Construction and Characterization of a Low Pressure Plasma Reactor Using DC Glow Discharge (original) (raw)
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An effective approach for designing a low pressure DC glow discharge plasma reactor
Journal of Electrostatics, 2017
Most plasma reactors are designed for research purposes and they are less appropriate for industry. To facilitate the engineering of an industrial reactor, an effective approach based only on the calculated Paschen curve, the simulation of the electric field and the breakdown reduced field is proposed. The results show that the experimental Paschen curve is different from the theoretical one; consequently the recalculation of the electric parameters is discussed. The experimental voltage/Current characteristic is used to identify the abnormal glow discharge regime and also to correlate the visual aspect of the discharge with its regimes.
Langmuir double probe is a very useful diagnostics for studying the plasma parameters at low pressure discharge and this paper reports the measurement of electron temperature (), ion saturation current () and electron density () in a low pressure DC glow discharge in air using I-V characteristics of double probe and the objective of the study is to investigate the effect of pressure and applied voltage on the plasma parameters in the discharge. In addition, Debye length (), plasma frequency (), floating potential () have also been calculated and their dependance on the applied voltage and working pressure have been studied. Measurements show that (), () and () gradually decrease on increasing the applied voltage or working pressure, but (), (), and () increases on increasing the applied voltage and working pressure. The maximum values of these parameters are obtained at 0.5 mbar pressure.
Characterization of a dc atmospheric pressure normal glow discharge
Plasma Sources Science and Technology, 2005
Atmospheric pressure dc glow discharges were generated between a thin cylindrical anode and a flat cathode. Voltage-current characteristics, visualization of the discharge and estimations of the current density indicate that the discharge is operating in the normal glow regime. Emission spectroscopy and gas temperature measurements using the 2nd positive band of N 2 indicate that the discharge forms a non-equilibirum plasma. Rotational temperatures are 700 K and 1550 K and vibrational temperatures are 5000 K and 4500 K for a 0.4 mA and 10 mA discharge, respectively. The discharge was studied for inter-electrode gap spacing in the range of 20 µm-1.5 cm. It is possible to distinguish a negative glow, Faraday dark space and positive column regions of the discharge. The radius of the primary column is about 50 µm and is relatively constant with changes in electrode spacing and discharge current. Estimations show that this radial size is important in balancing heat generation and diffusion and in preventing thermal instabilities and the transition to an arc.
In this research, the electrical characteristics of glow discharge plasma were studied. Glow discharge plasma generated in a home-made DC magnetron sputtering system, and a DC-power supply of high voltage as input to the discharge electrodes were both utilized. The distance between two electrodes is 4cm. The gas used to produce plasma is argon gas which flows inside the chamber at a rate of 40 sccm. The influence of work function for different target materials (gold, copper, and silver),-5cm in diameter and around 1mm thickness-different working pressures, and different applied voltages on electrical characteristics (discharge current, discharge potential, and Paschen's curve) were studied. The results showed that the discharge current and potential increase by increasing the applied voltage ranging between 300-700 V. Discharge current increased as working pressure increased in the beginning, and then semi-stabilized (slight increase) starting from 1×10 0 mbar, while discharge potential decreased at the beginning as working pressure increased and then semi-stabilized at the same point at which discharge current stabilized. The Paschen's curves were compared with each other. It was concluded that the lower breakdown voltage was associated with lower work function of the (Au, Cu, and Ag) cathode material. Breakdown voltages were (395, 398, and 420) for Ag, Cu and Au respectively.
Spectral Characteristics of DC Short Glow Discharge Plasma With Grid Electrodes
IEEE Access
The characteristics of post-cathode plasma maintained by a self-made DC short glow-discharge plasma generator with grid electrodes were measured by optical emission spectroscopy. The discharge existed in an abnormal glow discharge mode at a voltage of 250-400 V and a helium pressure of 3-15 Torr and a discharge gap of 3 mm. The results indicate that the intensity distribution of helium atom spectral lines in the post-cathode space differs from that in the post-anode space. The temperature of electron excitation in the post-cathode plasma reaches its peak of 1500-3000K at 5-6 mm from the grid cathode. The difference in the intensity distributions of helium atom spectral lines in the post-cathode and post-anode spaces is associated with electron generation mechanism in these cases. INDEX TERMS Glow discharge, grid anode, spectral characteristics, post-anode plasma, effective thickness of plasma.
Tikrit Journal of Pure Science, 2019
In the present study experimental measurements have been carried out to investigate the variation of air discharge voltage (V) and current (I) as a function of working pressure (p), in the ranges (300-500 V), (2-15 mA) and (0.09-0.13 Torr) respectively. Two thick, flat and circular electrodes of radius (4 cm) of Aluminum with a Pyrex cylinder tube of length (10 cm) and radius (3.5 cm) were used to generate the air glow discharge modes. The (V-p) characteristics have shown that an increasing in the discharge voltage of normal mode and reduction in that of abnormal mode with increasing the working pressure. It also displayed that the range of upper voltage from breakdown to abnormal glow has a minimum value (15.7 V) at (0.117 Torr). In addition to that, it is found that the (I-V) characteristics of air glow discharge modes are consistent with those reported in the literature for other gases, as argon, hydrogen and oxygen. It is expected that these observations can help to reduce ...
Exploration to generate atmospheric pressure glow discharge plasma in air
Plasma Science and Technology, 2018
Atmospheric pressure glow discharge (APGD) plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge (DBD) in non-uniform electric field are studied. It makes sure that APGD in air is formed by DBD in alternating current electric field with using the absorbing electron capacity of electret materials to provide initial electrons and to end the discharge progress. Through designing electric field to form two-dimensional space varying electric field and three-dimensional space varying electric field, the development of electron avalanches in airgap is suppressed effectively and a large space of APGD plasma in air is generated. Further, through combining electrode structures, a large area of APGD plasma in air is generated. On the other hand, by using the method of increasing the density of initial electrons, millimeter-gap glow discharge in atmospheric pressure air is formed, and a maximum gap distance between electrodes is 8 mm. By using the APGD plasma surface treatment device composed of contact electrodes, the surface modification of high polymer materials such as aramid fiber and polyester are studied and good effect of modifications is obtained. The present paper provides references for the researchers of industrial applications of plasma.
Plasma Chemistry and Plasma Processing, 2011
The miniaturized atmospheric pressure glow discharge (APGD) generated between a solid electrode and a flowing small size liquid cathode (dimension 2 mm) was investigated here using optical emission spectroscopy. The discharge was studied in an open air atmosphere, and the spectral characteristics of the plasma source was examined. Analysed APGD was operated at a discharge voltage of 1,100-1,700 V, a discharge current of 20 mA and gaps between a solid anode and a liquid cathode in the range from 0.5 to 3.5 mm. The emission intensities of the main species were measured as a function of various experimental conditions, including the solution flow rate, the gap between the electrodes, and the concentration of hydrochloric acid. The excitation temperature, the vibrational temperatures calculated from N 2 , OH, and NO bands, and the rotational temperatures determined from band of OH, N 2 and NO, were found to be dependent on these experimental parameters. The electron number density was determined from the Stark broadening of H b line. Additionally, the ionization temperature and degree were calculated using the Saha-Boltzmann equation, with the ion to atom ratio for magnesium (MgII/MgI). The results demonstrated that T exc (H), T vib (N 2 ), T vib (OH), T vib (NO) and T rot (OH) were well comparable (*3,800-4,200 K) for selected plasma generation conditions (gap C2.5 mm, HCl concentration C0.1 mol L -1 ), while the rotational temperatures determined from band of N 2 (*1,700-2,100 K) and band of NO (*3,000 K) were considerably lower. The electron number density was evaluated to be (3.4-6.8) 9 10 20 m -3 and the ionization temperature varied, throughout in the 4,900-5,200 K range.
Some fundamental aspects of glow discharges in plasma-assisted processes
Surface & Coatings Technology, 1987
The applicability of some theoretical models for ionization-assisted processes, such as those of Davis and Vanderslice and Child-Langmuir, are discussed using data obtained by the authors and other researchers in the field. Information derived from argon discharges is used as a basis, and provides a convenient foundation from which to compare different system layouts, such as the direct current diode, and various triode systems. Detailed information is given on the estimation of the cathode fall distance L and the LIX ratio, where X is the mean free path for charge exchange collision. This allows the estimation of energy distributions for both ions and neutrals. Other important parameters are also discussed, such as ionization efficiency, as well as the effect of additional species within the discharge.
Study on atmospheric pressure glow discharge based on AC-DC coupled electric field
Journal of Applied Physics, 2018
Based on the idea of increasing the number of initial electrons by changing the structures of the cathode, a method of generating the glow discharge plasma in the DC electric field by using the three-potential electrode structure is proposed. When the cathode takes the form of a spiral-contact electrode, a coupled electrode structure is designed. With this structure, the pre-discharge spiralcontact electrode provides a moderate number of seed electrons for the DC electric field. Moreover, the special electric field distribution of the coupled electrode structure can effectively suppress the occurrence of filamentary discharge and make possible the 8 mm-wide DC glow discharge under atmospheric pressure. The plasma generated in the DC field shows a feature of directional motion, promising great perspective in its application in surface treatment and other fields.