[Spectral characteristics of different discharge modes in air dielectric barrier discharge].

The electron energy in the transition from streamer discharge to glow-like discharge in dielectric barrier discharge in air was investigated by using emission spectra. The vibrational temperature was measured with the N2 second positive band (C3II(u) --> B3II(g)) of the emission spectrum. The average electron energy was investigated from the relative intensity of the nitrogen molecular ion line at 391.4 nm and the nitrogen molecular line at 337.1 nm. It was found that the vibrational temperature and the relative intensity of nitrogen molecular ion line at 391.4 nm increased abruptly in the transition from streamer discharge to glow-like discharge. It was also found that the pressure for the transition pressure from streamer discharge to glow-like discharge changed with different gap distances, but the product of the transition pressure and gas gap width remained constant.

[Influence of pressure on plasma temperature in air/argon dielecteic barrier discharge].

Electron excitation temperature and molecule vibrational temperature in argon/air dielectric barrier discharge (DBD) at different gas pressure with water electrodes were studied by using optical emission spectra. The spectral lines of Ar I 763. 51 nm(2P6 --> 1S5) and Ar I 772.42 nm(2P2 --> 1S3) were chosen to calculate electron excitation temperature by the relative intensity ratio method. The emission spectra of nitrogen band of second positive system ( C3 pi(u) --> B3 pi(g)) were measured at the same time. The molecule vibration temperature was estimated by the emission intensities of different bands with delta(nu) = -1, delta(nu) = -2, and delta(nU) = -3 in nitrogen band of second positive system, using Boltzmann's plot method. In addition, the relative line intensities of nitrogen (0-0) band of first negative system at 391.4 nm and (0-0) band of second positive system at 337.1 nm were also measured to study the variation of electron energy. It was found that the electron excitation temperature decreased from 4 700 to 3 300 K and the molecule vibrational temperature decreased from 3 200 to 2 900 K with increasing gas pressure from 20 to 60 kPa. Besides, the ratio of I(N2+)/I(N2) also decreased with pressure increasing from 20 to 60 kPa, indicating that the average electron energy decreases with the gas pressure increasing. These results are of great importance to the study of plasma dynamics of dielectric barrier discharge and also to the underlying industrial applications.

[Study on plasma temperature in dielectric barrier discharge at the middle value of pd].

The optical emission spectra of Ar/air dielectric barrier discharge (DBD) scanned from 300-800 nm near atmospheric pressure were obtained. Electron excitation temperature (T(exc)) and molecule vibrational temperature (T(v)) in Ar/air DBD at the middle value of pressure-distance (pd) product (about 6.4 x 10(3) Pa x cm) were studied. The ArI 763.51 nm(2P6 --> 1S5) and 772.42 nm(2P2 --> 1S3) lines were chosen to estimate T(exc). T(v) was measured by the N2 second positive band (C 3IIu --> B 3IIg). It was found that T(exc) and T(v) increase with increasing applied voltage. And the varying rate of T(exc) with increasing voltage is bigger than that of T(v).

[Measurement and analysis of discharge current in dielectric barrier glow discharge at atmospheric pressure].

Dielectric barrier discharge has become a hot issue in low temperature plasma research field because of wide prospect for its application in industry. In the present paper, an uniform glow discharge was realized in atmospheric pressure helium with a parallel planar dielectric barrier discharge device and an uniform plasma was generated in helium at atmospheric pressure. Electrical method was used to separate the discharge current from the total current signal and the waveform of discharge current could be obtained. The relations among the discharge current, applied voltage, gap voltage and wall charge during the uniform glow discharge were used to analyze the dynamical behavior of wall charges during their accumulation. The results show that the wall charges were mainly accumulated during the existence of discharge current pulse, while the quantity of wall charges continued to increase until the gap voltage changed its polarity after the disappearance of discharge current pulse, and finally the quantity of wall charges decreased until the next breakdown. These experimental results are important for the further study of wall charges' effect in the dielectric barrier glow discharge and its application in industry.