六边形晕斑图等离子体参数的光谱测量

Study on the Plasma Parameters of the Spot-Halo Hexagon Pattern with Optical Emission Spectrum

在空气与氩气按比例混合组成的气体放电中,研究了由中心点和六边形晕组成的六边形晕斑图。从照片中观察六边形晕斑图结构,发现中心点和六边形晕的亮度有明显的差异,说明中心点和六边形晕可能处的等离子体状态不同。利用发射光谱法,详细研究了该六边形晕斑图结构的中心点和六边形晕的等离子体参数随压强的变化关系。实验根据氮分子第二正带系(C^3Π_u→B^3Π_g)谱线计算了中心点和六边形晕的分子振动温度;通过氮分子离子(391.4nm)与氮分子(394.1nm)谱线强度比,反映中心点和六边形晕的电子平均能量;利用氩原子696.5nm(2P_2→1S_5)谱线的展宽,研究了电子密度。实验结果表明:六边形晕斑图主要范围是氩气含量从60%~75%、压强从30~46kPa。在相同的压强条件下,六边形晕比中心点的分子振动温度、电子平均能量均要高。随着压强从30kPa逐渐升高到46kPa,中心点和六边形晕的分子振动温度、电子平均能量是逐渐增大的。在相同的压强条件下,六边形晕比中心点的谱线展宽要大,且随着压强的升高而增加,表明电子密度随着压强的增大而升高。六边形晕和中心点的等离子体的状态不同,说明二者放电机制上的差异。进一步采用高速照相机对斑图的电流脉冲进行分脉冲瞬时拍摄,发现中心点是由先放电的体放电形成,而六边形晕是由放电晚于体放电的沿面放电形成。

The spot-halo hexagon pattern consisted of the center spot and hexagon halo in dielectric barrier discharge is researched, which filled with gas-mixture of argon and air. The pictures taken from the experiment shows that there is an obvious difference on brightness between the center spot and hexagon halo. All of these phenomena suggest that the center spot and hexagon halo are probably in different plasma state. The plasma parameters of the center spot and hexagon halo in the spot-halo hexagon pattern as a function of gas pressure are studied in details by using optical emission spectra. The emission spectra of the N2 second positive band （C^3Πu→B^3Πg） are measured, from which the molecule vibrational temperature of the center spot and hexagon halo are calculated. Based on the relative intensity of the line at 391.4 nm and the N2 line at 394. 1 nm, the change of the electron average energy of the center spot and hexagon halo as a function of gas pressure is investigated. The electron density is studied by using the broadening of the spectral line 696.5 nm. It is found that the main chart of the spot-halo hexagon pattern is the argon content from 60% to 75% and the pressure from 30 to 46 kPa. The molecule vibrational temperature and electron average energy of the hexagon halo are higher than those of the center spot at the same pressure. As the pressure gradually increased from 30 to 46 kPa, the molecule vibrational temperature and electron average energy of the center spot and hexagon halo are increased, too. The broadening of the spectral line of the hexagon halo is bigger than the center spot at the same pressure, which increases with the gas pressure increasing. It indicates that the electron density increases with gas pressure increasing. The different plasma state of the center spot and hexagon halo show that the different formations mechanism of them. It is found that there are volume discharges firstly and then comes surface discharges with e high speed camera.