Abstract
The dc breakdown strengths of C/sub 7/F/sub 14/ (perfluoromethylcyclohexane), C/sub 7/F/sub 14/ (perfluoroheptene-1), and C/sub 4/F/sub 6/ (hexafluorobutadiene) have been found to be superior to SF/sub 6/ by a factor of 2.1, 1.2, and 1.4, respectively. Electron attachment rates and cross sections have been measured for C/sub 6/F/sub 10/ (perfluorocyclohexene) and C/sub 6/F/sub 12/ (perfluorodimethylcyclobutane) and were found to be very large to energies of approx. 1 eV. They correlate nicely with the superior breakdown strengths of these systems which are more than twice that of SF/sub 6/. The dc breakdown voltage, V/sub s/, for c-C/sub 4/F/sub 8/, iso-C/sub 4/F/sub 8/, and SF/sub 6/ was extended to higher voltages (to 300 kV). For the former two compounds, V/sub s/ obeys Paschen's law, but it deviates from it for SF/sub 6/. Mixtures of our best dielectric fluorocarbon gases such as C/sub 4/F/sub 6/ and c-C/sub 4/F/sub 8/ with N/sub 2/ do not show a ''saturation'' effect as does SF/sub 6/ and exhibit a synergistic behavior. Very importantly, the direct effect of the inelastic scattering properties of the gas via low-lying (approx. 1 to 4 eV) negative ion resonances on its breakdown strength has been demonstrated. Construction of a new high pressure, high voltage, variable temperature test chamber continued. Fabrication of cylindrical electrodes of variable degree of surface roughness, material composition and radius for applied testing has been completed. The results of the first phase of our diverter studies are reported.
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