Electron swarm coefficients and dielectric strength of the binary mixtures of CF₃I with Ar, Xe and CO₂

Using a pulsed Townsend apparatus we have measured the flux electron drift velocity and longitudinal diffusion coefficient, the effective ionisation coefficients and its rates, and the limiting field strength of the gaseous mixtures CF 3 I-Ar, CF 3 I-Xe and CF 3 I-CO 2 , over the density-normalised electric field intensity, E/N, from 1 to 800 Td (1 Td=10 -17 V cm 2 ). Overall, the gas mixture compositions were varied from 0.1-70% CF 3 I. Measurements of the pure gases are also presented over wider E/N ranges. The limiting field strength, (E/N) lim , has also been assessed for all the gas mixture combinations, finding that the mixtures of Xe, N 2 and CO 2 with 70% CF 3 I have a limiting field strength very close to that of pure SF 6 . Emphasis is placed on the measurements of CF 3 I-Ar, where Penning ionisation effects occur at relatively high pressures. To our knowledge, no previous experimental values of these mixture coefficients have been reported in the literature. Whenever possible, we have compared our measured data with those calculated using two-term Boltzmann methods, finding agreement with our data ranging from good to excellent.