The Electron and Ion Transport Properties of C 4 F 7 N/CO 2 Gas Mixture Under High Pressure

The C4F7N/CO2gas mixture has attracted great attention as potential SF6gas substitute. There is still lack of research on the electron and ion transport properties of the C4F7N/CO2gas mixture under high pressure, which restricts the theoretical study of the gas charge transport mechanism. In this paper, a high-pressure gas ionization current experimental platform is built with pulsed X-ray as the ionization source. The ionization current of C4F7N/CO2mixture and SF6gas are measured under lowE/N(Eis the electric field andNis the gas density). An ion kinetic model considering electron and ion transport processes is established, and the genetic algorithm is used to calculate the swarm parameters such as ion mobility and corresponding rate coefficients. The results show that: the positive and negative ion mobilities in C4F7N/CO2mixture and SF6both decrease exponentially with increasing gas pressure. Under the same gas pressure, the ion mobility of C4F7N/CO2mixture is inversely proportional to the average molecular weight, and higher than that of SF6. In addition, the normalized ionization rate coefficientvi/Nand normalized detachment rate coefficientvd/Nof C4F7N/CO2mixture and SF6both increase linearly with the increase ofE/N. However, the normalized attachment rate coefficient (va1+va2)/Nin the C4F7N/CO2mixture and SF6 exhibit a trend of increasing first and then decreasing with the increase ofE/N. Meanwhile, thevi/Nand (va1+va2)/Nof SF6are higher than that of C4F7N/CO2mixture, but thevd/Nis lower than that of C4F7N/CO2mixture. This study can provide a microscopic reference for the theoretical study of the electron and ion transport processes of C4F7N/CO2gas mixture under high pressure.