The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas. Compared with electrostatic diagnostics, the optical method is independent of the radio frequency (RF) noise, magnetic field, and electric field. In this paper, an optical emission spectroscope was used to determine the plasma emission spectra, electron excitation energy population distributions (EEEPDs), growth rates of low-energy and high-energy electrons, and their intensity jumps with input powers. The 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into EEEPD. One discrete EEEPD has two clear different regions, namely the low-energy electron excitation region (neutral lines with threshold energy of 13–15 eV) and the high-energy electron excitation region (ionic lines with threshold energy ≥19 eV). The EEEPD variations with different diameters of discharge tubes (20 mm, 40 mm, and 60 mm) and different input RF powers (200–1800 W) were investigated. By normalized intensity comparison of the ionic and neutral lines, the growth rate of the ionic population was higher than the neutral one, especially when the tube diameter was less than 40 mm and the input power was higher than 1000 W. Moreover, we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled (H) mode to helicon (W) mode; therefore, the determination of W mode needs to be carefully considered.

电子的特性在确定等离子体的电离和加速过程中起主要作用。与静电诊断相比，光学方法与射频（RF）噪声，磁场和电场无关。本文使用光发射光谱仪确定等离子体发射光谱，电子激发能总体分布（EEEPD），低能和高能电子的增长率以及它们的强度随输入功率的变化而变化。使用具有最高信噪比的56条发射线及其相应的电子激发能将光谱转换为EEEPD。一个离散的EEEPD具有两个明显不同的区域，即低能电子激发区（阈值能量为13-15 eV的中性线）和高能电子激发区（阈值能量≥19eV的离子线）。研究了不同直径的放电管（20 mm，40 mm和60 mm）和不同的输入RF功率（200–1800 W）时的EEEPD变化。通过对离子线和中性线的归一化强度比较，发现离子人口的增长率高于中性线，特别是当管径小于40 mm且输入功率大于1000 W时。此外，我们发现低能电子和高能电子的强度在不同的输入功率下从电感耦合（H）模式向螺旋（W）模式跳跃；因此，需要仔细考虑W模式的确定。