高气压均匀直流辉光放电等离子体的光学特性

Optical properties of direct current glow discharge plasmas at high pressures

在高气压(大于100 Torr,1 Torr=1.33322×102Pa)平板位形的均匀直流辉光放电中,一定条件下观察到平行排列的明暗相间的等离子体辉纹.结合等离子体的光发射谱诊断,研究了气体组分对等离子体光学特性的影响.研究发现,随着甲烷浓度的增加,辉纹间距减小,相应的电子激发温度降低.当甲烷浓度增加时,等离子体中低电离能的粒种增加,粒子平均电离能减小,这种情况下,电子被电场加速较短的距离所获得的能量就可以激发粒子,产生可见的光发射,表现为辉纹间距缩短.随着氩气的引入,能够观察到明显的辉纹,且增大氩气含量,辉纹间距增加,这与氩的较高电离能有关,而相应的电子激发温度增加.研究结果表明,随着工作气体的改变,等离子体辉纹间距呈现出一种对电子温度的响应.

In this work, the parallel bright and dark plasma striations are observed in direct correct glow discharge plasmas at high pressures （〉100 Torr, 1 Torr =1.33322 × 102 Pa）, and the effect of working gas on the plasma optical property is studied by combining the measurements of optical emission spectra. With the increase of the methane concentration, the length of striations decreases and the corresponding electron excitation temperature reduces. As the concentration of methane increases, the species with the low ionization energy increases, and the average ionization energy of the species decreases. In this case, the electron accelerated in a smaller distance can obtain enough energy to excite the gas species and produce visible light emission, and thus the length of plasma striations becomes shorter. With the introduction of argon, the plasma striations appear clearly. The length of striations increases with the increase of argon content, which is also correlated with the higher ionization energy of argon, while the corresponding electron excitation temperature rises. The length of plasma striations shows a response to the electron temperature as working gas changes.