DC Breakdown Characteristics of C4F7N/CO2 Mixtures With Particle-in-Cell Simulation

The breakdown characteristics of C4F7N/CO2 mixtures under dc condition are investigated with a particle-in-cell method. The processes of elastic, excitation, ionization, and attachment collisions are all considered. The elastic cross section of electron scattering from C4F7N is modeled through quantum mechanical spherical complex optical potential formalism. Based on the cross-sectional data, the dielectric strength of pure C4F7N is studied. The threshold of breakdown is in good agreement with the experiment. Besides, the dielectric strength of C4F7N/CO2 mixtures is also obtained. The threshold of breakdown in 80% C4F7N and 20% CO2 is larger than that of pure C4F7N when the gas pressure is larger than 1300 torr. The results show that the energy loss of electrons is mainly caused by excitation collision with CO2 when the energy of electrons T-e is smaller than 5.5 eV. When EIP is small, the proportion of low-energy electrons is large and T-e increases with the ratio of C4F7N. Therefore, the effective ionization rate first decreases and then increases as the ratio of C4F7N increases.

Automated summary

The breakdown characteristics of C4F7N/CO2 mixtures under dc condition were investigated using a particle-in-cell method. The results showed that the breakdown threshold of the mixture increases with the proportion of C4F7N.