The embodiments provide a thermionic emission device and a method for tuning a work function in a thermionic emission device is provided. The method includes illuminating an N type semiconductor material of a first member of a thermionic emission device, wherein a work function of the N type semiconductor material is lowered by the illuminating. The method includes collecting, on one of the first member or a second member of the thermionic emission device, electrons emitted from one of the first member or the second member.

A cathode assembly for emitting charged particles, used in for example an electron gun as source for generating an electron beam is provided. The cathode assembly has a cathode including an emitting member and a carrier. The emitting member is mounted in the carrier, and the carrier is electrically connected to a holder. The cathode is heated by irradiation from an external source, whereby the emitting member emits charged particles from an emitting surface at an emitting temperature. The connection between the carrier and the holder provides a thermal barrier for reducing the amount of thermal energy transferred from the cathode to the holder.

A cathode device including an emitter element for generating electrons. The emitter element can have an outer periphery and a distal tip. The tip can have a first angled surface that angles inwardly from the outer periphery, and a second angled surface that angles inwardly and is separated and inwardly offset from the first angled surface by a shoulder. A graphite cap which can be solid, extends around the emitter element and has an internal angled surface that engages the first angled surface of the tip of the emitter element, forming a gap of a controlled size separating the internal angled surface of the graphite cap from the second angled surface of the tip of the emitter element.

Various methods and systems are provided for a cathode of an X-ray imaging system. A method for fabricating the cathode comprises machining a plurality of focusing features on a focusing element and welding the focusing element to a base assembly.

Various methods and systems are provided for a cathode of an X-ray imaging system. A method for fabricating the cathode comprises machining a plurality of focusing features on a focusing element and welding the focusing element to a base assembly.

A method of manufacturing carburized Lu.sub.2O.sub.3 doped Mo cathodes for thermionic emission for magnetrons is described. The Lu.sub.2O.sub.3 doped Mo powder is prepared by sol-gel method. The powder is reduced thoroughly in hydrogen atmosphere. Afterwards, the powder is die-pressed into pellets, followed by sintering in hydrogen and carburization in activated carbon powder to obtain the carburized Lu.sub.2O.sub.3 doped Mo cathode.

A method of manufacturing carburized Lu.sub.2O.sub.3 doped Mo cathodes for thermionic emission for magnetrons is described. The Lu.sub.2O.sub.3 doped Mo powder is prepared by sol-gel method. The powder is reduced thoroughly in hydrogen atmosphere. Afterwards, the powder is die-pressed into pellets, followed by sintering in hydrogen and carburization in activated carbon powder to obtain the carburized Lu.sub.2O.sub.3 doped Mo cathode.