Electron swarm coefficients and the limiting field strength of SF6–N2O mixtures

Abstract

The electron drift velocities and the effective ionization coefficients have been measured with a pulsed Townsend apparatus for the SF6–N2O mixtures (1–75% SF6) over the combined density-normalized electric field strength, E/N, from 130 to 420 Td (1 Townsend = 10−17 V cm2). Strong electron detachment effects have been observed for gas pressure mixtures above 1 Torr due mostly to NO−, arising as a dissociation product of N2O. In contrast, the influence of detachment due to the negative ions from SF6 is shown to be very small. It has been found that the limiting electric field strength, E/Nlim, of the SF6–N2O mixture is slightly superior (25–5%) to that of SF6–N2 for SF6 amounts of 0–50%, respectively.