Effect of a solid insulator on the spark yield of S2F 10 in SF6

Because of its toxicity S₂F₁₀ production in SF₆ discharges has been the focus of intensive study in recent years. In previous work we have examined the yield of S₂ F₁₀ for corona, spark and arc discharges and, in sparks, the effects of water and oxygen have been studied systematically. Here we report the influence of an insulating solid spacer on the production of S₂F₁₀ in SF₆ when subjected to spark discharges in the energy range 1.6-43 J/spark at a gas pressure of 1 atm. Analyses of the sparked gases were performed using a cryogenic enrichment gas chromatography technique with a sensitivity of less than 10 ppb (parts-per-billion) or 1 in 10 ⁸. With this sensitivity S₂F₁₀ can be detected after one or just a few spark(s), minimizing secondary effects of gas contamination, electrode erosion and insulator damage that can influence S₂F₁₀ production and make quantitative yield determinations difficult to establish. For these studies Teflon was used as the spacer sandwiched between two stainless steel electrodes. Energy measurements were made after recording the voltage and current waveforms. The amount of S₂F₁₀ produced per unit energy deposited into the discharge was found to be greater in the presence of the spacer than for a purely gas gap. Factors which influence S₂F₁₀ stability such as surfaces and water will also be discussed