Electron transport and swarm parameters in CO2and its mixtures with SF6

This is the authors' abstract. We don't add key points for this paper.

The pulsed Townsend technique has been used to measure the electron drift velocity, the density-normalized effective ionization coefficient, the density-normalized longitudinal diffusion coefficient ND L , and the `characteristic energy' of electrons D L / K , in CO 2 and its mixtures with SF 6 over a wide range of the density-reduced field strength E / N , from 100 to 700 Td (1 Townsend = 10 −17 V cm 2 ). The SF 6 content in the mixture was varied between 2% and 70%. It was observed that for small concentrations (2–5%) of SF 6 in the mixtures, the electron drift velocity is relatively close to that for pure CO 2 . A similar behaviour was observed for the longitudinal diffusion coefficients. In contrast, the influence of SF 6 in the mixture is strongly apparent in the values for the effective ionization coefficients. From the latter parameter, the critical field strength E / N crit for each SF 6 concentration could be derived, and it was found that its value is smaller than that measured for the SF 6 –N 2 mixtures.