An emitter is configured to emit charged particles. The emitter comprises a body, a metal layer and a charged particle source layer. The body has a point. The metal layer is of a first metal on at least the point. The charged particle source layer is on the metal layer. The point comprises a second metal other than the first metal.

A monolithic graphite heater for heating a thermionic electron cathode includes first and second electrically conductive arms, each one of the first and second electrically conductive arms having an electrode mount at a proximal end, a thermal apex at a distal end, and a transitional region between the electrode mount and the thermal apex; a cathode mount electrically and mechanically coupling each thermal apex to form a maximum Joule-heating region at or adjacent the cathode mount and decreasing Joule heating along each transitional region; and a press-fit aperture formed in the cathode mount, the press-fit aperture sized to receive at least a portion of the thermionic electron cathode for facilitating thermionic emission produced therefrom in response to operative heat power generation provided by the maximum Joule-heating region.

A cathode device includes an emitter tip for generating electrons. An elongate heater is included having proximal and distal ends. The emitter tip can be located at the distal end of the heater. Two spaced apart legs can extend away from the distal end of the heater, terminating at the proximal end and forming an elongate slot therebetween. Two electrical contacts can compressively engage respective opposite outer surfaces of the two legs at the proximal end of the heater to mechanically secure and electrically connect the two legs of the heater to respective electrical contacts at a junction that is at a location spaced away from the emitter tip to keep the junction cooler.

A cathode device includes an emitter tip for generating electrons. An elongate heater is included having proximal and distal ends. The emitter tip can be located at the distal end of the heater. Two spaced apart legs can extend away from the distal end of the heater, terminating at the proximal end and forming an elongate slot therebetween. Two electrical contacts can compressively engage respective opposite outer surfaces of the two legs at the proximal end of the heater to mechanically secure and electrically connect the two legs of the heater to respective electrical contacts at a junction that is at a location spaced away from the emitter tip to keep the junction cooler.