Electron density measurements in an atmospheric pressure air plasma by means of infrared heterodyne interferometry
Electron density measurements in an atmospheric pressure air plasma by means of infrared heterodyne interferometry
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DOI：
10.1088/0022-3727/33/18/310
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发表时间：
2000-09
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影响因子：
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通讯作者：
F. Leipold;R. Stark;A. El-Habachi;K. Schoenbach
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文献类型：
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作者：
F. Leipold;R. Stark;A. El-Habachi;K. Schoenbach
红外外差干涉仪已用于测量空气中直流大气压放电中电子密度的空间分布。高压辉光放电中电子密度的空间分辨率（特征尺寸为 100 µm）需要使用波长为 10.6 µm 的 CO2 激光器。对于此波长和大于 1011 cm-3 的电子密度，大气等离子体的折射率主要由重粒子而不是电子决定。通过考虑两种粒子种类的不同弛豫时间，将电子对折射率的贡献与重粒子的贡献分开。当放电以重复脉冲模式操作时，折射率最初的快速变化被认为是由于电子密度的增加，而随后缓慢的上升是由于气体加热引起的气体密度的降低。通过减少脉冲之间的时间，接近直流电条件，并通过外推法分别获得电子密度、气体密度和气体温度。采用计算反演方法确定了圆柱形放电中等离子体参数的径向分布。对于空气中的直流丝状放电，在电流为 10 mA 时，中心的电子密度为 1013 cm-3，在径向距离为 0.21 mm 时降至该值的一半。还获得了 σ = 1.1 mm 且中心最大值为 1000-2000 K 的高斯温度分布，但误差范围比电子密度的误差范围更大。
An infrared heterodyne interferometer has been used to measure the spatial distribution of the electron density in direct current, atmospheric pressure discharges in air. Spatial resolution of the electron density in the high-pressure glow discharge with characteristic dimensions on the order of 100 µm required the use of a CO2 laser at a wavelength of 10.6 µm. For this wavelength and electron densities greater than 1011 cm-3 the index of refraction of the atmospheric air plasma is mainly determined by heavy particles rather than electrons. The electron contribution to the refractive index was separated from that of the heavy particles by taking the different relaxation times of the two particle species into account. With the discharge operated in a repetitive pulsed mode, the initial rapid change of the refractive index was assumed to be due to the increase in electron density, whereas the following slower rise is due to the decrease in gas density caused by gas heating. By reducing the time between pulses, direct current conditions were approached, and the electron density as well as the gas density, and gas temperature, respectively, were obtained through extrapolation. A computation inversion method was used to determine the radial distribution of the plasma parameters in the cylindrical discharge. For a direct-current filamentary discharge in air, at a current of 10 mA, the electron density was found to be 1013 cm-3 in the centre, decreasing to half of this value at a radial distance of 0.21 mm. Gaussian temperature profiles with σ = 1.1 mm and maximum values of 1000-2000 K in the centre were also obtained with, however, larger error margins than for electron densities.