Analyses of nonequilibrium transport in atmospheric-pressure direct-current argon discharge under different modes  

作　　者：Ziming ZHANG Chuan FANG Yaoting WANG Lanyue LUO Heping LI 张子明;方川;汪耀庭;罗岚月;李和平(Department of Engineering Physics,Tsinghua University,Beijing 100084,People’s Republic of China)

机构地区：[1]Department of Engineering Physics,Tsinghua University,Beijing 100084,People’s Republic of China

出　　处：《Plasma Science and Technology》2024年第11期107-126,共20页等离子体科学和技术（英文版）

基　　金：supported by National Natural Science Foundation of China (No. 12075132)。

摘　　要：The key plasma parameters under different discharge modes, such as heavy-particle and electron temperatures, electron number density, and nonequilibrium volume of plasmas, play important roles in various applications of gas discharge plasmas. In this study, a self-consistent two-dimensional nonequilibrium fluid model coupled with an external circuit model is established to reveal the mechanisms related to the discharge modes, including the normal glow, abnormal glow,arc, and glow-to-arc transition modes, with an atmospheric-pressure direct-current(DC) argon discharge as a model plasma system. The modeling results show that, under different discharge modes, the most significant difference between the preceding four discharge modes lies in the current and energy transfer processes on the cathode side. On one hand, the current to the cathode surface is mainly delivered by the ions coming from the plasma column under the glow discharge mode due to the low temperature of the solid cathode, whereas the thermionic and secondary electrons emitted from the hot cathode surface play a very important role under the arc mode with a higher cathode surface temperature and higher ion flux toward the cathode. On the other hand, the energy transfer channel on the cathode side changes from mainly heating the solid cathode under the glow mode to simultaneously heating both the solid cathode and plasma column under the arc mode with an increase in the discharge current. Consequently, the power density in the cathode sheath(P_c) was used as a key parameter for judging different discharge modes, and the range of(0.28–1.2) × 10^(12) W m^(-3) was determined as a critical window of P_c corresponding to the glow-to-arc-mode transition for the atmospheric-pressure DC argon discharge, which was also verified by comparison with the experimental results in this study and the data in the previous literature.

关 键 词：atmospheric-pressure plasma direct-current gas discharge discharge mode mode transition power density in cathode sheath 

分 类 号：O53[理学—等离子体物理] O461.2[理学—物理]