Electromagnetic Wave Attenuation in Atmospheric Pressure Plasma

When an electromagnetic （EM） wave propagates in an atmospheric pressure plasma （APP） layer, its attenuation depends on the APP parameters such as the layer width, the electron density and its profile and collision frequency between electrons and neutrals. This paper proposes that a combined parameter -the product of the line average electron density n and width d of the APP layer （i.e., the total number of electrons in a unit volume along the wave propagation path） can play a more explicit and decisive role in the wave attenuation than any of the above individual parameters does. The attenuation of the EM wave via the product of n and d with various collision frequencies between electrons and neutrals is presented.     

The Oblique Incident Effects of Electromagnetic Wave in Atmospheric Pressure Plasma Layers

The propagating behaviours, i.e. phase shift, transmissivity, reflectivity and absorp- tivity, of an electromagnetic （EM） wave in a two-dimensional atmospheric pressure plasma layer are described by the numerical solutions of integral-differential Maxwell＇s equations through a generalized finite-difference-time-domain （FDTD） algorithm. These propagating behaviours are found to be strongly affected by five factors： two EM wave characteristics relevant to the oblique incident and three dimensionless factors. The two EM wave factors are the polarization mode （TM mode or TE mode） and its incident angle. The three dimensionless factors are： the ratio of the maximum electron density to the critical density no/nor, the ratio of the plasma layer width to the wave length d/λ, and the ratio of the collision frequency between electrons and neutrals to the incident wave frequency veo/f.     

Polymer Surface Treatment by Atmospheric Pressure Low Temperature Surface Discharge Plasma： Its Characteristics and Comparison with Low Pressure Oxygen Plasma Treatment

The polymer treatment with a low-temperature plasma jet generated on the atmospheric pressure surface discharge （SD） plasma is performed. The change of the surface property over time, in comparison with low pressure oxygen （O2） plasma treatment, is examined. As one compares the treatment by atmospheric pressure plasma to that by the low pressure O2 plasma of PS （polystyrene） the treatment effects were almost in complete agreement. However, when the atmospheric pressure plasma was used for PP（polypropylene）, it produced remarkable hydrophilic effects.     

Mixed Wastes Vitrification by Transferred Plasma

Thermal plasma technology provides a stable and long term treatment of mixed wastes through vitrification processes. In this work, a transferred plasma system was realized to vitrify mixed wastes, taking advantage of its high power density, enthalpy and chemical reactivity as well as its rapid quenching and high operation temperatures.
To characterize the plasma discharge, a temperature diagnostic is realized by means of optical emission spectroscopy （OES）. To typify the morphological structure of the wastes samples~ scan- ning electron microscopy （SEM）, and X-ray diffraction （XRD） techniques were applied before and after the plasma treatment.     

Inter-Calibration Between Plasma Instruments Onboard DEMETER

The in-situ measurements of the ionospheric plasma that we use come from two instruments of the scientific payload of the satellite DEMETER; the plasma analyser IAP （Instrument d＇analyse du plasma） and the Langmuir probe ISL （Instrument Sonde de Langmuir）. DEMETER is a micro-satellite realized by the CNES（Centre National d＇Etudes Spatiales, France） with a principal objective to seek a possible influence of the seismic activity on the electromagnetic waves in the ionosphere and on the ionospheric plasma. The satellite was placed on June 29, 2004, in a circular and quasi helio-synchronous orbit at -710 km altitude. The experiments function primarily at mid-latitudes （from ＋60° to -60°）. The IAP data were analysed to deduce the ion population （densities of the dominant ions, i.e. generally O^＋, H^＋ and He^＋） therefore the total ion density. The use of data IAP thus requires some precaution to make sure that the electric equilibrium conditions of the satellite, such as the satellite potential （Фsat）, are obtained during the treatment of routine, does not induce an error of measurement. When this potential is negative, the minority light ions H^＋ and He^＋ can be measured in a reliable way when their proportion is above 3% to 5% of that of O^＋. The critical limitation is： under certain conditions, the satellite potential becomes positive and reach a value about -0.5 V so that it becomes impossible to measure H^＋ ions. This is likely to involve a significant error on the composition and the density of the plasma. Therefore we carried out a calibration to estimate the missing density. The ISL experiment （Langmuir probe） provided the collected current/polarized tension characteristics of a cylindrical probe from which both electron density Ne and temperature Te were obtained. In some situations it is necessary to examine the accuracy of the electron density using another technique, for instance the high frequency （HF） spectrogram, provided by ICE （instrument champ     

Inactivation of Escherichia Coli Using Remote Low Temperature Glow Discharge Plasma

Low-temperature plasma is distinguished as a developing approach for sterilization which can deal with and overcome those problems such as thermal sensitivity and destruction by heat, formation of toxic by-products, higher costs and inefficiency in performances, caused by conventional methods. In this study, an experimental investigation was undertaken to characterize the effects of the operational parameters, such as treating time, discharge power and gas flow rate, of remote glow discharge air plasma. The results show that the inactivation of Escherichia coli can reach above 99.99% in less than 60 seconds and the optimal operational conditions for treating time, discharge power and gas flow rate were： 40 s, 80 W and 60 cm^3/min, respectively. The contribution of UV radiation during plasma germ deactivation is very limited.     

Plasma Limiter Based on Surface Wave Plasma Excited by Microwave

A novel plasma limiter, in which the plasma is excited by surface wave, is presented. The breakdown time of some gases filled in the limiter were calculated as a function of gas pres- sure, ionization degree and density of seed electrons under low pressure （0.01 -1 Torr） and high pressure （10 -1000 Torr） cases. The results show that the limiter filled with Xe with a pressure of 0.9 Torr, seed electron density of 10^16 m^-3, and ionization degree of 10^-4, has a breakdown time of approximate 19.6 ns.     

Calculation of Plasma Radiation in Electrothermal-Chemical Launcher简

A numerical model of radiation has been adopted for electrothermM-chemical （ETC） launcher, in which Monte Carlo method and statistical physics are employed to simulate the process of a capillary plasma source in an ETC launcher. The effect on propellant grains with different average absorption coefficients is discussed. The plasma-propellant interaction is also discussed when combined with a thermal model. Results show that the strong instantaneous radiation is responsible for the transmission of energy to the propellant grains leading to ignition. The efficiency of energy absorption in the propellant bed always maintains a high level. Radiant energy caused by plasma is concentrated around the plaslna injector. And the ＂hot zone＂ efficiency is mainly affected by the properties of propellant grains within a small field around the plasma injector.     

Plasma Response to Supersonic Molecular Beam Injection in J-TEXT简

Recently, hydrogen fueling experiments with supersonic molecular beam injection （SMBI） system have been performed in the J-TEXT tokamak. To evaluate the effects of the in- jection amount of SMBI on plasma behaviors, moderate and intensive SMBs have been separately injected and compared with each other in Ohmic discharges. With moderate SMBs, electron den- sity increases about twice as before, the size of magnetic island slightly decreases, and the edge toroidal rotation speed in a counter-current direction, measured by a high resolution spectrometer （Carbon V ion, 227.09 nm, r/a-= 0.7-0.8）, is accelerated from 8 km/s to 12 km/s. The state of higher electron density with moderate SMBI can be maintained for a long period, which indicates that plasma confinement is improved. However, with intensive SMBs, the accompanied magne- tohydrodynamic （MHD） activities are triggered, and the electron density increases moderately. The edge toroidal velocity is decreased, in certain cases even reversed in the co-current direction. The statistical result of experimental data for moderate and intensive SMBs suggests a preferred fueling amount （less than 3.2 ~ 1019） to improve the SMBI fueling efficiency in experiments.     

Heat Transfer Analysis of Two Kinds of Mechanically Jointed GBST1308/CuCrZr Plasma Facing Components of EAST

Doped graphite GBST1308, mechanically jointed to CuCrZr alloys, will be applied on EAST superconducting as plasma facing material （PFM）. Two joint structures called joint-1 and joint-2 were evaluated by means of thermal response tests using electron beam facility. The experimental results showed that the temperature differences of two joints were not significant, and the maximum surface temperature was about 1055℃ at a load of 4 MW/m^2, which had a good agreement with the simulated results by ANSYS code. The results indicated that the doped graphite GBST1308/CuCrZr mock-up can withstand heat flux deposition of 4 MW/m^2 except at the screw-fastened region, and joint-2 could be more suitable to higher heat flux region such as divertor target. But under the higher heat flux, both joints are unacceptable, an advanced PFM and its integration with the heat sink have to be developed, for example, vacuum plasma spraying tungsten coatings on the CuCrZr might be a good choice.     

Effect of Wall Charge on Striation in Plasma Display Cells

Different configurations and driving voltages have been employed to investigate the effect of the wall charge on the striations in macroscopic plasma display panel （PDP） cells. The experimental results show that a discharge channel near the dielectric layer is indispensable to striation occurring in the anode area during a discharge, while the pre-accumulated charge on the dielectric layer and the surface state are not important. The origin of the striation is related only to the physical process in the cell. The dielectric layer acts as a charge collector during a PDP discharge.     

A New Atmospheric Pressure Microwave Plasma Source （APMPS）

An atmospheric pressure microwave plasma source （APMPS） that can generate a large volume of plasma at an atmospheric pressure has been developed at Tsinghua University. This paper presents the design of this APMPS, the theoretical consideration of microwave plasma ignition and the simulation results, including the distributions of the electric field and power density inside the cavity as well as the accuracy of the simulation results. In addition, a method of producing an atmospheric pressure microwave plasma and some relevant observations of the plasma are also provided. It is expected that this research would be useful for further developing atmospheric pressure microwave plasma sources and expanding the scope of their applications.     

Dual Torch Plasma Arc Furnace for Medical Waste Treatment

In this paper, characteristics of a treatment and operated at atmospheric pressure dual torch plasma arc used for hazardous waste are studied, and also compared with those of the multi-torch plasma arc and the single torch plasma arc. The dual torch plasma arc is generated between the cathode and anode with argon as the working gas. The temperature distributions of the plasma arc are measured using a spectroscope and line pair method with the assumption of local thermodynamic equilibrium （LTE） for the DC arc current I=100 A and argon flow rate Q = 15 slpm. The measurements show that the temperatures of the dual torch arc plasma in the regions near the cathode, the anode and the center point are 10,000 K, 11,000 K and 9,000 K, respectively. And the high temperature region of the multi torch plasma arc is of double or much wider size than that of a conventional dual torch plasma arc and single plasma torch. Based on the preceding studies, a dual torch plasma arc furnace is developed in this study. The measured gas temperature at the center region of the argon arc is about 11,000 K for the case of I=200 A and Q=30 slpm operated in atmosphere.     

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.     

Physical Engineering Test and First Divertor Plasma Configuration in EAST

Physical engineering capability on the superconducting magnetic system of EAST was tested and first divertor plasma configuration in EAST was obtained. The extrapolation of the safety limit has verified the reliability of the system for long pulse operation. A stably controlled diverted plasmas configuration with an elongation n in excess of 1.8 and plasma current of up to 500 kA, by using the （copper） internal coils to control the vertical displacement instability was obtained by an optimized plasma control algorithm. Highly shaped plasma at various configurations, which almost covers all designed configurations for EAST, was generated stably. A number of operational issues, such as plasma initiation, ramp up and configuration control with constraints of superconducting coils, were successfully investigated. All of the results obtained proved both the capability of the superconducting poloidal magnets for operation under steady-state condition and effectiveness of the plasma control algorithm for EAST.     

Reliable Field Distortion Spark Gap for Plasma Focus

A simple, low cost, easily maintained, and reliable field distortion spark gap has been developed to operate at a voltage up to 30 kV. The header construction necessary to attach the spark gap switch to a single 12.5 μF, 40 kV （10 k J） capacitor is described. The main features of the spark gap are its wide range of voltage operation, high current capacity, low inductance and long lifetime. The performance of spark gap has been tested in a plasma focus and results are presented in this report.     

Electric-Arc Plasma Installation for Preparing Nanodispersed Carbon Structures

An electric-arc plasma installation operated in the hidden anode arrangement is constructed and used for the preparation of carbon nanostructures. A contracted plasma arc generated by a plasma torch using an inert gas is used as heat source. The average mass temperature of arc is higher than 10^4 K, while its power density, which is directly transferred onto the electrode （anode）, is - 2 kW/mm^2. The anode contact area formed on the electrode moves against the arc by way of shifting the electrode and is hidden completely in the interior of plasma gas stream moving towards it. As a result of both the direct plasma attack and the opposite movement of streams in the hidden anode contact area, a temperature higher than 6000 K is reached. Thus, intensive vaporization takes place, which forms a saturated plasma-gas-aerosol phase of the initial material of electrode （anode）. This gas phase is mixed in and carried by the plasma stream. Over that mixed plasma stream, a controlled process of quenching （fixation） is carried out by twisted turbulent fluid streams. After the fixation, the resultant carbon nano-structures are caught by a filter and collected in a bunker.     

Plasma Activation of Integrated Carbon Nanotube Electrodes for Electrochemical Detection of Catechol

In this study, integrated multi-wall carbon nanotube （MWCNT） electrodes were prepared in the holes of glass directly by microwave plasma chemical vapour deposition （MWPCVD）. The electrochemical behaviour of catechol at the integrated MWCNT electrodes was investigated. The oxygen plasma treated CNT electrodes had better electrochemical performance for the analysis of catechol than that of as-synthesized CNT electrodes. Both the as-synthesized CNTs and plasma treated CNTs were characterized by TEM（transmission electron microscopy, XPS（X-ray photoelectron spectroscopy） and Raman spectroscopy. The results revealed that the oxygen plasma activation is an effective method to enhance the electrochemical properties of CNT electrodes.