Spatially correlated breakdown events initiated by field electron emission in vacuum and high-pressure SF₆

An optical imaging technique is described that compares the spatial distribution of vacuum field emission sites on a planar cathode at fields of 10-20 Mv m -1 in high-pressure (10 bar) sulphur hexafluoride. It has been established that a direct correlation exists between the two processes provided a delay of at least 18 h is introduced between the two experiments. This observation indicates that a high-pressure breakdown event is associated with the switch-on of an electron emission site when a large burst of charge is suddenly injected into the electrically stressed gas.