Trichel脉冲放电为电晕放电中一种常见的不稳定现象。 为了进一步揭示Trichel脉冲的放电特性和放电机理, 本文利用针板放电结构, 在气压为600 Pa的空气环境下研究了Trichel脉冲放电的光学特性。 在平均电流为20~300 μA范围内, 放电分为Trichel脉冲放电模式和正常辉光放电模式。 在Trichel脉冲放电模式下, 平均极间电压随着平均电流的增高而降低; 正常辉光放电模式下, 平均极间电压随平均电流的增高基本保持不变。 实验拍摄并得到了不同平均电流时的发光图像, 从阴极针尖到阳极平板区域分为负辉区、 法拉第暗区、 正柱区和阳极辉区。 随着平均电流的增加, 负辉区、 正柱区以及阳极表面的发光增强, 负辉区体积基本保持不变, 法拉第暗区长度逐渐增加, 正柱区长度逐渐缩小。 在Trichel脉冲消失时, 负辉区发光向阴极针尖收缩, 正柱区向阳极板贴近, 并且两个区域发光明显增强。 利用光谱仪在300~800 nm波长范围内测量得到了不同平均电流时的发射光谱。 其中在300~450 nm波长范围内的发射光谱强度较高, 为氮分子的第二正带系(C³Π_u→B³Π_g)和氮分子离子的第一负带系($\mathrm{B}^{2} \Sigma_{\mathrm{u}}^{+}$→$\mathrm{X}^{2} \Sigma_{\mathrm{g}}^{+}$); 在650~800 nm附近发射光谱较弱, 为氮分子的第一正带发射谱(B³Π_g→$\mathrm{A}^{3} \Sigma_{\mathrm{u}}^{+}$)。 在此基础上, 根据N₂(C³П_u→B³П_g )第二正带系发射光谱拟合得到了不同平均电流时氮分子的振动和转动温度。 结果表明, 分子振动温度和转动温度均随平均电流的增加而增加, 分子振动温度在3 900~4 500 K, 分子转动温度在430~450 K。 同时利用氮分子离子谱线391.4 nm和氮分子第二正带系谱线394.2 nm强度比计算得到了不同平均电流时的电场强度。 随着平均电流的增加, 电场强度升高, 在145~200 kV·m^-1范围。 当Trichel脉冲消失时, 针尖附近分子振动温度和电场强度出现较为明显的升高。 此现象表明针尖附近的电子能量和电子密度随着脉冲的消失也出现了明显的升高。

Trichel pulse discharge is a common unstable phenomenon in the corona discharge. In order to further reveal the discharge mechanism and discharge characteristics of the Trichel pulse, the optical characteristics of Trichel pulse discharge are studied atapressure of 600Pa by using the needle plate discharge structure. At an average current of 20~300 μA, the discharge is divided into Trichel pulse discharge mode and normal glow discharge mode. In the Trichel pulse discharge mode, the average interelectrode voltage decreases with the increase of the average current. Under normal glow discharge mode, the average interelectrode voltage remains unchanged with the increase of average current. The luminescence images at different average currents are obtained. The region from the cathode needle tip to the anode plate is divided into negative glow region, Faraday dark region, positive column region, and anode glow region. With the increase of the average current, the luminescence in the negative glow region, the positive column region and the anode surface is significantly enhanced, the volume of the negative glow region remains unchanged, the length of the Faraday dark region gradually increases, and the length of the positive column region gradually decreases. When the Trichel pulse disappears, the luminescence in the negative glow region shrinks to the cathode tip, the positive column region shifts close to the anode plate, and the luminescence in these two regions is significantly enhanced. The emission spectra at different average currents are measured by an emission spectrometer in 300~800 nm. The emission spectrum intensity in the wavelength range of 300~450 nm is higher, the second positive band system (C³Π_u→B³Π_g) of nitrogen molecules and the first negative band system (($\mathrm{B}^{2} \Sigma_{\mathrm{u}}^{+}$→$\mathrm{X}^{2} \Sigma_{\mathrm{g}}^{+}$) of nitrogen molecular ions. The emission spectrum is weak near 650~800 nm, the first positive band emission spectrum of nitrogen molecules (B³Π_g→$\mathrm{A}^{3} \Sigma_{\mathrm{u}}^{+}$). According to N₂ (C³Π_u→B³Π_g) spectra, the vibrational and rotational temperatures of nitrogen molecules at different average currents are obtained by fitting the emission spectra of the second positive band system. The results show that the molecular vibrational temperature and rotational temperature increase with the increase of average current. The molecular vibrational temperature is 3 900~4 500 K, and the molecular rotation temperature is 430~450 K. This paper calculates the electric field intensity at different average currents using the intensity ratio of nitrogen molecule ion line 391.4 nm and nitrogen molecule second positive band spectral line 394.2 nm. The results show that the electric field intensity increases with the increase of the average discharge current, in the range of 145~200 kV·m^-1, which indicates that the electron energy increases with the increase of the average discharge current. When the Trichel pulse disappears, the molecular vibrational temperature and electric field intensity increase significantly, indicating that the electron energy and electron density near the tip of the needle increase.