The pressure dependence of the dielectric strength of SO₂and n-C₄F₁₀

The dielectric strengths of sulphur dioxide (SO 2 ) and n-perfluorobutane (n-C 4 F 10 ) have been investigated under DC voltages in uniform field geometries. The pressure range studied is between 3 and 265 kPa. The results show that the dielectric strength of both gases increases with the gas pressure, particularly in the pressure range below 100 kPa, even after allowing for the compressibility of the gases. An explanation of the phenomenon is discussed with reference to the pressure dependent electron attachment rate constant that has been measured in electron swarm experiments.