DC-driven subatmospheric glow discharges in the infrared-stimulated (original) (raw)
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Simulation of dc atmospheric pressure argon micro glow-discharge
Plasma Sources Science & Technology, 2006
A hybrid model was used to simulate a dc argon micro glow-discharge at atmospheric pressure. The simulations were carried out for a pin-plate electrode configuration with inter-electrode gap spacing of 200 µm together with an external circuit. The predicted voltage-current characteristics and current density profiles identify the discharge to be a normal glow-discharge. The neutral gas temperature predictions indicate that
DC normal glow discharges in atmospheric pressure atomic and molecular gases
Plasma Sources Science and Technology, 2008
DC glow discharges were experimentally investigated in atmospheric pressure helium, argon, hydrogen, nitrogen and air. The discharges were characterized by visualization of the discharges and voltage and current measurements for current of up to several milliamperes. Significant differences are seen in the gas temperature; however all the discharges appear to operate as temperature and pressure scaled versions of low pressure discharges. In the normal glow discharges, features such as negative glow, Faraday dark space and positive column regions are clearly observable. In hydrogen and to a lesser degree in helium and argon standing striations of the positive column were visible in the normal glow regime. Normal glow characteristics such as normal current density at the cathode and constant electric field in the positive column are observed although there are some unexplained effects. The emission spectra for each of the discharges were studied. Also the rotational and vibrational temperature of the discharges were measured by adding trace amounts of N 2 to the discharge gas and comparing modeled optical emission spectra of the N 2 2nd positive system with spectroscopic measurements from the discharge. The gas temperatures for a 3.5 mA normal glow discharge were around 420 K, 680 K, 750 K, 890 K and 1320 K in helium, argon, hydrogen, nitrogen and air, respectively. Measured vibrational and excitation temperatures indicate non-thermal discharge operation. Mixtures of gases achieved intermediate temperatures.
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.
Glow discharge plasma properties of gases of environmental interest
Brazilian Journal of Physics, 2004
Experiments in a low pressure glow discharge on gases of environmental relevance: CO2,CO y O2 are reported. We studied the various atomic processes: ionization, excitation and molecular dissociation with typical discharge parameters of p∼0.6 mbar, I≤ 0.1 A and V∼1100 Volts. We used visible and near UV spectroscopy to observe the emitted radiation on both electrodes on pure gases and hydrogen seeded mixtures. We also set up Langmuir probes in both electrodes.
Spectroscopic Investigation of Argon DC Glow Discharge in Plasma Medium
Journal of Naval Sciences and Engineering
In this study, UV-VIS-NIR (Ultraviolet Visible Near-Infrared) spectra emitted from Argon Glow discharge plasma in a low vacuum were recorded with a high-resolution Czerny-Turner type spectrometer. Argon plasma was produced at a pressure of 5mTorr and with a voltage of 584 V. Argon plasma was produced between two parallel stainless steel plates anode and cathode with a diameter of 15 cm, a thickness of 0.8 cm, and a distance of 13 cm between them. The radiative and collisional processes of the Argon plasma medium were modeled by the PrismSPECT atomic physics software (Software). The distributions of ion densities were calculated using the Saha-Boltzmann equation. The intensity of the excited energy levels of Ar(I) and Ar (II) ions were calculated in the electron temperature range of (0.4-3.5eV) and the mass density of (10-4-10-1gr/cm3). The UV-Visible-NIR spectra were simulated and compared with experimental spectra. The ratios of the intensities of the ArII/ArI (1s22s22p63s23p44f1/1...
Numerical Simulation of Glow Discharges in Air Mixtures under Low Pressure Conditions
Numerical Simulation of Glow Discharges in Air Mixtures under Low Pressure Conditions, 2016
Abstract Various options of numerical simulation of gas discharges in air like mixtures under low pressures are compared in the present work. It is demonstrated that a semi empirical one dimensional model typically used in applications based on a quasi analytical description of a glow discharge as a combination of cathode space and a positive glow gives only a qualitative description of the general trend for variation of electrical parameters of a discharge gap depending on gas mixture pressure. The model pretending to be a quantitative description is built on the basis of the averaged microscopic description of a gas discharge medium as part of the non local plasma model gradually complicated by means of expanding plasma component nomenclatures and elementary collisional and radiation processes flowing with them, which are taken into account as part of formalism of fluid equations for concentrations and energies.
Modelling of non-uniform DC driven glow discharge in argon gas
Physical properties of non-uniform DC-driven glow discharge in argon at pressure 1 torr are analyzed numerically. Spatially two-dimensional axial-symmetric model is based on the diffusion-drift theory of gas discharge. Results presented compare favorably with the classic theory of glow discharges and exhibit good agreement with the experimental result. Comparison with the result of spatially one-dimensional model is performed.
Spectroscopic Study of Argon DC Glow Discharge
IEEE Transactions on Plasma Science, 2007
In this paper, emission spectra of both positive column (PC) and negative glow (NG) regions of the dc glow discharge have been measured at different pressures and currents. The intensity of the lines in the NG is in the order of five times of that corresponding lines' intensity in the PC region. It is found that the line intensity increases linearly with the discharge current, while it increases as P α with the gas pressure. The electron temperature T e has been estimated using the line-to-lineintensity-ratio technique. It is found that T e derived by this technique generally decreases with the pressure. Also, T e in NG region is about 3/2 of that in the PC.
Physical Review E, 2001
The accuracy of secondary-electron emission coefficients, that are used as input data of discharge models, seriously influences the calculated discharge characteristics. As it is very difficult to consider all possible electron emission processes of a cold cathode separately, in most of the recent models an apparent secondary coefficient ␥ is applied, which is often assumed to be constant, even for a wide range of discharge conditions. In contrast with this common assumption, the present calculations-based on a heavy-particle hybrid modelshow that in abnormal glow discharges ␥ varies considerably with changing discharge conditions: a factor of 3 change of ␥ has been found in the range of reduced current densities (0.04 mA cm Ϫ2 Torr Ϫ2 р j/p 2 р4 mA cm Ϫ2 Torr Ϫ2 ) covered in this study. The present simulations also confirm that ionization by heavy particles plays a significant role in the ion production at the abnormal cathode fall. Moreover, it is shown, that the fast heavy particles reflected from the cathode surface play the dominant role in the gas heating.