Vapor shield for vacuum interrupters

A vacuum interrupter (VI) is provided having two arcing contacts, at least one of which is axially moveable, and a metal-vapor condensing shield which is shaped to allow the VI to withstand a high peak value of pulsed or sinusoidal high voltage applied to the cold contacts in their open position. In the region surrounding the open contacts, the vapor shield is shaped to deflect the trajectories of electrons which are emitted from the regions of high electric field stress along the facing edges of the negatively biased contact. The vapor shield causes electrons to be substantially deflected away from the intercontact edge region and onto a defocused area of lower electric field stress on the shield.