氩气含量对介质阻挡放电中单丝等离子体温度的影响

摘要

The single filament (also referred to as monofilament)which composed of two parts including the center spot and the outer halo is observed and researched for the first time in dielectric barrier discharge,which filled with gas-mixture of argon and air.The pictures taken from the experiment show that the diameter of the monofilament decreases with the increasing of the con-tent of the argon in the argon-air mixture,and at the same time there is an obvious difference on brightness between the center spot and the outer halo.All of these phenomenons suggest that the center spot and the outer halo are probably in different plas-ma state.The micro character of the center spot and the outer halo is researched seriously in the experiment by the time-resolved measurement with optical method.Three plasma temperatures of the center spot and the outer halo in single filament in different argon content are studied in details by using optical emission spectra.The emission spectra of the N2 second positive band(C 3Πu→B 3Πg )are measured,from which the molecule vibrational temperature of the center spot and the outer halo are calculated. Based on the relative intensity of the N+2 line at 391.4 nm and the N2 line at 394.1 nm,the changing relationship of the average electron energy of the center spot and the outer halo with argon content is investigated.The spectral lines of Ar I 763.2 nm (2P 6→1S 5 )and 772.077 nm (2P 2 →1S 3 )are chosen to estimate electron excitation temperature of the center spot and the outer halo by the relative intensity ratio method.The results show that the optical signal corresponding to the first lasge pulse is the center spot,whose signal intensity is a litter weaker;and the optical signal containing the whole pulse is the outer halo,whose signal intensity is stronger.The three plasma temperatures including the molecule vibrational temperature,average electron energy and electron excitation temperature of the outer halo are higher than those of the spot at the same argon content without exception.In addition,the molecule vibrational temperature of the center spot and the outer halo decrease with the argon content increases from 30% to 50%,while on the other hand,electron excitation temperature and average electron energy are decrease gradually.%在空气与氩气组成的混合气体放电中，首次研究了由中心点和外层晕组成的单丝。从照片中观察单丝结构，发现混合气体中氩气所占的比例越重，单丝的直径随之越小，同时中心点和外层晕的亮度有明显的差异，说明中心点和外层晕可能处于不同的等离子体状态。实验对单丝结构进行了光学时空分辨测量，研究了中心点和外层晕两层结构的微观特性。利用发射光谱法，详细地研究了该单丝结构的中心点和外层晕的等离子体参数随氩气含量的变化关系。实验根据氮分子第二正带系（C 3Πu →B 3Πg ）谱线计算了中心点和外层晕的分子振动温度；通过氮分子离子 N+2（391．4 nm）第一负带系谱线与氮分子 N2（394．1nm）谱线强度比，反映中心点和外层晕的电子平均能量随氩气含量的变化关系；利用氩原子763．2 nm（2P 6→1S 5）和772．077 nm（2P 2→1S 3）两条谱线的相对强度比法，估算了中心点和外层晕的电子激发温度。结果表明：中心点的光信号对应着第一个电流脉冲，且其光信号较弱；而外层晕的光信号同时对应着第一个和第二个电流脉冲，且其光信号较强。在相同的氩气含量条件下，外层晕比中心点的分子振动温度、电子平均能量以及电子激发温度均要高。随着氩气含量从30％逐渐增大到50％，中心点和外层晕的分子振动温度是逐渐减小的，而电子平均能量和电子激发温度均是逐渐增大的。