Abstract: A filament assembly can include: a button having a planar emitter region with one or more apertures extending from an emission surface of the planar emitter region to an internal surface opposite of the emission surface; an inlet electrical lead coupled to the button at a first side; an outlet electrical lead coupled to the button at a second side opposite of the first side; and a low work function object positioned adjacent to the internal surface of the planar emitter region and retained to the button. The planar emitter region can include a plurality of apertures. The low work function object can include a porous ceramic material having the barium, and may have a polished external surface. An electron gun can include the filament assembly. An additive manufacturing system can include the electron gun having the filament assembly.

Abstract: A filament assembly can include: a button having a planar emitter region with one or more apertures extending from an emission surface of the planar emitter region to an internal surface opposite of the emission surface; an inlet electrical lead coupled to the button at a first side; an outlet electrical lead coupled to the button at a second side opposite of the first side; and a low work function object positioned adjacent to the internal surface of the planar emitter region and retained to the button. The planar emitter region can include a plurality of apertures. The low work function object can include a porous ceramic material having the barium, and may have a polished external surface. An electron gun can include the filament assembly. An additive manufacturing system can include the electron gun having the filament assembly.

Abstract: In an example, a method to form a low work function insert includes preparing a mixture that includes a first powder that contains barium, a second powder that contains calcium, a third powder that contains at least one of aluminum, samarium, or magnesium, and a fourth powder that contains a refractory metal. The method may also include heating the mixture, contained in a crucible, in a furnace. Oxygen concentration in the furnace may be maintained at a low partial pressure during heating of the mixture in the furnace. The low work function of the insert allows electrons to be readily extracted from its surface.