LASER INTERFEROMETRY OF SF6 CORONAS

Radial profiles of gas density have been measured in positive and nega tive SF6 coronas at 101.3 kPa using optical interferometry. The result s show that, in DC SF6 coronas, the electrical power input is confined to a small volume around the point electrode and energy transfer by t he corona wind efficiently dissipates the heat generated there through out the discharge chamber. Consequently, temperature rises and neutral species density changes throughout the chamber are relatively small. The gas density profiles reveal a thin channel of reduced density exte nding well out into the discharge gap towards the plane electrode and regions of increased density in the outer regions of the discharge cha mber. This is consistent with the idea of a corona-driven circulation of gas around the discharge chamber.