Patent ID: 7215070

Claim:
A dispenser cathode which comprises: an emission surface comprising at least one emission area for emitting electrons and at least one non-emission area covered with emission-suppressing material and surrounding each emission area; a reservoir for material releasing, when heated, work-function-lowering particles, at least one passage connecting said reservoir and said emission surface for allowing diffusion of work-function-lowering particles from said reservoir to said emission surface, said at least one passage debouching in said non-emission area and within a diffusion length distance from an emission area for allowing diffusion of work-function-lowering particles from said reservoir to said emission area, and a membrane covering the emission side of said reservoir, said membrane being substantially impermeable to work-function-lowering particles, wherein said membrane has an emission side surface and a cathode side surface, said emission side surface having at least one emission area and at least one non-emission area surrounding said at least one emission area, wherein said emission area is coated with work-function-lowering material and said non-emission area is coated with emission-suppressing material.