光谱学与光谱分析, 2019, 39 (11): 3377, 网络出版: 2019-12-02  

空气中空心阴极不同放电模式下的发光特性

The Optical Characteristics of Hollow Cathode Discharge at Different Modes in Air
作者单位
1 河北大学物理科学与技术学院, 河北 保定 071002
2 河北农业大学理学院, 河北 保定 071001
摘要
为了进一步揭示空心阴极放电中放电模式的转换机制, 特别是空心阴极放电过程中自脉冲的形成机理, 利用柱型空心阴极放电结构, 在空气环境下研究了放电处于不同模式时的发光特性。 测量得到了不同放电模式下的伏安特性曲线、 放电发光图像、 自脉冲阶段的脉冲波形等。 实验结果表明随着放电电流的增加放电分为汤生放电模式、 自脉冲放电模式、 正常辉光放电模式和反常辉光放电模式。 虽然所用电源为直流电源, 但在自脉冲放电阶段电流和电压随时间呈周期性变化。 实验结果表明在不同的放电模式下具有不同的发光特性。 在由汤生放电转换为自脉冲放电模式和由自脉冲模式转换为正常辉光放电模式过程中, 放电腔的径向中心处和轴向孔口附近均存在光强的突变。 实验同时在200~700 nm范围内测量得到了不同电流时的发射光谱。 结果表明发射光谱主要集中在330~450 nm, 主要包括氮分子的第二正带系(C3Πu→B3Πg )和氮分子离子的第一负带系(B2Σ+u→X2Σ+g)。 其中氮分子离子第一负带系具有较强的发射光谱。 由于B2Σ+u激发电位较高, 因此该谱带较强发射光谱的存在表明空心阴极放电较其他放电形式更容易获得高激发态粒子和高能量电子。 在650~700 nm附近存在一弱的发光谱带, 主要为氮分子的第一正带发射谱(B3Πg→A3Σ+u)。 在此基础上根据双原子光谱发射理论, 结合氮分子第二正带系的三组顺序组带: Δν=-1, -2和-3, 利用玻尔兹曼斜率法计算得到了不同放电模式下氮气的分子振动温度。 结果表明在实验电流范围内分子振动温度在3 300 K左右, 随着电流的增加而升高, 并且在自脉冲消失时存在一突变迅速增强。 由于电子能量、 电子密度与分子振动温度密切相关, 因此该结果也表明随着放电电流的增加电子平均能量和电子密度不断增加, 当脉冲消失时, 电子平均能量和电子密度出现跃变升高。 最后, 对空心阴极放电中自脉冲的形成机理进行了讨论, 结果表明自脉冲放电源于放电模式的转换。
Abstract
In order to further reveal the mode transition of the hollow cathode discharge, and especially to explore the formation mechanism of self-pulse in the hollow cathode discharge, the optical characteristics of the discharge in different modes are studied in air by using a cylindrical hollow cathode. The V-I curve, luminescent image, and the waveform of the self-pulses are measured in different discharge modes. The experimental results show that with the increase of discharge current, the discharge can be divided into Townsend mode, self-pulsing discharge mode, normal glow discharge mode and abnormal glow discharge mode. Although the applied power source is a DC power source, the current and voltage periodically change with time during the self-pulse discharge phase. Results show that the optical characteristics at different modes are different. During the process transiting from the Townsend discharge to the self-pulsing discharge mode and from the self-pulsing mode to the normal glow discharge mode, there is a sudden change in light intensity at the region both in radial center of the hollow cathode and near the axial aperture. The emission spectra at different currents are measured in the range of 200 to 700 nm. The results show that the emission spectra mainly locates at the wavelength range of 330~450 nm, mainly including the second positive band system of nitrogen molecules (C3Πu→B3Πg) and the first negative band system of nitrogen molecular ions (B2Σ+u→X2Σ+g). The intensity of the first negative band system of nitrogen molecular ions is strong. Because the excited energy is high for B2Σ+u, which indicates that the hollow cathode discharge is more likely to obtain highly excited particles and high energy electrons than other types of discharge. In addition, a weak spectral band is located at 650~700 nm, which is the first positive band system of nitrogen molecules (B3Πg→A3Σ+u). On this basis, according to the theory of diatomic spectroscopy emission and the three spectral bands of the second positive band system of nitrogen molecules, the molecular vibrational temperature of nitrogen under different currents is calculated by using the emission spectrum of the second positive band system. The results show that the molecular vibrational temperature is about 3 300 K in the present, and it increases with the increase of discharge current, and there is a sudden increase when the pulse disappears. Since the electron energy and electron density are closely related to the molecular vibrational temperature, the results also indicate that the average electron energy and electron density increase with the increase of the discharge current. When the pulse disappears, the average energy and electron density appear to increase drastically. Finally, the formation mechanism of self-pulse in hollow cathode discharge is discussed. The results show that self-pulse discharge originates from the transition of discharge modes.

何寿杰, 包慧玲, 哈静, 赵凯悦, 渠宇霄, 张钊, 李庆. 空气中空心阴极不同放电模式下的发光特性[J]. 光谱学与光谱分析, 2019, 39(11): 3377. HE Shou-jie, BAO Hui-ling, HA Jing, ZHAO Kai-yue, QU Yu-xiao, ZHANG Zhao, LI Qing. The Optical Characteristics of Hollow Cathode Discharge at Different Modes in Air[J]. Spectroscopy and Spectral Analysis, 2019, 39(11): 3377.

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