介质阻挡放电白眼六边形斑图等离子体温度研究

利用水电极介质阻挡放电装置，在不同氩气含量的气体放电中，首次观察到了白眼六边形斑图，此斑图的白眼晶胞都是由点、环和晕三层结构组成的, 且其放电稳定性和持续性极好。从照片中可以观察到这三种结构有明显的亮度差异，说明白眼晶胞中点、环和晕可能处于不同的等离子体状态，同时在不同氩气含量下，白眼晶胞的颜色和亮度都有明显的差异，说明白眼晶胞的等离子体状态也有所不同。由于此次研究的白眼六边形斑图是在较低的电压下得到的，使得水电极的温度没有升高且放电现象没有发生变化，因此在实验过程中长时间的放电没有影响该斑图的等离子体状态。为此，本小组采用发射光谱法，研究了此斑图的白眼晶胞中的点、环和晕的两种等离子体参数：分子振动温度和电子密度随氩气含量的变化关系。利用氮分子第二正带系(C3Πu→B3Π_g)的发射谱线，计算了白眼晶胞中的点、环和晕的分子振动温度;实验采集了Ar Ⅰ(2P₂→1S₅)的发射谱线，通过白眼晶胞中的点、环和晕的谱线展宽随氩气含量的变化，来反映白眼晶胞的三层结构的电子密度的变化。实验发现：在同一氩气含量条件下，白眼晶胞中点、环和晕的分子振动温度从大到小为：晕、环、点，而电子密度从大到小为：点、环、晕;随着氩气含量从70%增大到90%，点的分子振动温度及电子密度均增加;环的分子振动温度基本保持不变，而其电子密度减小;晕的分子振动温度及电子密度均减小。实验结果说明白眼晶胞中的点、环和晕的等离子体状态不同。本工作结果，对于研究介质阻挡放电中具有多层结构的自组织斑图有重要意义。

Plasma Temperature of White-Eye Hexagonal Pattern in Dielectric Barrier Discharge

By using the water-electrode discharge experimental setup, the white-eye hexagonal pattern is firstly observed and investigated in the dielectric barrier discharge with the mixture of argon and air whose content can be varied whenever necessary, and the study shows that the white-eye cell is an interleaving of three different hexagonal sub-structures: the spot, the ring, and the halo. The white-eye hexagonal pattern has the excellent discharge stability and sustainability during the experiment. Pictures recorded by ordinary camera with long exposure time in the same argon content condition show that the spot, the ring, and the halo of the white-eye hexagonal pattern have different brightness, which may prove that their plasma states are different. And, it is worth noting that there are obvious differences not only on the brightness but also on the color of the white-eye cell in conditions of different argon content, which shows that its plasma state also changed with the variation of the argon content. The white-eye hexagonal pattern is observed at a lower applied voltage so that the temperature of the water electrodes almost keeps unchanged during the whole experiment, which is advantageous for the long term stable measurement. The plasma state will not be affected by the temperature of the electrodes during the continuous discharge. Based on the above phenomena, plasma temperatures of the spot, the ring, and the halo in white-eye hexagonal pattern including molecule vibrational temperature and variations of electron density at different argon content are investigated by means of optical emission spectroscopy (OES). The emission spectra of the N₂ second positive band(C3Π_u→B3Π_g)are measured, and the molecule vibrational temperature of the spot, the ring, and the halo of the white-eye hexagonal pattern are calculated by the emission intensities. Furthermore, emission spectra of Ar Ⅰ(2P₂→1S₅)is collected and the changes of its width with different argon content are used to estimate the variations of electron density of the spot, the ring, and the halo of the white-eye hexagonal pattern. In the same argon content condition, the molecule vibrational temperatures of halo, ring, and spot in the white-eye hexagonal pattern are in descending order, while the electron densities of halo, ring, and spot are in ascending order. With argon content increasing from 70% to 90%, both the molecule vibrational temperature and the electron density of the spot increase, while both of them of the halo decrease. And the molecule vibrational temperature of the ring keeps constant, while its electron density decreases. The experimental results indicate that the plasma state of the spot, the halo and the ring in a white-eye cell of the white-eye hexagonal pattern is different. These results are of great importance to the investigation of the multilayer structure of the patterns in dielectric barrier discharge and applications in industry.