PRODUCTION OF SO2F2, SOF4, (SOF2-50) SF6-CF4 MIXTURES EXPOSED TO NEGATIVE CORONAS(SF4), S2F10, S2OF10 AND S2O2F10 IN SF6 AND (50)

This study concerns the production of SO2F2, SOF4, (SOF2 + SF4), S2F10 , S2OF10 and S2O2F10 when SF6 is subjected to negative polarity corona discharges of varying durations (with transported charges of 1.5, 4 a nd 6 C) performed with a point-to-plane set-up using a stainless steel or aluminium plane electrode. During the experiments, the parameters varied were the way the measurement cell was prepared (clean and very clean), the SF6 pressure (50 to 400 kPa), the concentration of additiv es such as CF4 (0 to 50%) for total gas pressures of 200 kPa and 300 k Pa, water (0 to 0.2%) and oxygen (0 to 1%) for a total pressure of 300 kPa. Analyses were carried out using gas phase chromatography. The mo de of preparation of the cell proved to be representative of the actio n of impurities such as water and oxygen on each of the compounds stud ied. This effect was all the stronger when the SF6 pressure was low, I n the very clean conditions (effect of H2O and O-2 reduced to a minimu m) we observed a decrease of the quantities of the main products forme d as the SF6 pressure or the percentage of CF4 was increased. Concerni ng the effect of the small quantities of added water and oxygen studie d in both pure SF6 and in the 50-50 SF6-CF4 mixture, the results showe d that, overall, the oxygen and the water enhance the production of ai l the sulphur oxyfluorides from the SF6 fragments (except for SOF2 whi ch is inhibited by oxygen to the benefit of SOF4) and inhibit the prod uction of S2F10. The presence of 50% CF4, a fluorine source, inhibited the production of all the compounds studied independently of the tran sported charge, the metal used for the plane electrode and the percent ages of impurities (H2O, O-2) added.