Dielectric strengths of new gases and gas mixtures

It is emphasized that the most effective gaseous dielectrics are gas mixtures with components chosen on the basis of fundamental physicochemical knowledge, especially on low-energy electron-molecule interactions. On the basis of such lnowledge, especially on electron attachment and electron slowing down, a number of new gases and gas mixtures have been found with breakdown strengths superior to pure SF/sub 6/. These include the unitary gases c-C/sub 4/F/sub 8/ (perfluorocyclobutane), C/sub 4/F/sub 8/ (perfluorobutene-2), C/sub 4/F/sub 6/ (perfluoro-2-butyne), C/sub 6/F/sub 10/ (perfluorocyclohexene), C/sub 5/F/sub 8/ (perfluorocyclopentene), and C/sub 6/F/sub 12/ (perfluorodimethylcyclobutane), and the multicomponent gas mixtures 20% C/sub 4/F/sub 6/ + 80% SF/sub 6/, 40% C/sub 4/F/sub 6/ + 60% N/sub 2/, 50% C/sub 4/F/sub 6/ + 50% SF/sub 6/, and 30% C/sub 4/F/sub 6/ + 20% SF/sub 6/ + 50% N/sub 2/ with DC breakdown strengths relative to SF/sub 6/ of 1 equal to 1.4, 1.8, 2.2, 2.1, 2.2, 2,4, 1.3, 1.4, 1.75, and 1.33, respectively. Findings on these and other systems are presented and discussed. Also discussed are results on the dielectric strengths of some of the above new gases measured with cylindrical electrode geometries using different center conductor diameters. Finally, findings on the initial decomposition products of some of the new insulators caused by electron impact are presented and their implications assessed.