Yong-Xing Wang

Spectroscopic diagnosis of an atmospheric-pressure waveguide-based microwave N2–Ar plasma torch

An atmospheric-pressure N2–Ar plasma is investigated by means of optical emission spectroscopic diagnosis concerning the variation of its fundamental parameters, electron density and plasma temperature, and concentrations of ionized molecular nitrogen, atomic nitrogen, and excited argon with the tuning variables, such as the input power and the ratio of N2 in N2–Ar mixture gas, in the discharge region of the plasma torch. Moreover, qualitative discussions are delivered with respect to the mechanisms for nitrogen dissociation and influence of the Ar component on the N2 plasma discharge at atmospheric pressure.

Characteristic Investigation of an Atmospheric-Pressure Microwave N 2 –Ar Plasma Torch

Impedance matching is implemented to stabilize an atmospheric-pressure waveguide-based N₂-Ar plasma torch with the aid of the use of swirl gas. Optical emission spectroscopy is employed to diagnose the plasma torch with respect to the population of the electronic state N⁺₂ (B ²Σ⁺_u ) and N₂(B ³Π_g) versus the absorbed power and the ratio of N₂ component in the Ar-N₂ mixture by the measurement of the emission of intensity. The qualitative discussion based on the reaction routes is delivered to interpret the experimental results well.

Influence of the Contact Opening Speed on DC Vacuum Arc

Arc determines whether the vacuum switchgears can break current successfully, so it is significant to study its characteristics. In this paper, a hybrid high-speed actuator was designed, and a method of forced current zero was used to interrupt dc in a synthetic test circuit. With the different contact opening speeds, the processes of arc burning and current transferring were observed by a high-speed CMOS camera. Through the arc area obtained by an image processing technology, the influences of the opening speed on arc were researched, including the influences in the initial arc burning stage, in the forced current zero stage, and at the same electrode distance. The results indicate that with the increase of the opening speed in a certain range, the arc area in the forced current zero stage tends to be small, and the one in the initial arc burning stage spreads more quickly. Although the arc area increases with the opening speed in the initial arc burning stage, its impact on the whole dc current transferring process is slight when the contact opening speed is high. So, high opening speed is helpful to extinguish arc and transfer current. In addition, there is another discovery in the experiments. In a certain range, when the opening speed is higher, arc burns stably earlier, and the arc area is smaller in the stable burning stage. So, it is beneficial to inject the transferring current in this stage. Experimental results and analysis of the arc images prove that increasing the opening speed is useful to transfer the current successfully and recover the dielectric strength of the electrode distance.

The quenching effect of hydrogen on the nitrogen in metastable state in atmospheric-pressure N2-H2 microwave plasma torch

The atmospheric-pressure microwave N2-H2 plasma torch is generated and diagnosed by optical emission spectroscopy. It is found that a large amount of N atoms and NH radicals are generated in the plasma torch and the emission intensity of N2+ first negative band is the strongest over the spectra. The mixture of hydrogen in nitrogen plasma torch causes the morphology of the plasma discharge to change with appearance that the afterglow shrinks greatly and the emission intensity of N2+ first negative band decreases with more hydrogen mixed into nitrogen plasma. In atmospheric-pressure microwave-induced plasma torch, the hydrogen imposes a great influence on the characteristics of nitrogen plasma through the quenching effect of the hydrogen on the metastable state of N2.

Experimental study of propagation characteristics of a pulse-modulated surface-wave argon plasma at atmospheric pressure

An atmospheric-pressure, pulse-modulated surface wave argon plasma is investigated with respect to its propagation of the ionization front. The time-resolved photographs about the advance of the ionization front are taken using a high speed camera. The ionization front velocity and its rise time when propagating along the discharge tube are measured with respect to a series of values of input power, duty ratio, and the pulse repetition frequency. The interpretations are given on the basis of the ionization and diffusion processes. And it is also found that the reduced electric field and memory effect from previous discharge impose the influence on both the ionization front velocity and its rise time strongly.

Role of Discharge Tube in Determination of Operating Mode in Waveguide-Based Atmospheric-Pressure Microwave-Induced Plasma

The discharge mechanism of the atmospheric-pressure waveguide-based microwave plasma is investigated experimentally by considering the role of the discharge tube. When the radius of the aperture holes on the wide waveguide walls is equal to that of the thin-walled discharge tube, the plasma is induced in an equivalent resonator with a certain Q value, presenting a torch-like plasma. However, if there is a launching gap of enough interspace between the aperture holes and the discharge tube, a surfaguide plasma can be developed at atmospheric pressure.

Characteristic Study of an Atmospheric-Pressure Radio-Frequency Capacitive Argon/Nitrogen Plasma Discharge

A developed atmospheric-pressure capacitive discharge source driven by radio-frequency power supply at 13.56 MHz is capable of producing a homogeneous and cold glow discharge in N2/Ar. The measurements of its electrical parameters are made systematically with respect to the nitrogen component when diluted into argon plasma discharge at various concentration ratio, and the variation tendencies of the atomic nitrogen and the N2(C3Πu) states with the concentration ratio of nitrogen to argon are investigated by means of optical emission spectroscopy. It is shown that although the admixture of nitrogen into argon plasma changes the electric characteristics greatly, the vibrational distribution function alters slightly at the same mixture ratio, and the production of N-atom is proportional to the nitrogen component.

Effect of Transmission Line on Impedance Matching of Atmospheric-Pressure Radio-Frequency Capacitive Microplasma Discharge

In this paper, it is found that the coaxial transmission line between the matching box and the plasma reactor plays an important role in impedance matching of atmospheric-pressure radio-frequency capacitively coupled microplasma discharge characterized by very low capacitance value. The high output voltage across reactor terminal is generated when the external circuit is operating in resonant state driven by power supply. The experimental results show that coaxial transmission line exhibits capacitive characteristics within the working frequency range and its capacitance increases linearly with the length of the transmission lines; the resonant frequency and voltage across the terminal reactor decrease with the length of coaxial transmission line.

One-Dimensional Self-Organized Plasma Discharge in Atmospheric Air With Use of an Atmospheric Argon Plasma Column

A self-organized discharge pattern is formed in atmospheric air when the argon plasma column is made use as a powered electrode. The argon plasma column is generated in a long thin quartz tube by a floating electrode driven by an alternating-current power supply operating at a frequency of 45 kHz, which is capable of being employed as a plasma electrode.