RC-Coupled Atmospheric Glow Discharge in Air

Resistance and capacity-coupled glow discharge （RCCGD） is a new method to produce atmospheric pressure glow discharge in air. In RCCGD, each electrode is connected with both a resistor R and a capacitor C. The R and C can provide a negative feedback to prevent the transition from glow to spark discharge. The influence of coupled resistance, coupled capacity, inter-electrode gap and power source frequency on the discharge is studied and discussed.     

Study of Atmospheric Pressure Abnormal Glow Discharge

Atmospheric pressure abnormal glow discharge （APAGD） was carried out simply with a transformer of 1 ： 500 driven by a alternating current with a frequency of 50 Hz. Typical stable discharge parameters, namely voltage of 400 V to 850 V and current of 60 mA to 110 mA were measured by oscillograph. Simulation of the discharge process suggested that the stable discharge was supported by the impedance from the secondary coil of the transformer, which offered a negative feedback to prevent the discharge from turning into an arc. An interpretation was given for the oscillogram of the sinuous discharge current and square voltage. Furthermore, the electron temperature and electron density averaged in the discharge channel of APAGD were estimated.     

Transition from Spark Discharge to Constricted Glow Discharge in Atmospheric Air by Capacitor Coupled Discharge

The transition from a spark discharge to a constricted glow discharge in atmospheric air was studied with a capacitor coupled pin-to-water plasma reactor. The reason of the transition is considered to be of various factors, namely the change of the air gap due to the polarization of water molecules by the electric field, the feedback effect of the capacitors, and the ion trapping mechanism. The effects of the frequency of the power supply, inter-electrode gap, and coupled capacitance on the discharge transition were also investigated.     

Plasma Coaxial Discharge for Thin Film Deposition

A coaxial discharge, of 6 capacitors each with 7.71 μF, is used to explore plasma thin film coating by insert a graphite powder at the breach of the coaxial head. Plasma current sheath reached 25 kA, after 10 μs from the start of the discharge. The     

Study on Glow Discharge Plasma Used in Polyester Surface Modification

To achieve an atmospheric pressure glow discharge(APGD)in air and modify the surface of polyester thread using plasma,the electric field distribution and discharge characteristics under different conditions were studied.We found that the region with a strong electric field,which was formed in a tiny gap between two electrodes constituting a line-line contact electrode structure,provided the initial electron for the entire discharge process.Thus,the discharge voltage was reduced.The dielectric barrier of the line-line contact electrodes can inhibit the generation of secondary electrons.Thus,the transient current pulse discharge was reduced significantly,and an APGD in air was achieved.We designed double layer line-line contact electrodes,which can generate the APGD on the surface of a material under treatment directly.A noticeable change in the surface morphology of polyester fiber was visualized with the aid of a scanning electron microscope(SEM).Two electrode structures–the multi-row line-line and double-helix line-line contact electrodes–were designed.A large area of the APGD plasma with flat and curved surfaces can be formed in air using these contact electrodes.This can improve the efficiency of surface treatment and is significant for the application of the APGD plasma in industries.     

Self-Consistent Model for Pulsed Direct-Current N2 Glow Discharge

A self-consistent analysis of a pulsed direct-current (DC) N2 glow discharge is presented. The model is based on a numerical solution of the continuity equations for electron and ions coupled with Poisson‘s equation. The spatial-temporal variations of ionic and electronic densities and electric field are obtained. The electric field structure exhibits all the characteristic regions of a typical glow discharge (the cathode fall, the negative glow, and the positive column). Current-voltage characteristics of the discharge can be obtained from the model. The calculated current-voltage results using a constant secondary electron emission coefficient for the gas pressure 133.32 Pa are in reasonable agreement with experiment.     

Glow Discharge Induced Hydroxyl Radical Degradation of 2-Naphthylamine

In an aqueous solution, normal electrolysis at high voltages switches over spontaneously to glow discharge electrolysis and gives rise to hydroxyl radical, hydrogen peroxide, and aqueous electron, as well as several other active species. Hydroxyl radical directly attacks organic contaminants to make them oxidized. In the present paper, 2-naphthylamine is eventually degraded into hydrogen carbonate and carbon dioxide. The degradation process is analyzed by using an Ultraviolet (UV) absorption spectrum, high-performance liquid chromatography (HPLC) and chemical oxygen demand (COD). It is demonstrated that 2-naphthylamine (co =30 mg·1-1) is completely converted within 2h at 30℃and 600 V by glow discharge electrolysis, and the degradation is strongly dependent upon the presence of ferrous ions. COD is ascended in the absence of ferrous ions and descended in the presence of them.     

Glow Discharge Plasma Nitriding of AISI 304 Stainless Steel

Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction （XRD） to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase （TN） owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth （μm）. The results showed clear evidence of surface changes with substantial increase in surface hardness.     

Characteristics of a Normal Glow Discharge Excited by DC Voltage in Atmospheric Pressure Air

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 currentvoltage 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.     

Excited Electron Temperature and Molecular Vibration Temperature During Transition from Filamentary Discharge to Glow Discharge in Surface Discharge in Air

A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied voltage and discharge current were recorded simultaneously, and it was found that the discharge could transit from filamentary to glow with the decrease in pressure. Optical emission spectra during the transition from a filamentary discharge to a glow one were recorded. Excited electron temperature can be determined from the ratios of the relative intensities of spectral lines while molecular vibration temperature can be measured by analysing spectral lines of the N2 second positive band system. The results show that both the excited temperature and molecular vibration temperature increase with the decrease in the gas pressure. Qualitative explanations are given.     

Degradation of Chloroanilines in Aqueous Solution by Contact Glow Discharge Electrolysis

Contact glow discharge electrolysis of some chloroanilines in sodium sulfate was investigated in different initial concentrations.Each of them underwent the dechlorination,deamination theough oxidative degradation,and were eventually decomposed into hydrogen carbonate and carbon dioxide.It was testifies that the chlorine atomn and amidogen could be transformed into chloride ion and nitrite ion ,respectively.Fe^2 has a remarkable catalytic effect on the degradation of them.On the basis of the detailed analysis of the intermediate products and kinetic hehaviors,the reaction pathway was proposed,in which the attack of hydroxyl radical on the benzene ring of starting material might be a key step.     

Degradation of Methyl Orange in Water by Contact Glow Discharge Electrolysis

The degradation of methyl orange in a neutral phosphate buffer solution was investigated by means of contact glow discharge electrolysis （CGDE）. The methyl oranges were degraded and eventually decomposed into inorganic carbon when CGDE was conducted under the applied DC voltage of 480 V and current of ca. 80 mA. As the intermediate products, some phenolic compounds were detected as well as carboxylic acids. Experimental results showed that the oxidation process followed the first-order reaction law. Based on the analysis of the ultraviolet （UV） spectra of the solution and the intermediate products from High Pressure Liquid Chromatography-Mass Spectrum （HPLC-MS）, the reaction pathway was proposed. The attack of hydroxyl radicals was considered to be a key step to start the whole oxidation process.     

Effect of Ne Glow Discharge on Ion Density Control in LHD

Neon glow discharge cleaning was firstly attempted in Large Helical Device (LHD)instead of He glow discharge to remove hydrogen neutrals and to control the ion density n_i. TheNe glow discharge continued for 8 hours overnight after a three-day experiment. At the secondnight H_α emission became weaker than the emission usually observed in the He glow discharge. Aclear reduction of the hydrogen influx was also observed in neutral beam injection (NBI) dischargeswith Ne puff, whereas the neon recycling was strongly enhanced with appearance of a flat densityprofile. As a result, the lowest density limit was further reduced down to 0.2×10～(13) cm～(-3). Theuse of Ar puff formed a peaked density profile with a high T_i of 7 keV.     

PIC/MCC Simulation of Glow Discharge Plasma in Four-Anode Device

Numerical simulations by the code of Object-Oriented PIC （Particle-in-Cell） and the Monte Carlo Collision （MCC） method were carried out in order to obtain an insight into the characteristics of plasmas generated by glow discharges in low pressure helium in a four-anode DC glow discharge device. The results show that, the pressure, the external mirror magnetic field, and the virtual breadth of the annular electrode affect the radial distribution of the plasma density and temperature. The simulations are instructive for further experiments.     

Propagation Properties of Electromagnetic Wave in a Plasma Slab

In this paper, the calculated results about the propagation properties of electromag-netic wave in a plasma slab are described. The relationship of the propagation properties with frequencies of electromagnetic wave, and parameters of plasma (electron temperature, electron density, dimensionless collision frequency and the size of the plasma slab) is analyzed.     

An Experimental Study on Atmospheric Pressure Glow Discharge in Different Gases

Usually,the electrical breakdown of dielectric barrier discharge(DBD) at atmospheric pressure leads to a filamentary non-homogeneous discharge,However,it is also possible to obtain a diffuse DBD in homogeneous form,called atmospheric pressure glow discharge(APGD).We obtained a uniform APGD in helium and in the mixture of argon with alcohol,and studied the electrical characteristics of helium APGD.It if found that the relationship between discharge current and source frequency is different depending on the difference in gas gap when the applied voltage is kept constant.The discharge current shows an increasing trend with the increased frequency when gas gap is 0.8cm ,but the discharge current tends to decrease with the increased frequency when the gas gap increases.The discharge current always increases with the increased applied voltage when the source frequency is kept constant.We also observed a glow-like discharge in nitrogen at atmospheric pressure.