,0)band of the spectrum.     

大气压下柱型微空心阴极放电(英文)

The mechanism of micro-hollow cathode discharge at atmospheric pressure is investigated through simulations using two-dimensional fluid model combined with a transport model for metastable atoms.In the simulations,electric potential,electric field,particle density,and mean electron energy of the discharge are calculated.The results show that the two characteristic regions of the discharge,i.e.cathode drop and negative glow can be distinguished in the simulation.The cathode drop is characterized by strong electric field and high mean electron energy,while quasi-neutral plasma of high density and exists in the negative glow.The peak value of electron density can reach the order of 1017cm-3.The electron temperature varies from several eV to tens of eV.The influence of cathode dimension on the discharge characteristics is also investigated.     

大气压下重复频率纳秒脉冲气体放电中X射线的辐射特性(英文)

Pulsed discharges can generate high power densities and high equivalent electric fields in plasma to emit X-rays,which is closely related to discharge mechanism.In this paper,discharge characteristics and X-ray emission of typical nanosecond-pulse discharges(corona,diffuse,spark or arc)are reviewed.Especially,the diffuse discharges are observed at pulse repetition frequencies up to 1 kHz.Factors influencing the discharge characteristics and X-ray emission are analyzed,such as the gap spacing,parameters of the applied pulse(amplitude,pulse repetition frequency),anode and cathode materials,and curvature radius of cathode.It is concluded that the maximum X-ray intensity is obtained in a diffuse discharge,and the X-ray intensity is affected by the pulse repetition frequency,applied voltage,anode material,and curvature radius of cathode.For example,X-ray intensity increases with the pulse repetition frequency and the atomic numbers of the anode material,but it decrease with the increase of curvature radius.It is also shown that the cathode material has no obvious influence on the X-ray intensity.     

SF6对介质阻挡放电臭氧生成的影响（英文）

The influence mechanism of a small amount of SF6 on ozone generation in oxygen or air discharge is investigated.Some results are obtained by probing into the number of the high-energy electrons,which have the sufficiency energy for generating ozone.Introducing a small amount of SF6 into oxygen sharply decreases the number of high-energy electrons,because the electron density decreases sharply while the mean electron energy remains constant due to higher breakdown voltage and lower discharge power,and some high-energy electrons are consumed by the excitation and attachment of SF6.In contrast,when a small amount of SF6 is added into dry air discharge,despite the consumption of the excitation and attachment of SF6,the number of high energy electrons increases sharply,which is attributed to the higher mean electron energy and electron density resulted from higher breakdown voltage and discharge power.When the volume fraction of SF6 increases from 0 to 2.22%,the ozone mass concentration and the ozone yield increase by 45.7% and 29.7%,respectively.Therefore,though the oxygen source should avoid the presence of SF6,adding a small amount of SF6 can improve the ozone mass concentration and the efficiency of ozone generation.     

等离子体子弹环形结构的形成机制(英文)

The formation of plasma bullets’ring-shaped structure in atmospheric pressure helium is analyzed by using a coupled fluid model.The model consists of a two-dimension neutral gas flow module and a one-dimension plasma dynamics module.The obtained radial distributions of the electron’s number density and the nitrogen’s metastable number density have different structures under different types of reactions or air contents in the model.It shows that total electron impact ionization plays an important role in sustaining the discharge,and together with Penning process,they lead to the shifted-off structure of electron number density.Meanwhile,the ring structure of plasma bullets forms mainly due to the excitation reaction of nitrogen molecule on air contents.     

大气压氦气与氩气等离子体射流形成机理的对比研究(英文)

To compare the formation mechanisms of He and Ar atmospheric pressure plasma jets(APPJs),an intensified charge-coupled device(ICCD)are utilized to observe the dynamic process of APPJ.The experimental results show that,He APPJ is first ignited,which is independent of the dielectric barrier discharge(DBD)between the two wrapped electrodes when the high voltage placed at the downstream.The intensity and APPJ length under positive discharge pulses are bigger than that under negative discharge pulses due to the space charge effect.The He APPJ is formed by the DBD development when the high-voltage electrode placed at the upstream side of tube.However,the plasma plume in Ar APPJ is formed by the propagation of DBD whatever the high-voltage electrode is arranged on upstream or downstream side of ground electrode.The difference in formation mechanism between He and Ar APPJs is mainly caused by the gas properties.Moreover,during the discharges,Ar tends to lead to thermal instability and electron Maxwellian instability.     

镀TiO2喷嘴-筒状电极下负脉冲放电等离子体降解酸性橙Ⅱ（英文）

Many sub-products of pulsed discharge,such as ultraviolet light,strong electric fields,shock waves and active species,are effective in treating wastewater.To improve the efficiency of the discharge plasma technology in removing pollutants,adding TiO2 photo-catalyst to pulsed discharges could help.A negative-pulsed-discharge system,which has nozzle discharge electrodes with or without TiO2 coating,is used to degrade azo dye Acid Orange Ⅱ,and the effects of several key conditions(maximum pulse voltage,pulse repetition frequency,initial mass concentration of Acid Orange Ⅱ initial solution pH,treatment duration,the phase of discharge,and the existence of TiO2) on the degradation are experimentally investigated.The degradation of Acid Orange Ⅱ increases with maximum pulse voltage,pulse repetition frequency,and treatment duration,and it is larger when putting the discharge electrode on the solution surface than in air or inside the solution,i.e.the discharge in gas phase is more effective than that in gas-liquid phase or liquid phase.The degradation decreases as the initial mass concentration of the solution increases.It also relates to pH and is higher at acidic conditions than at neutral or alkaline conditions.Compared to treatments without TiO2,the ones using the nozzle discharge electrode with TiO2 coated increase the degradation of Acid Orange Ⅱ by 5 %.It is concluded that the proposed system with TiO2 added in can remove Acid Orange Ⅱ from wastewater effectively.     

微结构内纳秒脉冲空气放电中微通道的形成及高能电子的产生过程(英文)

The investigations results of the different types of high-voltage nanosecond atmospheric discharges(diffusive in the gaps "wire(cathode)-plane", "rod(cathode)-plane", spark "point-plane" and in homogeneous gaps "plane-plane", as well as streamerless discharges in homogeneous gaps "plane-plane") are present. It was found out that the current channels prints, left on the electrodes surface, has the microstructure. The microstructure is a cluster(up to 1 000) of the microchannels of 1~30 μm diameters almost evenly distributed on the channels section. It was found out that in some cases the discharges develop in the regime of microstructuring of the current channels, are accompanied by generation of high-energy electrons and x-ray radiation. In this case the generation of high-energy component is stipulated by the electrons runaway in the microchannels. The calculation results of the electric field in clusters of parallel microchannels in the frameworks of the model of a bundle of parallel long cylindrical conductors are present. It is shown that in the clusters with many microchannels in the result of mutual attenuation of their fields maximum strength of the radial field could be lower than the critical one, which is necessary for ionization multiplication and expansion. This provides long existence of microchannels groups of microns radii in the high-voltage nanosecond discharges. A physical model of the streamerless discharge microstructure formation at the result of instability development of the ionization process in the avalanche stage is developed. It was established that the instability has long wave character and leads to formation of self-similar spatial structure. It is shown that the microstructure of the streamer discharges could be explained in the frameworks of this model. Three-dimensional numerical simulation of dynamics of microchannels system of high-voltage nanosecond discharges in the air of atmospheric pressure is performed in hydrodynamic approximation. It is established that fast(≈10 ns) expansion and significant decreasing of the gas concentration in the microchannels takes place at the expense of ohmic heating of the microchannels. It is shown that the microchannels expansion provides increase of electric field and gas concentration ratio up to the values that are sufficient for high-energy electrons beams and bremsstrahlung generation in them.     

大气压氦气介质阻挡放电中交流驱动电压频率对击穿电压的影响(英文)

For dielectric barrier discharge(DBD)driven by AC voltage in helium at atmospheric,the relationship between the breakdown voltage and the driving frequency is experimentally investigated using a pair of parallel electrodes.The gap between the electrodes is 1 mm,4 mm,7 mm,and 10 mm,respectively.Meanwhile with an increment of 2 kHz,the applied AC voltage varies from 12 kHz to 30 kHz.In each experiment,the driving voltage increases slowly,till the helium-filled gap breaks down.Based on a number of experimental results and further analyses,conclusions are obtained as follows.(1)For a small gap(1 mm),the voltage that triggers the first breakdown(Uf)is close to the one that sustains steady breakdowns(Us).However,in the larger gaps(4,7,and 10 mm),Uf is obviously larger than Us.(2)For a fixed gap,Uf does not change significantly with the driving frequency,whereas in the gaps except the 1 mm one,Us drastically decreases with the increase of driving frequency.(3)The motion of residual space charges and the dissipation of positive column,two reasonable factors that explains asymmetrical discharges,are also main reasons for the effect of the driving frequency on the breakdown voltages.     

Drastic transitions of excited state and coupling regime in all-inorganic perovskite microcavities characterized by exciton/plasmon hybrid natures

Lead-halide perovskites are highly promising for various optoelectronic applications,including laser devices.However,fundamental photophysics explaining the coherent-light emission from this material system is so intricate and often the subject of debate.Here,we systematically investigate photoluminescence properties of all-inorganic perovskite microcavity at room temperature and discuss the excited state and the light–matter coupling regime depending on excitation density.Angle-resolved photoluminescence clearly exhibits that the microcavity system shows a transition from weak coupling regime to strong coupling regime,revealing the increase in correlated electron–hole pairs.With pumping fluence above the threshold,the photoluminescence signal shows a lasing behavior with bosonic condensation characteristics,accompanied by long-range phase coherence.The excitation density required for the lasing behavior,however,is found to exceed the Mott density,excluding the exciton as the excited state.These results demonstrate that the polaritonic Bardeen–Cooper–Schrieffer state originates the strong coupling formation and the lasing behavior.     

大气压下气流中小电流放电及其应用(英文)

The paper reviews the results of investigations of the low-current atmospheric-pressure discharges in gas flow.The attention is focused on the discharges in electrode systems of coaxial plasmatron and of so-called gliding arc.It is demonstrated that a considerable fraction of discharge current is carried by a plasma column operating in a regime of normal glow discharge with occasional transitions to spark.The nature of glow-to-spark transition is discussed.Beside the plasma column,a weakly ionized gas fills in the interelectrode gap and forms a plasma jet at the exit of electrode system.The jet contains the active chemical particles that play important role in different discharge applications.The applications in plasma assisted combustion systems,for surface treatment with a usage of plasma jet,and for biology and medicine are considered.     

大气压氩滑动电弧的光谱诊断(英文)

This work is devoted to the experimental investigation of an AC argon gliding arc discharge at atmospheric pressure.The dynamic behaviour of the argon gliding arc plasma is investigated by the oscillations of the electrical signals,while the time-resolved arc root motion behaviour on the electrode wall is analyzed by high-speed photography.It is found that the anode and cathode arc roots exhibit different motion behaviour on the electrode surface.In addition,emission spectroscopic technique has been employed to determine the axial distribution of the gas temperature and electron density in the argon gliding arc plasma.     

空气中电晕放电与绝缘液体中流注放电的测量和分析(英文)

Insulation is one of the most important parts in a high voltage equipment.There are gaseous,liquid and solid insulations which are commonly used.In a high voltage transformer for example the insulating materials are all used.During operation of a high voltage equipment high electric stress may occur.Under extreme condition failure of the insulation may take place.Excessive electric field in air may cause corona discharges while in liquid insulation discharges may take place in the form of streamer.This paper reports experimental results on the corona and streamer discharges in air and silicone oil.The discharges were artificially generated around a needle tip in a needle-plane electrode system with gap length of 4 mm under sinusoidal and triangular voltages.The needle was made of steel with tip radius of 3 μm and curvature angle of 30°.The needle was made by Ogura Jewelry.The discharge pulses were measured using personal-computer based partial discharge(PD)measurement system with sensitivity of better than 0.5 pC.The system is able to measure discharge in time sequential.Phase-resolved analysis of the discharges was done to interpret the physical processes behind the discharges.The experimental results showed that corona discharges took place at negative half cycles.The discharges were concentrated around 270° of phase angle of applied voltage.The discharge magnitude and discharge number of corona clearly dependent on the instantaneous of applied voltage.These were strongly supported by the application of triangular voltage.Streamer discharges occurred at both positive and negative half cycles.The discharges pulses concentrated around the peak of applied voltage at phase angle of 90° and 270°.Experimental results under sinusoidal and triangular voltages revealed that streamer discharge magnitude as well as probability of occurrence was strongly dependent on the instantaneous applied voltage.     

大气压针板介质阻挡放电中微流注、电晕和辉光放电相互转换研究（英文）

To discuss the modes of dielectric barrier discharge(DBD) between needle-to-plane electrodes in air,DBD is generated and observed on a needle-to-plane device at atmospheric pressure air.Fast images of the DBD are taken by using a charge couple device(CCD) cinema with a macro lens,while the electrical and photo-electricity waveforms of the DBD are recorded.The current waveforms show that under an applied voltage of 3 kV,there are numerous short current pulses in both positive and negative half-periods of discharges.However,under 6 kV,there are still the numerous short current pulses in the positive half-periods,but only one wide current pulse in each negative half-period.This difference is also found in the photoelectric signals.The streamer,corona and glow discharges are observed from the images of the discharges at different applied voltages.The structure of glow discharge in the negative period is exactly the same as that of the low pressure glow discharge.However,in the positive period of discharge there is always a streamer.In the negative period of discharge,while the applied voltage increases,the transition from corona to glow discharge is observed.The progress of a transition between streamer and glow discharge at 6 kV during one period is analyzed.The glow discharge appearance is determined by two factors: the discharge current is limited to a certain extent by the dielectric layer; the charges deposited on the dielectric layer during the last half period enhance the intensity of the electric field.At an insufficient applied voltage,the cathode drop leads to no glow discharge,but Trichel pulses.     

中功率激光器驱动电路的研究与设计

In order to improve the performance of the antenna at low frequency, short circuit branch and coupling feed structure are introduced into the folded broadband single antenna in this paper, then resonant frequency is merged into the antenna using method of stagger tuning, finally, a UWB antenna is designed to work between 800MHz～2700MHz. Analysis are conducted to determine the antenna’s properties. The short-circuit wire location, feeding point location and the length of folded strip are discussed in detail. The SAR is calculated by HFSS simulation software while the antenna is close to a 3D human head model. The research results show that the antenna can cover eight commonly used commercial frequency bands at present, and electromagnetic radiation of the antenna has tiny influence on the human head model.     

大气条件下纳秒脉冲放电及其声特性分析(英文)

There was no well-resolved mechanism of audible noise caused by corona discharge on UHV transmission lines. Hence we measured the sound pressure of pulsed discharges between needle-plane electrodes under different discharge conditions in air, for revealing the intrinsic relationship between discharge and its audible noise(AN). The relationship between discharge parameters and audio characte- ristics was drawn from the analysis of the electric and sound signals obtained in experiments. Experiment results showed that nanosecond pulsed discharges produce the sound pressure with a microsecond pulse lagging behind the discharge pulse in their waveforms. The peak value of the sound pulse decreases and its high frequency component gradually attenuates, when the measuring distance from discharges increases. The sound pulses correlate with the discharge current and voltage significantly, especially the current. The audible noise produced by repetitive pulsed discharge increases with the strength, duration, and pulse repetition rate of discharge.     

惰性气体对氧气介质阻挡放电臭氧生成的影响(英文)

This paper reports the results of an experimental study of the effect of inert gases He,Ar and Kr on ozone generation in a Dielectric Barrier Discharge(DBD) fed by pure oxygen.The chemical reaction mechanisms related to the process of ozone generation are discussed.The experimental results show that ozone concentration decrease with decreasing oxygen content in all He+O2,Ar+O 2 and Kr+O 2 mixtures mainly owing to the decrease of oxygen content.The conversion ratio of oxygen into ozone increases with increasing oxygen content in He+O2 mixtures,but the addition of Ar and Kr can improve the conversion ratio due to the increase of free electrons density and excited oxygen molecules required for ozone formation through ionization and Penning effect.The effect of Kr is more significant for the lower first ionization energy of metastable state compared with other gases.It is probable that the ozone concentration,and ozone production efficiency increase with Kr addition when the reduced electric field and mean electron energy are high enough.     

氦气与D2O混合气中阻挡放电灯工作的物理过程（英文）

This paper presents both results of a numerical modeling and an experimental study of the influence of various parameters on the radiation characteristics of barrier discharge lamp working in He/D2O mixture.It is obtained that the intensity of ultraviolet radiation is a non-monotonic function of both the water and the helium pressures.The experimental results also show that the increase of both the discharge voltage and the discharge pulse frequency leads to the increase of radiation intensity.The comparison between the experimentally obtained data and the results of numerical modeling allows us to define the mechanism controlling the ultraviolet radiation in He/D2O mixture at various parameters.     

SF6断路器的热开断性能的数值预测（英文）

The design technology for HV SF6 gas circuit breakers is very demanding.A numerical method for prediction of the thermal interruption capability of SF6 gas circuit breakers is established based on the two-dimensional magneto-hydrodynamic(MHD) model and a commercial CFD(computational fluid dynamics) software,FLUENT.Nozzle ablation effect is considered by introducing an independent mass conservation equation for the ablated material to the overall conservation equations of mass,momentum,and energy.The ohmic heating and the radiation of the electric arc are considered in the model by adding relevant source terms.To predict the thermal interruption capability,the arc conductance 200 ns before current zero is used as an indicator.The CFD model is applied for the high current arcing phase,and Mayr arc model is used near the current zero period.The arc conductance at 200 ns before current zero(G200) for various arcing periods are computed by the present method.It shows that there exist a limit of the G200.For those whose arcing periods are within the arcing window,the related G200 are below the limit,therefore result a successful current interruption,and vice versa.The validation of the developed computer simulation tool is therefore verified.The numerical prediction by the simulation tool is verified by the direct interrupting test of 550 kV gas circuit breaker(GCB).The developed computer simulation tool was applied in the design of a 550 kV GCB.Significant benefits have been achieved in terms of both the cost saving and shorten of the development cycle.