Investigation of low-pressure CO₂ dielectric barrier discharge characteristics and plasma dynamic evolution processes

Dielectric barrier discharge (DBD) process is rich in nonlinear phenomena, emission spectrum and two-terminal current contain a lot of particle transport and electromagnetic radiation information, and there is a direct mapping relationship with discharge characteristics. The differences of DBD characteristics between air and carbon dioxide (CO2) under the excitation of a voltage amplitude of 10 kV and a frequency of 3 kHz were investigated by combining optical and electrical measurements. The spectral analysis results show that the emission spectrum of air discharge is mainly composed of N2 molecular band spectrum, the second positive band is the strongest band in the emission spectrum, but the intensity of N^+ fluorescence line is weak. In the CO2 discharge plasma, the intensity of CO characteristic spectral line at 518.991 nm is the highest. The two-terminal current signal shows that the phase and amplitude of the two-terminal current of DBD are very different, and the amplitude of CO2 discharge current is one order of magnitude larger than that of air. The time-frequency analysis of the two-end current signal shows that the current signal generated by the gas ionization process has wide-band characteristics within the radio frequency (RF) range.The bandwidth of air and CO2 discharge currents in the negative half-period is greater than that of the positive half-period discharge currents, and the proportion of high-frequency energy in the frequency band of the current signal increases compared with the positive half-period discharge. Through the analysis of the discharge evolution image and its fractal dimension calculation results, it is found that the bifurcation number and bending degree of CO2 discharge channel are larger than that of air, and the larger electron affinity of CO2 molecule can realize the local electric field regulation in the discharge channel, resulting in CO2 ion wind effect greater than air ion wind effect.