Limit-Field Behavior of Various Gas Mixtures Discussed in the Framework of a Boltzmann-Equation Analysis

Theoretical limit fields for SF6/N2, CC12F2/N2, CC12F2/SF6 and CC12F2/SF6/N2 gas mixtures obtained from a Boltzmann-equation analysis are compared with experimental values measured in a steady-state discharge, and with data from other swarm experiments as well as with breakdown-potential measurements taken from the literature. Good agreement is found between experimental and calculated limit-field values; the largest relative difference in magnitude, which occurs for the case of the ternary mixtures, is of the order of 10%. Discussion based on considerations of the electron energy distribution functions and collision integrals such as the ionization and attachment frequencies demonstrates that the theoretical model is successful in relating the limit-field behavior to the interplay of the microscopic processes involved.