介质阻挡放电点燃大气压直流均匀放电的光谱研究

由于大气压均匀放电等离子体在工业领域具有广泛的应用前景，为了获得大尺寸的大气压均匀等离子体，采用氩气作为工作气体，在大气压空气环境中利用同轴介质阻挡放电点燃了针-板电极间的大气隙(气隙宽度达到5 cm)直流均匀放电。研究发现，同轴介质阻挡放电能够有效降低针-板电极间的击穿电压。该均匀放电由等离子体柱、等离子体羽、阴极暗区和阴极辉区组成。其中等离子体柱和阴极辉区都是连续放电。而等离子体羽不同位置的放电是不同时的。事实上，等离子体羽放电是由从阴极向着等离子体柱移动的发光光层(即等离子体子弹)叠加而成。利用电学方法测量了放电的伏安特性曲线，发现其与低气压正常辉光放电类似，均具有负斜率。采集了放电的发射光谱，发现存在N₂第二正带系、氩原子和氧原子谱线。通过Boltzmann plot方法对放电等离子体电子激发温度进行了空间分辨测量，发现等离子体柱的电子激发温度比等离子体羽的电子激发温度低。通过分析放电机制，对以上现象进行了定性解释。这些研究结果对大气压均匀放电等离子体源的研制和工业应用具有重要意义。

Spectral Investigation on the Direct-Current Uniform Discharge Ignited by a Dielectric Barrier Discharge at Atmospheric Pressure

Atmosphere pressure uniform plasma has the broad application prospect in the industrial field. In order to get a atmosphere pressure uniform plasma in large scale, a large gap uniform discharge (up to 5 cm) was initiated between a needle anode and a plate cathode, which was ignited under a low sustaining voltage by a coaxial dielectric barrier discharge in ambient air with argon used as working gas. The characteristics of the discharge were investigated. The coaxial dielectric barrier discharge can lower the voltage for gas breakdown effectively. The results showed that the atmospheric pressure uniform discharge included a plasma column near the anode, a plasma plume, a dark space and a cathode glow. The plasma column and the cathode glow were continuous discharges, while in the plasma plume region the discharges at different positions initiated at different time. In fact, the plasma plume behaved like a “plasma bullet” which traveled from the cathode to the plasma column. Through electrical method, the voltage-current characteristic was investigated. The voltage-current curve had a negative slope, whichwas similar with the normal glow discharge at low pressure. By analyzing the optical emission spectrum from the discharge, the optical emission spectrum was composed of the second positive system of nitrogen molecules, the spectral lines from argon atom and oxygen atom. By Boltzmann plot method, the spatially-resolved excited electron temperature was obtained. It was found that the excited electron temperature of the plasma column was lower than that of the plasma plume. These experimental phenomena were explained qualitatively. These results are of great importance to the development of atmospheric pressure uniform discharge plasma source and its application in industrial field.