Nonequilibrium discharges in air and nitrogen plasmas at atmospheric pressure (original) (raw)
Related papers
Journal of Physics: Conference Series, 2010
Main subject of this paper is low current atmospheric pressure gas discharges powering with DC power supplies. These discharges are widely used for generation of nonthermal or non-equilibrium plasma in air and nitrogen which are much cheaper compared to rare gases like He or Ar. Molecular nitrogen as plasma forming gas has a unique capability to accumulate huge energy in vibration, electron (metastables) and dissociated (atomic) states. Besides, all active species have a long lifetime , and they can be therefore transported for a long distance away from the place of their generation. Different current modes (diffusive and constricted) of these discharges are discussed. Experimental and numerical results on generation of chemically active species in the diffusive and constricted mode are presented.
Characterization of pulsed discharge plasma at atmospheric pressure
Surface and Coatings Technology, 2007
Experiments are performed to improve a pulsed corona discharge system for methane destruction at atmospheric pressure. The corona discharge is energized by 6-12 µs wide voltage pulses (0.3-7 kV) at a repetition frequency of 1.050 kHz. The characteristic of methane destruction is observed by a mass spectrometer. We have found that methane destruction depends on the parameters such as: pulse width, input pulse voltage, repetition frequency, discharge current and discharge time. The effects of argon gas on methane destruction were also observed. The structural geometry of the soot, resulting from discharge process, is observed by transmission electron microscope. The main aim of this study is to show that the discharge could help as for the production of hydrogen and carbon nanotubes.
Journal of Applied Physics, 2010
In atmospheric pressure air preheated from 300 to 1000 K, the nanosecond repetitively pulsed ͑NRP͒ method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space ͑applied voltage, pulse repetition frequency, ambient gas temperature, and interelectrode gap distance͒ of each discharge regime. In particular, the experimental conditions necessary for the glow regime of NRP discharges have been determined, with the notable result that there exists a minimum and maximum gap distance for its existence at a given ambient gas temperature. The minimum gap distance increases with decreasing gas temperature, whereas the maximum does not vary appreciably. To explain the experimental results, an analytical model is developed to explain the corona-to-glow ͑C-G͒ and glow-to-spark ͑G-S͒ transitions. The C-G transition is analyzed in terms of the avalanche-to-streamer transition and the breakdown field during the conduction phase following the establishment of a conducting channel across the discharge gap. The G-S transition is determined by the thermal ionization instability, and we show analytically that this transition occurs at a certain reduced electric field for the NRP discharges studied here. This model shows that the electrode geometry plays an important role in the existence of the NRP glow regime at a given gas temperature. We derive a criterion for the existence of the NRP glow regime as a function of the ambient gas temperature, pulse repetition frequency, electrode radius of curvature, and interelectrode gap distance.
Transverse dc glow discharges in atmospheric pressure air
IEEE Transactions on Plasma Science, 2000
We present experimental investigations of DC glow discharges in atmospheric pressure air with the aim of producing nonequilibrium air plasmas with high electron density (~10 12 cm -3 ) and relatively low gas temperature (less than 2000 K). Such plasmas are potentially interesting for many applications, including air pollution control. The discharge of our study is ignited by a streamer-to-spark transition, but thanks to an appropriate ballast resistor, it operates in a pulseless regime with currents from 2 to 500 mA, current densities of 1-10 A/cm 2 , and electric fields of 3000-300 V/cm. Spectroscopic and electrical measurements show that the discharge is of the glow type and generates a nonequilibrium air plasma. We also describe an innovative approach where thermionic cathodes and tubes with swirl gas flow are employed. With this approach, electron densities of up to 10 13 -10 14 cm -3 can be obtained and the production of relatively large plasma volumes is possible.
Overview of Atmospheric Pressure Discharges Producing Nonthermal Plasma
2001
Recently, much attention has been paid to gas discharges producing nonthermal plasma because of many potential benefits in industrial applications. Historically, past work focused on Dielectric Barrier (silent) Discharges (DBD) and pulse-periodical corona discharges. Recently, a number of new different discharge techniques succeeded in producing stable gas discharge at atmospheric pressure. Among these are repetitively pulsed glow discharge; continuous glow discharge in a gas flow; hollow-cathode atmospheric pressure discharge; RF and microwave (MW) discharges. Several new variants of the DBD have been demonstrated over a rather wide range of frequencies. All these forms of gas discharge are characterized by a strong nonequilibrium plasma state. We attempt to classify these discharges with respect to their properties, and an overview of possible applications is made. Conditions for the existence of homogenous and filamentary forms of each of the discharge types are discussed.
Journal of Applied Physics, 2011
This paper presents the results of the experimental studies of a pulsed discharge in atmospheric pressure air in an inhomogeneous electric field for various parameters of voltage pulses. It is shown that in a wide range of experimental conditions, including those with a positive electrode of small curvature radius, a diffuse discharge is ignited in the gap. In particular, a diffuse discharge is ignited at a pulse repetition frequency of 1 kHz and a voltage pulse amplitude of 25and25 and 25and40 kV across a high-resistance load. With voltage pulses of $ 220 kV in amplitude and low repetition frequencies, an extended ($70 cm) diffuse discharge is observed in gaps of 13-40 mm. It is confirmed that the diffuse form of discharges in an inhomogeneous electric field at increased pressures is attributed to the generation of runaway electrons and x-rays.
Characterization of the large area plane-symmetric low-pressure DC glow discharge
Spectrochimica Acta Part B: Atomic Spectroscopy, 2016
Electron density and temperature as well as nitrogen dissociation degree in the low-pressure (10-50 mTorr) large area plane-symmetric DC glow discharge in Ar-N 2 mixtures are studied by probes and spectral methods. Electron density measured by a hairpin probe is in good agreement with that derived from the intensity ratio of the N 2 2nd positive system bands I C ,1− 3 /I C ,0− 2 and from the intensity ratio of argon ions and atom lines I ArII /I ArI , while Langmuir probe data provides slightly higher values of electron density. Electron density in the low-pressure DC glow discharge varies with the discharge conditions in the limits of~10 8-10 10 cm −3. The concept of electron temperature can be used in low-pressure glow discharges with reservations. The intensity ratio of (0-0) vibrational bands of N 2 1st negative and 2nd positive systems I 391.4 /I 337.1 exhibits the electron temperature of 1.5-2.5 eV when argon fraction in the mixture is higher than nitrogen fraction and this ratio quickly increases with nitrogen fraction up to 10 eV in pure nitrogen. The electron temperature calculated from Langmuir probe I-V characteristics assuming a Maxwellian EEDF, gives T e~0 .3-0.4 eV. In-depth analysis of the EEDF using the second derivative of Langmuir probe I-V characteristics shows that in a low-pressure glow discharge the EEDF is non-Maxwellian. The EEDF has two populations of electrons: the main background non-Maxwellian population of "cold" electrons with the mean electron energy of~0.3-0.4 eV and the small Maxwellian population of "hot" electrons with the mean electron energy of~1.0-2.5 eV. Estimations show that with electron temperature lower than 1 eV the rate of the direct electron impact ionization of N 2 is low and the main mechanism of N 2 ionization becomes most likely Penning and associative ionization. In this case, assumptions of the intensity ratio I N 2 + ,391 /I N 2 ,337 method are violated. In the glow discharge, N 2 dissociation degree reaches about 7% with the argon fraction in the Ar-N 2 mixture b 10% and decreases afterwards approaching to~1-2% when the argon percentage becomes 90% and higher. The atomic nitrogen species is produced by electron-impact processes such as, collisions between electrons and nitrogen molecules or between electrons and N 2 + ions. At small Ar fraction in Ar-N 2 mixtures, the atomic nitrogen species is most likely produced by the collisions between electrons and N 2 + ions.
Nanosecond Repetitively Pulsed Glow Discharges in Atmospheric Pressure Air at 300K
2015
Non-equilibrium air plasmas with high densities of reactive species and low gas heating are produced at 1 atm, 300 K with nanosecond repetitively pulsed glow discharges. The domain of existence of the glow regime is explored. Optical and chemical diagnostics are used to characterize the densities of ozone and nitric oxides in the post-discharge.
Plasma Sources Science and Technology, 2006
DC normal glow (NG) discharges were created in atmospheric pressure air for a pin to plate type geometry. The rotational and vibrational temperatures of the discharge were measured by comparing modelled optical emission spectra with spectroscopic measurements from the discharge. The temperatures were measured as a function of discharge current, ranging from 50 µA to 30 mA, and discharge length, ranging from 50 µm to 1 mm. Rotational temperatures from 400 to 2000 K were measured over this range. Vibrational temperatures vary from 2000 K to as high as 5000 K indicating a non-equilibrium plasma discharge. Spectroscopic measurements were compared using several different vibrational bands of the 2nd positive system of N 2 , the 1st negative system of N + 2 and the UV transitions of NO. NO and N + 2 transitions were also used to determine the electronic temperature and N + 2 density. The discharge temperature appears to be controlled by two cooling mechanisms: (1) radial conductive cooling which results in an increase in temperature with increasing discharge current and (2) axial cooling to the electrodes which results in a temperature saturation with increase in discharge current. The measured discharge temperature initially increases rapidly with discharge current then becomes nearly constant at a higher discharge current. Thus, radial cooling appears to dominate at lower discharge currents and the axial cooling at higher discharge currents. The vibrational temperature decreases with increasing rotational temperature due to increased vibrational to translation relaxation but the discharge remains non-thermal and stable over the range studied. The discharge appears to have a maximum vibrational temperature at the low current limit of the NG regime.